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Cloud – Wikipedia

In meteorology, a cloud is an aerosol consisting of a visible mass of minute liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body.[1] Water or various other chemicals may compose the droplets and crystals. On Earth, clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture (usually in the form of water vapor) from an adjacent source to raise the dew point to the ambient temperature. They are seen in the Earth’s homosphere (which includes the troposphere, stratosphere, and mesosphere). Nephology is the science of clouds, which is undertaken in the cloud physics branch of meteorology.

There are two methods of naming clouds in their respective layers of the atmosphere; Latin and common. Cloud types in the troposphere, the atmospheric layer closest to Earth’s surface, have Latin names due to the universal adaptation of Luke Howard’s nomenclature. Formally proposed in 1802, it became the basis of a modern international system that divides clouds into five physical forms that appear in any or all of three altitude levels (formerly known as tages). These physical types, in approximate ascending order of convective activity, include stratiform sheets, cirriform wisps and patches, stratocumuliform layers (mainly structured as rolls, ripples, and patches), cumuliform heaps, and very large cumulonimbiform heaps that often show complex structure. The physical forms are divided by altitude level into ten basic genus-types. The Latin names for applicable high-level genera carry a cirro- prefix, and an alto- prefix is added to the names of the mid-level genus-types. Most of the genera can be subdivided into species and further subdivided into varieties. A very low stratiform cloud that extends down to the Earth’s surface is given the common name, fog, but has no Latin name.

Two cirriform clouds that form higher up in the stratosphere and mesosphere have common names for their main types. They are seen infrequently, mostly in the polar regions of Earth. Clouds have been observed in the atmospheres of other planets and moons in the Solar System and beyond. However, due to their different temperature characteristics, they are often composed of other substances such as methane, ammonia, and sulfuric acid as well as water.

Taken as a whole, homospheric clouds can be cross-classified by form and level to derive the ten tropospheric genera, the fog that forms at surface level, and the two additional major types above the troposphere. The cumulus genus includes three species that indicate vertical size. Clouds with sufficient vertical extent to occupy more than one altitude level are officially classified as low- or mid-level according to the altitude range at which each initially forms. However they are also more informally classified as multi-level or vertical.

The origin of the term cloud can be found in the old English clud or clod, meaning a hill or a mass of rock. Around the beginning of the 13th century, the word came to be used as a metaphor for rain clouds, because of the similarity in appearance between a mass of rock and cumulus heap cloud. Over time, the metaphoric usage of the word supplanted the old English weolcan, which had been the literal term for clouds in general.[2][3]

Ancient cloud studies were not made in isolation, but were observed in combination with other weather elements and even other natural sciences. In about 340 BC the Greek philosopher Aristotle wrote Meteorologica, a work which represented the sum of knowledge of the time about natural science, including weather and climate. For the first time, precipitation and the clouds from which precipitation fell were called meteors, which originate from the Greek word meteoros, meaning ‘high in the sky’. From that word came the modern term meteorology, the study of clouds and weather. Meteorologica was based on intuition and simple observation, but not on what is now considered the scientific method. Nevertheless, it was the first known work that attempted to treat a broad range of meteorological topics.[4]

After centuries of speculative theories about the formation and behavior of clouds, the first truly scientific studies were undertaken by Luke Howard in England and Jean-Baptiste Lamarck in France. Howard was a methodical observer with a strong grounding in the Latin language and used his background to classify the various tropospheric cloud types during 1802. He believed that the changing cloud forms in the sky could unlock the key to weather forecasting. Lamarck had worked independently on cloud classification the same year and had come up with a different naming scheme that failed to make an impression even in his home country of France because it used unusual French names for cloud types. His system of nomenclature included twelve categories of clouds, with such names as (translated from French) hazy clouds, dappled clouds and broom-like clouds. By contrast, Howard used universally accepted Latin, which caught on quickly after it was published in 1803.[5] As a sign of the popularity of the naming scheme, the German dramatist and poet Johann Wolfgang von Goethe composed four poems about clouds, dedicating them to Howard. An elaboration of Howard’s system was eventually formally adopted by the International Meteorological Conference in 1891.[5] This system covered only the tropospheric cloud types, but the discovery of clouds above the troposphere during the late 19th century eventually led to the creation separate classification schemes for these very high clouds.[6]

Terrestrial clouds can be found throughout most of the homosphere, which includes the troposphere, stratosphere, and mesosphere. Within these layers of the atmosphere, air can become saturated as a result of being cooled to its dew point or by having moisture added from an adjacent source.[7] In the latter case, saturation occurs when the dew point is raised to the ambient air temperature.

Adiabatic cooling occurs when one or more of three possible lifting agents cyclonic/frontal, convective, or orographic causes a parcel of air containing invisible water vapor to rise and cool to its dew point, the temperature at which the air becomes saturated. The main mechanism behind this process is adiabatic cooling.[8] As the air is cooled to its dew point and becomes saturated, water vapor normally condenses to form cloud drops. This condensation normally occurs on cloud condensation nuclei such as salt or dust particles that are small enough to be held aloft by normal circulation of the air.[9][10]

Frontal and cyclonic lift occur when stable air is forced aloft at weather fronts and around centers of low pressure by a process called convergence.[11] Warm fronts associated with extratropical cyclones tend to generate mostly cirriform and stratiform clouds over a wide area unless the approaching warm airmass is unstable, in which case cumulus congestus or cumulonimbus clouds will usually be embedded in the main precipitating cloud layer.[12] Cold fronts are usually faster moving and generate a narrower line of clouds which are mostly stratocumuliform, cumuliform, or cumulonimbiform depending on the stability of the warm air mass just ahead of the front.[13]

Another agent is the convective upward motion of air caused by daytime solar heating at surface level.[9] Airmass instability allows for the formation of cumuliform clouds that can produce showers if the air is sufficiently moist.[14] On moderately rare occasions, convective lift can be powerful enough to penetrate the tropopause and push the cloud top into the stratosphere.[15]

A third source of lift is wind circulation forcing air over a physical barrier such as a mountain (orographic lift).[9] If the air is generally stable, nothing more than lenticular cap clouds will form. However, if the air becomes sufficiently moist and unstable, orographic showers or thunderstorms may appear.[16]

Along with adiabatic cooling that requires a lifting agent, there are three major non-adiabatic mechanisms for lowering the temperature of the air to its dew point. Conductive, radiational, and evaporative cooling require no lifting mechanism and can cause condensation at surface level resulting in the formation of fog.[17][18][19]

There are several main sources of water vapor that can be added to the air as a way of achieving saturation without any cooling process: water or moist ground,[20][21][22] precipitation or virga,[23] and transpiration from plants[24]

Tropospheric classification is based on a hierarchy of categories with physical forms and altitude levels at the top.[25][26] These are cross-classified into a total of ten genus types, most of which can be divided into species and further subdivided into varieties which are at the bottom of the hierarchy.[27]

Clouds in the troposphere assume five physical forms based on structure and process of formation. These forms are commonly used for the purpose of satellite analysis.[25] They are given below in approximate ascending order of instability or convective activity.[28]

Non-convective stratiform clouds appear in stable airmass conditions and, in general, have flat sheet-like structures that can form at any altitude in the troposphere.[29] The stratiform group is divided by altitude range into the genera cirrostratus (high-level), altostratus (mid-level), stratus (low-level), and nimbostratus (multi-level).[26] Fog is commonly considered a surface-based cloud layer.[16] The fog may form at surface level in clear air or it may be the result of a very low stratus cloud subsiding to ground or sea level. Conversely, low stratiform cloud results when advection fog is lifted above surface level during breezy conditions.

Cirriform clouds in the troposphere are of the genus cirrus and have the appearance of detached or semi-merged filaments. They form at high tropospheric altitudes in air that is mostly stable with little or no convective activity, although denser patches may occasionally show buildups caused by limited high-level convection where the air is partly unstable.[30] Clouds resembling cirrus can be found above the troposphere but are classified separately using common names.

Clouds of this structure have both cumuliform and stratiform characteristics in the form of rolls, ripples, or elements.[31] They generally form as a result of limited convection in an otherwise mostly stable airmass topped by an inversion layer.[32] If the inversion layer is absent or higher in the troposphere, increased air mass instability may cause the cloud layers to develop tops in the form of turrets consisting of embedded cumuliform buildups.[33] The stratocumuliform group is divided into cirrocumulus (high-level), altocumulus (mid-level), and stratocumulus (low-level).[31]

Cumuliform clouds generally appear in isolated heaps or tufts.[34][35] They are the product of localized but generally free-convective lift where there are no inversion layers in the troposphere to limit vertical growth. In general, small cumuliform clouds tend to indicate comparatively weak instability. Larger cumuliform types are a sign of greater atmospheric instability and convective activity.[36] Depending on their vertical size, clouds of the cumulus genus type may be low-level or multi-level with moderate to towering vertical extent.[26]

The largest free-convective clouds comprise the genus cumulonimbus which have towering vertical extent. They occur in highly unstable air[9] and often have fuzzy outlines at the upper parts of the clouds that sometimes include anvil tops.[31] These clouds are the product of very strong convection that can penetrate the lower stratosphere.

Tropospheric clouds form in any of three levels (formerly called tages) based on altitude range above the Earth’s surface. The grouping of clouds into levels is commonly done for the purposes of cloud atlases, surface weather observations[26] and weather maps.[37] The base-height range for each level varies depending on the latitudinal geographical zone.[26] Each altitude level comprises two or three genus types differentiated mainly by physical form.[38][31]

The standard levels and genus-types are summarised below in approximate descending order of the altitude at which each is normally based.[39] Multi-level clouds with significant vertical extent are separately listed and summarized in approximate ascending order of instability or convective activity.[28]

High clouds form at altitudes of 3,000 to 7,600m (10,000 to 25,000ft) in the polar regions, 5,000 to 12,200m (16,500 to 40,000ft) in the temperate regions and 6,100 to 18,300m (20,000 to 60,000ft) in the tropics.[26] All cirriform clouds are classified as high and thus constitute a single genus cirrus (Ci). Stratocumuliform and stratiform clouds in the high altitude range carry the prefix cirro-, yielding the respective genus names cirrocumulus (Cc) and cirrostratus (Cs). When limited-resolution satellite images of high clouds are analysed without supporting data from direct human observations, it becomes impossible to distinguish between individual forms or genus types, which are then collectively identified as high-type (or informally as cirrus-type even though not all high clouds are of the cirrus form or genus).[40]

Non-vertical clouds in the middle level are prefixed by alto-, yielding the genus names altocumulus (Ac) for stratocumuliform types and altostratus (As) for stratiform types. These clouds can form as low as 2,000m (6,500ft) above surface at any latitude, but may be based as high as 4,000m (13,000ft) near the poles, 7,000m (23,000ft) at mid latitudes, and 7,600m (25,000ft) in the tropics.[26] As with high clouds, the main genus types are easily identified by the human eye, but it is not possible to distinguish between them using satellite photography. Without the support of human observations, these clouds are usually collectively identified as middle-type on satellite images.[40]

Low clouds are found from near surface up to 2,000m (6,500ft).[26] Genus types in this level either have no prefix or carry one that refers to a characteristic other than altitude. Clouds that form in the low level of the troposphere are generally of larger structure than those that form in the middle and high levels, so they can usually be identified by their forms and genus types using satellite photography alone.[40]

These clouds have low to middle level bases that form anywhere from near surface to about 2,400m (8,000ft) and tops that can extend into the high altitude range. Nimbostratus and some cumulus in this group usually achieve moderate or deep vertical extent, but without towering structure. However, with sufficient airmass instability, upward-growing cumuliform clouds can grow to high towering proportions. Although genus types with vertical extent are often informally considered a single group,[58] the International Civil Aviation Organization (ICAO) distinguishes towering vertical clouds more formally as a separate group or sub-group. It is specified that these very large cumuliform and cumulonimbiform types must be identified by their standard names or abbreviations in all aviation observations (METARS) and forecasts (TAFS) to warn pilots of possible severe weather and turbulence.[59] Multi-level clouds are of even larger structure than low clouds, and are therefore identifiable by their forms and genera, (and even species in the case of cumulus congestus) using satellite photography.[40]

This is a diffuse dark-grey non-convective stratiform layer with great horizontal extent and moderate to deep vertical development. It lacks towering structure and looks feebly illuminated from the inside.[60] Nimbostratus normally forms from mid-level altostratus, and develops at least moderate vertical extent[58][61] when the base subsides into the low level during precipitation that can reach moderate to heavy intensity. It commonly achieves deep vertical development when it simultaneously grows upward into the high level due to large scale frontal or cyclonic lift.[62] The nimbo- prefix refers to its ability to produce continuous rain or snow over a wide area, especially ahead of a warm front.[63] This thick cloud layer may be accompanied by embedded towering cumuliform or cumulonimbiform types.[61][64] Meteorologists affiliated with the World Meteorological Organization (WMO) officially classify nimbostratus as mid-level for synoptic purposes while informally characterizing it as multi-level.[26] Independent meteorologists and educators appear split between those who largely follow the WMO model[58][61] and those who classify nimbostratus as low-level, despite its considerable vertical extent and its usual initial formation in the middle altitude range.[65][66]

These clouds are sometimes classified separately from the other vertical or multi-level types because of their ability to produce severe turbulence.[59]

Genus types are commonly divided into subtypes called species that indicate specific structural details which can vary according to the stability and windshear characteristics of the atmosphere at any given time and location. Despite this hierarchy, a particular species may be a subtype of more than one genus, especially if the genera are of the same physical form and are differentiated from each other mainly by altitude or level. There are a few species, each of which can be associated with genera of more than one physical form.[72] The species types are grouped below according to the physical forms and genera with which each is normally associated. The forms, genera, and species are listed in approximate ascending order of instability or convective activity.[28]

Genus and species types are further subdivided into varieties whose names can appear after the species name to provide a fuller description of a cloud. Some cloud varieties are not restricted to a specific altitude level or form, and can therefore be common to more than one genus or species.[73]

Of the stratiform group, high-level cirrostratus comprises two species. Cirrostratus nebulosus has a rather diffuse appearance lacking in structural detail.[74] Cirrostratus fibratus is a species made of semi-merged filaments that are transitional to or from cirrus.[75] Mid-level altostratus and multi-level nimbostratus always have a flat or diffuse appearance and are therefore not subdivided into species. Low stratus is of the species nebulosus[74] except when broken up into ragged sheets of stratus fractus (see below).[58][72][76]

Cirriform clouds have three non-convective species that can form in mostly stable airmass conditions. Cirrus fibratus comprise filaments that may be straight, wavy, or occasionally twisted by non-convective wind shear.[75] The species uncinus is similar but has upturned hooks at the ends. Cirrus spissatus appear as opaque patches that can show light grey shading.[72]

Stratocumuliform genus-types (cirrocumulus, altocumulus, and stratocumulus) that appear in mostly stable air have two species each. The stratiformis species normally occur in extensive sheets or in smaller patches where there is only minimal convective activity.[77] Clouds of the lenticularis species tend to have lens-like shapes tapered at the ends. They are most commonly seen as orographic mountain-wave clouds, but can occur anywhere in the troposphere where there is strong wind shear combined with sufficient airmass stability to maintain a generally flat cloud structure. These two species can be found in the high, middle, or low level of the troposphere depending on the stratocumuliform genus or genera present at any given time.[58][72][76]

The species fractus shows variable instability because it can be a subdivision of genus-types of different physical forms that have different stability characteristics. This subtype can be in the form of ragged but mostly stable stratiform sheets (stratus fractus) or small ragged cumuliform heaps with somewhat greater instability (cumulus fractus).[72][76][78] When clouds of this species are associated with precipitating cloud systems of considerable vertical and sometimes horizontal extent, they are also classified as accessory clouds under the name pannus (see section on supplementary features).[79]

These species are subdivisions of genus types that can occur in partly unstable air. The species castellanus appears when a mostly stable stratocumuliform or cirriform layer becomes disturbed by localized areas of airmass instability, usually in the morning or afternoon. This results in the formation of cumuliform buildups arising from a common stratiform base.[80] Castellanus resembles the turrets of a castle when viewed from the side, and can be found with stratocumuliform genera at any tropospheric altitude level and with limited-convective patches of high-level cirrus.[81] Tufted clouds of the more detached floccus species are subdivisions of genus-types which may be cirriform or stratocumuliform in overall structure. They are sometimes seen with cirrus, cirrocumulus, altocumulus, and stratocumulus.[82]

A newly recognized species of stratocumulus or altocumulus has been given the name volutus, a roll cloud that can occur ahead of a cumulonimbus formation.[83] There are some volutus clouds that form as a consequence of interactions with specific geographical features rather than with a parent cloud. Perhaps the strangest geographically specific cloud of this type is the Morning Glory, a rolling cylindrical cloud that appears unpredictably over the Gulf of Carpentaria in Northern Australia. Associated with a powerful “ripple” in the atmosphere, the cloud may be “surfed” in glider aircraft.[84]

More general airmass instability in the troposphere tends to produce clouds of the more freely convective cumulus genus type, whose species are mainly indicators of degrees of atmospheric instability and resultant vertical development of the clouds. A cumulus cloud initially forms in the low level of the troposphere as a cloudlet of the species humilis that shows only slight vertical development. If the air becomes more unstable, the cloud tends to grow vertically into the species mediocris, then congestus, the tallest cumulus species[72] which is the same type that the International Civil Aviation Organization refers to as ‘towering cumulus’.[59]

With highly unstable atmospheric conditions, large cumulus may continue to grow into cumulonimbus calvus (essentially a very tall congestus cloud that produces thunder), then ultimately into the species capillatus when supercooled water droplets at the top of the cloud turn into ice crystals giving it a cirriform appearance.[72][76]

All cloud varieties fall into one of two main groups. One group identifies the opacities of particular low and mid-level cloud structures and comprises the varieties translucidus (thin translucent), perlucidus (thick opaque with translucent or very small clear breaks), and opacus (thick opaque). These varieties are always identifiable for cloud genera and species with variable opacity. All three are associated with the stratiformis species of altocumulus and stratocumulus. However, only two varieties are seen with altostratus and stratus nebulosus whose uniform structures prevent the formation of a perlucidus variety. Opacity-based varieties are not applied to high clouds because they are always translucent, or in the case of cirrus spissatus, always opaque.[73][85]

A second group describes the occasional arrangements of cloud structures into particular patterns that are discernible by a surface-based observer (cloud fields usually being visible only from a significant altitude above the formations). These varieties are not always present with the genera and species with which they are otherwise associated, but only appear when atmospheric conditions favor their formation. Intortus and vertebratus varieties occur on occasion with cirrus fibratus. They are respectively filaments twisted into irregular shapes, and those that are arranged in fishbone patterns, usually by uneven wind currents that favor the formation of these varieties. The variety radiatus is associated with cloud rows of a particular type that appear to converge at the horizon. It is sometimes seen with the fibratus and uncinus species of cirrus, the stratiformis species of altocumulus and stratocumulus, the mediocris and sometimes humilis species of cumulus,[87][88] and with the genus altostratus.[89]

Another variety, duplicatus (closely spaced layers of the same type, one above the other), is sometimes found with cirrus of both the fibratus and uncinus species, and with altocumulus and stratocumulus of the species stratiformis and lenticularis. The variety undulatus (having a wavy undulating base) can occur with any clouds of the species stratiformis or lenticularis, and with altostratus. It is only rarely observed with stratus nebulosus. The variety lacunosus is caused by localized downdrafts that create circular holes in the form of a honeycomb or net. It is occasionally seen with cirrocumulus and altocumulus of the species stratiformis, castellanus, and floccus, and with stratocumulus of the species stratiformis and castellanus.[73][85]

It is possible for some species to show combined varieties at one time, especially if one variety is opacity-based and the other is pattern-based. An example of this would be a layer of altocumulus stratiformis arranged in seemingly converging rows separated by small breaks. The full technical name of a cloud in this configuration would be altocumulus stratiformis radiatus perlucidus, which would identify respectively its genus, species, and two combined varieties.[76][73][85]

Supplementary features and accessory clouds are not further subdivisions of cloud types below the species and variety level. Rather, they are either hydrometeors or special cloud types with their own Latin names that form in association with certain cloud genera, species, and varieties.[76][85] Supplementary features, whether in the form of clouds or precipitation, are directly attached to the main genus-cloud. Accessory clouds, by contrast, are generally detached from the main cloud.[90]

One group of supplementary features are not actual cloud formations, but precipitation that falls when water droplets or ice crystals that make up visible clouds have grown too heavy to remain aloft. Virga is a feature seen with clouds producing precipitation that evaporates before reaching the ground, these being of the genera cirrocumulus, altocumulus, altostratus, nimbostratus, stratocumulus, cumulus, and cumulonimbus.[90]

When the precipitation reaches the ground without completely evaporating, it is designated as the feature praecipitatio.[91] This normally occurs with altostratus opacus, which can produce widespread but usually light precipitation, and with thicker clouds that show significant vertical development. Of the latter, upward-growing cumulus mediocris produces only isolated light showers, while downward growing nimbostratus is capable of heavier, more extensive precipitation. Towering vertical clouds have the greatest ability to produce intense precipitation events, but these tend to be localized unless organized along fast-moving cold fronts. Showers of moderate to heavy intensity can fall from cumulus congestus clouds. Cumulonimbus, the largest of all cloud genera, has the capacity to produce very heavy showers. Low stratus clouds usually produce only light precipitation, but this always occurs as the feature praecipitatio due to the fact this cloud genus lies too close to the ground to allow for the formation of virga.[76][85][90]

Incus is the most type-specific supplementary feature, seen only with cumulonimbus of the species capillatus. A cumulonimbus incus cloud top is one that has spread out into a clear anvil shape as a result of rising air currents hitting the stability layer at the tropopause where the air no longer continues to get colder with increasing altitude.[92]

The mamma feature forms on the bases of clouds as downward-facing bubble-like protuberances caused by localized downdrafts within the cloud. It is also sometimes called mammatus, an earlier version of the term used before a standardization of Latin nomenclature brought about by the World Meterorological Organization during the 20th century. The best-known is cumulonimbus with mammatus, but the mamma feature is also seen occasionally with cirrus, cirrocumulus, altocumulus, altostratus, and stratocumulus.[90]

A tuba feature is a cloud column that may hang from the bottom of a cumulus or cumulonimbus. A newly formed or poorly organized column might be comparatively benign, but can quickly intensify into a funnel cloud or tornado.[90][93][94]

An arcus feature is a roll cloud with ragged edges attached to the lower front part of cumulus congestus or cumulonimbus that forms along the leading edge of a squall line or thunderstorm outflow.[95] A large arcus formation can have the appearance of a dark menacing arch.[90]

Several new supplementary features have been formally recognized by the World Meteorological Organization (WMO). The feature fluctus can form under conditions of strong atmospheric wind shear when a stratocumulus, altocumulus, or cirrus cloud breaks into regularly spaced crests. This variant is sometimes known informally as a KelvinHelmholtz (wave) cloud. This phenomenon has also been observed in cloud formations over other planets and even in the sun’s atmosphere.[96] Another highly disturbed but more chaotic wave-like cloud feature associated with stratocumulus or altocumulus cloud has been given the Latin name asperitas. The supplementary feature cavum is a circular fall-streak hole that occasionally forms in a thin layer of supercooled altocumulus or cirrocumulus. Fall streaks consisting of virga or wisps of cirrus are usually seen beneath the hole as ice crystals fall out to a lower altitude. This type of hole is usually larger than typical lacunosus holes. A murus feature is a cumulonimbus wall cloud with a lowering, rotating cloud base than can lead to the development of tornadoes. A cauda feature is a tail cloud that extends horizontally away from the murus cloud and is the result of air feeding into the storm.[83]

Supplementary cloud formations detached from the main cloud are known as accessory clouds.[76][85][90] The heavier precipitating clouds, nimbostratus, towering cumulus (cumulus congestus), and cumulonimbus typically see the formation in precipitation of the pannus feature, low ragged clouds of the genera and species cumulus fractus or stratus fractus.[79]

A group of accessory clouds comprise formations that are associated mainly with upward-growing cumuliform and cumulonimbiform clouds of free convection. Pileus is a cap cloud that can form over a cumulonimbus or large cumulus cloud,[97] whereas a velum feature is a thin horizontal sheet that sometimes forms like an apron around the middle or in front of the parent cloud.[90] An accessory cloud recently officially recognized the World meteorological Organization is the flumen, also known more informally as the beaver’s tail. It is formed by the warm, humid inflow of a super-cell thunderstorm, and can be mistaken for a tornado. Although the flumen can indicate a tornado risk, it is similar in appearance to pannus or scud clouds and does not rotate.[83]

Clouds initially form in clear air or become clouds when fog rises above surface level. The genus of a newly formed cloud is determined mainly by air mass characteristics such as stability and moisture content. If these characteristics change over time, the genus tends to change accordingly. When this happens, the original genus is called a mother cloud. If the mother cloud retains much of its original form after the appearance of the new genus, it is termed a genitus cloud. One example of this is stratocumulus cumulogenitus, a stratocumulus cloud formed by the partial spreading of a cumulus type when there is a loss of convective lift. If the mother cloud undergoes a complete change in genus, it is considered to be a mutatus cloud.[98]

The genitus and mutatus categories have been expanded to include certain types that do not originate from pre-existing clouds. The term flammagenitus (Latin for ‘fire-made’) applies to cumulus congestus or cumulonimbus that are formed by large scale fires or volcanic eruptions. Smaller low-level “pyrocumulus” or “fumulus” clouds formed by contained industrial activity are now classified as cumulus homogenitus (Latin for ‘man-made’). Contrails formed from the exhaust of aircraft flying in the upper level of the troposphere can persist and spread into formations resembling any of the high cloud genus-types and are now officially designated as cirrus, cirrostratus, or cirrocumulus homogenitus. If a homogenitus cloud of one genus changes to another genus type, it is then termed a homomutatus cloud. Stratus cataractagenitus (Latin for ‘cataract-made’) are generated by the spray from waterfalls. Silvagenitus (Latin for ‘forest-made’) is a stratus cloud that forms as water vapor is added to the air above a forest canopy.[83]

Stratocumulus clouds can be organized into “fields” that take on certain specially classified shapes and characteristics. In general, these fields are more discernible from high altitudes than from ground level. They can often be found in the following forms:

These patterns are formed from a phenomenon known as a Krmn vortex which is named after the engineer and fluid dynamicist Theodore von Krmn,.[101] Wind driven clouds can form into parallel rows that follow the wind direction. When the wind and clouds encounter high elevation land features such as a vertically prominent islands, they can form eddies around the high land masses that give the clouds a twisted appearance.[102]

Although the local distribution of clouds can be significantly influenced by topography, the global prevalence of cloud cover in the troposphere tends to vary more by latitude. It is most prevalent in and along low pressure zones of surface tropospheric convergence which encircle the Earth close to the equator and near the 50th parallels of latitude in the northern and southern hemispheres.[105] The adiabatic cooling processes that lead to the creation of clouds by way of lifting agents are all associated with convergence; a process that involves the horizontal inflow and accumulation of air at a given location, as well as the rate at which this happens.[106] Near the equator, increased cloudiness is due to the presence of the low-pressure Intertropical Convergence Zone (ITCZ) where very warm and unstable air promotes mostly cumuliform and cumulonimbiform clouds.[107] Clouds of virtually any type can form along the mid-latitude convergence zones depending on the stability and moisture content of the air. These extratropical convergence zones are occupied by the polar fronts where air masses of polar origin meet and clash with those of tropical or subtropical origin.[108] This leads to the formation of weather-making extratropical cyclones composed of cloud systems that may be stable or unstable to varying degrees according to the stability characteristics of the various airmasses that are in conflict.[109]

Divergence is the opposite of convergence. In the Earth’s troposphere, it involves the horizontal outflow of air from the upper part of a rising column of air, or from the lower part of a subsiding column often associated with an area or ridge of high pressure.[106] Cloudiness tends to be least prevalent near the poles and in the subtropics close to the 30th parallels, north and south. The latter are sometimes referred to as the horse latitudes. The presence of a large-scale high-pressure subtropical ridge on each side of the equator reduces cloudiness at these low latitudes.[110] Similar patterns also occur at higher latitudes in both hemispheres.[111]

The luminance or brightness of a cloud is determined by how light is reflected, scattered, and transmitted by the cloud’s particles. Its brightness may also be affected by the presence of haze or photometeors such as halos and rainbows.[112] In the troposphere, dense, deep clouds exhibit a high reflectance (70% to 95%) throughout the visible spectrum. Tiny particles of water are densely packed and sunlight cannot penetrate far into the cloud before it is reflected out, giving a cloud its characteristic white color, especially when viewed from the top.[113] Cloud droplets tend to scatter light efficiently, so that the intensity of the solar radiation decreases with depth into the gases. As a result, the cloud base can vary from a very light to very-dark-grey depending on the cloud’s thickness and how much light is being reflected or transmitted back to the observer. High thin tropospheric clouds reflect less light because of the comparatively low concentration of constituent ice crystals or supercooled water droplets which results in a slightly off-white appearance. However, a thick dense ice-crystal cloud appears brilliant white with pronounced grey shading because of its greater reflectivity.[112]

As a tropospheric cloud matures, the dense water droplets may combine to produce larger droplets. If the droplets become too large and heavy to be kept aloft by the air circulation, they will fall from the cloud as rain. By this process of accumulation, the space between droplets becomes increasingly larger, permitting light to penetrate farther into the cloud. If the cloud is sufficiently large and the droplets within are spaced far enough apart, a percentage of the light that enters the cloud is not reflected back out but is absorbed giving the cloud a darker look. A simple example of this is one’s being able to see farther in heavy rain than in heavy fog. This process of reflection/absorption is what causes the range of cloud color from white to black.[114]

Striking cloud colorations can be seen at any altitude, with the color of a cloud usually being the same as the incident light.[115] During daytime when the sun is relatively high in the sky, tropospheric clouds generally appear bright white on top with varying shades of grey underneath. Thin clouds may look white or appear to have acquired the color of their environment or background. Red, orange, and pink clouds occur almost entirely at sunrise/sunset and are the result of the scattering of sunlight by the atmosphere. When the sun is just below the horizon, low-level clouds are gray, middle clouds appear rose-colored, and high clouds are white or off-white. Clouds at night are black or dark grey in a moonless sky, or whitish when illuminated by the moon. They may also reflect the colors of large fires, city lights, or auroras that might be present.[115]

A cumulonimbus cloud that appears to have a greenish or bluish tint is a sign that it contains extremely high amounts of water; hail or rain which scatter light in a way that gives the cloud a blue color. A green colorization occurs mostly late in the day when the sun is comparatively low in the sky and the incident sunlight has a reddish tinge that appears green when illuminating a very tall bluish cloud. Supercell type storms are more likely to be characterized by this but any storm can appear this way. Coloration such as this does not directly indicate that it is a severe thunderstorm, it only confirms its potential. Since a green/blue tint signifies copious amounts of water, a strong updraft to support it, high winds from the storm raining out, and wet hail; all elements that improve the chance for it to become severe, can all be inferred from this. In addition, the stronger the updraft is, the more likely the storm is to undergo tornadogenesis and to produce large hail and high winds.[116]

Yellowish clouds may be seen in the troposphere in the late spring through early fall months during forest fire season. The yellow color is due to the presence of pollutants in the smoke. Yellowish clouds are caused by the presence of nitrogen dioxide and are sometimes seen in urban areas with high air pollution levels.[117]

Stratocumulus stratiformis and small castellanus made orange by the sun rising

An occurrence of cloud iridescence with altocumulus volutus and cirrocumulus stratiformis

Sunset reflecting shades of pink onto grey stratocumulus stratiformis translucidus (becoming perlucidus in the background)

Stratocumulus stratiformis perlucidus before sunset. Bangalore, India.

Late-summer rainstorm in Denmark. Nearly black color of base indicates main cloud in foreground probably cumulonimbus.

Particles in the atmosphere and the sun’s angle enhance colors of stratocumulus cumulogenitus at evening twilight

Clouds exert numerous influences on Earth’s troposphere and climate. First and foremost, they are the source of precipitation, thereby greatly influencing the distribution and amount of precipitation. Because of their differential buoyancy relative to surrounding cloud-free air, clouds can be associated with vertical motions of the air that may be convective, frontal, or cyclonic. The motion is upward if the clouds are less dense because condensation of water vapor releases heat, warming the air and thereby decreasing its density. This can lead to downward motion because lifting of the air results in cooling that increases its density. All of these effects are subtly dependent on the vertical temperature and moisture structure of the atmosphere and result in major redistribution of heat that affect the Earth’s climate.[118]

The complexity and diversity of clouds is a major reason for difficulty in quantifying the effects of clouds on climate and climate change. On the one hand, white cloud tops promote cooling of Earth’s surface by reflecting shortwave radiation (visible and near infrared) from the sun, diminishing the amount of solar radiation that is absorbed at the surface, enhancing the Earth’s albedo. Most of the sunlight that reaches the ground is absorbed, warming the surface, which emits radiation upward at longer, infrared, wavelengths. At these wavelengths, however, water in the clouds acts as an efficient absorber. The water reacts by radiating, also in the infrared, both upward and downward, and the downward longwave radiation results in increased warming at the surface. This is analogous to the greenhouse effect of greenhouse gases and water vapor.[118]

High-level genus-types particularly show this duality with both short-wave albedo cooling and long-wave greenhouse warming effects. On the whole, ice-crystal clouds in the upper troposphere (cirrus) tend to favor net warming.[119][120] However, the cooling effect is dominant with mid-level and low clouds, especially when they form in extensive sheets.[119] Measurements by NASA indicate that on the whole, the effects of low and mid-level clouds that tend to promote cooling outweigh the warming effects of high layers and the variable outcomes associated with vertically developed clouds.[119]

As difficult as it is to evaluate the influences of current clouds on current climate, it is even more problematic to predict changes in cloud patterns and properties in a future, warmer climate, and the resultant cloud influences on future climate. In a warmer climate more water would enter the atmosphere by evaporation at the surface; as clouds are formed from water vapor, cloudiness would be expected to increase. But in a warmer climate, higher temperatures would tend to evaporate clouds. Both of these statements are considered accurate, and both phenomena, known as cloud feedbacks, are found in climate model calculations. Broadly speaking, if clouds, especially low clouds, increase in a warmer climate, the resultant cooling effect leads to a negative feedback in climate response to increased greenhouse gases. But if low clouds decrease, or if high clouds increase, the feedback is positive. Differing amounts of these feedbacks are the principal reason for differences in climate sensitivities of current global climate models. As a consequence, much research has focused on the response of low and vertical clouds to a changing climate. Leading global models produce quite different results, however, with some showing increasing low clouds and others showing decreases.[121][122] For these reasons the role of tropospheric clouds in regulating weather and climate remains a leading source of uncertainty in global warming projections.[123][124]

Polar stratospheric clouds show little variation in structure and are limited to a single very high range of altitude of about 15,00025,000m (49,20082,000ft), so they are not classified into altitude levels, genus types, species, or varieties in the manner of tropospheric clouds.[6]

Polar stratospheric clouds form in the lowest part of the stratosphere during the winter, at the altitude and during the season that produces the coldest temperatures and therefore the best chances of triggering condensation caused by adiabatic cooling. They are typically very thin with an undulating cirriform appearance.[125] Moisture is scarce in the stratosphere, so nacreous and non-nacreous cloud at this altitude range is restricted to polar regions in the winter where the air is coldest.[6]

Polar mesospheric clouds form at a single extreme altitude range of about 80 to 85km (50 to 53mi) and are consequently not classified into more than one level. They are given the Latin name noctilucent because of their illumination well after sunset and before sunrise. They typically have a bluish or silvery white coloration that can resemble brightly illuminated cirrus. Noctilucent clouds may occasionally take on more of a red or orange hue.[126] They are not common or widespread enough to have a significant effect on climate.[127] However, an increasing frequency of occurrence of noctilucent clouds since the 19th century may be the result of climate change.[128]

Noctilucent clouds are the highest in the atmosphere and form near the top of the mesosphere at about ten times the altitude of tropospheric high clouds.[129] From ground level, they can occasionally be seen illuminated by the sun during deep twilight. Ongoing research indicates that convective lift in the mesosphere is strong enough during the polar summer to cause adiabatic cooling of small amount of water vapour to the point of saturation. This tends to produce the coldest temperatures in the entire atmosphere just below the mesopause. These conditions result in the best environment for the formation of polar mesospheric clouds.[127] There is also evidence that smoke particles from burnt-up meteors provide much of the condensation nuclei required for the formation of noctilucent cloud.[130]

Distribution in the mesosphere is similar to the stratosphere except at much higher altitudes. Because of the need for maximum cooling of the water vapor to produce noctilucent clouds, their distribution tends to be restricted to polar regions of Earth. A major seasonal difference is that convective lift from below the mesosphere pushes very scarce water vapor to higher colder altitudes required for cloud formation during the respective summer seasons in the northern and southern hemispheres. Sightings are rare more than 45 degrees south of the north pole or north of the south pole.[126]

Cloud cover has been seen on most other planets in the solar system. Venus’s thick clouds are composed of sulfur dioxide (due to volcanic activity) and appear to be almost entirely stratiform.[131] They are arranged in three main layers at altitudes of 45 to 65km that obscure the planet’s surface and can produce virga. No embedded cumuliform types have been identified, but broken stratocumuliform wave formations are sometimes seen in the top layer that reveal more continuous layer clouds underneath.[132] On Mars, noctilucent, cirrus, cirrocumulus and stratocumulus composed of water-ice have been detected mostly near the poles.[133][134] Water-ice fogs have also been detected on Mars.[135]

Both Jupiter and Saturn have an outer cirriform cloud deck composed of ammonia,[136][137] an intermediate stratiform haze-cloud layer made of ammonium hydrosulfide, and an inner deck of cumulus water clouds.[138][139] Embedded cumulonimbus are known to exist near the Great Red Spot on Jupiter.[140][141] The same category-types can be found covering Uranus, and Neptune, but are all composed of methane.[142][143][144][145][146][147] Saturn’s moon Titan has cirrus clouds believed to be composed largely of methane.[148][149] The CassiniHuygens Saturn mission uncovered evidence of polar stratospheric clouds[150] and a methane cycle on Titan, including lakes near the poles and fluvial channels on the surface of the moon.[151]

Some planets outside the solar system are known to have atmospheric clouds. In October 2013, the detection of high altitude optically thick clouds in the atmosphere of exoplanet Kepler-7b was announced,[152][153] and, in December 2013, in the atmospheres of GJ 436 b and GJ 1214 b.[154][155][156][157]

Clouds play an important role in various cultures and religious traditions. The ancient Akkadians believed that the clouds were the breasts of the sky goddess Antu[159] and that rain was milk from her breasts.[159] In Exodus 13:21-22, Yahweh is described as guiding the Israelites through the desert in the form of a “pillar of cloud” by day and a “pillar of fire” by night.[158] In the ancient Greek comedy The Clouds, written by Aristophanes and first performed at the City Dionysia in 423 BC, the philosopher Socrates declares that the Clouds are the only true deities[160] and tells the main character Strepsiades not to worship any deities other than the Clouds, but to pay homage to them alone.[160] In the play, the Clouds change shape to reveal the true nature of whoever is looking at them,[161][160][162] turning into centaurs at the sight of a long-haired politician, wolves at the sight of the embezzler Simon, deer at the sight of the coward Cleonymus, and mortal women at the sight of the sight of the effeminate informer Cleisthenes.[161][162][160] They are hailed the source of inspiration to comic poets and philosophers;[160] they are masters of rhetoric, regarding eloquence and sophistry alike as their “friends”.[160] In China, clouds are symbols of luck and happiness.[163] Overlapping clouds are thought to imply eternal happiness[163] and clouds of different colors are said to indicate “multiplied blessings”.[163]

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Shared Web Hosting Plans – Fast & Secure Shared Hosting …

How much disk space and bandwidth is included with myplan?

For packages supporting unmetered disk space or data transfer (bandwidth), we do not have defined limitations. These resources are “unmetered”, meaning you are not billed according to the amount of disk space or bandwidth used. While of course these resources are not infinite, we believe our customers should have all the resources necessary to build an online presence and 99.95% of customers will have more than enough disk space and bandwidth to meet theirneeds.

That said, we do require all customers to be fully compliant with our Terms of Service and utilize disk space and bandwidth in a manner consistent with the normal operation of a website. While rare, we occasionally constrain accounts utilizing more resources than should be the case in the normal operation of a personal or small businesswebsite.

We regularly examine customer bandwidth and disk space utilization data in a series of statistical analyses and use the results to define “normal”. Although these tests vary from month to month, one thing remains constant: 99.95% of our customers fall into “normal” range. If your account’s bandwidth or disk space utilization causes any concern, you will receive an email asking you to reduce usage. We strive to provide at least 48 hours notice to allow customers to make adjustments before we take any correctiveaction.

It is very rare for a customer to exceed normal usage while managing a website. Typically, customers only experience issues if they use their accounts for storage (for example large multimedia files) or file sharing. Our hosting services are not intended to support these activities, and in accordance with our Terms of Service your disk space and bandwidth usage must be integrated into the normal operation of a website. We offer various plans that better address high bandwidth and large storage requirements. Please contact us fordetails.

For plans or packages featuring unlimited websites, domains, or email accounts, we do not enforce any official limitations. Customers are able to utilize as many of these features as they wish. That said, these are of course not infinite resources and there are inherent maximums associated with the technology powering them. For example, while email account creation is unlimited, these rely on the file storage available on the account. Therefore customers need to be operating within the Terms of Service to ensure resources are available to fully enable email functionality. Customers operating within the Terms of Service have yet to come up against technical boundaries for email, domains, orwebsites.

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What is an Altcoin? – CCN

Litecoin is the biggest Altcoin

Even if they do not accurately understand how it works, most people are at least somewhat familiar with Bitcoin. However, once they begin to get involved with cryptocurrency, they may be surprised to learn that there are actually hundreds of types of cryptocurrencies known as altcoins. Altcoins are anintriguingfacet of the cryptocurrency landscape, but they are not foreveryone. Altcoin newcomers often have many questions, and this guide will provide a brief overview of altcoins to help beginners decide whether or not to invest in them as part of their cryptocurrency portfolio.


The word altcoin is an abbreviation of Bitcoin alternative, and thus describes every single cryptocurrency except for Bitcoin. Altcoins are referred to as Bitcoin alternatives because, at least to some extent, most altcoins hope to either replace or improve upon at least one Bitcoin component.

There are hundreds of altcoins (CoinMarketCap listed 478 at the time this guide was written), and more appear each day. Mostaltcoins are little more than Bitcoin clones, changing only minor characteristics such as its transactions speed, distribution method, or hashing algorithm. Most of these coins do not survive for very long. One exception is Litecoin, which was one of the first altcoins.In addition to using a different hashing algorithm than Bitcoin, Litecoin has a much higher number of currency units. For this reason, Litecoin has branded itself as silver to Bitcoins gold.

The top 5 altcoins according to CoinMarketCap

However, some altcoins innovate by experimenting with useful features Bitcoin does not offer. For example, Darkcoin hopes to provide a platform for completely anonymous transactions, BitShares describes itself as a fair version of Wall Street, and Ripple serves as a protocol users can employ to make inter-currency payments with ease. Some altcoin ecosystems, such as CounterParty and Mastercoin, even utilize the Bitcoin blockchain to secure their platform.

Many Bitcoin enthusiasts argue that altcoins are completely unnecessary and will not succeed because they cannot rival the infrastructure Bitcoin boasts. However, altcoins serve an important role. Decentralization is one of Bitcoins most prominent goals, and altcoins further decentralize the cryptocurrency community. Moreover, altcoins allow developers to experiment with unique features. While it is true that Bitcoin can copy these features if the developers or community desires, fully-functioning altcoins are much better cryptocurrency laboratories than Bitcoins testnet. Finally, Altcoins give Bitcoin healthy competition. Altcoins give cryptocurrency users alternative options and forces Bitcoins developers to remain active and continue innovating. If users do not feel that Bitcoin satisfies their digital desires, they can adopt an altcoin. If enough users left Bitcoin for a particular altcoin, the Bitcoin developers would have to adopt the features the community desired or risk losing its place as the preeminent cryptocurrency.

Namecoin was the first altcoin. It seeks to decentralize the world of online identities.

Created in April 2011, Namecoin was the first altcoin. Although it also functions as a currency, Namecoins primary purpose is to decentralize domain-name registration, which makes internet censorship much more difficult. As its place among the top ten cryptocurrency market caps suggests, Namecoin has remained one of the most successful altcoins throughout its short lifespan.

Due to how recent cryptocurrency was invented and how rapidly the landscape changes, all cryptocurrency investments carry a great deal of risk. Even Bitcoinby far the most stable cryptocurrencyexhibits price volatility on a regular basis.

By comparison, however, altcoins are exponentially more volatile. Because they have such low market caps (the total value of all coins combined), altcoin markets are highly prone to price manipulation. Wealthy traderscolloquially called whalesoften inject large amounts of capital into low-priced coins to build hype and cause the price to skyrocket. Once the price has risen considerably, the whales sell their coins on exchanges at a massive profit, hurting many gullible investors in the process. This method is known as a pump and dump. Not only does this hurt greedy traders who did not take the time to do their homework, but it often proves to be the breath of an altcoins brief lifespan.

To avoid losing all your money in a pump and dump, focus on long-term investments in coins you believe have immense potential and exhibit overall health. Generally, healthy altcoins possess strong communities, exhibit high liquidity, and have developers who proactively improve the coins source code (though not necessary, many users also prefer developers who reveal their true identities).CoinGeckos comprehensive coin metric analysis algorithm statistically analyzes these three important factors and ranks coins according to overall strength.

CoinGeckos coin ranking chart ranks coins according to overall health.

If you do choose to invest in altcoins, it is important to remember somebasic tenets of investing. Avoid the hype that coin communities propagate. Investors have an agenda, so you should not take their word at face value. Only invest in coins you have researched. It is unwiseto invest in something you do not understand. Making an ill-informed investment is the first step to losing your hard-earned money. Take the time to research the coins you are considering for long-term investments, and research day-trading before you attempt to become a high-volume, short-term trader. Most importantly, never invest more than you can afford to lose. Far too many people have lost their life savings by centralizing them in volatile investments.

As with Bitcoin, there are a variety of ways to obtain altcoins. The most basic way to obtain altcoins is to accept them as payment for goods or services. If you are interested in doing this, place an ad showcasing your skill-set ona cryptocurrency job board.

You can also trade for altcoins on cryptocurrency exchanges. Most exchange use Bitcoin as an intermediary (although a few include fiat pairs), so if you do not already own bitcoins you will need to buy some before you can trade for altcoins. Some of the most-trafficked exchanges include BTER,Bittrex, MintPal,Cryptsy, and BTC38 (Chinese-only).

Many altcoin communities also sponsor giveaways to increase exposure of their coin and enticenew users to join their communities. This is a great way to acquire coins if you are low on fundsor do not have marketable skills.

Featured images from Shutterstock.

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Cloud Hosting Services | Cloud and Hosting | Sungard AS

With a range of self-managed, managed cloud, hosting and security offerings to choose from, Sungard AS can help you build resiliency into your production environment, while simplifying data protection and how you deliver IT services to your company.

Choose a self-managed, public cloud solution for the flexibility to spin up servers quickly and test applications before they go live. Or opt for a managed, multi-tenant cloud service for production workloads, which includes operating system patches and updates, data back-up and management and SLAs of 99.95% per virtual machine.

To protect your most sensitive data, our hosted private cloud service combines the scalability and agility of an elastic infrastructure with the security and performance advantages of dedicated compute and storage. Both managed cloud and self-managed options are available.

Sometimes, you may want to avoid owning, managing and maintaining your own systems, but without moving applications to the cloud. For those situations, we offer a broad selection of hosting solutions, including managed services for storage and computing environmentsfrom Wintel platforms to mid-range and mainframe systemsas well as proactive monitoring for optimal performance and always-on availability. Our secure facilities are audited to SSAE 16 Type II and certified to the ISO 20000-1 standard.

Our security approach encompasses cloud and hosted data, as well as in-house workloads and applications. Starting with a vulnerability assessment, this managed service provides multiple layers of protection, from network and web application firewalls, VPNs, intrusion detection/prevention and access management tools to integrity monitoring and log management, with 24/7 coverage by our security experts.

Sungard AS can help you provide the speed, agility and protection your business demands by aligning the right cloud, hosting and security services with your IT transformation and business goals. Our team of consultants will assist you in navigating even the most complicated IT environment, applying our proven expertise in technology and integration with the offerings of our partners to tailor a solution to meet your needs.

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Which Types of Encryption are Most Secure?

by Top Ten Reviews Contributor

Encryption can protect your consumer information, emails and other sensitive data as well as secure network connections. Today, there are many options to choose from, and finding one that is both secure and fits your needs is a must. Here are four encryption methods and what you should know about each one.


The Advanced Encryption Standard, AES, is a symmetric encryption algorithm and one of the most secure. The United States Government use it to protect classified information, and many software and hardware products use it as well. This method uses a block cipher, which encrypts data one fixed-size block at a time, unlike other types of encryption, such as stream ciphers, which encrypt data bit by bit.

AES is comprised of AES-128, AES-192 and AES-256. The key bit you choose encrypts and decrypts blocks in 128 bits, 192 bits and so on. There are different rounds for each bit key. A round is the process of turning plaintext into cipher text. For 128-bit, there are 10 rounds; 192-bit has 12 rounds; and 256-bit has 14 rounds.

Since AES is a symmetric key encryption, you must share the key with other individuals for them to access the encrypted data. Furthermore, if you dont have a secure way to share that key and unauthorized individuals gain access to it, they can decrypt everything encrypted with that specific key.


Triple Data Encryption Standard, or 3DES, is a current standard, and it is a block cipher. Its similar to the older method of encryption, Data Encryption Standard, which uses 56-bit keys. However, 3DES is a symmetric-key encryption that uses three individual 56-bit keys. It encrypts data three times, meaning your 56-bit key becomes a 168-bit key.

Unfortunately, since it encrypts data three times, this method is much slower than others. Also, because 3DES uses shorter block lengths, it is easier to decrypt and leak data. However, many financial institutions and businesses in numerous other industries use this encryption method to keep information secure. As more robust encryption methods emerge, this one is being slowly phased out.


Twofish is a symmetric block cipher based on an earlier block cipher Blowfish. Twofish has a block size of 128-bits to 256 bits, and it works well on smaller CPUs and hardware. Similar to AES, it implements rounds of encryption to turn plaintext into cipher text. However, the number of rounds doesnt vary as with AES; no matter the key size, there are always 16 rounds.

In addition, this method provides plenty of flexibility. You can choose for the key setup to be slow but the encryption process to be quick or vice versa. Furthermore, this form of encryption is unpatented and license free, so you can use it without restrictions.


This asymmetric algorithm is named after Ron Rivest, Adi Shamir and Len Adelman. It uses public-key cryptography to share data over an insecure network. There are two keys: one public and one private. The public key is just as the name suggests: public. Anyone can access it. However, the private key must be confidential. When using RSA cryptography, you need both keys to encrypt and decrypt a message. You use one key to encrypt your data and the other to decrypt it.

According to Search Security, RSA is secure because it factors large integers that are the product of two large prime numbers. Additionally, the key size is large, which increases the security. Most RSA keys are 1024-bits and 2048-bits long. However, the longer key size does mean its slower than other encryption methods.

While there are many additional encryption methods available, knowing about and using the most secure ones ensures your confidential data stays secure and away from unwanted eyes.

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Cloud computing: A complete guide | IBM

Enterprises eager to undergo digital transformations and modernize their applications are quick to see the value of adopting a cloud computing platform. They are increasingly finding business agility or cost savings by renting software. Each cloud computing service and deployment model type provides you with different levels of control, flexibility and management. Therefore, its important to understand the differences between them.

Common convention points to public cloud as the delivery model of choice; but, when considering the right architecture of cloud computing for your applications and workloads, you must begin by addressing the unique needs of your business.

This can include many factors, such as government regulations, security, performance, data residency, service levels, time to market, architecture complexity, skills and preventing vendor lock-in. Add in the need to incorporate the emerging technologies, and you can see why IT leaders are challenging the notion that cloud computing migration is easy.

At first glance, the types of cloud computing seem simple: public, private or a hybrid mix of both. In reality, the choices are many. Public cloud can include shared, dedicated and bare metal delivery models. Fully and partially managed clouds are also options. And, in some cases, especially for existing applications where architectures are too complex to move or the cost-benefit ratio is not optimal, cloud may not be the right choice.

The right model depends on your workload. You should understand the pluses and minuses of each cloud deployment model and take a methodical approach to determining which workloads to move to which type of cloud for the maximum benefit.

Dive deeper into specific cloud service and deployment models, cloud computing architecture and cloud computing examples

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Cryptocurrency Exchange Says It Can’t Access $190 Million …

QuadrigaCX says it can’t reach millions of dollars’ worth of bitcoin and other cryptocurrency after its CEO died during a December trip to India. The CEO’s laptop is encrypted, the company says. Dan Kitwood/Getty Images hide caption

QuadrigaCX says it can’t reach millions of dollars’ worth of bitcoin and other cryptocurrency after its CEO died during a December trip to India. The CEO’s laptop is encrypted, the company says.

The QuadrigaCX cryptocurrency exchange says it can’t access some $190 million in bitcoin and other funds after its founder and CEO, Gerald Cotten, died at age 30 without sharing the password for his encrypted laptop.

Cotten was “the sole officer and director” of the Canadian cryptocurrency exchange when he died, said his widow, Jennifer Robertson, in an affidavit that is part of the company’s request for court assistance as it seeks protection from its creditors.

The debt filing comes weeks after Robertson announced that Cotten had died an event she described as “a shock to all of us.”

“Gerry died due to complications with Crohn’s disease on December 9, 2018 while travelling in India,” Robertson wrote, “where he was opening an orphanage to provide a home and safe refuge for children in need.”

Robertson, who is executor of Cotten’s estate, also announced that Quadriga has put new limits on daily withdrawals, trying to keep pace with demand and resolve transaction problems that lingered through much of last year.

In an update on its website about the debt filing, the exchange says it is facing “significant financial issues” that are keeping it from disbursing customers’ funds.

The company says that it has “very significant cryptocurrency reserves” but that it can’t locate or secure those reserves.

As of the end of January, Quadriga had some 115,000 users with balances in their accounts, Robertson said. Those users’ cryptocurrency was valued at $137 million in mid-December, with another $53 million in the form of government currency. The bulk of the holdings are in bitcoin; smaller amounts are held in other popular cryptocurrencies, including Litecoin and Ethereum.

Even before Cotten’s death, Quadriga was struggling to cope with transaction delays and other problems after legal disputes with a large bank and payment processors resulted in tens of millions of dollars being frozen.

In large part, Quadriga’s biggest crisis lies in how it (as well as many other exchanges) stores cryptocurrency customers’ funds in “hot wallets” that are used for quick-turnaround withdrawals and payments and in “cold wallets” that are stored offline to protect them from thieves and hackers.

Similar to how bank customers might split their checking and savings accounts, the cold wallets hold far more money; they are tapped only when hot wallets run low or when a user wants to make a large withdrawal. What is particularly problematic for Quadriga is that its CEO seems to be the only person who held the keys to those transactions.

“The transfer of coins from the cold wallet to the hot wallet was performed manually by [Cotten],” the affidavit from Robertson states.

Quadriga did not have offices or a bank account of its own; in the court filing, Robertson said, “Gerry ran the business through his laptop, mostly at our home, but also wherever he happened to be.”

“I do not have any documents or records” for the business, Robertson added, saying that she had searched the couple’s home in Fall River, Nova Scotia, and other locations but had found nothing.

The laptop that Cotten used to move funds between cold wallets and hot wallets is encrypted and locked leaving the exchange paralyzed after Cotten’s death, Robertson said.

“I do not know the password or recovery key,” she added. “Despite repeated and diligent searches, I have not been able to find them written down anywhere.”

Robertson said she and Quadriga have hired a security expert to try to break the encryption on Cotten’s laptop and an encrypted USB key. But she added that so far, the expert has had only limited success.

Saying “there should be in excess of $180 million [Canadian] of coins in cold storage” or $137 million Robertson wrote that the company is still trying to access the wallets, in addition to looking into the possibility that Cotten had used other exchanges to secure some of the funds.

That has left Quadriga customers wondering when and whether they’ll see their money. Discussion boards on Reddit are peppered with skeptical comments about the company’s efforts to work out its issues, and some users say they have upwards of $80,000 or $100,000 that has been locked away from them.

“This is a tough lesson learned. I would probably avoid [cryptocurrency] in the future,” Quadriga user Elvis Cavalic of Calgary, Alberta, told the CBC news agency. After not being able to withdraw $15,000 [Canadian], he said, “They’ve left us completely in the dark. I’m kind of preparing for the worst.”

In the debt filing, Robertson said she has faced threats and has seen speculation online about whether Cotten is actually alive some comments on Reddit and elsewhere have speculated that his death could be an elaborate ruse to siphon money away from the exchange’s customers.

Robertson’s affidavit notes that a copy of Cotten’s death certificate was submitted to the court, with the J.A. Snow Funeral Home stating that he died on Dec. 9, 2018, in Jaipur, India.

In seeking protection from creditors, Robertson said she had convened a board of directors to run the company. And she asked the court to give Quadriga “additional time to find whatever stores of cryptocurrency may be available” and resolve other outstanding issues.

“If this cannot be done in an orderly fashion, many, if not all users, may suffer damage,” she wrote.

The next legal step for the company is expected Tuesday, when it will ask the Nova Scotia Supreme Court to appoint Ernst & Young to monitor its debt proceedings as an independent third party.

When Quadriga was fully operational, its users could use a variety of means to fund an account with the exchange, from online transfers and automatic deposits to paying via cash or a debit card at thousands of Canada Post locations. Robertson said the many types of deposits made it difficult for the company to stop the inflow of money even as it lost its ability to access or disburse funds.

Robertson said Quadriga would consider selling its cryptocurrency platform as an option to fulfill its obligations to customers and creditors. Other companies have already come forward to express interest, she said, warning that the platform’s value would almost certainly be undercut if the company faced a legal threat from its users.

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Cryptocurrency Exchange Says It Can’t Access $190 Million …

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FusionCloud Full-Stack Private Cloud – Huawei Enterprise

FusionSphere Openstack

FusionSphere OpenStack is Huaweis commercial OpenStack release with a built-in Huawei KVM virtualization engine based on open-source OpenStack. It incorporates enterprise-level enhancements to its computing, storage, network management, installation and maintenance, security, and reliability. This solution is the optimal commercial OpenStack choice for enterprise private cloud, carrier NFV, and public cloud service providers.

The ManageOne solution provides a unified Data Center (DC) management platform and supports agile operation and simplified O&M. The solution offers reliable service quality assurance and distributed cloud DC coordination. ManageOne has the following features: – DCs are physically distributed and logically centralized. – Centrally managed multiple DCs, heterogeneous virtualization platforms, and O&M activities.Based on the Virtual Data Center (VDC) mode, a data center can be used to provide different resource services for different departments and services, allowing for separation of resource construction and usage, while matching enterprise and carrier management modes.

Huaweis hybrid cloud solution, FusionBridge, supports eight unified services and provides standard OpenStack APIs. It enables automatic cross-cloud network connection while providing uniform images, resource view, and service catalog. This solution helps enterprises readily deploy services across clouds, shortens deployment time, and facilitates cross-platform operations and O&M.

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FusionCloud Full-Stack Private Cloud – Huawei Enterprise

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JSON Object Signing and Encryption (JOSE)

HS256 HMAC using SHA-256 alg Required [IESG] [RFC7518, Section 3.2] n/a HS384 HMAC using SHA-384 alg Optional [IESG] [RFC7518, Section 3.2] n/a HS512 HMAC using SHA-512 alg Optional [IESG] [RFC7518, Section 3.2] n/a RS256 RSASSA-PKCS1-v1_5 using SHA-256 alg Recommended [IESG] [RFC7518, Section 3.3] n/a RS384 RSASSA-PKCS1-v1_5 using SHA-384 alg Optional [IESG] [RFC7518, Section 3.3] n/a RS512 RSASSA-PKCS1-v1_5 using SHA-512 alg Optional [IESG] [RFC7518, Section 3.3] n/a ES256 ECDSA using P-256 and SHA-256 alg Recommended+ [IESG] [RFC7518, Section 3.4] n/a ES384 ECDSA using P-384 and SHA-384 alg Optional [IESG] [RFC7518, Section 3.4] n/a ES512 ECDSA using P-521 and SHA-512 alg Optional [IESG] [RFC7518, Section 3.4] n/a PS256 RSASSA-PSS using SHA-256 and MGF1 with SHA-256 alg Optional [IESG] [RFC7518, Section 3.5] n/a PS384 RSASSA-PSS using SHA-384 and MGF1 with SHA-384 alg Optional [IESG] [RFC7518, Section 3.5] n/a PS512 RSASSA-PSS using SHA-512 and MGF1 with SHA-512 alg Optional [IESG] [RFC7518, Section 3.5] n/a none No digital signature or MAC performed alg Optional [IESG] [RFC7518, Section 3.6] n/a RSA1_5 RSAES-PKCS1-v1_5 alg Recommended- [IESG] [RFC7518, Section 4.2] n/a RSA-OAEP RSAES OAEP using default parameters alg Recommended+ [IESG] [RFC7518, Section 4.3] n/a RSA-OAEP-256 RSAES OAEP using SHA-256 and MGF1 with SHA-256 alg Optional [IESG] [RFC7518, Section 4.3] n/a A128KW AES Key Wrap using 128-bit key alg Recommended [IESG] [RFC7518, Section 4.4] n/a A192KW AES Key Wrap using 192-bit key alg Optional [IESG] [RFC7518, Section 4.4] n/a A256KW AES Key Wrap using 256-bit key alg Recommended [IESG] [RFC7518, Section 4.4] n/a dir Direct use of a shared symmetric key alg Recommended [IESG] [RFC7518, Section 4.5] n/a ECDH-ES ECDH-ES using Concat KDF alg Recommended+ [IESG] [RFC7518, Section 4.6] n/a ECDH-ES+A128KW ECDH-ES using Concat KDF and “A128KW” wrapping alg Recommended [IESG] [RFC7518, Section 4.6] n/a ECDH-ES+A192KW ECDH-ES using Concat KDF and “A192KW” wrapping alg Optional [IESG] [RFC7518, Section 4.6] n/a ECDH-ES+A256KW ECDH-ES using Concat KDF and “A256KW” wrapping alg Recommended [IESG] [RFC7518, Section 4.6] n/a A128GCMKW Key wrapping with AES GCM using 128-bit key alg Optional [IESG] [RFC7518, Section 4.7] n/a A192GCMKW Key wrapping with AES GCM using 192-bit key alg Optional [IESG] [RFC7518, Section 4.7] n/a A256GCMKW Key wrapping with AES GCM using 256-bit key alg Optional [IESG] [RFC7518, Section 4.7] n/a PBES2-HS256+A128KW PBES2 with HMAC SHA-256 and “A128KW” wrapping alg Optional [IESG] [RFC7518, Section 4.8] n/a PBES2-HS384+A192KW PBES2 with HMAC SHA-384 and “A192KW” wrapping alg Optional [IESG] [RFC7518, Section 4.8] n/a PBES2-HS512+A256KW PBES2 with HMAC SHA-512 and “A256KW” wrapping alg Optional [IESG] [RFC7518, Section 4.8] n/a A128CBC-HS256 AES_128_CBC_HMAC_SHA_256 authenticated encryption algorithm enc Required [IESG] [RFC7518, Section 5.2.3] n/a A192CBC-HS384 AES_192_CBC_HMAC_SHA_384 authenticated encryption algorithm enc Optional [IESG] [RFC7518, Section 5.2.4] n/a A256CBC-HS512 AES_256_CBC_HMAC_SHA_512 authenticated encryption algorithm enc Required [IESG] [RFC7518, Section 5.2.5] n/a A128GCM AES GCM using 128-bit key enc Recommended [IESG] [RFC7518, Section 5.3] n/a A192GCM AES GCM using 192-bit key enc Optional [IESG] [RFC7518, Section 5.3] n/a A256GCM AES GCM using 256-bit key enc Recommended [IESG] [RFC7518, Section 5.3] n/a EdDSA EdDSA signature algorithms alg Optional [IESG] [RFC8037, Section 3.1] [RFC8032] RS1 RSASSA-PKCS1-v1_5 with SHA-1 JWK Prohibited [W3C_Web_Cryptography_Working_Group] [] [draft-irtf-cfrg-webcrypto-algorithms] RSA-OAEP-384 RSA-OAEP using SHA-384 and MGF1 with SHA-384 alg Optional [W3C_Web_Cryptography_Working_Group] [] n/a RSA-OAEP-512 RSA-OAEP using SHA-512 and MGF1 with SHA-512 alg Optional [W3C_Web_Cryptography_Working_Group] [] n/a A128CBC AES CBC using 128 bit key JWK Prohibited [W3C_Web_Cryptography_Working_Group] [] [draft-irtf-cfrg-webcrypto-algorithms] A192CBC AES CBC using 192 bit key JWK Prohibited [W3C_Web_Cryptography_Working_Group] [] [draft-irtf-cfrg-webcrypto-algorithms] A256CBC AES CBC using 256 bit key JWK Prohibited [W3C_Web_Cryptography_Working_Group] [] [draft-irtf-cfrg-webcrypto-algorithms] A128CTR AES CTR using 128 bit key JWK Prohibited [W3C_Web_Cryptography_Working_Group] [] [draft-irtf-cfrg-webcrypto-algorithms] A192CTR AES CTR using 192 bit key JWK Prohibited [W3C_Web_Cryptography_Working_Group] [] [draft-irtf-cfrg-webcrypto-algorithms] A256CTR AES CTR using 256 bit key JWK Prohibited [W3C_Web_Cryptography_Working_Group] [] [draft-irtf-cfrg-webcrypto-algorithms] HS1 HMAC using SHA-1 JWK Prohibited [W3C_Web_Cryptography_Working_Group] [] [draft-irtf-cfrg-webcrypto-algorithms]

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JSON Object Signing and Encryption (JOSE)

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Chessdom | Chess, chess news, live chess games

Written by Guy Haworth and Nelson Hernandez Reading, UK and Maryland, USA This is the…

Former world champion Vladimir Kramnik (43) has just announced that he will end his career as a professional chess player….

GM Pantsulaia Levan (Georgia) with 8.5 points emerged the Champion after the tenth and final round in the 11th Chennai…

Former National Champion International Master G Akash shared the lead with 4.0 points after the fourth round of the 11th…

The second edition of TCEC Cup, the minor trophy of the Top Chess Engine Championship, is going to start this…

The second edition of TCEC Cup, the minor trophy of the Top Chess Engine Championship, is going to start this…

In a brief post FIDE announced that a bank account is opened with Caixa Bank, one of the largest banks…

The first super tournament of the year is about to start…

The Portuguese Chess Federation will hold the Portugal Open from 2-10th February 2019 at the Pavilho Casal Vistoso in Lisbon….

The 19-years old Grandmaster Bai Jinshi from China has won the 28th Annual North American Open that was held from…

The King Salman World Blitz Chess Championship concluded today in the Manege, St. Petersburg, with Magnus Carlsen (Norway) and Kateryna…

FIDE and Kirsan Ilyumzhinov have concluded a Settlement Agreement, which was approved by the FIDE Ethics Commission and by the…

The King Salman World Rapid Championship 2018 concluded today in St.Petersburg with Russian young star Daniil Dubov claiming the gold…

The US Chess Federation is pleased to announce that Grandmaster (GM) Leinier Domnguez, originally from Cuba and currently living in…

Interview with Mark Lefler and Larry Kaufman…

American Grandmaster Hikaru Nakamura defeated Frenchman Maxime Vachier-Lagrave in the London Chess Classic and Grand Chess Tour Final by the…

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Chessdom | Chess, chess news, live chess games

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