"lead to the formation of cirrus clouds. The researchers speculated that this might even produce a positive feedback, where the increasing upper atmospheric moisture further warms the earth, resulting in an increasing number of ""cumulus congestus"" clouds carrying more moisture into the upper atmosphere. Cumulus clouds are a genus of free-convective low-level cloud along with the related limited-convective cloud stratocumulus. These clouds form from ground level to at all latitudes. Stratus clouds are also low-level. In the middle level are the alto- clouds, which consist of the limiited-convective stratocumuliform cloud altocumulus and the stratiform cloud altostratus. Mid-level clouds form from"
"However, why they have this shape or how they are formed is not known, but recent evidence suggests that the interaction of both radiation and precipitation may help to organize them on the mesoscale. The individual convective cells that collectively make up an actinoform cloud are quite shallow, with heights generally less than , and would be classified as stratocumulus clouds by an observer on the ground. Given the extensive mesoscale organization of these clouds, it is appropriate to describe them as mesoscale stratocumulus cloud systems (MSCS) in analogy with their deeper counterpart, the Mesoscale convective system. Actinoform clouds were"
"Polar stratospheric cloud Polar stratospheric clouds (PSCs), also known as nacreous clouds (, from ""nacre"", or mother of pearl, due to its iridescence), are clouds in the winter polar stratosphere at altitudes of . They are best observed during civil twilight, when the Sun is between 1 and 6 degrees below the horizon, as well as in winter and in more northerly latitudes. They are implicated in the formation of ozone holes. The effects on ozone depletion arise because they support chemical reactions that produce active chlorine which catalyzes ozone destruction, and also because they remove gaseous nitric acid, perturbing"
"Mesoscale convective system A mesoscale convective system (MCS) is a complex of thunderstorms that becomes organized on a scale larger than the individual thunderstorms but smaller than extratropical cyclones, and normally persists for several hours or more. A mesoscale convective system's overall cloud and precipitation pattern may be round or linear in shape, and include weather systems such as tropical cyclones, squall lines, lake-effect snow events, polar lows, and Mesoscale Convective Complexes (MCCs), and generally form near weather fronts. The type that forms during the warm season over land has been noted across North America, Europe, and Asia, with a"
"Small Magellanic Cloud The Small Magellanic Cloud (SMC), or ""Nubecula Minor"", is a dwarf galaxy near the Milky Way. Classified as a dwarf irregular galaxy, the SMC has a diameter of about 7,000 light-years, contains several hundred million stars, and has a total mass of approximately 7 billion solar masses. The SMC contains a central bar structure and is speculated to once be a barred spiral galaxy that was disrupted by the Milky Way to become somewhat irregular. At a distance of about 200,000 light-years, the SMC is among the nearest intergalactic neighbors of the Milky Way and is one"
"Smith's Cloud Smith's Cloud is a high-velocity cloud of hydrogen gas located in the constellation Aquila at Galactic coordinates ""l"" = 39°, ""b"" = −13°. The cloud was discovered in 1963 by Gail Bieger, ""née"" Smith, who was an astronomy student at Leiden University in the Netherlands. Using the National Science Foundation's Robert C. Byrd Green Bank Telescope, radio astronomers have found that Smith's cloud has a mass of at least one million solar masses and measures long by wide in projection. The cloud is between and from Earth and has an angular diameter of 10 to 12 degrees, approximately"
"Cloud condensation nuclei Cloud condensation nuclei or CCNs (also known as cloud seeds) are small particles typically 0.2 µm, or 1/100th the size of a cloud droplet on which water vapor condenses. Water requires a non-gaseous surface to make the transition from a vapour to a liquid; this process is called condensation. In the atmosphere, this surface presents itself as tiny solid or liquid particles called CCNs. When no CCNs are present, water vapour can be supercooled at about −13°C (8°F) for 5–6 hours before droplets spontaneously form (this is the basis of the cloud chamber for detecting subatomic particles)."
"South Pacific convergence zone The South Pacific Convergence Zone (SPCZ), a reverse-oriented monsoon trough, is a band of low-level convergence, cloudiness and precipitation extending from the Western Pacific Warm Pool at the maritime continent south-eastwards towards French Polynesia and as far as the Cook Islands (160W, 20S). The SPCZ is a portion of the Intertropical Convergence Zone (ITCZ) which lies in a band extending east-west near the Equator but can be more extratropical in nature, especially east of the International Date Line. It is considered the largest and most important piece of the ITCZ, and has the least dependence upon"
"Scud (cloud) Pannus, or scud clouds, is a type of fractus cloud at low height above ground, detached, and of irregular form found beneath nimbostratus or cumulonimbus clouds. These clouds are often ragged or wispy in appearance. When caught in the outflow (downdraft) beneath a thunderstorm, scud clouds will often move faster than the storm clouds themselves. When in an inflow (updraft) area, scud clouds tend to rise and may exhibit lateral movement ranging from very little to substantial. Pannus clouds are formed as the warmer (and often more moist) updraft of a thunderstorm lifts the relatively warm air near"
"Cirrus cloud Cirrus (cloud classification symbol: Ci) is a genus of atmospheric cloud generally characterized by thin, wispy strands, giving the type its name from the Latin word ""cirrus"", meaning a ringlet or curling lock of hair. This cloud can form at any altitude between and above sea level. The strands of cloud sometimes appear in tufts of a distinctive form referred to by the common name of ""mares' tails"". From the surface of Earth, cirrus typically appears white, or a light grey in color. It forms when water vapor undergoes deposition at altitudes above in temperate regions and above"
"South Atlantic Convergence Zone The South Atlantic convergence zone, or SACZ, is an elongated axis of clouds, precipitation, and convergent winds oriented in a northwest-southeast manner across southeast Brazil into the southwest Atlantic Ocean. By definition, the feature is a monsoon trough. It is strongest in the warm season. Thunderstorm activity along the feature magnifies over three or more days when the Madden–Julian oscillation passes into the region, due to the enhanced upper divergence. Low level winds over Rondônia are tied to the strength of this zone, where westerly wind anomalies correlate to active phases of the South American monsoon,"
"defined as when cloud shield reaches maximum area. Its eccentricity (minor axis/major axis) is greater than or equal to 0.7 at maximum extent. MCCs commonly develop from the merging of thunderstorms into a squall line which eventually meet the MCC criteria. Furthermore, some MCC formation can be tracked from the plains in Colorado back to the Rocky Mountains. These are called ""orogenic"" complexes. The characteristics of the meteorological environment that MCCs form in are strong warm air advection into the formation environment by a southerly low-level jet stream (wind maximum), strong moisture advection which increases the relative humidity of the"
"Arcus cloud An arcus cloud is a low, horizontal cloud formation, usually appearing as an accessory cloud to a cumulonimbus. Roll clouds and shelf clouds are the two main types of arcus. Arcus clouds most frequently form along the leading edge or ""gust fronts"" of thunderstorm outflow; some of the most dramatic arcus formations mark the gust fronts of derecho-producing convective systems. Roll clouds also may arise in the absence of thunderstorms, forming along the shallow cold air currents of some sea breeze boundaries and cold fronts. A shelf cloud is a low, horizontal, wedge-shaped arcus cloud. A shelf cloud"
"nitrogen and chlorine cycles in a way which increases ozone depletion. The stratosphere is very dry; unlike the troposphere, it rarely allows clouds to form. In the extreme cold of the polar winter, however, stratospheric clouds of different types may form, which are classified according to their physical state and chemical composition. Due to their high altitude and the curvature of the surface of the Earth, these clouds will receive sunlight from below the horizon and reflect it to the ground, shining brightly well before dawn or after dusk. PSCs form at very low temperatures, below . These temperatures can"
"Mesoscale convective complex A mesoscale convective complex (MCC) is a unique kind of mesoscale convective system which is defined by characteristics observed in infrared satellite imagery. They are long-lived, often form nocturnally, and commonly contain heavy rainfall, wind, hail, lightning, and possibly tornadoes. A mesoscale convective complex has either an area of cloud top of 100,000 km or greater with temperature less than or equal to -32 °C, or an area of cloud top of 50,000 km with temperature less than or equal to -52 °C. Size definitions must be met for 6 hours or greater. Its maximum extent is"
"region preceding the Magellanic Clouds. It is thought to have a velocity of −300 km/s in the GSR frame. One of the HVCs in the Leading Arm shows a composition very similar to the SMC. This seems to support the idea that the gas that comprises it was pulled off of the galaxy and accelerated in front of it via tidal forces which pull apart satellite galaxies and assimilate them into the Milky Way. This is another well-studied HVC found in the Southern Hemisphere. To read more, please see the article Smith's Cloud. High-velocity cloud High-velocity clouds (HVCs) are large"
"a pattern where the upper level jet splits into two streams. The resultant mesoscale convective system (MCS) forms at the point of the upper level split in the wind pattern in the area of best low level inflow. The convection then moves east and toward the equator into the warm sector, parallel to low-level thickness lines. When the convection is strong and linear or curved, the MCS is called a squall line, with the feature placed at the leading edge of the significant wind shift and pressure rise which is normally just ahead of its radar signature. This feature is"
"stratocumuliform cloud. Like cumulus clouds, they form at low levels and via convection. However, unlike cumulus clouds, their growth is almost completely retarded by a strong inversion. As a result, they flatten out like stratus clouds, giving them a layered appearance. These clouds are extremely common, covering on average around twenty-three percent of the earth's oceans and twelve percent of the earth's continents. They are less common in tropical areas and commonly form after cold fronts. Additionally, stratocumulus clouds reflect a large amount of the incoming sunlight, producing a net cooling effect. Stratocumulus clouds can produce drizzle, which stabilizes the"
"clouds that form from to in polar areas, in temperate areas, and in tropical areas. Although altostratus forms mostly in the middle level of the troposphere, strong frontal lift can push it into the lower part of the high-level. The main hight-level stratiform cloud is cirrostratus which is composed of ice crystals that often produce halo effects around the sun. Cirrostratus forms at altitudes of in high latitudes, in temperate latitudes, and in low, tropical latitudes. Of the non-stratiform clouds, cumulonimbus and cumulus congestus are the most closely related to nimbostratus because of their vertical extent and ability to produce"
"of instability or convective activity. High clouds form at altitudes of in the polar regions, in the temperate regions and in the tropics. 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"
"cold fronts. This outrunning occurs in a pattern where the upper level jet splits into two streams. The resultant mesoscale convective system (MCS) forms at the point of the upper level split in the wind pattern at the area of the best low-level inflow. The convection then moves east and equatorward into the warm sector, parallel to low-level thickness lines. When the convection is strong and linear or curved, the MCS is called a squall line, with the feature placed at the leading edge where the significant wind shifts and pressure rises. Even weaker and less organized areas of thunderstorms"
"Cirrocumulus cloud Cirrocumulus is one of the three main genus-types of high-altitude tropospheric clouds, the other two being cirrus and cirrostratus. They usually occur at an altitude of to . Like lower altitude cumuliform and stratocumuliform clouds, cirrocumulus signifies convection. Unlike other high-altitude-tropospheric clouds like cirrus and cirrostratus, cirrocumulus includes a small amount of liquid water droplets, although these are in a supercooled state. Ice crystals are the predominant component, and typically, the ice crystals cause the supercooled water drops in the cloud to rapidly freeze, transforming the cirrocumulus into cirrostratus. This process can also produce precipitation in the form"
"ambient cloud deck. If scud are rising and moving towards the main updraft, sometimes marked by a rain-free base (RFB) or wall cloud, then the thunderstorm is still developing from rising scud. In addition to forming in inflow, fractus also form in outflow. Scud are very common on the leading edge of a thunderstorm where warm, moist air is lifted by the gust front. Scud are usually found under shelf clouds. Fractus cloud Fractus clouds (""scuds"") are small, ragged cloud fragments that are usually found under an ambient cloud base. They form or have broken off from a larger cloud,"
"Circumhorizontal arc A circumhorizontal arc is an optical phenomenon that belongs to the family of ice halos formed by the refraction of sun- or moonlight in plate-shaped ice crystals suspended in the atmosphere, typically in cirrus or cirrostratus clouds. In its full form, the arc has the appearance of a large, brightly spectrum-coloured band (red being the topmost colour) running parallel to the horizon, located far below the Sun or Moon. The distance between the arc and the Sun or Moon is twice as far as the common 22-degree halo. Often, when the halo-forming cloud is small or patchy, only"
"is called ""Cumulus homogenitus"" and abbreviated as CUa. If a ""homogenitus"" cloud of one genus changes to another genus type, it is termed a ""homomutatus"" cloud. The international cloud classification divide the different ""genera"" in three main groups of clouds according to their altitude: Homogenitus clouds will be generated by different sources at those different levels. Despite the fact that the three genera of high clouds, ""Cirrus"", ""Cirrocumulus"" and ""Cirrostratus"", form at the top of the troposphere, far from the earth surface, they may have an anthropogenic origin. In this case, the process that causes their formation is almost always"
"by warm, moist air being lifted slowly to a very high altitude. When a warm front approaches, cirrostratus clouds become thicker and descend forming altostratus clouds, and rain usually begins 12 to 24 hours later. A stratocumulus cloud is another type of a cumuliform or stratiform cloud. Like stratus clouds, they form at low levels; but like cumulus clouds, they form via convection. Unlike cumulus clouds, their growth is almost completely retarded by a strong inversion, causing them to flatten out like stratus clouds and giving them a layered appearance. These clouds are extremely common, covering on average around twenty-three"
"Sun can remain continuously just above the horizon; as a result the walls of a round depression will receive more intense sunlight, and sublimate much more rapidly than the floor. The walls sublimate and recede, while the floor remains the same. As the seasonal frost disappears, the pit walls appear to darken considerably relative to the surrounding terrain. The SCFs have been observed to grow in size, year by year, at an average rate of 1 to 3 meters, suggesting that they are formed in a thin layer (8m) of carbon dioxide ice lying on top of water ice. Later"
"to traditional approaches, satellite images do not account for cloud composition. Oktas are often referenced in aviation weather forecasts and low level forecasts: SKC = Sky clear (0 oktas); FEW = Few (1 to 2 oktas); SCT = Scattered (3 to 4 oktas); BKN = Broken (5 to 7 oktas); OVC = Overcast (8 oktas); NSC = nil significant cloud; CAVOK = ceiling and visibility okay. Okta In meteorology, an okta is a unit of measurement used to describe the amount of cloud cover at any given location such as a weather station. Sky conditions are estimated in terms of"
"Stratocumulus cloud A stratocumulus cloud belongs to a genus-type of clouds characterized by large dark, rounded masses, usually in groups, lines, or waves, the individual elements being larger than those in altocumulus, and the whole being at a lower height, usually below . Weak convective currents create shallow cloud layers because of drier, stable air above preventing continued vertical development. Vast areas of subtropical and polar oceans are covered with massive sheets of stratocumulus. These may organize into distinctive patterns which are currently under active study. In subtropics, they cover the edges of the horse latitude climatological highs, and reduce"
"the surface. These clouds condense as the warm, moist air saturates through ascent and is pushed outward from the storm. Scud clouds are very commonly found on the leading edge of a storm front. In this area of a storm, scud are commonly associated with shelf clouds. Pannus clouds may also form when an updraft ingests precipitation-cooled air from the downdraft. Scud forming in this region of the storm, if moving laterally, will tend to move inward towards the dominant updraft. Rising scud may condense and organize into a wall cloud. Pannus clouds can often be mistaken for a developing"
"produce severe weather. A mesoscale convective system (MCS) is a complex of thunderstorms that becomes organized on a scale larger than the individual thunderstorms but smaller than extratropical cyclones, and normally persists for several hours or more. A mesoscale convective system's overall cloud and precipitation pattern may be round or linear in shape, and include weather systems such as tropical cyclones, squall lines, lake-effect snow events, polar lows, and Mesoscale Convective Complexes (MCCs), and they generally form near weather fronts. Most mesoscale convective systems develop overnight and continue their lifespan through the next day. The type that forms during the"
"according to WMO classification, nimbostratus. These clouds are formed from ice crystals, supercooled water droplets, or liquid water droplets. Low-étage clouds form at less than . The two genera that are strictly low-étage are stratus, and stratocumulus. These clouds are composed of water droplets, except during winter when they are formed of supercooled waterdroplets or ice crystals if the temperature at cloud level is below freezing. Two additional genera usually form in the low altitude range, but may be based at higher levels under conditions of very low humidity. They comprise the genera cumulus, and cumulonimbus, which along with nimbostratus,"
"Cumulonimbus cloud Cumulonimbus (from Latin ""cumulus"", ""heaped"" and ""nimbus"", ""rainstorm"") is a dense, towering vertical cloud, forming from water vapor carried by powerful upward air currents. If observed during a storm, these clouds may be referred to as thunderheads. Cumulonimbus can form alone, in clusters, or along cold front squall lines. These clouds are capable of producing lightning and other dangerous severe weather, such as tornadoes. Cumulonimbus progress from overdeveloped cumulus congestus clouds and may further develop as part of a supercell. Cumulonimbus is abbreviated Cb. Towering cumulonimbus clouds are typically accompanied by smaller cumulus clouds. The cumulonimbus base may"