Instruct: Given a question, retrieve relevant documents that can help answer the question.
Query: How high can clouds reach in the atmosphere?
Towering cumulonimbus clouds are typically accompanied by smaller cumulus clouds. The cumulonimbus base may extend several miles across and occupy low to middle altitudes - formed at altitude from approximately 200 to 4,000m (700 to 10,000ft). Peaks typically reach to as much as 12,000m (39,000ft), with extreme instances as high as 21,000m (69,000ft) or more.[2] Well-developed cumulonimbus clouds are characterized by a flat, anvil-like top (anvil dome), caused by wind shear or inversion near the tropopause. The shelf of the anvil may precede the main cloud's vertical component for many miles, and be accompanied by lightning. Occasionally, rising air parcels surpass the equilibrium level (due to momentum) and form an overshooting top culminating at the maximum parcel level. When vertically developed, this largest of all clouds usually extends through all three cloud regions. Even the smallest cumulonimbus cloud dwarfs its neighbors in comparison.
Due to reflectivity, clouds cool the earth by around , an effect largely caused by stratocumulus clouds. However, at the same time, they heat the earth by around by reflecting emitted radiation, an effect largely caused by cirrus clouds. This averages out to a net loss of . Cumulus clouds, on the other hand, have a variable effect on heating the earth's surface. The more vertical "cumulus congestus" species and cumulonimbus genus of clouds grow high into the atmosphere, carrying moisture with them, which can 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.
The atmosphere of Neptune is similar to that of Uranus. It is about 80% hydrogen, 19% helium, and 1.5% methane. However the weather activity on Neptune is much more active, and its atmosphere is much bluer than that of Uranus. The upper levels of the atmosphere reach temperatures of about 55 K, giving rise to methane clouds in its troposphere, which gives the planet its ultramarine color. Temperatures rise steadily deeper inside the atmosphere.
Neptune has extremely dynamic weather systems, including the highest wind speeds in the Solar System, thought to be powered by the flow of internal heat. Typical winds in the banded equatorial region can possess speeds of around 350 m/s, while storm systems can have winds reaching up to around 900 m/s, nearly the speed of sound in Neptune's atmosphere. Several large storm systems have been identified, including the Great Dark Spot, a cyclonic storm system the size of Eurasia, the Scooter, a white cloud group further south than the Great Dark Spot, and the Wizard's eye/Dark Spot 2, a southern cyclonic storm.
Throughout the Little Ice Age, the world experienced heightened volcanic activity. When a volcano erupts, its ash reaches high into the atmosphere and can spread to cover the whole earth. The ash cloud blocks out some of the incoming solar radiation, leading to worldwide cooling that can last up to two years after an eruption. Also emitted by eruptions is sulfur, in the form of sulfur dioxide gas. When it reaches the stratosphere, it turns into sulfuric acid particles, which reflect the sun's rays, further reducing the amount of radiation reaching Earth's surface.
The shape of the shock wave is influenced by variation of the speed of sound with altitude, and the temperature and humidity of different atmospheric layers determines the appearance of the Wilson clouds. Condensation rings around or above the fireball are a commonly observed feature. Rings around the fireball may become stable, becoming rings around the rising stem. Higher-yield explosions cause intense updrafts, where air speeds can reach . The entrainment of higher-humidity air, combined with the associated drop in pressure and temperature, leads to the formation of "skirts" and "bells" around the stem. If the water droplets become sufficiently large, the cloud structure they form may become heavy enough to descend; in this way, a rising stem with a descending bell around it can be produced. Layering of humidity in the atmosphere, responsible for the appearance of the condensation rings as opposed to a spherical cloud, also influences the shape of the condensation artifacts along the stem of the mushroom cloud, as the updraft causes laminar flow. The same effect above the top of the cloud, where the expansion of the rising cloud pushes a layer of warm, humid, low-altitude air upwards into cold, high-altitude air, first causes the condensation of water vapour out of the air and then causes the resulting droplets to freeze, forming "ice caps" (or "icecaps"), similar in both appearance and mechanism of formation to scarf clouds.
Lidars have been proven useful for classification of cloud types (i.e., cumuli versus cirrus). Cloud boundaries can be retrieved from a ground-based lidar operating at a visible and/or near-infrared band. Cloud-base height can be identified by the time difference between the transmittance of the laser pulse to the sky and the detection of the backscattered light by the telescope. The laser beam is always attenuated when it penetrates through the clouds. However, when a powerful laser (e.g., Nd:YAG laser with high energy per pulse) is used, cloud tops can be retrieved too. Another physical parameter that can be retrieved is the cloud phase. By using a linear polarized laser beam, a linear particle depolarization ratio (δ) can be defined as the ratio of measured perpendicular backscatter intensity over parallel backscatter intensity with respect to the transmitter polarization axis:
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The lowest part of the atmosphere is the region with the largest influence of human activity emission of water vapor, warm air, and condensation nuclei. When the atmosphere is stable, the additional contribution of warm and moist air from emissions enhances fog formation or layers of "Stratus homoogenitus" ("Sth"). If the air is not stable, this warm and moist air emitted by human activities creates a convective movement that can reach the lifted condensation level producing an anthropic cumulus cloud, or "Cumulus homogenitus" ("Cuh"). This type of clouds may be also observed over the polluted air covering some cities or industrial areas in high-pressure conditions.
A coronal cloud is the cloud of hot plasma gas surrounding a coronal mass ejection. It is usually made up of protons and electrons. When a coronal mass ejection occurs, it is the coronal cloud that usually reaches Earth and causes damage to electrical equipment and space satellites, not the ejection or flare itself. The damage is mostly the result of the high amount of electricity moving through the atmosphere.
Cirrocumulus floccus is a type of cirrocumulus cloud. The name "cirrocumulus floccus" is derived from Latin, meaning "a lock of wool". Cirrocumulus floccus appears as small tufts of cloud with rounded heads, but ragged bottoms. The cloud can produce virga, precipitation that evaporates before reaching the ground. Like cirrocumulus castellanus, cirrocumulus floccus is an indicator of atmospheric instability at the level of the cloud. In fact, cirrocumulus floccus can form from cirrocumulus castellanus, being the evolutionary state after the base of the original cloud has dissipated.
Mars' dust storms can kick up fine particles in the atmosphere around which clouds can form. These clouds can form very high up, up to 100km (62mi) above the planet.[15] The clouds are very faint and can only be seen reflecting sunlight against the darkness of the night sky. In that respect, they look similar to the mesospheric clouds, also known as noctilucent clouds on Earth, which occur about 80km (50mi) above our planet.
The color of a cloud, as seen from the Earth, tells much about what is going on inside the cloud. Dense deep tropospheric 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. 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. Thin clouds may look white or appear to have acquired the color of their environment or background. High tropospheric and non-tropospheric clouds appear mostly white if composed entirely of ice crystals and/or supercooled water droplets.
Castellanus clouds are evidence of mid-atmospheric instability and a high mid-altitude lapse rate. They may be a harbinger of heavy showers and thunderstorms and, if surface-based convection can connect to the mid-tropospheric unstable layer, continued development of Castellanus clouds can produce cumulonimbus clouds.
Sulfuric acid is produced in the upper atmosphere of Venus by the Sun's photochemical action on carbon dioxide, sulfur dioxide, and water vapor. Ultraviolet photons of wavelengths less than 169 nm can photodissociate carbon dioxide into carbon monoxide and atomic oxygen. Atomic oxygen is highly reactive. When it reacts with sulfur dioxide, a trace component of the Venusian atmosphere, the result is sulfur trioxide, which can combine with water vapor, another trace component of Venus's atmosphere, to yield sulfuric acid. In the upper, cooler portions of Venus's atmosphere, sulfuric acid exists as a liquid, and thick sulfuric acid clouds completely obscure the planet's surface when viewed from above. The main cloud layer extends from 45–70 km above the planet's surface, with thinner hazes extending as low as 30 km and as high as 90 km above the surface. The permanent Venusian clouds produce a concentrated acid rain, as the clouds in the atmosphere of Earth produce water rain.
A lightning strike or lightning bolt is an electric discharge between the atmosphere and an Earth-bound object. They mostly originate in a cumulonimbus cloud and terminate on the ground, called cloud to ground (CG) lightning. A less common type of strike, called ground to cloud (GC), is upward propagating lightning initiated from a tall grounded object and reaches into the clouds. About 25% of all lightning events worldwide are strikes between the atmosphere and earth-bound objects. The bulk of lightning events are intra-cloud (IC) or cloud to cloud (CC), where discharges only occur high in the atmosphere.
The circulation in Venus's troposphere follows the so-called cyclostrophic flow.[3] Its windspeeds are roughly determined by the balance of the pressure gradient and centrifugal forces in almost purely zonal flow. In contrast, the circulation in the Earth's atmosphere is governed by the geostrophic balance.[3] Venus's windspeeds can be directly measured only in the upper troposphere (tropopause), between 60–70km, altitude, which corresponds to the upper cloud deck.[24] The cloud motion is usually observed in the ultraviolet part of the spectrum, where the contrast between clouds is the highest.[24] The linear wind speeds at this level are about 100±10m/s at lower than 50° latitude. They are retrograde in the sense that they blow in the direction of the retrograde rotation of the planet.[24] The winds quickly decrease towards the higher latitudes, eventually reaching zero at the poles. Such strong cloud-top winds cause a phenomenon known as the super-rotation of the atmosphere.[3] In other words, these high-speed winds circle the whole planet faster than the planet itself rotates.[23] The super-rotation on Venus is differential, which means that the equatorial troposphere super-rotates more slowly than the troposphere at the midlatitudes.[24] The winds also have a strong vertical gradient. They decline deep in the troposphere with the rate of 3m/sperkm.[3] The winds near the surface of Venus are much slower than that on Earth. They actually move at only a few kilometres per hour (generally less than 2m/s and with an average of 0.3 to 1.0m/s), but due to the high density of the atmosphere at the surface, this is still enough to transport dust and small stones across the surface, much like a slow-moving current of water.[1][25]
Cumulus congestus clouds are characteristic of unstable areas of the atmosphere which are undergoing convection. They are often characterized by sharp outlines and great vertical development. Because they are produced by strong updrafts, they are typically taller than they are wide, and cloud tops can reach , or higher in the tropics. Cumulus congestus clouds are formed by the development of cumulus mediocris generally, though they can also be formed from altocumulus castellanus or stratocumulus castellanus as well. The "congestus" species of cloud can only be found in the genus "cumulus" and is designated as "towering cumulus" (Tcu) by the International Civil Aviation Organization. Congestus clouds are capable of producing severe turbulence and showers of moderate to heavy intensity. This species is classified as vertical or multi-étage and is coded C2 in the synop report. These clouds are usually too large and opaque to have any opacity or pattern-based varieties.
Venusian clouds are thick and are composed mainly (75-96%) of sulfuric acid droplets.[37] These clouds obscure the surface of Venus from optical imaging, and reflect about 75%[38] of the sunlight that falls on them.[1] The geometric albedo, a common measure of reflectivity, is the highest of any planet in the Solar System. This high reflectivity potentially enables any probe exploring the cloud tops sufficient solar energy such that solar cells can be fitted anywhere on the craft.[39] The density of the clouds is highly variable with the densest layer at about 48.5km, reaching 0.1 g/m3 similar to the lower range of cumulonimbus storm clouds on Earth.[40]
The amount of solar radiation reaching ground level in rugged terrain, or due to variable cloudiness, is parameterized as this process occurs on the molecular scale. This method of parameterization is also done for the surface flux of energy between the ocean and the atmosphere in order to determine realistic sea surface temperatures and type of sea ice found near the ocean's surface. Also, the grid size of the models is large when compared to the actual size and roughness of clouds and topography. Sun angle as well as the impact of multiple cloud layers is taken into account. Soil type, vegetation type, and soil moisture all determine how much radiation goes into warming and how much moisture is drawn up into the adjacent atmosphere. Thus, they are important to parameterize.
The amount of solar radiation reaching ground level in rugged terrain, or due to variable cloudiness, is parameterized as this process occurs on the molecular scale. Also, the grid size of the models is large when compared to the actual size and roughness of clouds and topography. Sun angle as well as the impact of multiple cloud layers is taken into account. Soil type, vegetation type, and soil moisture all determine how much radiation goes into warming and how much moisture is drawn up into the adjacent atmosphere. Thus, they are important to parameterize.
Moreover, the International Cloud Atlas (ICA) is not entirely precise regarding how to determine the genus of a convective cloud. Per the ICA (1975, p. 15–16), the base of a cumulus cloud is usually between the surface and . This height limit originates from observations in temperate climates where the surface temperature and humidity are about average. It does not take into account how the cloud is formed. In the American West, the base of cumulus clouds can reach , since the combination of a low dew point () and high temperature (up to ) will yield a very high convective condensation level. While the ICA allows that a cumulus cloud can have a base higher than (by saying that cumulus clouds "usually" have their bases at or below this height), guidance given on page 16 of the ICA could lead to misclassification of a high cumulus cloud. This guidance says that a cloud's genus can be determined "by making a choice from among the genera normally encountered in the etage (height range) corresponding to its height." This could lead the observer to rule out cumulus as a possible genus for a cloud that has all the ICA-described characteristics of a cumulus except that its base is above the "Low" etage (surface to ). The observer, conscientiously trying to comply with ICA classification guidance, might then misclassify this cloud as an altocumulus (perhaps altocumulus floccus), although the instability creating it is at a different level compared to an altocumulus.
Clouds form when the dewpoint of water is reached in the presence of condensation nuclei in the troposphere. The atmosphere is a dynamic system, and the local conditions of turbulence, uplift and other parameters give rise to many types of clouds. Various types of cloud occur frequently enough to have been categorized. Furthermore, some atmospheric processes can make the clouds organize in distinct patterns such as wave clouds or actinoform clouds. These are large-scale structures and are not always readily identifiable from a single point of view.
The species "Cumulus fractus" is ragged in appearance and can form in clear air as a precursor to cumulus humilis and larger cumulus species-types; or it can form in precipitation as the supplementary feature "pannus" (also called scud) which can also include stratus fractus of bad weather. "Cumulus humilis" clouds look like puffy, flattened shapes. "Cumulus mediocris" clouds look similar, except that they have some vertical development. "Cumulus congestus" clouds have a cauliflower-like structure and tower high into the atmosphere, hence their alternate name "towering cumulus". The variety "Cumulus radiatus" forms in radial bands called cloud streets and can comprise any of the four species of cumulus.
Cumulus supplementary features are most commonly seen with the species congestus. "Cumulus virga" clouds are cumulus clouds producing virga (precipitation that evaporates while aloft), and "cumulus praecipitatio" produce precipitation that reaches the Earth's surface. "Cumulus pannus" comprise shredded clouds that normally appear beneath the parent cumulus cloud during precipitation. "Cumulus arcus" clouds have a gust front, and "cumulus tuba" clouds have funnel clouds or tornadoes. "Cumulus pileus" clouds refer to cumulus clouds that have grown so rapidly as to force the formation of pileus over the top of the cloud. "Cumulus velum" clouds have an ice crystal veil over the growing top of the cloud.
Cumulonimbus clouds are the final form of growing cumulus clouds. They form when "cumulus congestus" clouds develop a strong updraft that propels their tops higher and higher into the atmosphere until they reach the tropopause at in altitude. Cumulonimbus clouds, commonly called thunderheads, can produce high winds, torrential rain, lightning, gust fronts, waterspouts, funnel clouds, and tornadoes. They commonly have anvil clouds.
The amount of solar radiation reaching the ground, as well as the formation of cloud droplets occur on the molecular scale, and so they must be parameterized before they can be included in the model. Atmospheric drag produced by mountains must also be parameterized, as the limitations in the resolution of elevation contours produce significant underestimates of the drag. This method of parameterization is also done for the surface flux of energy between the ocean and the atmosphere, in order to determine realistic sea surface temperatures and type of sea ice found near the ocean's surface. Sun angle as well as the impact of multiple cloud layers is taken into account. Soil type, vegetation type, and soil moisture all determine how much radiation goes into warming and how much moisture is drawn up into the adjacent atmosphere, and thus it is important to parameterize their contribution to these processes. Within air quality models, parameterizations take into account atmospheric emissions from multiple relatively tiny sources (e.g. roads, fields, factories) within specific grid boxes.
Depending on the atmospheric conditions at the upper part of the troposphere, where the plane is flying, these high clouds rapidly disappear or persist. When the air is dry and stable, the water rapidly evaporates inside the contrails and can only observed up to several hundreds of meters from the plane. On the other hand, if humidity is high enough it exists an ice oversaturation and the "homogenitus" get wide and it can exist for hours. In the later case, depending on the wind conditions "Cca" may evolve to "Cirrus homogenitus" ("aCi"), or "Cirrostratus homogenitus" ("Csa"). The existence and persistence of these three types of high anthropogenic clouds may indicate the approximation of air stability. In some cases, when there is a large density of air traffic, these high "homogenitus" may inhibit the formation of natural high clouds, because the contrails capture most of the water vapor.