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Cumulus cloud

Cumulus clouds are detached, low-level clouds with a distinctive puffy or cotton-like appearance, featuring flat bases and rounded tops that form through the convection of warm, moist air rising into cooler altitudes where water vapor condenses.^[1] These clouds are dense and exhibit sharp outlines, typically developing below 6,500 feet (2,000 meters) in altitude, though their vertical extent can vary significantly depending on atmospheric conditions.^[2] They represent a key indicator of atmospheric instability and moisture, often appearing on clear days but capable of evolving into more severe weather systems.^[1] Cumulus clouds form primarily through thermal updrafts, where surface heating causes parcels of air to rise, cool adiabatically, and reach the lifting condensation level, leading to droplet formation and visible cloud structure.^[1] The flat base corresponds to the altitude of condensation, while the dome-shaped top results from continued upward motion.^[2] In stable conditions, they remain small and scattered, but in unstable environments with sufficient moisture and lift, they can grow rapidly, sometimes exceeding 20,000 feet in height before transitioning to cumulonimbus.^[3] The primary subtypes of cumulus clouds are classified by their vertical development: cumulus humilis, which are flat and wide with minimal height, often called "fair weather" clouds and associated with sunny, benign conditions; cumulus mediocris, featuring moderate vertical growth comparable to their width, indicating stronger convection but typically without precipitation; and cumulus congestus, or towering cumulus, with pronounced vertical extent and bulging tops, serving as precursors to thunderstorms and capable of producing showers or hail under favorable conditions.^[3] These species all occur at low levels below 6,500 feet, composed mainly of liquid water droplets, and play a crucial role in the Earth's hydrological cycle by facilitating the initial stages of precipitation processes.^[2]

Definition and Characteristics

Morphological Features

Cumulus clouds are characterized by their detached, puffy, cauliflower-like appearance, featuring a flat base and rounded, dome-shaped tops formed through adiabatic cooling and subsequent condensation of rising moist air parcels.^[4] The flat base arises at the level where air reaches saturation, while the bulging tops result from the expansion and cooling of buoyant updrafts that promote droplet formation.^[5] This morphology gives cumulus clouds a distinct, isolated structure, often resembling cotton balls or florets clustered together.^[1] The clouds display significant vertical development, with sharp, well-defined outlines maintained by turbulent mixing at their boundaries, which limits the diffusion of moisture and prevents blurring into surrounding clear air.^[6] These boundaries enhance the crisp edges observed visually, distinguishing cumulus from more diffuse cloud types. In temperate regions, the typical base height of cumulus clouds ranges from 1 to 2 km above the ground, corresponding to the lifting condensation level (LCL) where rising air cools to its dew point.^[1] This height varies with surface moisture and temperature but generally positions the bases within the lower troposphere.^[7] Internally, cumulus clouds consist of dynamic cumulus cells—bubble-like elements driven by updrafts of 1–5 m/s and accompanying downdrafts that facilitate mixing and circulation within the cloud volume.^[6] These cells contribute to the cloud's turbulent, organized structure, supporting ongoing convective activity. Cumulus clouds appear bright white when illuminated by direct sunlight due to Mie scattering of visible wavelengths by water droplets, scattering all colors equally to the observer.^[8] In contrast, shadowed undersides exhibit darker gray or bluish tones, as they receive only diffuse skylight without direct solar illumination, reducing overall brightness.^[8]

Altitude and Extent

Cumulus clouds typically form with bases at altitudes ranging from 300 to 2,000 meters in low-latitude regions, where warmer surface temperatures lower the lifting condensation level, facilitating earlier onset of condensation during ascent.^[3] In polar regions, base heights rise to 1,500 to 3,000 meters due to cooler surface conditions that elevate the condensation level, though exact values vary with local humidity and temperature profiles.^[9] These base altitudes are fundamentally tied to surface temperature, as higher temperatures promote more vigorous convection and lower the height at which air parcels reach saturation. The vertical extent of cumulus clouds varies by developmental stage; fair-weather cumulus, or cumulus humilis, generally reach tops up to 2 kilometers above the surface, remaining confined to the lower troposphere with limited upward growth.^[1] In contrast, more developed cumulus congestus forms can extend to tops of 6 kilometers, driven by stronger updrafts that push cloud parcels into cooler mid-level air, though they stop short of anvil development seen in cumulonimbus.^[10] These top heights reflect the balance between convective energy and atmospheric stability, with fair-weather varieties dissipating before significant precipitation. Horizontally, individual cumulus clouds measure 0.5 to 3 kilometers in diameter, appearing as isolated puffy masses or loose groups that collectively cover less than 5% of the sky in fair-weather conditions.^[11] This limited extent underscores their discrete nature, contrasting with more expansive stratiform clouds, and contributes to their role as indicators of benign weather without widespread obscuration.^[12] Cumulus cloud development exhibits pronounced diurnal variations, peaking in the afternoon when solar heating maximizes surface fluxes and convective instability.^[13] Bases form shortly after sunrise as thermals build, but maximum vertical and horizontal growth occurs mid-afternoon, often leading to scattered coverage before evening dissipation as radiative cooling stabilizes the boundary layer.^[14] Base heights are commonly measured using ceilometers, ground-based lidars that detect the first backscattered signal from cloud droplets overhead, providing real-time vertical profiles with resolutions down to tens of meters.^[15] Horizontal extent and overall coverage are assessed via satellite imagery, such as from geostationary sensors that capture visible and infrared contrasts to delineate cloud boundaries and fractional sky coverage across large areas.^[16] These methods complement each other, with ceilometers offering precise local base data and satellites enabling synoptic-scale extent mapping.

Formation and Dynamics

Convective Mechanisms

Cumulus clouds form primarily through thermal convection, a process driven by surface heating that creates buoyant air parcels warmer and less dense than their surrounding environment, causing them to rise vertically.^[5] These parcels, often originating as thermals from sun-warmed land or water surfaces, ascend due to positive buoyancy until they cool adiabatically and reach saturation.^[17] As the rising air expands and cools at the dry adiabatic lapse rate of approximately 9.8 °C/km, its relative humidity increases, leading to condensation when it reaches 100%.^[18] The height at which this condensation occurs is known as the lifting condensation level (LCL), marking the base of the cumulus cloud.^[19] A common approximation for the LCL height in meters is given by the formula:

\text{LCL} \approx 125 \times (T - T_d)

where T is the surface air temperature in °C and T_d is the dew point temperature in °C; this empirical relation assumes standard atmospheric conditions and provides a practical estimate for cloud base height.^[20] Cumulus development relies on conditional instability in the atmosphere, where the environmental lapse rate is greater than the moist adiabatic rate (approximately 6 °C/km) but less than the dry adiabatic rate of 9.8 °C/km, making dry air parcels stable until they become saturated and release latent heat upon condensation.^[21] This latent heat release enhances buoyancy in the moist parcel, allowing it to accelerate upward and sustain cloud growth beyond the LCL.^[18] Without sufficient conditional instability, rising parcels would lack the positive buoyancy needed for significant vertical development. Entrainment of drier environmental air into the cloud's edges plays a key role in limiting cumulus growth by mixing and evaporating cloud droplets, which erodes the cloud boundaries and reduces overall buoyancy.^[22] This process, occurring primarily at the cloud's periphery through turbulent mixing, prevents unchecked expansion and contributes to the isolated, puffy structure of cumulus clouds.^[23] The formation of cumulus clouds follows a pronounced diurnal cycle tied to solar heating, typically initiating around 10 AM local time as surface temperatures rise, peaking in development and coverage between 2 PM and 4 PM, and dissipating by evening as radiative cooling stabilizes the boundary layer.^[24] This cycle reflects the daily variation in thermal forcing, with morning boundary layer growth providing the initial trigger for convection.^[25]

Environmental Influences

Surface heating from solar radiation drives the initiation of cumulus clouds by warming the ground and the adjacent air layer, creating buoyant thermals that rise and cool adiabatically until saturation occurs. This process is intensified over land compared to oceans due to contrasts in heat capacity and albedo, where land surfaces absorb and re-emit energy more rapidly, fostering stronger updrafts. In arid regions, low soil moisture and sparse vegetation lead to greater sensible heat flux and more vigorous convection, while urban areas exhibit enhanced heating via the urban heat island effect, which promotes low-level convergence and cloud development.^[5]^[26]^[27] Low-level moisture availability is essential for sustaining cumulus growth, as it determines the water vapor content available for condensation within rising parcels. Significant development typically requires surface dew points exceeding 10°C, ensuring sufficient humidity to form visible clouds rather than dissipating dry thermals. Without adequate moisture, even strong surface heating results in limited cloud formation, as parcels fail to reach saturation before mixing with drier air aloft.^[28] Wind shear, particularly in the lower troposphere, modulates the organization and longevity of cumulus clouds by altering updraft trajectories and entrainment rates. Moderate vertical shear can tilt cloud elements, promoting organized structures such as cloud streets aligned parallel to the mean wind or clusters in regions of convergence, which enhance collective buoyancy. Conversely, strong or abrupt directional changes in wind shear disrupt individual clouds, increasing dilution and inhibiting sustained growth into larger aggregates.^[29] Temperature inversion layers, often situated at altitudes of 2-3 km in subsidence-dominated environments like subtropical high-pressure systems, act as a lid that restricts vertical development of cumulus clouds. These inversions, associated with descending air in trade wind regimes, create stable stratification that suppresses updrafts, confining clouds to shallow layers beneath the cap and preventing transition to deeper convective forms.^[30] Cumulus clouds exhibit pronounced seasonal variations, occurring more frequently during summer months when enhanced solar insolation increases surface temperatures and atmospheric instability. Warmer conditions promote greater low-level moisture convergence and lapse rates conducive to convection, contrasting with winter's reduced heating and stable profiles that limit cloud formation.^[31]^[32]

Classification and Varieties

Cumulus Humilis

Cumulus humilis represents the initial, immature stage of cumulus cloud development, featuring minimal vertical growth and a flattened appearance that signifies a stable atmospheric environment. These clouds exhibit thin, flattened tops at low altitudes, with a horizontal extent roughly comparable to their height.^[33]^[34] This limited vertical development, ranging from tens to a few hundred meters, arises from weak convective updrafts driven by daytime surface heating.^[35] These clouds prevail under fair-weather conditions in clear skies accompanied by light winds, commonly aligning in rows or "cloud streets" parallel to the prevailing wind direction due to organized thermal circulations.^[36] Composed primarily of water droplets, sometimes including supercooled varieties at higher levels, cumulus humilis maintain sharp outlines and shaded undersides but lack the protuberances seen in more developed forms.^[37] Their presence indicates insufficient atmospheric moisture to sustain further upward growth despite surface heating, resulting in isolated, puffy formations that resemble scattered cotton balls.^[38] Cumulus humilis typically endure for 10-30 minutes before evaporating rapidly in the subsiding dry air surrounding the updrafts, without producing any precipitation.^[39] This short lifetime underscores their role as transient features of benign weather, dissipating as the thermal activity wanes. Historically, the World Meteorological Organization has classified them within the cumulus genus as indicative of "good weather," emphasizing their association with stable, non-precipitating conditions.^[40]^[41]

Cumulus Mediocris and Congestus

Cumulus mediocris clouds represent an intermediate stage in the development of cumulus formations, characterized by moderate vertical extent at low to middle altitudes. These clouds exhibit a cauliflower-like texture due to small protuberances and sproutings at their summits, distinguishing them from flatter varieties while maintaining sharp outlines overall. Composed primarily of water droplets, they generally do not produce significant precipitation, though in tropical regions they hold potential for very light showers under conditions of enhanced moisture.^[42]^[43]^[44] Cumulus congestus marks a more advanced non-precipitating phase, featuring greater vertical development with pronounced height. Their upper portions display a pronounced bulging, cauliflower-resembling structure from intense sprouting, occasionally spreading laterally upon encountering stable layers without forming a true anvil. These clouds frequently produce virga, where precipitation falls but evaporates before reaching the ground, particularly in drier mid-levels.^[45]^[10]^[3] The progression from cumulus humilis to mediocris and then to congestus occurs through sustained updrafts exceeding 5 meters per second, which enable continued vertical growth beyond initial fair-weather limits. According to World Meteorological Organization (WMO) criteria, cumulus congestus is specifically distinguished from mediocris by the occasional reach of precipitation to the ground, manifesting as showers of rain, snow, or pellets, though not yet at thunderstorm intensity. These forms are more prevalent in humid equatorial zones, where abundant moisture and instability support their frequent occurrence and role in the tropical convective spectrum.^[46]^[47]^[10]^[48]

Meteorological Role

Weather Prediction Indicators

Isolated cumulus humilis clouds, with their limited vertical development and scattered appearance, serve as reliable indicators of stable atmospheric conditions and fair weather, typically associated with clear skies and no immediate precipitation risk.^[2] These clouds form in environments where convection is weak, signaling that sunny conditions are likely to continue without significant changes in the short term. The transition to cumulus mediocris or congestus, marked by increasing vertical growth and more pronounced cauliflower-like tops, often signals rising atmospheric instability, potentially heralding the approach of a weather front and the development of showers.^[3] Such evolving clouds suggest that precipitation could occur if moisture and uplift intensify, serving as an early cue for meteorologists to monitor for convective activity.^[10] Cumulus cloud streets, elongated rows of these clouds aligned in parallel formations, provide visual clues to wind patterns at the level of the planetary boundary layer, with their orientation directly reflecting the prevailing wind direction.^[49] The spacing and alignment of these streets can also hint at wind intensity, as tighter formations often correspond to stronger shear or convection driven by surface heating.^[50] Rapid growth in cumulus clouds, particularly into towering forms, acts as a critical warning for pilots of impending turbulence due to strong updrafts and downdrafts within the developing convection.^[51] Sailors similarly rely on these visual signs during daylight hours to anticipate rough seas from associated wind shifts and instability, adjusting routes to avoid hazardous areas.^[3] Modern weather forecasting integrates observations of cumulus evolution with Geostationary Operational Environmental Satellite (GOES) imagery, enabling real-time tracking of cloud development and movement to predict convective initiation.^[52] GOES data allows forecasters to monitor cumulus growth rates and patterns over large areas, improving short-term warnings for showers or thunderstorms by detecting subtle changes in cloud texture and motion.^[53]

Climate Feedback Processes

Cumulus clouds play a significant role in Earth's energy balance by reflecting a substantial portion of incoming shortwave solar radiation due to their high albedo, typically ranging from 0.6 to 0.8 for low-level varieties.^[54] This reflection exerts a cooling effect on the planetary surface. In contrast, their influence on longwave radiation involves trapping outgoing terrestrial radiation, as cumulus clouds exhibit an emissivity near 1 in the infrared spectrum, behaving nearly as blackbodies.^[55] However, the thin vertical extent of shallow cumulus limits this greenhouse warming effect compared to thicker cloud types like stratocumulus or nimbostratus, resulting in a net radiative cooling dominance for these clouds.^[56] In tropical regions, shallow cumulus clouds contribute to climate regulation by participating in boundary layer dynamics, where their updrafts entrain dry air from above the inversion layer, thereby stabilizing the boundary layer and suppressing the development of deeper convective clouds.^[57] This process helps maintain a balance in the trade-wind regions, preventing excessive vertical mixing that could otherwise lead to widespread deep convection and associated precipitation.^[58] Such stabilization influences the overall hydrological cycle by modulating moisture transport and convective available potential energy in the tropics. As assessed in the IPCC Sixth Assessment Report (2021), cloud feedbacks, including those involving low-level clouds such as cumulus, contribute to an overall positive feedback in warming climates, though low-cloud feedbacks remain a major source of uncertainty in climate sensitivity projections. Increased atmospheric moisture content, following the Clausius-Clapeyron relation, can influence cloud formation, but the net effect for shallow cumulus is not definitively positive and depends on regional dynamics.^[56] This uncertainty is particularly pronounced in low-latitude regimes, where warmer temperatures boost low-level humidity, potentially altering the prevalence of shallow cumulus and energy fluxes.^[59] Additionally, transitions from marine stratocumulus to broken cumulus cloud regimes, often driven by subsidence weakening or aerosol perturbations, significantly impact global circulation patterns by reducing regional albedo and enhancing shortwave absorption, which can intensify the subtropical high-pressure systems and shift the intertropical convergence zone.^[60] These transitions represent a key uncertainty in climate projections, as they can amplify warming through diminished cloud radiative cooling over vast oceanic areas.^[56]

Low- and Mid-Level Layered Clouds

Stratocumulus clouds differ markedly from cumulus in their horizontal layering and lack of isolation, forming widespread, low-level sheets or patches with bases typically between 300 and 2,000 meters above the ground. These clouds emerge through stratiform cooling mechanisms, such as radiative cooling at the inversion layer top, which promotes uniform condensation across a stable boundary layer rather than the discrete, buoyant updrafts characteristic of cumulus formation. This results in a more continuous, gray-to-white expanse that often covers large areas, contrasting with the separated, dome-shaped outlines of cumulus.^[61]^[62] Altocumulus clouds, situated in the mid-levels from approximately 2 to 7 kilometers, present as layered patches or bands without the vertical vigor of cumulus, often arising from atmospheric wave instabilities that gently lift moist air parcels. Unlike the thermally driven convection in cumulus, which produces sharp, protruding tops, altocumulus develops flatter, ripple-like structures due to these wave-induced perturbations, emphasizing horizontal extent over height. This distinction highlights how mid-level layered clouds prioritize stability and subtle lifting over the intense updrafts required for cumulus development.^[63]^[64]^[61] While both cumulus and these layered clouds depend on sufficient low- to mid-level moisture for droplet formation, cumulus necessitates stronger convective forces from surface heating or instability to achieve its vertical growth, whereas layered types form with milder ascent in more stable conditions. Observationally, cumulus displays a pronounced diurnal pattern, peaking in the afternoon over land before dissipating, in contrast to the more persistent nature of stratocumulus and altocumulus, which can linger for hours or days, particularly over oceans. Hybrid varieties like altocumulus castellanus serve as transitional features, exhibiting cumulus-like turrets sprouting from a layered base, signaling instability that may evolve into more developed cumulus forms.^[1]^[61]^[47]

High-Level and Vertical Development Clouds

High-level clouds like cirrocumulus form at altitudes between 5 and 13 kilometers, where temperatures are sufficiently low for ice crystals to dominate their composition, contrasting with the liquid water droplets that characterize the warmer, lower-level cumulus clouds.^[61] These cirrocumulus clouds often appear as small, rippled patches or waves, resulting from gravity waves propagating through moist upper air layers, which induce periodic instabilities unlike the thermally driven, isolated updrafts of cumulus. In evolutionary terms, cirrocumulus represent a stable, high-altitude manifestation of wave-induced convection, while cumulus exhibit more dynamic, buoyancy-driven growth limited to the lower troposphere. Cumulus clouds serve as precursors to cumulonimbus through progressive vertical development, where initial fair-weather cumulus evolve into towering cumulonimbus via sustained updrafts that penetrate higher atmospheric layers.^[65] In mature cumulonimbus, overshooting updrafts can extend beyond the anvil top, reaching altitudes of 10 to 15 kilometers, forming dome-like protrusions that mark intense convection far surpassing typical cumulus heights of 1 to 2 kilometers.^[66] This structural escalation highlights the transitional role of cumulus in thunderstorm genesis, with the anvil spreading laterally due to upper-level winds, a feature absent in non-developing cumulus. Rare formations such as horseshoe clouds illustrate wind shear's influence on cumulus structure, where strong directional or speed changes with height distort the cloud into a vortex-like, U-shaped appearance, often signaling environmental conditions conducive to severe weather.^[67] These distortions arise when an updraft encounters shear, wrapping part of the cumulus into a horizontal tube that resembles a horseshoe, providing an early visual cue for potential storm intensification.^[68] Both cumulus and high-level vertical development clouds arise from atmospheric instability, but cumulus growth is frequently constrained by capping inversions—warm layers aloft that suppress further ascent and promote cloud dissipation or spreading.^[69] This limitation prevents most cumulus from achieving the deep vertical extents of cumulonimbus, emphasizing how environmental stability gradients dictate evolutionary paths from shallow convection to profound storm systems.^[70] Satellite detection further distinguishes cumulus from high-level clouds through infrared brightness temperatures, with cumulus exhibiting warmer values (typically 250–270 K) due to their lower tops, compared to the colder signatures (below 220 K) of cirrocumulus ice-crystal layers.^[71] These spectral differences enable remote sensing algorithms to differentiate convective bases from upper-atmosphere features, aiding in the monitoring of vertical development transitions.

Extraterrestrial Analogues

Observations on Other Planets

Observations of cumulus-like clouds on Venus have been inferred from spacecraft data, revealing convective cells and cumulus-like columns in the cloud tops at altitudes of 50-60 km, primarily composed of sulfuric acid aerosols rather than water vapor, resembling haze layers more than distinct puffy structures.^[72] These features arise from updrafts in the thick carbon dioxide atmosphere, but the extreme temperatures and pressures limit their vertical development compared to terrestrial cumulus.^[73] On Mars, rare water-ice clouds exhibiting cumulus-like morphology have been documented during dust storms and orographic lifting, as observed by the Viking orbiters in the 1970s and later by the Mars Reconnaissance Orbiter (MRO) since 2006.^[74] These clouds form at altitudes of 10-20 km in the thin carbon dioxide atmosphere, often appearing as detached, fluffy formations over elevated terrain like the Tharsis volcanoes, though their transient nature and low water vapor availability make them infrequent.^[75] MRO's instruments, including the Mars Climate Sounder, have mapped these ice particles, confirming their role in brief convective episodes.^[76] Titan, Saturn's largest moon, hosts methane-driven convection that produces cumulus analogues, particularly in polar regions, as evidenced by Cassini spacecraft observations from 2004 to 2017.^[77] These clouds form from methane vapor condensation at altitudes of 10-40 km in the nitrogen-methane atmosphere, with seasonal outbursts noted over the south pole, reaching heights up to 42 km in some systems.^[78] A 2025 AI-based analysis of Cassini images further mapped these patchy, streaky methane clouds, confirming their tropospheric convective features analogous to Earth's water-based cumulus but driven by Titan's hydrocarbon cycle.^[79]^[80] In the atmospheres of Jupiter and Saturn, moist convection involving ammonia generates cumulus-like cloud features within the banded structures, with observations from Voyager, Galileo, Juno, and Cassini revealing convective storm systems spanning several bars in pressure (equivalent to tens of kilometers vertically).^[81] These clouds form in layers where ammonia reacts with hydrogen sulfide to produce ammonium hydrosulfide particles, as updated by 2025 Juno data analysis showing the visible cloud decks primarily composed of NH4SH mixed with photochemical products rather than pure ammonia ice, amid the hydrogen-helium envelopes powering zonal jets and large-scale disturbances; deeper water clouds may contribute to more intense convection.^[82]^[83]^[84] Detecting and characterizing cumulus-like clouds on these bodies is complicated by extreme environmental conditions, such as Venus's corrosive sulfuric acid and high pressures, Mars's sparse atmosphere limiting condensation, Titan's frigid temperatures favoring methane over water, and the gas giants' immense scales and radiative opacity obscuring deep convection.^[73] These factors alter cloud morphology, reducing puffiness and longevity relative to Earth analogs, while remote sensing challenges like atmospheric scattering further hinder precise morphological analysis.^[81]

Implications for Exoplanet Atmospheres

Earth-like cumulus clouds serve as key analogs in modeling the scattering effects of low-level water clouds on exoplanets within habitable zones, particularly in transmission spectroscopy observations conducted by the James Webb Space Telescope (JWST) since 2022. These clouds' Rayleigh and Mie scattering properties can flatten spectral features, complicating the detection of molecular absorbers like water vapor or oxygen in transit light curves. For instance, JWST observations of the habitable zone super-Earth LHS 1140 b revealed a featureless near-infrared transmission spectrum consistent with high-altitude haze or clouds, where cumulus-like low clouds would contribute to broadband scattering and reduce the amplitude of atmospheric signals.^[85] General circulation models (GCMs) incorporating shallow convection schemes, which emulate the formation and transport of cumulus clouds on Earth, predict significant cloud coverage on habitable exoplanets such as those in the TRAPPIST-1 system. These parameterizations account for subgrid-scale moist convection, leading to estimates of 20-50% global cloud cover on TRAPPIST-1e under aquaplanet conditions, with thicker layers over the dayside due to substellar heating. Such models highlight how cumulus-like clouds regulate surface temperatures and modulate outgoing longwave radiation, influencing the planet's overall habitability.^[86]^[87] In reflected light observations, the high albedo of cumulus clouds can mask surface biosignatures, such as vegetation red edges or ocean glint, by dominating the planetary spectrum and obscuring lower-atmospheric or surface signals from direct imaging missions. However, for gaseous biosignatures like O₂ and O₃, low-lying cumulus analogs may enhance detectability by increasing the reflected flux, though high clouds could counteract this effect. This dual role underscores the need for cloud microphysics in retrieval analyses.^[88] Exoplanet cloud compositions diverge markedly from Earth's water-based cumulus, with hot Jupiters featuring silicate or manganese sulfide particles at high temperatures (>900 K), transitioning to hydrocarbon hazes in cooler regimes, which alter opacity and spectral imprints compared to aqueous droplets. Recent studies from 2023-2025, including GCM simulations of tidally locked worlds like Proxima Centauri b, incorporate cumulus parameterization in global cloud blanket scenarios to assess atmospheric circulation and potential water cloud formation under flare-star irradiation.^[89]^[90]

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[PDF] 6 Clouds - UBC EOAS
Cloud streets or cloud lines are rows of fair- weather cumulus-humilis clouds (Fig. 6.9) that are roughly parallel with the mean wind direction. They form ...
[37]
Cumulus humilis | International Cloud Atlas
Cumulus humilis is composed of water droplets (sometimes supercooled). An observer flying through it has the impression of being in dense fog.
[38]
Fair Weather Cumulus Clouds: puffy cotton balls floating in the sky
Fair weather cumulus have a lifetime of anywhere from 5-40 minutes and show only slight vertical growth, with the tops designating the limit of the rising air.
[39]
Fair Weather Cumulus Clouds: puffy cotton balls floating in the sky
Fair weather cumulus have the appearance of floating cotton and have a lifetime of 5-40 minutes. Known for their flat bases and distinct outlines.
[40]
CL = 1 | International Cloud Atlas
Cumulus humilis or Cumulus fractus of dry weather or both. Humilis: little vertical extent and seemingly flattened. Fractus: ragged.
[41]
[PDF] International Atlas of Clouds and of States of the Sky
— SPECIES. Among the more remarkable species one may note : 1° Cumulus humilis (PL i). Cumulus with little vertical development, and seemingly flattened.
[42]
Cumulus mediocris (Cu med) | International Cloud Atlas
Cumulus of moderate vertical extent, with small protuberances and sproutings at their tops. Cumulus mediocris generally produce no precipitation.<|control11|><|separator|>
[43]
Types of convective clouds - Severe Weather Europe
Feb 21, 2025 · Cumulus mediocris develops from Cumulus humilis and displays more vertical development up to 3000 m altitude. They generally do not produce ...
[44]
Cumulus mediocris | International Cloud Atlas
This cloud is composed of water droplets (sometimes supercooled). Visibility is variable, and often very poor or even zero. There may be light to moderate icing ...<|control11|><|separator|>
[45]
Cumulus mediocris cloud - Wikipedia
Cumulus mediocris clouds do not generally produce precipitation of more than very light intensity, but can further advance into clouds such as Cumulus ...Missing: tropics | Show results with:tropics
[46]
Numerical simulation of tropical cumulus congestus during TOGA ...
Jul 24, 2013 · A fewer number of deeper cumulus congestus clouds extend in height up to ∼7 km. ... Echo tops corresponding to congestus (∼4–6 km) are ...
[47]
Cumulus congestus cloud - Wikipedia
Since strong updrafts produce (and primarily compose) them, the clouds are typically taller than they are wide; cloud tops can reach 6 km (3.7 mi; 20,000 ft), ...
[48]
Radar Observations of Updrafts, Downdrafts, and Turbulence in Fair ...
Although the clouds have a horizontal depth of only about 700 m, updraft velocities of about 5.5 m s1 were observed. These updrafts, which are only about 400 m ...
[49]
[PDF] MANUAL ON THE OBSERVATION OF CLOUDS AND OTHER ...
HEIGHT, ALTITUDE, VERTICAL EXTENT. It is often important to refer to the level at which certain parts of a cloud occur. Two concepts can be used for the ...
[50]
A climatology of tropical congestus using CloudSat - Wall - 2013
May 2, 2013 · [1] Cumulus congestus clouds have long been identified as an important part of the spectrum of convective clouds in the tropics.
[51]
Cloud Streets and Gravity Waves in the Mid-Atlantic | NESDIS
Nov 29, 2018 · On Nov. 28, a cold front associated with a large storm over the Northeast delivered gusty winds to the Mid-Atlantic.Missing: prediction | Show results with:prediction
[52]
Curving Cloud Streets in Brazil - NASA Earth Observatory
Jun 18, 2014 · Cumulus cloud streets trace the direction, and sometimes the intensity, of winds. As puffy cumulus clouds form in the warmth of morning sunlight, they line up ...
[53]
https://www.nesdis.noaa.gov/news/cloud-streets-over-the-great-lakes
[54]
Forecasting Convective Initiation by Monitoring the Evolution of ...
Through the incorporation of satellite tracking of moving cumulus clouds, this work represents a significant advance in the use of routinely available GOES ...
[55]
"Cloud Streets" Over the Great Lakes | NESDIS
Dec 27, 2017 · As winds from the west or northwest blow over the lakes, the cold air picks up warmth and water vapor from the lake surface, giving rise to ...
[56]
Albedo | EARTH 103: Earth in the Future - Penn State
Albedo (% reflectance). Whole Planet, 0.31. Cumulonimbus Clouds, 0.9. Stratocumulus Clouds, 0.6. Cirrus Clouds, 0.5. Water, 0.06 - 0.1. Ice & Snow, 0.7 - 0.9.
[57]
Clouds & Radiation Fact Sheet - NASA Earth Observatory
Mar 1, 1999 · Low, thick clouds primarily reflect solar radiation and cool the surface of the Earth. High, thin clouds primarily transmit incoming solar ...
[58]
[PDF] A Simple Model for Cloud Radiative Transfer of West Atlantic Cumulus
When we increase the droplets concentration, emissivity. 85 gets even closer to 1, which indicates that the cumulus emits nearly all longwave flux that it can.
[59]
[PDF] The Earth's Energy Budget, Climate Feedbacks and Climate Sensitivity
an increase in the equator-to-pole gradient in atmospheric moisture with global warming, with moisture in the tropics increasing more than at the poles as ...
[60]
[PDF] Effect of shallow cumulus convection on the eastern Pacific climate ...
Sep 12, 2006 · Shallow cumulus updrafts penetrate the inversion that caps the planetary boundary layer (PBL). The updrafts entrain warm dry air into the PBL ...
[61]
[PDF] REVIEW Stratocumulus Clouds - Atmospheric Sciences
Strong longwave cooling at the cloud top drives convective instability that helps to enhance, maintain, and sharpen the temperature inversion immediately above.
[62]
Chapter 7: The Earth's Energy Budget, Climate Feedbacks, and ...
This chapter assesses the present state of knowledge of Earth's energy budget: that is, the main flows of energy into and out of the Earth system.
[63]
[PDF] Stratocumulus to cumulus transition in the presence of elevated ...
Dec 11, 2015 · humidity-dependent optical properties (single scattering albedo, 𝜔o, asymmetry parameter, and extinction ... 8 at relative humidity (RH) of 0.7 at ...
[64]
Ten Basic Clouds | National Oceanic and Atmospheric Administration
Mar 28, 2023 · Cumulonimbus (Cb). The thunderstorm cloud, this is a heavy and dense cloud in the form of a mountain or huge tower. The upper portion is usually ...The Four Core Types of Clouds · A 'Hole' Lot of Clouds 2 · NWS Cloud Chart
[65]
Explanatory remarks and special clouds | International Cloud Atlas
When Cumulus have great vertical extent (a low base and a high stable layer), the Cumulus is of the species congestus; the vertical extent of Cumulus in ...<|separator|>
[66]
Classifying clouds - World Meteorological Organization WMO
... cloud's character. These include: - Stratus/strato: flat/layered and smooth. - Cumulus/cumulo: heaped up/puffy. - Cirrus/cirro: feathers, wispy. - Nimbus/nimbo ...
[67]
Levels | International Cloud Atlas
The troposphere can be vertically divided into three levels, formerly known as “étages”: high, middle and low. Each level is defined by the range of heights.
[68]
Life Cycle of a Thunderstorm - NOAA
May 23, 2023 · Air within the cloud is dominated by upwardly-moving, warm, moist air currents called updrafts with some turbulent eddies around the edges. The ...Missing: internal | Show results with:internal
[69]
Overshooting Tops & Anvil - Module 8 - Wild Weather
The trademark of a strong cumulonimbus cloud is the overshooting top, a "cauliflower-like" cloud structure extending above the anvil of the storm like a dome.
[70]
What is a horseshoe cloud? - AccuWeather
Mar 12, 2018 · One cloud that has been specifically named after an object is the horseshoe cloud, one of the rarest documented cloud formations.
[71]
[PDF] Features Indicating Strong/Severe Storms
Anvil: The anvil is the elongated cloud at the top of the storm that spreads downwind with upper level steering winds. The anvil will appear solid, not.
[72]
Cumulus Clouds - ScienceDirect.com
Boundary layer cumuli are cumulus clouds whose vertical extent is limited ... capping inversion, often viewed as the top of the atmospheric boundary layer.
[73]
Factors influencing cloud area at the capping inversion for shallow ...
Apr 28, 2009 · ... cumulus clouds spread out under the capping inversion into stratocumulus. These include the strength of the surface fluxes, which also ...
[74]
[PDF] Chapter 2 Cloud type identification by satellites
On the other hand, because the satellite observes clouds from a great distance above the earth, the cloud types are identified by the cloud top temperature and.
[75]
Morphology of the cloud tops as observed by the Venus Express ...
Close-up snapshots reveal plenty of morphological details like convective cells, cloud streaks, cumulus-like columns, wave trains. Different kinds of small ...
[76]
Clouds and Hazes of Venus | Space Science Reviews
Nov 27, 2018 · This paper reviews the current status of our knowledge of the Venus cloud system focusing mainly on the results acquired after the Venera, Pioneer Venus and ...
[77]
[PDF] Martian clouds observed by Mars Global Surveyor Mars Orbiter ...
Compared with the MGS observa- tions, the Viking era water ice clouds are more extensive near the upland regions including Arabia Terra, and the clouds near ...
[78]
Mars Clouds (Chapter 5) - The Atmosphere and Climate of Mars
Jul 5, 2017 · MCS observations provide the first detailed description of the vertical distribution of Mars water ice ... Viking era water-ice clouds, J. Geophys ...
[79]
Estimating the altitudes of Martian water-ice clouds above the Mars ...
This study retrieved estimated altitudes of Martian water-ice clouds through a comparison of observations taken by the Mars Science Laboratory (MSL, Curiosity) ...
[80]
Seasonal changes in Titan's meteorology - Turtle - AGU Journals
Feb 8, 2011 · Deep convection on Titan requires high near-surface methane relative humidity [Barth and Rafkin, 2010] and thus responds to surface heating ...
[81]
[PDF] Convective cloud heights as a diagnostic for methane environment ...
Cloud tops have been reported between 14 and 25 km. Higher res- olution Cassini data have shown smaller portions of the cloud system can reach up to 42 km. We ...
[82]
The interaction of deep convection with the general circulation in ...
The goal of this study is to better quantify through cloud resolving modeling the effects of deep convective methane storms on their environment.
[83]
Moist Convection in the Giant Planet Atmospheres - MDPI
For example, pure ammonia clouds on Jupiter and Saturn are unlikely to form large convective cells, while methane and water clouds on the ice giants and water ...
[84]
A three-dimensional model of moist convection for the giant planets II
Ammonia storms develop easier but with a much smaller intensity unless very large abundances of ammonia (10 times solar) are present in Saturn's atmosphere. The ...
[85]
Moist convection: A mechanism for producing the vertical structure of ...
This paper examines cumulus cloud formation and vertical motion on Jupiter as a potential mechanism for producing the Equatorial Plumes.
[86]
Transmission Spectroscopy of the Habitable Zone Exoplanet LHS ...
Jul 10, 2024 · Here we present two JWST/NIRISS transit observations of LHS 1140 b, one of which captures a serendipitous transit of LHS 1140 c.
[87]
A new convection scheme for GCMs of temperate sub-Neptunes
Conversely, stronger entrainment leads to shallow cumulus convection. ... Additionally, another good reason to validate our model on TRAPPIST-1e is the existing ...
[88]
The TRAPPIST-1 Habitable Atmosphere Intercomparison (THAI). II ...
Sep 15, 2022 · The study models TRAPPIST-1e with moist atmospheres, finding a temperate climate, but with intermodel differences in temperature and cloud ...
[89]
Clouds can enhance direct imaging detection of O2 and O3 on terrestrial exoplanets
### Summary: Impact of Clouds on Biosignature Detection in Reflected Light for Exoplanets
[90]
https://ui.adsabs.harvard.edu/abs/2025epsc.conf.1216K/abstract
[91]
Climates of tidally locked exo-terrestrial planets with a global cloud ...
Clouds pose significant uncertainties in models for exoplanetary atmosphere. Traditionally, conventical GCMs with low resolution have used cumulus ...