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Cirrus cloud

Cirrus clouds are high-altitude, non-precipitating clouds composed exclusively of ice crystals, appearing as delicate, white, wispy filaments, patches, or veils with minimal shading.^[1]^[2] They form in the upper troposphere at altitudes generally exceeding 6 kilometers (20,000 feet), where temperatures drop below -40°C, enabling direct deposition of water vapor into ice crystals without intermediate liquid phase.^[3]^[4] Classified as a distinct genus (Ci) by the World Meteorological Organization, cirrus exhibit species variations such as fibratus (thread-like), uncinus (hooked), and spissatus (dense patches), reflecting diverse formation mechanisms including wind shear on existing clouds or outflow from thunderstorms.^[5] These clouds influence atmospheric radiative balance by transmitting most incoming solar radiation while absorbing and re-emitting terrestrial longwave radiation, yielding a net warming effect on Earth's surface. Often preceding warm fronts or upper-level disturbances, cirrus serve as indicators of approaching synoptic-scale weather changes, though they typically signify fair conditions during their presence.^[7]

Physical Characteristics

Appearance and Morphology

Cirrus clouds present a wispy, fibrous, or feathery appearance, manifesting as delicate white filaments, hair-like strands, or tufts that are short and detached.^[1] These structures often form patches or narrow bands covering only small areas of the sky, with a silky sheen or translucent quality due to the sparse arrangement of their constituent particles.^[1] From the ground, they appear as thin, high-altitude streaks that may color vividly yellow or red near sunrise or sunset from light scattering.^[1] The characteristic fibrous texture results from fall streaks, where elongated trails of particles create long, thin streamers resembling brush strokes or mare's tails, sometimes straight, comma-shaped, or tangled.^[8] ^[9] In denser forms, cirrus can veil the sun's outline while remaining semi-transparent, and from above in sunlight, thin varieties resemble haze layers, whereas denser ones exhibit a milky opacity.^[10] Morphological variations are classified into species such as fibratus, featuring parallel, fine hair-like fibers; uncinus, with hooked or curved ends forming comma-like shapes; spissatus, appearing as dense, sheet-like patches that obscure celestial bodies; castellanus, displaying small cumuliform turrets; and floccus, consisting of small tufts with ragged lower edges.^[11] Additional varieties include duplicatus, characterized by two or more layers superposed with gaps revealing the sky between them.^[11] These distinct forms highlight the diverse structural configurations observable in cirrus clouds.^[11]

Altitude, Composition, and Microphysics

Cirrus clouds form at high altitudes in the upper troposphere, typically between 5 and 14 kilometers above sea level, with mid-latitude bases often exceeding 6 kilometers and tropical occurrences extending to 13-18 kilometers.^[2]^[12] These elevations correspond to ambient temperatures below -40°C, conditions under which supercooled liquid water is unstable and freezes into ice crystals.^[13] In polar regions, cirrus altitudes are generally lower due to the compressed tropospheric height, ranging from approximately 3 to 6 kilometers.^[12] The composition of cirrus clouds is exclusively ice crystals, devoid of supercooled liquid droplets owing to the sub-homogeneous freezing temperatures.^[2] These crystals exhibit non-spherical morphologies, including pristine habits such as hollow columns, bullet rosettes, and aggregates, with maximum dimensions spanning 10 to 5000 micrometers.^[14]^[15] Ice water content (IWC) remains low, typically between 10^{-6} and 10^{-3} grams per cubic meter, as measured in situ by research aircraft.^[16] Microphysical processes in cirrus are dominated by heterogeneous ice nucleation on solid aerosols, such as mineral dust, soot, or volcanic ash, which initiate crystal formation at lower ice supersaturations than homogeneous freezing.^[17]^[18] Recent aircraft campaigns and laboratory studies from 2020-2025 reveal that these nucleants promote specific habits like hollow columnar crystals, influencing sedimentation and radiative effects through altered fall speeds and optical properties.^[19]^[20] Satellite observations from instruments like CALIPSO corroborate these findings by profiling vertical distributions and particle effective sizes derived from lidar backscatter.^[21]

Historical and Classification Context

Early Discovery and Naming

In 1802, French naturalist Jean-Baptiste Lamarck published the first systematic classification of clouds, distinguishing types based on form and altitude, including high-altitude varieties resembling wisps or streaks.^[22] This work laid groundwork for later nomenclature, though Lamarck's terms did not gain widespread adoption. Independently, British pharmacist and meteorologist Luke Howard developed a parallel system, presenting his "Essay on the Modification of Clouds" to the Askesian Society in December 1802 and publishing it in the Philosophical Magazine in 1803.^[23] Howard categorized clouds into three primary genera—cirrus, cumulus, and stratus—emphasizing their morphological distinctions.^[24] Howard coined "cirrus" for the highest clouds, characterized as detached, white, and fibrous formations resembling curls or locks of hair, deriving the term directly from the Latin cirrus meaning "curl" or "tuft of hair."^[25] This naming captured the delicate, streaked appearance of these ice-crystal clouds, observed at altitudes exceeding 5 kilometers, and marked the first standardized Latin-based terminology for cloud types, influencing subsequent meteorological frameworks.^[24] Early sketches by Howard himself documented cirrus morphology, highlighting their persistence in fair weather and occasional alignment with upper-air currents.^[23] By the mid-19th century, meteorologists such as those contributing to the Royal Meteorological Society noted cirrus formations as indicators of stable high-pressure systems or precursors to frontal passages, based on empirical correlations with barometric trends and wind shifts.^[26] Instrumental progress accelerated documentation; in 1879, Swedish meteorologist Hugo Hildebrandsson pioneered the use of photography for cloud studies at Uppsala Observatory, enabling precise records of cirrus variability and motion that surpassed hand-drawn illustrations.^[22] These photographic advancements facilitated quantitative analysis of cirrus streaks and fall patterns, refining early qualitative descriptions.^[22]

Modern Classification Systems

The World Meteorological Organization (WMO) maintains the primary modern classification system for cirrus clouds through its International Cloud Atlas, defining the genus Cirrus (Ci) as detached clouds appearing as white, delicate filaments, patches, or narrow bands with a fibrous, hair-like structure, composed exclusively of ice crystals.^[5] This system delineates ten species based on morphological characteristics: fibratus (nearly straight or curved fine filaments without endings), uncinus (hooked filaments resembling mare's tails), spissatus (thick enough to blur the sun or moon), castellatus (tufts with distinct rounded tops), floccus (small tufts with ragged bases), intortus (irregularly tangled filaments), radiatus (arranged in parallel bands converging toward a point), duplicatus (superimposed layers at slightly different altitudes), undulatus (wavelike arrangement), and mammatus (pouch-like protuberances, typically associated with spissatus).^[27] Supplementary features include virga (pendulous streaks of precipitation falling from the cloud base but evaporating before reaching the ground, often as fall streaks) and incus (anvil-shaped top on cumulonimbus-derived cirrus).^[28] Cirrus integrates into the WMO's three-level (étage) tropospheric classification as a high-level cloud genus, occupying altitudes generally above 6 km in temperate latitudes (up to 18 km in tropics and down to 3 km in polar regions during winter), alongside Cirrostratus (Cs) and Cirrocumulus (Cc).^[29] This vertical partitioning facilitates synoptic analysis by grouping clouds by formation height and typical ice-crystal dominance in the high étage, where temperatures fall below -40°C, enabling homogeneous nucleation.^[30] Satellite observations since the 2006 launch of CALIPSO have refined subtype identification through lidar profiling of vertical structure, ice particle sizes, and optical depths, enabling global mapping of cirrus occurrence and microphysical properties that corroborate and extend WMO morphological criteria.^[31] For instance, CALIPSO data distinguish in-situ cirrus (forming directly from ice supersaturation at temperatures below -38°C) from those of liquid or mixed-phase origin, providing empirical validation for species like uncinus linked to wind shear in stable layers.^[31] Data-driven classifications from recent analyses, such as 2025 studies using multi-year lidar and radar datasets, further delineate cirrus regimes by formation mechanisms (e.g., in-situ versus convective outflow), with global occurrence frequencies varying by subtype—fibratus dominating in synoptic settings (up to 40% in midlatitudes) and spissatus prevalent near anvils (peaking at 70% in tropical convection zones)—enhancing predictive models beyond traditional visual taxonomy. These updates emphasize temperature thresholds (e.g., cloud-top below -38°C for pure ice cirrus) and regional distributions, informed by long-term satellite archives showing subtype refinements tied to dynamical contexts like jet streams.^[32]

Formation Mechanisms

Natural Processes

Cirrus clouds form in the upper troposphere through the freezing of supercooled water vapor when air parcels cool to temperatures typically below -40°C, leading to ice supersaturation.^[33] This cooling occurs primarily via adiabatic expansion in rising air, where the decrease in pressure causes expansion and temperature drop, increasing relative humidity with respect to ice (RHi) until nucleation thresholds are met. Ice nucleation proceeds via homogeneous or heterogeneous mechanisms. Homogeneous freezing involves the spontaneous formation of ice within supercooled solution droplets at RHi thresholds of approximately 130-140%, dependent on temperature; this dominates in strong updrafts where supersaturations build rapidly without sufficient ice-nucleating particles (INPs).^[34] Heterogeneous nucleation, conversely, occurs on INPs such as mineral dust or black carbon at lower RHi (around 100-120%), producing fewer but larger ice crystals; empirical measurements indicate it prevails in most cirrus, with homogeneous contributing in pristine conditions.^[35]^[36] In situ cirrus arise directly from nucleation in slowly ascending air parcels, often linked to large-scale synoptic uplift, where adiabatic cooling sustains supersaturation for extended periods.^[37] Anvil cirrus, by contrast, result from convective detrainment, wherein ice particles are ejected from overshooting tops of thunderstorms or tropical cyclone outflows, spreading horizontally as the parent convection weakens.^[38] These processes yield distinct microphysical properties, with anvil cirrus featuring higher ice water content from liquid-origin freezing.^[39] Recent modeling from 2025 identifies formation regimes by temperature: anvil (liquid-origin) cirrus dominate above -60°C with higher ice crystal numbers and weaker temperature dependence, while in situ cirrus prevail at colder thresholds, exhibiting stronger negative correlations between ice concentration and temperature due to homogeneous nucleation sensitivity.^[39]^[40] These thresholds align with empirical data showing homogeneous freezing limits near 235 K (-38°C), shifting regimes toward pure ice processes at cirrus altitudes.^[41]

Anthropogenic Influences

Persistent contrails, a primary anthropogenic influence on cirrus cloud formation, arise when water vapor and soot particles from aircraft exhaust condense and freeze into ice crystals in ice-supersaturated regions of the upper troposphere, typically at altitudes of 8–13 km.^[42] These soot particles act as heterogeneous ice nuclei, facilitating the rapid formation of line-shaped ice clouds that can persist and spread laterally due to wind shear, evolving into irregular cirrus sheets distinct from natural cirrus morphology.^[43] Unlike short-lived contrails that sublimate quickly, persistent variants require ambient relative humidity with respect to ice exceeding 100%, allowing ice crystal growth and advection into broader cloud fields.^[44] Empirical modeling estimates indicate that contrail cirrus contributes approximately 62 mW/m² to aviation's effective radiative forcing as of 2019, surpassing the forcing from aviation CO₂ emissions (around 30–40 mW/m²) due to the clouds' shortwave reflection and longwave trapping effects.^[45] This net positive forcing stems from cirrus-level optics, where increased ice crystal concentrations enhance greenhouse warming, with global aviation traffic amplifying coverage in high-density corridors like the North Atlantic.^[46] Key factors governing persistent contrail formation and evolution include cruise altitude (favoring colder, humid layers above 10 km), ambient humidity thresholds for supersaturation, and regional traffic density, which correlates with contrail frequency in supersaturated zones. Recent analyses highlight that contrail cirrus lifetimes, averaging 2–3 hours but extending beyond 5 hours in 20% of cases, are primarily limited by ice crystal sedimentation into subsaturated lower levels and synoptic-scale advection dispersing crystals beyond supersaturated regions.^[47]^[48]

Meteorological Role

Indicators in Weather Forecasting

Cirrus clouds, particularly the streaked form known as "mare's tails" or Cirrus uncinus, have long served as empirical indicators of impending atmospheric changes in traditional weather forecasting. These high-altitude wisps often appear 12 to 24 hours ahead of advancing warm fronts or low-pressure systems, signaling the initial influx of moist air into the upper troposphere.^[49]^[3] Observers note their alignment from the southwest or west, aligning with prevailing wind patterns that precede frontal passages.^[50] The persistence and gradual thickening of cirrus layers further suggest increasing upper-level moisture, potentially evolving into cirrostratus and foreshadowing lower cloud development and precipitation within the following day.^[3] In contrast, rapid dispersal or fragmentation of cirrus without thickening typically points to subsiding air and stable high-pressure conditions, reducing the likelihood of near-term weather disruptions.^[50] These visual cues, rooted in sailor lore such as "Mare's tails and mackerel scales make tall ships take in their sails," emphasize cirrus as harbingers of transition rather than immediate events.^[51] In contemporary numerical weather prediction (NWP) models, cirrus observations contribute to short-term forecasts by initializing ice microphysics schemes and validating upper-tropospheric humidity fields. Satellite-derived cirrus coverage and ground-based lidar measurements refine model outputs, improving predictions of frontal timing and moisture advection over 6 to 48 hours.^[52] However, accurate cirrus prognostication remains challenging due to sensitivities in ice nucleation and advection parameterization.^[53]

Associations with Synoptic Systems

In mid-latitudes, cirrus clouds commonly appear as thin veils preceding warm fronts in extratropical cyclones, resulting from large-scale ascent and upper-tropospheric cooling associated with synoptic-scale disturbances.^[54] These formations are often linked to baroclinic systems, where prefrontal lifting generates widespread ice crystal layers at altitudes of 6–12 km.^[55] Synoptic cirrus in these regions predominates in storm track areas, with empirical observations showing higher frequencies during cold seasons tied to jet stream influences.^[56] In tropical latitudes, cirrus clouds frequently originate as anvils from deep convection, where overshooting updrafts in thunderstorms or mesoscale convective complexes detrain ice particles into stable upper levels, spreading into expansive sheets due to divergence aloft.^[38] These anvil cirrus persist for hours to days post-convection, covering significant fractions of tropical skies and correlating with the intensity and scale of underlying convective clusters.^[57] In regions like the South China Sea, such cirrus exhibit seasonal peaks driven by enhanced convection during monsoon periods.^[58] Seasonal variations in cirrus occurrence are pronounced in monsoon-influenced mid-latitude sites, such as central China, where frequencies reach maxima of approximately 40% during southwest and northeast monsoon phases, attributed to increased synoptic forcing and moisture availability, contrasting with winter minima around 25%.^[59] A 2025 analysis of cirrus from diverse mechanisms confirms synoptic types are more prevalent in subtropical subsidence zones, with minimal thickness variations across seasons except slight thinning in winter.^[32] Cirrus clouds also associate with jet stream dynamics, forming characteristic "shields" or bands where transverse upper-level divergence along jet streaks induces adiabatic cooling and ice supersaturation, promoting nucleation and alignment of fibers parallel to wind shear.^[32] These jet-related cirrus maintain consistent altitudes near the jet core, with empirical correlations to positive vorticity advection and diffluence patterns enhancing their spatial extent.^[60]

Radiative Properties and Climate Impact

Net Radiative Forcing

Cirrus clouds exert a net positive radiative forcing at the top of the atmosphere (TOA) due to their high altitude, which minimizes shortwave reflection while allowing significant trapping of upwelling longwave radiation from Earth's surface; this longwave greenhouse effect typically outweighs shortwave cooling for optically thin clouds with optical depths below approximately 16.^[61] ^[62] Observations indicate that thin cirrus produce positive TOA forcing, with daytime estimates ranging from 0.07 to 0.67 W/m² globally, though regional variations exist, such as subarctic values between -1.67 and 1.10 W/m² annually depending on cloud height and temperature.^[63] ^[64] The Clouds and the Earth's Radiant Energy System (CERES) satellite data reveal that cirrus clouds amplify net warming, particularly in humid tropical regions where frequent anvil cirrus from deep convection enhance longwave trapping; sensitivity analyses confirm positive net forcing for typical thin cirrus optical properties observed in these areas.^[62] Global modeling of orographic cirrus, a subset of natural cirrus, yields a net TOA forcing of +0.33 W/m², underscoring the warming contribution from persistent high-altitude ice clouds.^[65] Forcing magnitude varies with optical depth and cloud cover: thinner clouds (low optical depth) drive net warming, while thicker variants can shift toward cooling, though cirrus predominantly fall in the warming regime across global distributions.^[61] ^[63] Anthropogenic contrail cirrus, formed from aircraft exhaust, adds to this forcing, with 2019 estimates placing its global effective radiative forcing at 0.062 W/m², roughly three times the forcing from aviation CO₂ emissions alone; recent assessments project potential tripling to 0.16 W/m² by 2050 under current traffic growth trends.^[66] ^[42] This increment arises from persistent ice-supersaturated regions where contrails spread into cirrus-like sheets, exhibiting similar radiative properties to natural cirrus but with higher spatial variability tied to flight corridors.^[67] Overall, cirrus-related forcing contributes positively to Earth's energy imbalance, with natural components estimated in the range of 0.3 to 1 W/m² when aggregating daytime and regional effects, though precise global partitioning remains uncertain due to observational challenges in distinguishing cirrus subtypes.^[65] ^[63]

Controversies and Geoengineering Proposals

Proposals for cirrus cloud thinning (CCT) emerged in the early 2010s as a form of solar radiation management, involving the seeding of cirrus clouds with ice-nucleating particles to increase ice crystal formation rates, thereby reducing cloud optical thickness and lifetime to enhance longwave radiation escape to space.^[68] A 2013 modeling study by Storelvmo et al. suggested that such interventions could yield a global radiative cooling of approximately 2.5 W/m², potentially offsetting 1-2°C of warming under high-emission scenarios, though this assumed uniform seeding efficacy without accounting for heterogeneous atmospheric responses.^[68] Subsequent analyses, however, have highlighted physical constraints, including the limited availability of suitable nucleation agents and the risk of over-seeding leading to denser rather than thinner clouds due to supersaturation dynamics.^[69] Critics argue that CCT's side effects undermine its viability, with global climate models indicating potential disruptions to the hydrological cycle, such as altered precipitation patterns including regional droughts or intensified extremes.^[70] For instance, simulations targeting non-tropical cirrus have shown circulation changes propagating to tropical regions, exacerbating uneven rainfall distribution rather than providing balanced cooling.^[71] These risks stem from cirrus' role in modulating upper-tropospheric stability, where thinning could inadvertently amplify storm tracks or suppress convective outflows, effects not fully captured in early optimistic models.^[72] Empirical field trials remain absent as of 2025, confining assessments to simulations that vary widely in predicted efficacy, with more conservative estimates suggesting global temperature reductions below 0.5°C even under aggressive deployment due to incomplete coverage and feedback loops.^[73] Debates over anthropogenic contrail cirrus—persistent aircraft-induced cirrus clouds—center on mitigation strategies like flight path rerouting to avoid ice-supersaturated regions, which could reduce contrail radiative forcing by up to 59% according to targeted modeling, but at the cost of 2-10% increased fuel consumption per flight due to detours or altitude adjustments.^[74] This trade-off elevates net climate impacts when incorporating full lifecycle emissions, as additional fuel burn raises CO₂ outputs that persist for centuries, potentially offsetting short-term contrail benefits whose forcing is estimated at 0.057 W/m² globally but contested for overemphasizing non-CO₂ effects without rigorous uncertainty bounds.^[75] Alternative approaches, such as sustainable aviation fuels with reduced aromatic content, show promise in limiting soot emissions that nucleate contrails, yet scalability remains limited by production constraints and higher costs, with no large-scale deployments verified to date.^[76] From 2023 onward, broader critiques of cirrus-related geoengineering emphasize geopolitical hazards, including localized thinning inducing transboundary precipitation shifts that could spark resource conflicts in vulnerable regions like the Sahel or Southeast Asia.^[77] Model intercomparisons reveal inconsistent outcomes across general circulation models, with some projecting negligible net cooling after feedbacks, underscoring the absence of causal validation beyond theoretical seeding experiments.^[78] Proponents' reliance on idealized simulations overlooks empirical gaps, such as variable nucleation efficiency in real atmospheres, rendering CCT and contrail interventions speculative at best amid unquantified risks to aviation-dependent economies.^[70]

Observational and Optical Features

Detection and Measurement

Cirrus clouds are primarily detected and measured using remote sensing techniques that leverage active and passive sensors to capture their high-altitude, optically thin nature. Satellite-based lidars, such as the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the CALIPSO mission, provide vertical profiles of cirrus layers with resolutions down to 60 meters vertically and 330 meters horizontally, enabling precise determination of cloud altitude, geometric thickness, and ice water content (IWC) through backscatter and depolarization measurements.^[31] ^[79] These active sensors excel at identifying subvisible and thin cirrus that passive instruments often miss, with algorithms like the selective iterated boundary location (SIBYL) distinguishing cloud boundaries from clear air via threshold-based layer detection.^[80] Passive satellite sensors, including the Moderate Resolution Imaging Spectroradiometer (MODIS) on Aqua and Terra platforms, derive cirrus properties such as cloud top pressure, effective radius, and optical depth from infrared and visible channels, though they require validation against active sensors for thin layers due to potential underestimation of high-altitude cirrus.^[81] ^[82] Radar systems like the CloudSat Cloud Profiling Radar complement lidars by measuring reflectivity in denser cirrus regions to estimate IWC and particle size distribution, but their sensitivity limits detection of optically thin clouds with low radar reflectivity.^[83] Multi-sensor fusion from the A-Train constellation (e.g., combining MODIS, CALIPSO, and CloudSat) enhances accuracy by cross-validating altitude and microphysical properties, with CALIPSO often retrieving higher cirrus tops than radar alone.^[82] Ground-based networks, such as the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) program sites, employ continuous lidar and millimeter-wave cloud radars to generate long-term cirrus datasets, including macrophysical properties like cover fraction and trends over decades.^[84] For instance, ARM facilities have facilitated comparisons of cirrus optical depths and radiative effects with satellite data, revealing consistent midlatitude trends in cloud occurrence.^[85] These sites provide vertically resolved profiles, supporting studies of cirrus evolution with temporal resolutions suitable for diurnal cycle analysis.^[86] In situ measurements from high-altitude aircraft probes offer direct microphysical data, including ice crystal size spectra and habits, using instruments like the Particle Measuring Systems (PMS) optical array probes and the Cloud and Aerosol Spectrometer (CAS).^[87] ^[88] These probes, deployed in campaigns such as the Cirrus-EU, quantify small ice particles down to micrometer scales, validating remote sensing-derived IWC and revealing spatial inhomogeneities in cirrus structure.^[89] Detecting thin cirrus poses challenges due to their low optical depth and similarity to clear-sky scattering, often leading to false negatives in single-wavelength passive retrievals.^[90] Multi-wavelength lidar approaches, incorporating depolarization ratios and backscatter at 532 nm and 1064 nm, mitigate this by differentiating ice particles from aerosols and resolving subvisual layers invisible to radar.^[91] Ground-based Raman lidars further address signal attenuation in thin layers through nitrogen Raman scattering for extinction profiling.^[92]

Associated Phenomena

Cirrus clouds, consisting primarily of non-spherical ice crystals, generate several optical phenomena via refraction, reflection, and diffraction of sunlight. The 22° solar halo, formed by refraction through the faces of hexagonal ice crystals, encircles the sun at an angular radius of approximately 22 degrees and is frequently observed in cirrus or cirrostratus decks.^[93] Sundogs, or parhelia, manifest as vivid colored spots positioned symmetrically at the 22° halo's 3 and 9 o'clock positions, resulting from refraction and dispersion in horizontally oriented plate crystals.^[93] ^[94] Coronas arise from diffraction of light by the edges of small ice crystals or thin cloud patches, producing faint, colored rings closely surrounding the sun or moon, with red on the outside and blue within.^[95] Iridescence appears as spectral color bands in localized thin cirrus regions, attributable to diffraction from nearly uniform crystal sizes diffracting coherent light waves.^[96] Glories, involving concentric colored rings around an observer's shadow cast on the cloud, and Bishop's rings, diffuse brownish coronas centered on the sun, occur infrequently with cirrus due to requirements for specific small-particle backscattering or diffraction, often linked to exceptional crystal distributions rather than typical cirrus morphology.^[97] ^[98] ^[99] Aircraft transiting uniform cirriform layers can perturb supercooled droplets, initiating heterogeneous nucleation of ice and subsequent fallout of ice crystals as virga, forming fallstreak holes—circular or elliptical voids amid otherwise continuous cloud fields.^[100] ^[101] Despite individual ice crystals being transparent, cirrus clouds exhibit a white appearance owing to multiple scattering events among the crystals, which diffusely reflect and redistribute sunlight across all visible wavelengths without preferential absorption.^[33] ^[102]

Relations to Other Clouds

Within the Cirriform Family

The cirriform family comprises high-level clouds occurring above 5 kilometers altitude, primarily composed of ice crystals, and includes cirrus, cirrostratus, and cirrocumulus.^[1] These clouds are distinguished by their morphology and formation mechanisms within the World Meteorological Organization's classification system.^[7] Cirrus clouds appear as detached, white, and delicate filaments, strands, patches, or hooks, lacking defined edges and shading, often resulting from wind shear dispersing ice crystals into streaks.^[1] In contrast, cirrostratus forms a uniform, veil-like sheet or layer covering the whole or significant portion of the sky, typically evolving from spreading cirrus through horizontal expansion.^[103]^[104] Cirrocumulus, meanwhile, consists of small, rippled elements or white patches arranged in rows, resembling grains or puffs, arising from instabilities rather than the fibrous separation seen in cirrus.^[7]^[1] Despite their shared ice-crystal composition, cirrus exhibits more dynamic behavior driven by upper-level winds, producing transient streaks, whereas cirrostratus remains relatively static as a persistent layer, and cirrocumulus displays quasi-convective rippling from wave-like perturbations.^[1] Empirical observations indicate transitions within the family, such as cirrus patches merging into cirrostratus sheets or developing cirrocumulus elements during atmospheric destabilization.^[104]^[7]

Interactions and Transitions

Cirrus clouds often initiate sequences of cloud evolution during warm frontal passages, initially appearing as detached wisps that spread into cirrostratus sheets as moisture increases aloft.^[105] Under continued ascent and rising relative humidity, these cirrostratus layers thicken and descend, transitioning into altostratus as ice crystals aggregate and temperatures warm slightly, signaling approaching precipitation. This progression reflects the frontal lift overriding warmer air, with cirrus serving as the high-level precursor to mid-level stratiform clouds.^[106] In conditions of increasing upper-tropospheric humidity, individual cirrus uncinus formations—characterized by hooked, fibrous trails—can expand laterally through sublimation and advection, evolving into broader cirrostratus decks as ice crystals spread and multiply via homogeneous nucleation.^[107] This transition occurs when uniform weak updrafts dominate over strong wind shear, allowing the cloud elements to merge into a more uniform veil rather than maintaining discrete uncini shapes.^[108] Cirrus-generated virga, consisting of falling ice crystals that evaporate before reaching lower levels, can seed underlying supercooled liquid clouds by providing ice nuclei, thereby initiating heterogeneous ice formation and potentially enhancing precipitation efficiency in mixed-phase clouds below.^[109] Observational data indicate this seeding occurs frequently when vertical separations between cirrus and lower clouds range from 100 m to 10 km, with ice crystals from virga acting as effective seeds for warmer-layer glaciation.^[110] Such interactions underscore cirrus's role in modulating lower-cloud microphysics without direct overlap. Recent studies of anvil cirrus detached from deep convective cores reveal their tendency to spread horizontally and descend, merging with mid-level altocumulus or altostratus in mesoscale convective systems through detrainment and radiative cooling.^[111] In tropical environments, these anvil outflows interact with convectively generated moisture, fostering hybrid cloud structures where cirrus ice influences mid-level particle habits and optical properties, as documented in aircraft and satellite observations from 2009 onward.^[112] This merging can prolong convective lifecycle by stabilizing the mid-troposphere, though it depends on ambient humidity and shear profiles.^[113]

Extraterrestrial Analogues

In Martian Atmosphere

Cirrus-like clouds in the Martian atmosphere consist of water ice crystals forming thin, wispy structures akin to terrestrial cirrus but attenuated by the planet's low atmospheric pressure and minimal water vapor content. These clouds occur at altitudes of 10 to 50 km, where temperatures permit ice sublimation and condensation cycles.^[114]^[115] Seasonal aphelion clouds, prominent during Mars' farthest orbital point from the Sun, manifest as a near-equatorial belt of water ice wisps observed via remote sensing and rover imagery. NASA's Curiosity rover documented these in 2017 through time-lapse sequences showing rapid scooting motion across the sky, indicative of wind shear in the thin upper atmosphere.^[116]^[117] Orbiters confirm diurnal vertical migrations, with clouds descending near the surface at night and ascending up to 20 km daytime.^[118] Dust aerosols prevalent in Mars' atmosphere serve as nucleation sites, promoting ice crystal formation despite water vapor scarcity—unlike Earth's abundant hydrological cycle—resulting in more frequent but transient cirrus analogues.^[119]^[120] For early Mars' climate, simulations hypothesize global cirrus decks in CO₂-H₂O atmospheres (with ≥0.25 bar CO₂) could enhance greenhouse warming to sustain liquid water, yet viability demands >75% cloud cover under precise conditions; realistic fractions yield negligible net forcing.^[121]^[122] This contrasts with empirical modern observations, where clouds exert limited radiative impact due to sparse coverage and high altitudes.^[123]

In Outer Planet Atmospheres

Cirrus-like clouds in Jupiter's atmosphere cap zones of upwelling air, consisting of condensed ammonia crystals that form high-altitude, wispy features analogous to terrestrial cirrus, though recent citizen science analysis of Juno data indicates these upper clouds may primarily comprise ammonium hydrosulfide particles intermixed with photochemical smog rather than pure ammonia ice.^[124]^[125] Saturn's atmosphere exhibits similar banded structures with upwelling regions producing ammonia cirrus clouds, reflecting vertical convection in its hydrogen-helium envelope.^[126] On ice giants Uranus and Neptune, sparse data reveal high-altitude cirrus analogues formed from methane condensation. Voyager 2 images from its 1989 Neptune flyby captured bright, linear cirrus-type clouds of frozen methane, evolving rapidly over hours and casting shadows on deeper haze layers, indicative of strong vertical shear and upwelling dynamics.^[127] Subsequent Hubble Space Telescope observations spanning 1994 to 2022 documented Neptune's bright cloud cover fluctuating with the 11-year solar cycle, peaking near solar maximum as enhanced ultraviolet flux drives methane photolysis and subsequent ice particle formation aloft, with abundance dropping to near-zero during solar minimum phases around 2020.^[128] These clouds trace mesoscale waves and serve as tracers of atmospheric circulation without exerting radiative effects comparable to Earth's cirrus. Uranus shows analogous but fainter methane cirrus streaks, observed episodically in ground-based and Hubble imagery, linked to seasonal upwelling in its stratified atmosphere.^[129] Titan, Saturn's largest moon, hosts high-altitude methane ice cirrus clouds near the tropopause, detected by Cassini spacecraft as thin, wispy features with particle sizes and optical properties echoing Earth's ice cirrus but composed of methane condensates from convective lofting of humid air parcels.^[130] These clouds precipitate sporadically, contributing to Titan's methane cycle by seeding convective storms and surface rainfall analogs, thereby influencing tropospheric dynamics and hydrocarbon haze distribution without significant radiative feedback akin to terrestrial systems.^[131]

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Cloud classification summary | International Cloud Atlas
Genera. Species. Varieties ; Genera · (listed by frequency of observation) ; Cirrus · fibratus · uncinus · spissatus · castellanus · floccus · intortus · radiatus
[12]
A Summary of the Physical Properties of Cirrus Clouds. - ADS
The properties examined (with typical values and measured ranges) are cloud-center altitude (9 km, 4 to 20 km), cloud thickness (1.5 km, 0.1 to 8 km), crystal ...
[13]
https://ww2010.atmos.uiuc.edu/%28Gh%29/guides/mtr/cld/cldtyp/hgh/crs.rxml
[14]
A Review of Ice Particle Shapes in Cirrus formed In Situ and in Anvils
Jul 25, 2019 · A recent review of cirrus clouds by Heymsfield et al. (2017) focuses on nucleation processes, size distributions, and ice water content (IWC) ...
[15]
Ice water content assessment in the single-, dual-, and triple ...
Mar 1, 2021 · The size of ice cloud particles ranges from microns to centimeters and their habits vary from simple pristine ice crystals to extremely ...<|separator|>
[16]
Measurements of ice water content in tropopause region Arctic cirrus ...
[7] In this paper we present measurements of the ice water content of Arctic tropopause region cirrus clouds made from the NASA DC-8 during the Stratospheric ...
[17]
Identification of two ice-nucleating regimes for dust-related cirrus ...
Oct 11, 2022 · We propose a method to identify two ice-nucleating regimes of dust-related cirrus clouds, ie, (1) the sole presence of heterogeneous nucleation and (2) ...
[18]
Ice nucleation by volcanic ash greatly alters cirrus cloud properties
May 9, 2025 · This finding highlights the unique role of VA in altering cirrus cloud microphysics through heterogeneous ice nucleation. DISCUSSION.Missing: habits | Show results with:habits
[19]
[PDF] Prior heterogeneous ice nucleation events increase likelihood of ...
Feb 4, 2025 · Prior heterogeneous ice nucleation events, using mineral dust, deplete ice-nucleating particles, creating conditions for more likely ...
[20]
Ice nucleation onto model nanoplastics in the cirrus cloud regime
Feb 4, 2025 · The study found that nanoplastics can act as effective ice nucleating particles (INPs) in cirrus and cold mixed-phase clouds, and after aging, ...
[21]
[PDF] Airborne validation of cirrus cloud properties derived from CALIPSO ...
Oct 12, 2011 · Also, CALIPSO has an orbital height of about 705 km, much higher than the typical. ER‐2 altitude of 20 km, giving CALIOP a greater distance.<|separator|>
[22]
Preface to the 1939 edition | International Cloud Atlas
The first published classification of clouds only dates back to the beginning of the 19th century and was the work of Lamarck (1802).
[23]
Gathering clouds - Science Museum Blog
Nov 23, 2022 · Cloud study of Cumulus blowing in high wind, by Luke Howard, 1803, on loan from Royal Meteorological Society · Cloud study of nimbus rainclouds, ...
[24]
The Useful Pursuit of Shadows | American Scientist
The names Howard chose for his three major types of clouds conveyed a sense of their outward characteristics: Cirrus (from Latin for "fiber" or "hair"): " ...
[25]
Cloud study of Cirrus | Science Museum Group Collection
Howard identified three basic families of clouds, using Latin names: cirrus ('curl of hair'), stratus ('layer') and cumulus ('heap' or 'pile').
[26]
Cloud names and classifications - Met Office
Luke Howard's 1802 cloud classification system, dividing clouds into stratus, cumulus, and cirrus, is still used today, aiding in weather prediction and ...
[27]
Species | International Cloud Atlas
Cirrus fibratus (Ci fib) - Besson 1921, CCH 1953 Nearly straight or more or less irregularly curved white filaments, which are always fine and do not terminate ...
[28]
Supplementary features and accessory clouds
Cirrus, usually of the species spissatus, sometimes shows mamma or fluctus.
[29]
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.
[30]
[PDF] MANUAL ON THE OBSERVATION OF CLOUDS AND OTHER ...
(a) Cirrus, Cirrocumulus and Cirrostratus for the high etage (high level clouds);. (b) Altocumulus for the middle etage (middle level clouds);. (c) ...
[31]
Cirrus Cloud Properties as Seen by the CALIPSO Satellite and ...
Krämer et al. (2016) proposed a new cirrus classification based on the environment in which cirrus form. In situ cirrus clouds form at temperatures colder than ...Introduction · Cirrus cloud data · Results · Origin of cirrus clouds
[32]
Characteristics of Cirrus Clouds from Different Formation Mechanisms
Aug 8, 2025 · Cirrus clouds are composed of ice crystals and are characterized by low temperatures and thin optical depths. They absorb longwave radiation ...Cloudsat And Calipso Joint... · Observed Cirrus And Its... · Results<|separator|>
[33]
Cirrus Clouds in: Meteorological Monographs ... - AMS Journals
Jan 1, 2017 · Cirrus clouds are detached, white, delicate filaments or patches composed of ice crystals, forming in the upper troposphere above 8 km.
[34]
Dissecting cirrus clouds: navigating effects of turbulence on ... - Nature
Apr 6, 2025 · Homogeneous freezing of aqueous solution droplets is the most fundamental pathway to nucleate ice crystals in cirrus. Lack of knowledge about ...
[35]
Studies on the Competition Between Homogeneous and ...
Jan 25, 2022 · Cirrus ice crystals are produced heterogeneously on ice-nucleating particles (INPs) and homogeneously in supercooled liquid solution ...2 Methodology · 2.6 Supersaturation For... · 4.1 Analysis Of Ice...
[36]
Measurements of the concentration and composition of nuclei for ...
Measurements support that cirrus formation occurs both by heterogeneous nucleation by insoluble particles and homogeneous (spontaneous) freezing of particles ...
[37]
[PDF] Freezing thresholds and cirrus cloud formation mechanisms inferred ...
Oct 27, 2003 · Based on these facts, we have performed APSC simula- tions of cirrus formation in adiabatically rising air parcels, at the average INCA ...Missing: adiabatic | Show results with:adiabatic
[38]
Tropical Cirrus in Global Storm‐Resolving Models: 1. Role of Deep ...
Dec 17, 2021 · Near the tropopause, cirrus can form through convective anvil detrainment as well as in situ ice nucleation (Jensen, Toon, Selkirk, et al., 1996) ...Missing: cyclones | Show results with:cyclones
[39]
Tropical cirrus evolution in a kilometer-scale model with improved ...
Sep 8, 2025 · We find that in situ cirrus dominate at colder temperatures and lower ice water contents, while anvil cirrus prevail at temperatures > −60 °C.
[40]
[PDF] Cirrus formation regimes – data-driven identification and ... - ACP
Jul 14, 2025 · In this study, we define cirrus clouds as all clouds with a cloud-top temperature colder than −38 °C. This definition includes, for example, the ...
[41]
(PDF) Cirrus formation regimes – data-driven identification and ...
Aug 7, 2025 · The horizontal black line at 235 K marks the homogeneous freezing threshold, and hence the shift from the mixed-phase to the cirrus regime. ...
[42]
Understanding the role of contrails and contrail cirrus in climate ...
Aug 23, 2024 · This suggests that soot cirrus formed from processed aviation soot may have a weaker influence on cirrus cloud formation than previously thought ...
[43]
Revisiting Contrail Ice Formation: Impact of Primary Soot Particle ...
Sep 26, 2024 · Contrail ice crystals form when aerosol particles present in aircraft exhaust plumes activate into water droplets in water-supersaturated ...
[44]
Process-oriented analysis of aircraft soot-cirrus interactions ... - Nature
Jun 17, 2021 · Aircraft-induced clouds (AIC) that originate from emitted soot particles include young, line-shaped contrails and the older, irregular-shaped ...
[45]
[PDF] Description and evaluation of a new contrail cirrus ... - HAL
Oct 16, 2025 · Their estimated con- trail radiative forcing (respectively, the contrail effec- tive radiative forcing) for the year 2019 is 62.1 mW·m2. ( ...
[46]
Impact of host climate model on contrail cirrus effective radiative ...
Jan 15, 2025 · Estimates of aviation effective radiative forcing (ERF) indicate that contrail cirrus is currently its largest contributor, although with a ...Missing: m² | Show results with:m²
[47]
Synoptic and microphysical lifetime constraints for contrails - ACP
Aug 25, 2025 · Contrail lifetime is constrained mainly by the sedimentation of ice crystals into lower levels that are subsaturated, by the blowing out of ...
[48]
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025JD044488
[49]
Weather: Forecasting by Clouds - InfoPlease
Are cirrus clouds drifting by? That by itself is okay, but if the cirrus clouds appear to be thickening into cirrostratus on the western horizon, I know ...<|separator|>
[50]
Cloud Guide: Types of Clouds and Weather They Predict!
Cirrus: Thin, feather-like, wispy clouds, which are strands of ice crystals. Weather prediction: A change is on its way! wispy white Cirrus Clouds in a blue sky ...
[51]
Predicting the Weather With Clouds - Sunsail
Jul 21, 2016 · ... mare's tails make tall ships carry low sails”. If they look a little low and have lots of ripples, you could be in for some stormy weather.
[52]
Estimating the Impact of Assimilating Cirrus Cloud–Contaminated ...
The assimilation of hyperspectral infrared sounders (HIS) observations aboard Earth-observing satellites has become vital to numerical weather prediction, yet ...
[53]
Cirrus cloud diagnosis using numerical weather-prediction model ...
Aug 9, 2025 · The accurate prediction of cirrus clouds, including subvisual cirrus, is often difficult for operational numerical weather prediction (NWP) ...
[54]
Comparisons of cirrus clouds and their linkages to meteorology at ...
Cirrus clouds are less frequent but located at higher altitudes in the warm season than cold season at the SACOL and SGP sites.
[55]
[PDF] 9 Midlatitude Cloud Systems - NASA Technical Reports Server (NTRS)
The pre-frontal cirrus are accompanied by low thin cloud decks, while part of the cold frontal clouds are formed by two distinct thick layers of low and ...
[56]
The Composite Characteristics of Cirrus Clouds: Bulk Properties ...
Furthermore, cirrus that occur over Oklahoma during the cold season are typically associated with synoptic-scale meteorological events, such as subtropical jet ...
[57]
Anvil Productivities of Tropical Deep Convective Clusters and Their ...
The anvil productivity of tropical deep convection depends on the convection scale, convective life stage or intensity, and large-scale environment.2. Data And Methodology · A. Cloudsat Data Products · B. Convective Rainy Core...
[58]
Study reveals cirrus cloud traits over the South China Sea - Phys.org
Jun 13, 2024 · The seasonal change of convective cirrus cloud fractions is mainly driven by bottom-up positive specific humidity anomalies, while the non- ...
[59]
Temporal and vertical distributions of the occurrence of cirrus clouds ...
Jun 28, 2022 · The occurrence reaches a maximum (∼ 40 %) during the SW and NE monsoon seasons, and it shows a minimum (∼ 25 %) during the winter season. The ...
[60]
[PDF] THE POLEWARD BOUNDARY OF JET STREAM CIRRUS SHIELDS
Jul 11, 1989 · The two most common hypotheses suggest that either the cirrus clouds are formed as the result of differential vertical motion on each side of ...
[61]
Tropical cirrus cloud radiative forcing: Sensitivity studies
The net radiative forcing of cirrus near the tropical tropopause is positive (heating) for cloud optical depths less than about 16 and negative (cooling) for ...
[62]
[PDF] Study of the radiative effect of thin cirrus clouds using ... - nasa ceres
As shown in the sensitivity study, thin cirrus clouds have a net positive cloud radiative forcing at the top of atmosphere and a net negative forcing at the ...
[63]
Daytime Cirrus Cloud Top-of-the-Atmosphere Radiative Forcing ...
A slight positive annual net forcing (warming) is estimated overall. However, a net daytime cooling contribution is found from the very thinnest clouds, a ...
[64]
[PDF] Cirrus Cloud Top-of-the-Atmosphere Net Daytime Forcing in the ...
Two-year averaged daytime TOA CRF is estimated at between -1.08 and 0.78 W·m-2 (-. 0.49 to 1.10 W·m-2 in 2017, and -1.67 to 0.47 W·m-2 in 2018). This subarctic ...
[65]
Orographic Cirrus and Its Radiative Forcing in NCAR CAM6
May 6, 2023 · Cirrus clouds play an important role in the Earth's radiative energy budget, thereby affecting the climate state and climate change.
[66]
The social costs of aviation CO 2 and contrail cirrus - Nature
Sep 29, 2025 · The radiative forcing (RF) of contrail cirrus is substantial, though short-lived, uncertain, and heterogeneous, whereas the RF from CO₂ ...
[67]
Global aviation contrail climate effects from 2019 to 2021 - ACP
May 27, 2024 · We simulate the global contrail RF for 2019–2021 using reanalysis weather data and improved engine emission estimates along actual flight trajectories.
[68]
The climatic effects of modifying cirrus clouds in a ... - AGU Journals
Mar 20, 2014 · [2013]. It was found that cirrus cloud thinning could have a radiative cooling effect of 2.5 W m−2. The cooling effect could be reversed, ...
[69]
Cirrus cloud thinning using a more physically based ice ... - ACP
Sep 7, 2022 · Cirrus cloud thinning (CCT) is a relatively new radiation management proposal to counteract anthropogenic climate warming by targeting Earth's terrestrial ...
[70]
Cirrus Cloud Thinning - Geoengineering Monitor
Cirrus Cloud Thinning (CCT) is a solar geoengineering proposal which aims to eliminate or thin cirrus clouds to allow heat to escape into space.
[71]
(PDF) The climatic effects of cirrus cloud thinning - ResearchGate
Jan 9, 2015 · It was found that targeting cirrus clouds everywhere outside of the tropics results in changes to the circulation and precipitation even in the ...
[72]
Cirrus cloud seeding: a climate engineering mechanism with ...
Dec 28, 2014 · We present a global modelling study of a so far understudied CEM, namely the seeding of cirrus clouds to reduce their lifetimes in the upper troposphere.
[73]
To what extent can cirrus cloud seeding counteract global warming?
Seeding decreases the damage by about 50% in ECHAM, and by 85% in CESM over the 21 selected land regions. Climate damage due to CO2 increase is significantly ...
[74]
https://sites.research.google/gr/contrails/
[75]
Aviation Contrails: What We Know — and What We Don't - RMI
Jul 26, 2024 · Contrails have a significant climate impact, potentially ranging from half to over three times that of CO 2 emissions from aviation.
[76]
Powering aircraft with 100 % sustainable aviation fuel reduces ice ...
Mar 27, 2024 · Powering aircraft by sustainable aviation fuels (SAFs) is a pathway to reduce the climate impact of aviation by lowering aviation lifecycle CO 2 emissions.
[77]
Can geoengineering fix the climate? Hundreds of scientists say not ...
Dec 25, 2022 · Critics fret that unilateral action to alter the climate could spark conflict if one part of the world benefits, while another suffers knock-on ...
[78]
Cirrus Cloud Thinning - SRM360
Nov 26, 2024 · SRM360 explores the potential advantages and challenges of an idea to reduce climate change effects by thinning heat-trapping cirrus clouds.
[79]
Projects | CALIPSO - ASDC
The CALIPSO satellite comprises three instruments, the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP Lidar), the Imaging Infrared Radiometer (IIR), ...Missing: refinements | Show results with:refinements
[80]
A simple multiscale layer detection algorithm for CALIPSO ...
Dec 1, 2021 · The CALIPSO team uses the selective iterated boundary location (SIBYL) algorithm based on threshold arrays to find aerosol and cloud layers at ...Missing: radar | Show results with:radar
[81]
[PDF] Effectiveness of Cirrus Detection with MODIS Cloud Mask data - AMT
Oct 1, 2024 · detect cirrus clouds as accurately as the CALIPSO does. Specifically, we aim to assess whether MODIS Cloud Mask, when examining its individual ...
[82]
Comparison of AIRS, MODIS, CloudSat and CALIPSO cloud top ...
Sep 11, 2007 · ... lidar retrieves higher altitudes of cirrus clouds, which the radar does not observe. Overall, MODIS CTPs mirror the radar's CTPs very closely.
[83]
[PDF] Combining Cloud Properties of MODIS, CALIPSO, and CloudSat for ...
NASA A-train mission provides cloud properties measured from active and passive sensors in close proximity. CloudSat and CALIPSO lag Aqua by 1 to 2 minutes.
[84]
The ARM Radar Network: At the Leading Edge of Cloud and ...
The US DOE ARM facility significantly upgrade and expand its surveillance radar capabilities toward providing holistic and multiscale observations of clouds ...
[85]
Evaluation of Cirrus Cloud Properties Derived from MODIS Data ...
Aug 7, 2025 · In this paper, cirrus cloud properties derived from ground-based remote sensing data are compared with similar cloud properties derived from ...
[86]
Comparison of the CALIPSO satellite and ground‐based ...
Nov 10, 2011 · CALIPSO is capable of near-global observations of cirrus clouds whereas the ARM TWP observations provide a point measurement at three sites.Missing: networks | Show results with:networks
[87]
In Situ Observations of the Microphysical Properties of Wave, Cirrus ...
For the past three decades, aircraft measurements of the size and shape of ice crystals in cirrus clouds have relied mostly on the PMS optical array probes ...
[88]
[PDF] Aircraft measurements of microphysical properties of subvisible ...
Mar 18, 2008 · The CAPS contains two particle probes, a cloud and aerosol spectrometer (CAS), which measures forward and backward scattered light to count and ...
[89]
Airborne observations of the microphysical structure of two ...
Oct 18, 2016 · We present detailed airborne in situ measurements of cloud microphysics in two midlatitude cirrus clouds, collected as part of the Cirrus ...
[90]
Detecting thin cirrus in Multiangle Imaging Spectroradiometer ...
Apr 16, 2010 · Horizontally inhomogeneous fields of very thin cirrus provide inherent difficulties for the MISR retrieval approach, and, in addition ...Missing: challenges | Show results with:challenges
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Variability in cirrus cloud properties using a PollyXT Raman lidar ...
Apr 17, 2020 · Generally, subvisible cirrus detection is a challenging component in satellite retrievals.Missing: approaches | Show results with:approaches<|control11|><|separator|>
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[PDF] A decadal cirrus clouds climatology from ground-based and ... - ACP
Abstract. This study provides an analysis of cirrus cloud properties at midlatitude in the southern part of France from ground-based and spaceborne lidars.
[93]
What Causes Halos, Sundogs and Sun Pillars?
Halos: A halo is a ring or light that forms around the sun or moon as the sun or moon light refracts off ice crystals present in a thin veil of cirrus clouds.
[94]
[PDF] Light, Color and Atmospheric Optics
Sunlight bending through ice crystals in cirriform clouds produces bands of color called sundogs, or parhelia, on both sides of the sun on this cold winter day ...
[95]
Atmospheric Optical Phenomena (except Rainbows and Auroras)
Sep 16, 2025 · Circumhorizontal arc. Circumhorizontal arcs are visually similar in some ways to cloud iridescence, but are in fact part of the halo family.
[96]
What makes a rainbow? - MetService Blog
Nov 23, 2016 · Cloud irisation (also called iridescence) is caused by sunlight diffracting around cloud droplets Diffraction is the bending of light as it ...
[97]
Glory | International Cloud Atlas
Glory: One or more sequences of coloured rings, seen by an observer around their own shadow on a cloud consisting mainly of numerous small water droplets.
[98]
Bishop's Ring | International Cloud Atlas
A Bishop's ring is a whitish ring, centered on the Sun or Moon, with a slightly bluish tinge inside and reddish brown outside, caused by diffraction of light ...
[99]
Can cirrus clouds produce glories? - PubMed
Mar 20, 1998 · Although it is concluded that multiple-ringed glories can be accounted for only through the backscattering of light from particles that are ...
[100]
Fallstreak - What Are They? - National Weather Service
A fallstreak hole (also known as a "hole punch cloud") is a large circular or elliptical gap that can appear in cirrocumulus or altocumulus clouds.
[101]
Fallstreak Clouds | NESDIS - NOAA
Fallstreak holes, also known as hole punch clouds, are a “supercool” phenomenon, where large circular or elliptical gaps appear in mid- to high-level ...
[102]
Captured cirrus ice particles in high definition - ACP - Copernicus.org
May 11, 2021 · Cirrus clouds composed of small ice crystals are often the first solid matter encountered by sunlight as it streams into Earth's atmosphere.
[103]
Cloud Classification - National Weather Service
Unlike cirrus, cirrostratus clouds form more of a widespread, veil-like layer (similar to what stratus clouds do in low levels).Missing: dynamics | Show results with:dynamics
[104]
[PDF] The Clouds Outside My Window - National Weather Service
Cirrus clouds that have formed a layer are called cirrostratus clouds. Sometimes cirrostratus clouds cause a halo around the sun or moon, which can be an ...
[105]
Cloud Types
If the cirrostratus cloud thickens into an altostratus, it is indicative of an approaching weather disturbance. Cirrostratus often form thin veils through which ...
[106]
Extensive Cirrus Clouds -- UIUC Cloud Catalog
With the progression of time, these clouds will likely thicken into altostratus and eventually into the lower and more dense nimbostratus, as the advancing ...
[107]
[PDF] Numerical Simulation of Cirrus Clouds - Fire Case Study and ... - DTIC
Aug 12, 1991 · Cirrus clouds can take many forms depending on vertical velocity, wind shear, rela- tive humidity, and static stability. Cirrostratus form with ...
[108]
[PDF] deposition coefficient, habit, and ventilation influences on cirriform ...
Cirriform clouds are atmospheric phenomena of importance, due to their role in global radiative and water vapor budgets. Despite their importance, many of ...
[109]
How frequent is natural cloud seeding from ice cloud layers - ACP
Apr 1, 2021 · Vertical distances between the cirrus and the lower-lying cloud are distributed uniformly between 100 m and 10 km. They are found to not vary ...
[110]
[PDF] How frequent is natural cloud seeding from ice cloud layers - ACP
Apr 1, 2021 · Braham (1967) noted the possibility of ice crystals from cirrus clouds acting as seeds for ice formation in lower- lying warmer clouds. In this ...
[111]
Cirrus clouds and deep convection in the tropics: Insights from ...
Nov 4, 2009 · The close association of cirrus with convective clouds implies that tropical cirrus are linked to deep convective activity, with the likely exception of TTL ...
[112]
[PDF] The evolution of deep convective systems and their associated ...
They showed that if the cirrus cloud-top height is increased and the optical depth decreased, there is potential for much greater warming. The lifecycle of deep ...
[113]
[PDF] The Life Cycle and Net Radiative Effect of Tropical Anvil Clouds
In-cloud convection acts to thin initially thick anvil clouds and loft and maintain thin cirrus. The maintenance of anvil clouds is tied to the recycling of ...
[114]
Mars Clouds (Chapter 5) - The Atmosphere and Climate of Mars
Jul 5, 2017 · As all Mars clouds are ice, here we distinguish cirrus clouds as the collection of thin, fibrous, sheet, and wavy forms distinct from puffy, ...
[115]
Nacreous clouds on Mars: imaging cloud formation ... - NASA ADS
From the intensity fall-off in ultraviolet photometry and images, we estimate a cloud altitude of 30-45 km; thus we interpret these as likely water ice clouds.<|separator|>
[116]
Watch Martian Clouds Scoot, Thanks to NASA's Curiosity
Aug 9, 2017 · Wispy, early-season clouds resembling Earth's ice-crystal cirrus clouds move across the Martian sky in some new image sequences from NASA's Curiosity Mars ...
[117]
Clouds Sailing Overhead on Mars, Unenhanced - NASA Science
Aug 9, 2017 · The near-equatorial Martian cloud pattern observed at that time of year is called the "aphelion cloud belt." These new images from Curiosity ...
[118]
Mars rover spots clouds shaped by gravity waves | Science | AAAS
Mar 22, 2017 · Satellites circling Mars have seen aphelion clouds sitting close to the surface at night, then rising 20 kilometers up in the afternoon. Such a ...
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https://ui.adsabs.harvard.edu/abs/2018oeps.book..114M/abstract
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Cloudy Sols Are Here Again - NASA Science
Feb 3, 2023 · Mars clouds are very much like Earth's cirrus clouds but thinner. While Earth clouds can contain liquid water, the low temperatures and pressures on Mars only ...
[121]
Could cirrus clouds have warmed early Mars? - ScienceDirect.com
Jan 1, 2017 · Cirrus clouds can warm early Mars if cloud cover exceeds 75% for very specific conditions. Cirrus clouds do not warm early Mars at more realistic cloud ...
[122]
Could Cirrus Clouds Have Warmed Early Mars? - PMC
One hypothesis is that Mars could have been kept warm by global cirrus cloud decks in a CO 2- H 2 O atmosphere containing at least 0.25 bar of CO 2.
[123]
[1608.03891] Could Cirrus Clouds Have Warmed Early Mars? - arXiv
Aug 12, 2016 · One hypothesis is that Mars could have been kept warm by global cirrus cloud decks in a CO2-H2O atmosphere containing at least 0.25 bar of CO2 ( ...Missing: observations | Show results with:observations
[124]
Toward an Understanding of the Structure of Jupiter's Atmosphere ...
They suggest the possibility that the upwelling of ammonia observed at the equator may be balanced by downwelling at latitudes higher than 40°, which are not ...
[125]
Astronomers “Astonished” as Citizen Scientists Reveal Jupiter's ...
Jan 9, 2025 · Once thought to be made of ammonia ice, these clouds are now believed to consist of ammonium hydrosulphide mixed with smog. The discovery, ...<|separator|>
[126]
11.3 Atmospheres of the Giant Planets - Astronomy 2e | OpenStax
Mar 9, 2022 · The light zones on Jupiter are regions of upwelling air capped by white ammonia cirrus clouds. ... as is the case on Jupiter and Saturn.
[127]
Voyager at Neptune - NASA Science
The bright cirrus-like clouds of Neptune change rapidly, often forming and dissipating over · This image of Neptune was taken by NASA Voyager 2 wide-angle ...
[128]
Neptune's Disappearing Clouds Linked to the Solar Cycle
Aug 17, 2023 · They form above most of the methane in Neptune's atmosphere and consequently are not blue, but reflect all colors of sunlight. Hubble picks up ...
[129]
Uranus/Neptune
Uranus's atmosphere is similar to Jupiter's and Saturn's in its primary composition of hydrogen and helium, but it contains more "ices" such as water, ammonia, ...
[130]
Surprise Hidden in Titan's Smog: Cirrus-Like Clouds
Feb 3, 2011 · Scientists report details about thin, wispy clouds of ice particles, similar to Earth's cirrus clouds, on Saturn's largest moon, smoggy Titan. ...
[131]
Titan's Meteorology Over the Cassini Mission: Evidence for ...
May 29, 2018 · Plain Language Summary. We monitored methane clouds in the atmosphere of Saturn's moon Titan for over 13 years, using images from the Cassini ...