Occurrence and characteristics of lower tropospheric ice crystals in the arctic

Curry, Judith A.; Meyer, F. G.; Radke, Lawrence F.; Brock, C. A.; Ebert, Elizabeth E.

doi:10.1002/joc.3370100708

Cited by 108 publications

(40 citation statements)

References 42 publications

(33 reference statements)

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“…This is consistent with consistent with the mean annual cycle of aerosols which has its peak in winter in minimum in later summer. The temperatures at which mixed-phase clouds were observed during BASE were much warmer than those reported for springtime clouds by Curry et al [1990]. This is consistent with that expected under the relatively more pristine conditions observed during BASE which tends to promote ice nucleation.…”

Section: Processes That Determinesupporting

confidence: 85%

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Cloud‐aerosol interactions during autumn over Beaufort Sea

Pinto¹,

Curry²,

Intrieri³

2001

J. Geophys. Res.

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Abstract. Cloud and aerosol properties were observed by aircraft in autumn over the Beaufort Sea during the 1994 Beaufort and Arctic Storms Experiment (BASE). The microphysical properties (particle size, concentration, mass, and phase) and vertical structure of autumn clouds are examined as a function of height and minimum in-cloud temperature, rmi n. Below 2 km, liquid clouds were observed at rmi n between -5 ø and-9øC, mixed-phase clouds were observed between -5 ø and -20øC, and clear-sky ice crystal precipitation was observed at rmi n as warm as -14øC. Between 2 and 5 km all clouds were mixed-phase and typically consisted of a thin layer of liquid with ice extending well below the liquid layer. These mixed-phase clouds were found at rmi n as low as -32øC. All clouds observed above 5.5 km were composed entirely of ice at rmi n as warm as -33øC. The concentration of ice crystals is observed to increase exponentially with decreasing rmi n. The Hallet-Mossop ice multiplication process did not appear to be an important in the production of ice crystals in the mixed-phase cloud observed in this study. The atmosphere was relatively clean with condensation nuclei (CN) concentrations rarely exceeding 300 cm -3. The smallest CN concentrations (as low as 50 cm -3) were observed in the boundary layer and just above the surface where precipitation and nucleation scavenging have cleansed the air. Thin layers of very large CN concentrations were often observed within and just above low-level clouds possibly resulting from gas-to-particle conversion which requires clean and humid air typical of lower Arctic atmosphere.

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Section: Processes That Determinesupporting

confidence: 85%

“…The radiative importance of arctic clouds in determining Arctic climate has been summarized by Curry et al [1996]. In view of this importance, recent field campaigns have made intensive observations of arctic clouds and radiation and other aspects of the arctic environment.…”

Section: Introductionmentioning

confidence: 99%

Cloud‐aerosol interactions during autumn over Beaufort Sea

Pinto¹,

Curry²,

Intrieri³

2001

J. Geophys. Res.

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“…Results show that the alteration of ice nucleation by acidic aerosols leads to an averaged cooling of 2°C near the surface. An analysis of aerosol and weather observations, which were taken during the same years at Alert, have shown that acidic aerosols favour low-level ice crystals precipitating to the surface, a common phenomenon in the Arctic during winter (Curry et al, 1990). However, the time and spatial resolution of the aerosol dataset (aerosols were measured only once a week near the surface) were not high enough to unravel this potential link between acidic aerosols and precipitating ice crystals.…”

Section: Introductionmentioning

confidence: 99%

Assessment of the dehydration‐greenhouse feedback over the Arctic during February 1990

Girard

Stefanof

2006

Intl Journal of Climatology

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Abstract:The effect of pollution-derived sulfuric acid aerosols on the aerosol-cloud-radiation interactions is investigated over the Arctic for February 1990. Observations suggest that acidic aerosols can decrease the heterogeneous nucleation rate of ice crystals and lower the homogeneous freezing temperature of haze droplets. On the basis of these observations, we hypothesize that the cloud thermodynamic phase is modified in polluted air mass (Arctic haze). Cloud ice number concentration is reduced, thus promoting further ice crystal growth by the Bergeron-Findeisen process. Hence, ice crystals reach larger sizes and low-levkel ice crystal precipitation from mixed-phase clouds increases. Enhanced dehydration of the lower troposphere contributes to decreased water vapour greenhouse effect and cools the surface. A positive feedback is created between surface cooling and air dehydration, accelerating cold air production. This process is referred to as the dehydration-greenhouse feedback (DGF).Simulations performed using an Arctic regional climate model for February 1990 are used to assess the potential effect of the DGF on the Arctic climate during February. Results show that the DGF has an important effect on cloud, atmospheric dehydration, and temperature over the Central and Eurasian Arctic, which is the coldest part of the Arctic. Cloud ice is significantly reduced and the total atmospheric water path is decreased by as much as 12%. This results in a surface cooling ranging between 0 and −3 K. Moreover, the lower tropospheric cooling over the Eurasian and Central Arctic strengthens the atmospheric circulation at the upper level, thus increasing the aerosol transport from the mid-latitudes and enhancing the DGF. Over warmer areas, the increased aerosol concentration (caused by the DGF) leads to longer cloud lifetime, which contributes to warm these areas.

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“…[2] Successful climate modeling in the polar regions is hampered by uncertainties in understanding of arctic clouds, caused by difficulties in observations and by the unusual forms of these clouds [e.g., Curry et al, 1990Curry et al, , 1996Randall et al, 1998]. These unusual cloud forms include plumes formed near open leads and polynyas.…”

Section: Introductionmentioning

confidence: 99%

A springtime cloud over the Beaufort Sea polynya: Three‐dimensional simulation with explicit spectral microphysics and comparison with observations

Khvorostyanov

Curry

Gültepe³

et al. 2003

J. Geophys. Res.

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[1] This paper addresses the formation of a cloud system associated with an arctic polynya in Beaufort Sea during springtime. Data were obtained as a part of the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE) Arctic Clouds Experiment from the Canadian Convair 580 aircraft during 25 April 1998. These data include in situ observations of cloud microphysics and meteorological variables and remote measurements from satellite and airborne lidar. A three-dimensional cloud-resolving model with explicit bin-resolving cloud microphysics is used to simulate the atmospheric boundary layer and cloud evolution associated with the polynya. After initialization with the aircraft sounding profiles, a quasi-steady polynya-induced atmospheric boundary layer (ABL) and a cloud system form. Strong turbulence in the ABL occurs above the polynya, the internal thermal boundary layer (ITBL) develops and grows upward in the downwind direction, and the ABL downwind of the polynya is separated into two decoupled layers. The cloud forms in the middle of the polynya, and its upper boundary lifts downwind while the lower boundary lowers and reaches the surface beyond the polynya southern boundary as a light fog. Farther to the south, the fog evaporates and transforms into an elevated cloud plume that extends for several tens of kilometers downwind. This cloud morphology is in good agreement with the lidar observations, which showed a cloud layer extending for more than 100 km downwind, and with the numerous previous observations. The simulated microphysical properties of a mixed cloud are similar to those observed. A new ice nucleation scheme resulted in cloud plume gradual crystallization along the wind and eventual transformation into diamond dust. Detailed evaluation of the water budget, supersaturation, and crystal size spectra showed that the ice crystal supersaturation relaxation times are 10-60 min; thus deposition on the crystals is rather slow, and only 1-5% of the available vapor is deposited on the crystals. The large ice crystal supersaturation relaxation time explains the relatively slow growth and gravitational fallout of the ice crystals, as well as the extensive propagation downwind of the plume.

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Occurrence and characteristics of lower tropospheric ice crystals in the arctic

Cited by 108 publications

References 42 publications

Cloud‐aerosol interactions during autumn over Beaufort Sea

Cloud‐aerosol interactions during autumn over Beaufort Sea

Assessment of the dehydration‐greenhouse feedback over the Arctic during February 1990

A springtime cloud over the Beaufort Sea polynya: Three‐dimensional simulation with explicit spectral microphysics and comparison with observations

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