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Testing the influence of small crystals on ice size spectra using Doppler lidar observations

Westbrook, C. D. and Illingworth, A. J. (2009) Testing the influence of small crystals on ice size spectra using Doppler lidar observations. Geophysical Research Letters, 36 . L12810 . ISSN 0094-8276

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To link to this article DOI: 10.1029/2009GL038186

Abstract/Summary

Analysis of the vertical velocity of ice crystals observed with a 1.5micron Doppler lidar from a continuous sample of stratiform ice clouds over 17 months show that the distribution of Doppler velocity varies strongly with temperature, with mean velocities of 0.2m/s at -40C, increasing to 0.6m/s at -10C due to particle growth and broadening of the size spectrum. We examine the likely influence of crystals smaller than 60microns by forward modelling their effect on the area-weighted fall speed, and comparing the results to the lidar observations. The comparison strongly suggests that the concentration of small crystals in most clouds is much lower than measured in-situ by some cloud droplet probes. We argue that the discrepancy is likely due to shattering of large crystals on the probe inlet, and that numerous small particles should not be included in numerical weather and climate model parameterizations.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Science > School of Mathematical and Physical Sciences > Department of Meteorology
ID Code:1983
Uncontrolled Keywords:shattering; small crystals; cirrus
Additional Information:An edited version of this paper was published by AGU. Copyright (2009) American Geophysical Union
Publisher:American Geophysical Union

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