The size distribution and mass-weighted terminal velocity of low-latitude tropopause cirrus crystal populations

AMS Citation:
Schmitt, C. G., and A. J. Heymsfield, 2009: The size distribution and mass-weighted terminal velocity of low-latitude tropopause cirrus crystal populations. Journal of the Atmospheric Sciences, 66, 2013-2028, doi:10.1175/2009JAS3004.1.
Date:2009-07-01
Resource Type:article
Title:The size distribution and mass-weighted terminal velocity of low-latitude tropopause cirrus crystal populations
Abstract: Ice crystal terminal velocities govern the lifetime of radiatively complex, climatologically important, low-latitude tropopause cirrus clouds. To better understand cloud lifetimes, the terminal velocities of low-latitude tropopause cirrus cloud particles have been estimated using data from aircraft field campaigns. Data used in this study were collected during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE) and the Pre-Aura Validation Experiment (Pre-AVE). Particle properties were measured with the NCAR video ice particle sampler (VIPS) probe, thus providing information about particles in a poorly understood size range. Data used in this study were limited to high-altitude nonconvective thin clouds with temperatures between -56° and -86°C. Realistic particle terminal velocity estimates require accurate values of particle projected area and mass. Exponential functions were used to predict the dimensional properties of ice particles smaller than 200 microns and were found to predict ice water content measurements well when compared to power-law representations. The shapes of the particle size distributions were found to be monomodal and were well represented by exponential or gamma functions. Incorporating these findings into terminal velocity calculations led to lower values of mass-weighted terminal velocities for particle populations than are currently predicted for low-latitude ice clouds. New parameterizations for individual particle properties as well as particle size distribution properties are presented and compared to commonly used parameterizations. Results from this study are appropriate for use in estimating the properties of low-latitude thin and subvisible cirrus at temperatures lower than -56°C.
Subject(s):Cloud microphysics, Cloud parameterizations
Peer Review:Refereed
Copyright Information:Copyright 2009 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work.
OpenSky citable URL: ark:/85065/d72j6cwr
Publisher's Version: 10.1175/2009JAS3004.1
Author(s):
  • Carl Schmitt - NCAR/UCAR
  • Andrew Heymsfield - NCAR/UCAR
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