NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Effective Radius of Ice Cloud Particle Populations Derived from Aircraft ProbesThe effective radius(r(sub e)) is a crucial variable in representing the radiative properties of cloud layers in general circulation models. This parameter is proportional to the condensed water content (CWC) divided by the extinction (sigma). For ice cloud layers, parameterizations for r(sub e), have been developed from aircraft in-situ measurements 1) indirectly, using data obtained from particle spectrometer probes and assumptions or observations about particle shape and mass to get the ice water content (IWC) and area to get sigma, and recently 2) from probes that measure IWC and sigma directly. This study compares [IWC/sigma] derived from the two methods using data sets acquired from comparable instruments on two aircraft, one sampling clouds at mid-levels and the other at upper-levels during the CRYSTAL-FACE field program in Florida in 2002. The sigma and IWC derived by each method are compared and evaluated in different ways for each aircraft data set. Direct measurements of sigma exceed those derived indirectly by a factor of two to two and a half. The IWC probes, relying on ice sublimation, appear to measure accurately except when the IWC is high or the particles too large to sublimate completely during the short transit time through the probe. The IWC estimated from the particle probes are accurate when direct measurements are available to provide constraints and useful information in high IWC/large particle situations. Because of the discrepancy in sigma estimates between the direct and indirect approaches, there is a factor of 2 to 3 difference in [IWC/sigma] between them. Although there are significant uncertainties involved in its use, comparisons with several independent data sources suggest that the indirect method is the more accurate of the two approaches. However, experiments are needed to resolve the source of the discrepancy in sigma.
Document ID
20050147502
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Heymsfield, Andrew J.
(National Center for Atmospheric Research Boulder, CO, United States)
Schmitt, Carl
(National Center for Atmospheric Research Boulder, CO, United States)
Bansemer, Aaron
(National Center for Atmospheric Research Boulder, CO, United States)
vanZadelhoff, Gerd-Jan
(Royal Netherlands Meteorological Inst. De Bilt, Netherlands)
McGill, Matthew J.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Twohy, Cynthia
(Oregon State Univ. Corvallis, OR, United States)
Date Acquired
August 23, 2013
Publication Date
February 1, 2005
Subject Category
Meteorology And Climatology
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available