HR: 1340h
AN: A13C-1374 [Abstracts]
TI: Microphysical Properties of a Tropical Subvisible Cloud
AU: * Baumgardner, D
EM: darrel.baumgardner@gmail.com
AF: Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Mexico City, DF 04150,
Mexico
AU: Gandrud, B
EM: gandrud@dropletmeasurement.com
AF: Droplet Measurement Technologies, 5710 Flatiron Parkway, Boulder, CO 80301, United
States
AU: Kok, G
EM: glkok@dropletmeasurement.com
AF: Droplet Measurement Technologies, 5710 Flatiron Parkway, Boulder, CO 80301, United
States
AB:
Measurements of the microphysical properties of a very thin, tropical cirrus layer have been made as part of the
NASA sponsored Tropical Composition, Clouds and Climate Coupling Experiment, (TC4), which was based in
Costa Rica during July and August, 2007. The size distribution and water content were measured with two
instruments, the Cloud, Aerosol and Precipitation Spectrometer (CAPS) and the Cloud Spectrometer and
Impactor (CSI) that were mounted on the NASA WB57F. These instruments are upgraded versions of instruments
previously flown on this aircraft and provide much more sensitivity to low levels of ice water content, greater
accuracy of measurement in the 20-50 μm cloud particle range and less susceptibility to contamination from
ice fragmentation.
On August 6, 2007, the WB57F made a vertical profile through a 800 m cirrus cloud with an average temperature
of -75° C. The ice crystal concentrations increased by a factor of 10 from cloud base to 400 m then
remained almost constant over the remaining 400 m. The ice water contents also increased by a factor of ten
from 0.1 to 1 mg m-3 over the lower 400 m then decreased again by a similar factor until reaching cloud top.
The relationship between the number concentration and ice water content will be discussed in relation to the
possible processes that could explain this link.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0320 Cloud physics and chemistry
DE: 0321 Cloud/radiation interaction
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting