Cloud Radiation
ing that the cloud does not contain enough liquid water to emit radiation like
a perfect blackbody. A doubling of carbon dioxide in the Earth's atmosphere is
The enhancements in surface infrared radiation related to changing cloud liq-
uid water content and emissivity are on the order of tens of watts per square
meter.
The FTIR cloud emission spectra can be used to estimate the effective radius
of the cloud droplet size distribution (Lubin 1994), which in turn can indicate
whether or not continental air masses are influencing cloud microphysics.
Radiative transfer analysis of the AOS-94 cloudy sky emission spectra suggest
that 30% of the stratiform clouds sampled have effective droplet radii of 7 m
or smaller, in which case they are probably influenced by continental air masses
and aerosol concentrations. By showing this type of microphysical phenome-
non, along with the large variability in cloud optical depth that can occur (0
50), this program has illustrated that the summer atmosphere in the high
Arctic is as dynamically and radiatively complex as that over any other conti-
nent or ocean.
REFERENCE
Lubin, D. (1994) Infrared radiative properties of the maritime Antarctic
atmosphere. Journal of Climate, 7: 121140.
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