Dp. Duda et Jd. Spinhirne, SPLIT-WINDOW RETRIEVAL OF PARTICLE-SIZE AND OPTICAL DEPTH IN CONTRAILS LOCATED ABOVE HORIXONTALLY INHOMOGENEOUS ICE CLOUDS, Geophysical research letters, 23(25), 1996, pp. 3711-3714
Multichannel radiometer measurements-of a newly formed contrail taken
from a NASA ER-2 aircraft over northern Oklahoma during the FIRE Cirru
s-II experiment are used in a split-window retrieval of the contrail's
particle size and optical depth. The effect of horizontal inhomogenei
ty in an underlying cirrus layer on the contrail retrieval is studied
through the use of multi-dimensional radiative transfer model simulati
ons. Estimates of the contrail's effective radius are significantly sm
aller (5 - 7 mu m) than those in the underlying cirrus (21 mu m). The
effect of horizontal inhomogeneity in the underlying cirrus on contrai
l particle size and optical depth retrievals is generally smaller than
the corresponding effects of particle shape or spectral variations in
surface emissivity on the retrievals. The differences in particle siz
e retrievals are 10 percent or less as a result of the inhomogeneity,
while they are from 10 to 40 percent for ice cylinders, and range from
1 to 40 percent for ice spheroids. Horizontal inhomogeneity affected
the optical depth retrievals by only one or two percent, while surface
emissivity variations affected the retrievals by 12 to 24 percent, an
d particle shape produced differences as large as 9 percent.