Dr. Cutten et al., MULTIWAVELENGTH COMPARISON OF MODELED AND MEASURED REMOTE TROPOSPHERIC AEROSOL BACKSCATTER OVER PACIFIC-OCEAN, JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 101(D5), 1996, pp. 9375-9389
Aerosol concentrations and size distributions in the middle and upper
troposphere over the remote Pacific Ocean were measured with a forward
scattering spectrometer probe (FSSP) nn thp NASA DC-8 aircraft during
NASA's Global Backscatter Experiment (GLOBE) in May-June 1990, The FS
SP size channels were recalibrated based on refractive index estimates
from flight-level aerosol volatility measurements with a collocated l
aser optical particle counter (LOPC). The recalibrated FSSP size distr
ibutions were averaged over 100-s intervals, fitted with lognormal dis
tributions and used to calculate aerosol backscatter coefficients at s
elected wavelengths, The FSSP-derived backscatter estimates were avera
ged over 300-s intervals to reduce large random fluctuations. The smoo
thed FSSP aerosol backscatter coefficients were then compared with LOP
C-derived backscatter values and with backscatter measured at or near
flight level from four lidar systems operating at 0.53, 1.06, 9.11, 9.
25, and 10.59 mu m. Agreement between FSSP-derived and lidar-measured
backscatter was generally best at flight level in homogeneous aerosol
fields and at high backscatter values. FSSP data often underestimated
low backscatter values especially at the longer wavelengths due to poo
r counting statistics for larger particles (> 0.8 mu m diameter) that
usually dominate aerosol backscatter at these wavelengths. FSSP data a
lso underestimated backscatter at shorter wavelengths when particles s
maller than the FSSP lower cutoff diameter (0.35 mu m) made significan
t contributions to the total backscatter.