LIDAR AEROSOL BACKSCATTER CROSS-SECTIONS IN THE 2-MU-M NEAR-INFRARED WAVELENGTH REGION

Lidar backscatter cross-sectional measurements at 1.064, 0.532, and 1. 54 mu m were acquired during November 1989 and May-June 1990 around th e Pacific region by the NASA DC-8 aircraft as part of the Global Backs catter Experiment. The primary motivation for the Global Backscatter E xperiment was the study of lidar backscatter cross sections for the de velopment of a spaceborne wind-sensing lidar. Direct backscatter measu rements obtained by the NASA Goddard Space Flight Center visible and i nfrared lidar are compared with backscatter cross sections calculated from aerosol size distributions obtained by particle counters. Results for one flight with pronounced aerosol layers in the upper tropospher e southeast of Japan are presented. Because 2-mu m region wavelengths are possible candidates for a spaceborne wind-sensing lidar, the visib le and infrared lidar backscatter cross sections at 1.064, 0.532, and 1.54 mu m are extrapolated to the 2-mu m region. The extrapolated 2-mu m cross sections are compared with lidar measurements at 9 mu m. A si gnificant range in the ratio of 2-9-mu m backscatter cross sections is found, but a large number of points concentrate near ratios of three to ten. A large number of 1.064- and 1.54-mu m cross sections were bin ned to provide an estimate of backscatter for various percentiles for the flight. The ratio of the 50-percentile backscatter values at 1.064 and 1.54 mu m suggest a lambda(-1.9) to lambda(-3.0) wavelength depen dence of aerosol backscatter cross section in the near infrared for th e observational case. (C) 1996 Optical Society of America