Abstract

NASA Goddard's Stratospheric Ozone Lidar Trailer Experiment (STROZ-LITE) was designed to utilize the DIAL (Differential Absorption Lidar) technique in measuring atmospheric ozone. After the 1991 eruption of Mt. Pinatubo, it became impossible to make accurate measurements of ozone in the region most contaminated by volcanic aerosols (10-30km). The system formally collected light returns at only the emitted laser wavelengths (308 and 351nm). It has since been modified so that the respective signals at 332 and 382nm produced by Raman scattering from nitrogen molecules could also be acquired. This was done so that ozone could be calculated in the aerosol affected region of the atmosphere. Using the same DIAL scheme, but now with the Raman channels at 332nm and 382nm as the on and off-line wavelengths, an accurate ozone measurement can be made between 10 and 30km (McGee et. al, 1992). In making these modifications, a measure of atmospheric aerosol backscatter can be obtained quite simply. With careful normalization, the ratio of 351 to 382nm return signal can directly give the 351nm aerosol scattering ratio (ASR), defined as the Rayleigh plus Mie backscatter divided by only Rayleigh backscatter, since the 351nm signal contains components of both aerosol and molecular backscatter while the 382nm signal contains only molecular backscatter from nitrogen. Whiteman et. al. (1992) describes this procedure in greater detail. With available ancillary atmospheric pressure and temperature data, an Aerosol Volume Backscatter Cross Section profile at 351nm can be quickly calculated from ASR profiles since the Rayleigh cross section at 351nm is well known. The STROZ-LITE system is also now able to determine a measure of aerosol extinction from the 382nm channel. Transmission at this wavelength contains a term for the sum of 351nm plus 382nm aerosol extinction, which can be solved for directly. By assuming a reasonable wavelength dependence, aerosol extinction profiles at 351nm can be computed.

© 1993 Optical Society of America