A study of boundary layer aerosol and wind profiles using incoherent Doppler lidar.

摘要

Light detection and ranging (lidar) systems in use today measure a variety of atmospheric parameters including profiles of aerosol backscatter, wind, and limited trace chemical species. Lidar systems are particularly useful tools for field studies because of their portability, flexibility, and wealth of data they provide. A lidar system has been built at the University of Michigan capable of measuring wind speed and direction as well as aerosol/molecular scattering profiles using an incoherent (direct detection) technique. This mobile lidar instrument was used in the field for the first time during the 1992 Southern Oxidants Research Program on Ozone Non-Attainment (SORP-ONA) field intensive in Atlanta, Georgia.;The technical portion of the dissertation begins with descriptions of the lidar instrument components and derivations of the analytical equations which describe instrument throughput. The equations have been parameterized into a computer model to predict instrument performance under a variety of atmospheric conditions. The model predicts lidar wind measurements with 2 m/s accuracy or better with integration times of 2 minutes or less. New algorithms to process wind velocity and aerosol/molecular scattering information from the data are developed and discussed. Lidar data taken in Ann Arbor, Michigan and during the SORP-ONA Atlanta Field Intensive are presented as proof of concept and for scientific analysis. Wind field data are compared with a co-located rawinsonde for accuracy. An RMS difference of 3.1 m/s in measured wind speed was seen with mean winds of 8-10 m/s.;Aerosol data are used to study boundary layer aerosol morphology, including testing of the uniform mixing hypothesis, estimation of mixing height, and calculation of total boundary layer column aerosol. Strong layering and structure was seen in the aerosol data indicating the uniform mixing assumption was not always valid, even on relatively hot summer days. Constrained mixing height estimates from the lidar showed a 0.85 correlation with rawinsonde-derived mixing height estimates. Based on these findings, it was concluded that the incoherent Doppler lidar technique is extremely useful for both wind profile measurements and aerosol loading determination.