<title>Lidar Measurements Of Tropospheric Gases</title>

Abstract

This paper describes measurements of pollutants and water vapor in the troposphere using the DIfferential Absorption Lidar (DIAL) technique. Emphasis is placed on research that has been conducted at the NASA Langley Research Center (LaRC) with ground-based and airborne lidar systems. Measurements of sulfur dioxide in power plant plumes have been made with a mobile DIAL system operated near 300 nm. Comparisons of sulfur dioxide concentrations determined with the DIAL system and in-stack monitors were found to be in agreement to within 18 percent. Vertical water vapor profiles have been measured with a ground-based lidar system using the water vapor absorption line at 724.3 nm. Rawinsonde and DIAL water vapor profile data were shown to agree within 10 percent to an altitude of 2.5 km. A multipurpose airborne DIAL system was recently developed at LaRC to investigate a wide range of tropospheric gases. The first remote measurements of ozone profiles from an aircraft were made in May 1980. Subsequently, the airborne DIAL system participated in a major field study with the EPA to investigate elevated pollution episodes. Results from these experiments are presented in this paper. Simulations are also discussed for airborne DIAL measurements of sulfur dioxide, water vapor, and nitrogen dioxide. An extensive study of the scientific rationale and potential experiments with a Shuttle Lidar System has recently been completed by NASA. The application of a spaceborne lidar to uniquely measure tropospheric gases in the late 1980's is addressed in this paper.