NASA LASE water vapor differential absorption lidar measurements and performance evaluation

Abstract

The Lidar Atmospheric Sensing Experiment (LASE) is a highly engineered and autonomous Differential Absorption Lidar (DIAL) system developed at NASA Langley Research Center (LaRC) to measure high-resolution water vapor and aerosol profiles in the troposphere. LASE is being developed as a precursor to the deployment of a spaceborne DIAL system for global measurement of high-resolution water vapor profiles. The LASE system uses a tunable Ti:sapphire laser that is frequency locked to pre-selected water vapor lines in the 815-nm region. LASE is undergoing a series of engineering test flights onboard a high-altitude ER-2 aircraft to evaluate its initial performance before deployment on field programs. During the first engineering test flight conducted near NASA Ames Research Center in May 1994, LASE was operated in the backscattered lidar mode and obtained high-quality aerosol profiles in the 0-20 km altitude region. During a subsequent engineering flight series conducted near NASA Wallops Flight facility in September 1994, water vapor and aerosol profiles were obtained simultaneously under a variety of cloud and background conditions. This paper discusses the results of the water vapor and aerosol measurements made during these flights. These measurements will be used to evaluate the performance of the instrument and for comparison with predicted values of atmospheric signals and water vapor profiles derived from in situ measurements from radiosondes launched in the vicinity of LASE measurements. These results will be used to refine the LASE system for a final engineering test series planned for early 1995. Plans for the validation of the LASE instrument with other in situ and remote sensors and the anticipated field program participation are also discussed. >