Lidar-Observed Haze Layers Associated with Thermal Structure in the Lower Atmosphere

Abstract

Daytime observations of the vertical temperature and humidity structure in the atmosphere below 1 km made with a Cricketsonde rocket system are compared with simultaneous observations from a ruby lidar (laser radar). Observations were made at the SRI field site in Palo Alto, Calif., during August 1968 in the absence of low clouds when haze and pollution were visually evident. Analyses of the data show a direct relationship between Cricketsonde and lidar data. Invariably, the temperature profile obtained by the Cricketsonde includes a subsidence inversion during the early morning. Either this inversion persists throughout the day or it is destroyed by surface heating, and the temperature lapse approaches the dry adiabat by midafternoon. The lidar observes a deep layer of particulate matter, the upper boundary of which rises in height from morning to afternoon. When a subsidence inversion is observed, the largest change in optical density is detected at the level of the inversion. However, concentrations of particulate matter are also observed by the lidar at higher levels. By monitoring the time change in intensity and in internal stratification of the aerosol layer, the lidar can follow the life cycle of the temperature inversion.