AIR-QUALITY MONITORING BY OPTICAL AND ACOUSTIC RADARS AT PUNE, INDIA

The co-located optical (argon-ion lidar) and acoustic (Doppler sodar) radar systems at the Indian institute of Tropical Meteorology (IITM), Pune (18 degrees 32'N, 73 degrees 51'E, 559 m AMSL), India, have been employed to study the nocturnal aerosol pollution dynamics or air qual ity. Both the systems have been operated simultaneously in order to sa mple the common atmospheric volume. The results of the experiments thu s conducted on same typical nights are presented in this paper. The ti me-height cross section of the mean, horizontal and vertical component s of the wind field derived from the sodar observations indicate that the wind is either easterly or northerly with its vertical component n egative (downdraft) for most of the observational period, The interest ing feature is that the winds are either calm or relatively weaker in the night-time boundary layer compared with those in the region aloft. This is more evident in the north-south direction in which the lidar and sodar equipment are located, Furthermore, the regions where stable /elevated layer formation is active are found to be associated with th e smallest wind gradients, leading to accumulation of aerosol particle s or larger temperature structure parameters. The time evolution of th e mixed-layer heights and the associated ventilation coefficients, det ermined from the combined lidar-aerosol and sodar-wind observations, a re found to be useful to explain the transport and diffusion of pollut ants across the elevated temperature inversions over the experimental station. The details of the experimental techniques are presented and their value for application in the study of regional air quality and p ollution potential is discussed.