MONITORING AIR-POLLUTION RELATED METEOROLOGY USING SODAR - STATE-OF-THE-ART

Hazardous situations in air pollution can many a times be avoided in c ase short term local weather forecasting of the boundary layer meteoro logy becomes available. Amongst the various remote sensing techniques, it has been seen that acoustic remote sensing (SODAR) of the lower at mosphere can be employed to determine and predict the atmospheric boun dary layer meteorological parameters. In specific, information can be obtained about thermal stratification, mixing height, low level distur bances, depth of the planetary boundary layer, stability classificatio n, wind velocity, wind variances, turbulence parameters, and diffusion characteristics etc. when SODAR is used in conjunction with surface l evel measurements of the usual meteorological parameters. In the paper a brief description of the acoustic remote sensing technique and a re view of the work done during the last two decades to determine the var ious air quality related meteorological parameters has been given. The methodology to determine mixing height, stability classification and diffusion and dispersion characteristics using mostly the information from the SODAR echograms has also been described. The SODAR echograms obtained at Delhi for the period May 1977 to April 1982 have been proc essed and analyzed using pattern recognition to determine these parame ters. Doppler SODAR information of wind speed and direction have not b een treated for the above purpose. Using the Gaussian dispersion model , pollution concentration downwind of a emission source (in the presen t case it is a cement factory at Nimbahera, Chittorgarh, India) has al so been computed with the help of SODAR determined data. It has been f ound that measured values with the help of high volume sampler conform to the estimated pollution concentration. A peak in the value of the estimated pollution concentration during the fumigation period has als o been seen.