An integrated analysis of aerosols, trace gases and particulate matter over tropical urban region, Hyderabad, India using ground based measurements and satellite data (pp. 293-330)
Authors: (K. V. S. Badarinath, Shailesh Kumar Kharol, Anu Rani Sharma and Krishna Prasad Vadrevu)
Abstract: Aerosols and trace gas emissions in urban areas constitute one of the major sources of pollution that is of prime concern in the climate change studies. In this study, we report integrated and comprehensive results from aerosols and trace gases over a typical urban environment of Hyderabad, south India. Intensive ground based measurements were undertaken to quantify variations in aerosol optical depth (AOD), particle size distribution, particulate matter, aerosol backscattering, in addition to black carbon, carbon monoxide and ozone. Several remote sensing products, i.e., MODIS, TOMS-OMI, KALPANA and DMSP-OLS have been invoked to characterize large scale variations in aerosol optical depth, ozone and to assess influence of dust and fire events over the study area. We also used robust Mesoscale Meteorological model (MM5) to understand variations in local as well as regional scale meteorology. Also, aerosol radiative forcing has been assessed using SBDART model. Results from ground based measurements for aerosols and trace gases showed clear diurnal and temporal variations. The aerosol optical depth values at 380, 440, 500, 675, 870 and 1020 nm showed a significant spectral dependence and presence of aerosols of different size distributions and chemical composition. A sharp peak in black carbon concentrations occurred during morning and evening hours and has been attributed to traffic patterns in the study area. The high standard deviations of AOD found on certain Julian days during January to first fortnight of April were attributed to frequent forest fire events towards north of the study area. In contrast, high AOD loadings during second fortnight of April to May were attributed to dust aerosols transported from Thar Desert. These results were supported from MODIS, IRS-P4 OCM, DMSP-OLS and KALPANA satellite remote sensing products as well as back trajectory air transport model. Results on UV irradiance suggested relatively higher attenuation of UV radiation from smoke than dust particles. Further, Radiative forcing due to enhanced loading of aerosols associated with crop residue burning was found to be -107.81 Wm-2 compared to –53 Wm-2 under normal conditions. We also present results relating to aerosol vertical distribution from LIDAR measurements as well implications of long-range transport of aerosols and dust particles influencing urban environment in the study area.