Observation-based 3-D view of aerosol radiative properties over Indian Continental Tropical Convergence Zone: implications to regional climate

Spatial and vertical distributions of aerosol radiative properties over Indian Continental Tropical Convergence Zone (CTCZ) up to 6 km altitude during the pre-monsoon and monsoon seasons of 2008 have been measured and reported for the first time. Inter-seasonal and intra-seasonal comparisons of different aerosol properties below and above the boundary layer are carried out in and among different regions of CTCZ. During pre-monsoon, aerosol layers were found to be present up to altitude as high as 6 km over the Indo-Gangetic Plains and Himalayan foothills. A large increase in absorption coefficients (by two to five times) near the Himalayan foothills and coastal India than the background values may be attributed to extensive biomass burning as supported by fire counts data. During monsoon, the aerosols were mostly confined to lower troposphere. However, absorbing aerosols were found to rebuild much faster than scattering aerosols after rains. Heating rates were very high over urban city of Bareilly peaking around 2 km during the pre-monsoon. The HR values over urban Kanpur during monsoon were comparable to Bareilly during pre-monsoon. Negligible latitudinal gradient of heating rate from the Himalayan foothill to central India was observed during both the seasons.