Estimate of Radiative Forcing of Biomass Burning Aerosols in South Asian Region during the Period of TRACE-P

This study is aimed to estimate the radiative impact of biomass burning aerosols in south Asia during the experimental period of TRAnsport and Chemical Evolution over the Pacific (TRACE-P) in March 2001. We coupled the USA NOAA HYbrid Single-Particle Lagrangian Integrated Transport model (HYSPLIT) with a solar radiative transfer model (CLIRAD-SW) to simulate the spatial and temporal distribution of black and organic carbon (BC/OC) particles, and further to estimate their radiative forcing. The meteorological data adopted are both NCEP's GDAS and MM5 outputs with a spatial resolution of 2.5^o x 2.5^o and 45 x 45 km, separately. Emissions of black carbon and organic carbon from biomass burning sources were based on the work of Streets et al. (2003). The results show that Indochina mostly had the monthly mean concentration of biomass burning aerosols more than 5 µg m^-3. The maximum value reached as high as 200 µg m^-3 in northern Myanmar. Aerosol optical properties such as single scattering albedo (ω₀) and asymmetry parameter (g) at 0.55 µm wavelength and RH at 50% were estimated to be 0.82 and 0.65, respectively. The maximum value of monthly aerosol optical depth (AOD) ranged from 0.09 to 0.3 depending on the change of the RH values. The monthly mean clear sky shortwave TOA radiative forcing ranged from -0.9 to -3.5 W m^-2, and surface radiative forcing ranged from -1 to -25 W m^-2 in south and southeast Asian regions, presenting a cooling effect on the atmosphere.