Effect of forest fire and biomass-burning aerosols on rainfall characteristics in the Upper-Northern Thailand

Abstract

Biomass burning in the northern Thailand probably provides strong input of aerosols into the atmosphere, with potential effects on cloud and rainfall, over an entire burning season. This research was focus on effect of biomass burning aerosols on clouds and rainfall using multiple regression analysis and AOT for indicating aerosol concentrations from satellite MODIS (Terra / Aqua) and AERONET station since 2003-2012.  The results indicated that average AOT of the Northern Thailand showed the highest value in pre-monsoon season especially in March with 0.5 unitless and decreased in June to July. It corresponded with hotspot data were mostly occurring in pre-monsoon season. Furthermore, almost all of the aerosols that were found during monsoon season as the big particles, caused by salt spray combine with water vapor. In the other hand, almost all of the aerosols during pre-monsoon were the small particles which come from the black carbon caused by biomass burning. There was high positive relationship with rainfall with cloud water content (CWC) and cloud fraction (CF), but it was found that were negative relationship with aerosol optical thickness (AOT) and hotspot (HP). There was moderate relationship between rainfall amount with AOT, cloud fraction (CF), cloud water content (CWC) and hotspot (HP) in all provinces of the northern Thailand. It was noticed that in any year there were the high biomass burning aerosols which caused rain later than usual about 1-2 months.