Vertical Profiling of Aerosol Types Observed across Monsoon Seasons with a Raman Lidar in Penang Island, Malaysia

ABSTRACT

Although technology has advanced in the past few decades, the understanding of the effect of aerosol on Earth’s climate has remained largely unknown. Even if considerable effort has been made by researchers around the world to study this pressing issue, the non-uniform distribution of aerosols is still a huge challenge on global aerosol characterization studies. Without extensive and reliable measurements from most regions in the world, a complete understanding of aerosol characteristics cannot be achieved. In this study, a Raman LIDAR was used to acquire data to calculate the range-dependent extinction-to-backscattering ratio during a very particular period: when the Northeast monsoon season shifts to the Southwest monsoon season. During this time period, monsoonal winds change direction, leading to changes in aerosol type and properties above Penang Island due to the global atmospheric circulation. From the retrieved extinction-to-backscattering ratio, it is possible to differentiate the aerosol types present at various altitudes. It was found that background marine and urban aerosols were present above Penang Island, as marine and urban aerosols were present both below and above the PBL height regardless of the monsoon season. Additionally, biomass burning aerosols and aged forest fire aerosols were occasionally found, which were normally associated with cases of pollution, such as those in early March 2014 and June 2014. Finally, it was found that during a haze episode, the entire atmospheric column was dominated by wood burning aerosols. AERONET sunphotometer data have been used to validate LIDAR findings. Radiative effect of background and transported aerosols are evaluated with the Fu-Liou-Gu radiative transfer model.