Investigating aerosol properties in Peninsular Malaysia via the synergy of satellite remote sensing and ground-based measurements

Abstract

Atmospheric aerosols play an important role in climate change and air quality. Aerosol studies that are related to their spatio-temporal variation and trends are useful in order to understand their roles and impacts on solar radiation and clouds. The main objectives of this study are to validate the Terra Moderate Resolution Imaging Spectroradiometer (MODIS) Aerosol Optical Depth (AOD) products, analyse the spatio-temporal evolution and trend of AOD from Terra and Aqua MODIS sensors, to identify aerosol types and their origin, and to investigate the effects of aerosol on solar radiation. The Terra MODIS AOD was found to correlate significantly with Aerosol Robotic Network (AERONET) AOD with R2 = 0.86.The spatial pattern of MODIS AOD in Peninsular Malaysia shows highest AOD values at western stations whereas the lowest AOD values were recorded at Cameron highlands. The AOD trend over a period of 10 years shows a neutral-to-declining trend, while that from Aqua exhibits an increasing trend. AERONET AODs exhibit either insignificant diurnal variation or higher values during afternoon, while their short-term availability does not allow for trend analysis. Moreover, the Particulate Matter below 10 micron (PM10) concentrations exhibits a general positive trend over the examined locations suggesting increase in aerosols near the ground. The identification of sources and destination of aerosols revealing that aerosols during the dry season are mainly originated from the west and southwest, while in the wet season they are mostly associated with the northeast monsoon winds from the South China Sea. Four types of aerosols were identified and the AOD was found negatively correlated with solar radiation with low R2 but statistically significant.