Long-term variations and comparison of aerosol optical properties based on MODIS and ground-based data in Thailand

Abstract

Comparison and analysis of Moderate Resolution Imaging Spectroradiometer (MODIS), Aerosol Robotic Network (AERONET), and SKYNET aerosol optical depth (AOD) products were investigated at four AERONET and two SKYNET stations in Thailand from 2006 to 2020. AERONET Level 2.0 and MODIS Deep Blue (DB) Collection 6.1 data were applied. Aqua and Terra MODIS AODs (satellite AODs) were compared to AERONET and SKYNET AODs (ground based AODs). Ground-based and satellite AODs were in good agreement, giving a high correlation (R2 = 0.75) in Ubon Ratchathani, associated with biomass burning. The long-term trend in AOD was analyzed. Both satellite and ground based AODs demonstrate increasing trends in AOD over Thailand associated with the urbanized area and traffic congestion. Aerosol particles are categorized into dust, sea salt, and biomass burning, containing fine and coarse modes. A variation between satellite data measurements depended on surface reflectances, such as the large water body surrounding (Songkhla) and the impact of surface albedo (Chiang Mai). Higher AOD values were observed between February to April. In addition, meteorological parameters are directly related to aerosol concentrations, while no significant connection could be developed in the observed values between Angstrom exponent (AE) and Meteorological parameters. Meteorological parameters and temperature inversion more influenced AOD concentrations in February. Nevertheless, the hypothesis showed 95% confidence interval of AODs retrieved from satellite data fell within the confidence range. Therefore, satellite aerosol products are sufficiently accurate for estimating aerosol climatology.