Analysis of the origin of peak aerosol optical depth in springtime over the Gulf of Tonkin

Abstract

By aggregating MODIS (moderate-resolution imaging spectroradiometer) AOD (aerosol optical depth) and OMI (ozone monitoring instrument) UVAI (ultra violet aerosol index) datasets over 2010-2014, it was found that peak aerosol loading in seasonal variation occurred annually in spring over the Gulf of Tonkin (17-23 °N, 105-110 °E). The vertical structure of the aerosol extinction coefficient retrieved from the spaceborne lidar CALIOP (cloud-aerosol lidar with orthogonal polarization) showed that the springtime peak AOD could be attributed to an abrupt increase in aerosol loading between altitudes of 2 and 5 km. In contrast, aerosol loading in the low atmosphere (below 1 km) was only half of that in winter. Wind fields in the low and high atmosphere exhibited opposite transportation patterns in spring over the Gulf of Tonkin, implying different sources for each level. By comparing the emission inventory of anthropogenic sources with biomass burning, and analyzing the seasonal variation of the vertical structure of aerosols over the Northern Indo-China Peninsula (NIC), it was concluded that biomass burning emissions contributed to high aerosol loading in spring. The relatively high topography and the high surface temperature in spring made planetary boundary layer height greater than 3 km over NIC. In addition, small-scale cumulus convection frequently occurred, facilitating pollutant rising to over 3 km, which was a height favoring long-range transport. Thus, pollutants emitted from biomass burning over NIC in spring were raised to the high atmosphere, then experienced long-range transport, leading to the increase in aerosol loading at high altitudes over the Gulf of Tonkin during spring.

Research on the typical parameters of aerosol optical properties in China's maritime areas

“…A large number of scholars at home and abroad have demonstrated the feasibility of using satellite data to analyze aerosol optical properties. At present, research on aerosol optical parameters based on CALIOP satellite data is mostly focused on inland areas [3][4][5][6][7][8] , and there is less research on aerosols at sea [9][10] .The existing research mainly verifies and evaluates the accuracy of a single satellite product, or combines it with mathematical statistical analysis to analyze the single optical parameters of multiple products. There is relatively little research on the systematic analysis and evaluation of aerosol optical characteristics parameters using multi-source satellite data products in specific regions.Therefore, this article utilizes the long-term satellite observation data of AHI H8 sensor and spaceborne LiDAR CALIPSO to explore and analyze the optical characteristics of atmospheric aerosols in the eastern.…”