Reproducing the measured spatio-temporal aerosol profile and associated extreme aerosol events over Southeast Asia and downwind using a new, multi-sensor, remote-sensing constrained 4-dimensional emissions inventory coupled into WRF-CHEM

Abstract:

In parts of Southeast Asia affected by the Asian monsoon, the contribution of biomass burning to the total aerosol emissions is significant and has further continued to increase in recent decades. Recently, biomass burning in these areas has led to aerosol levels exceeding 500ug/m3 on a daily average basis over a short duration in regions which otherwise are considered to be clean. However, the current generation of atmospheric chemical transport models, such as WRF-CHEM, are not able to predict these extreme events well, even after scaling is applied.

In order to better match the spatio-temporal distribution and intensity of biomass burning, we generated a new 4-D emission inventory based on remotely sensed measurements of NO₂ from OMI and CO from MOPITT to investigate the extreme events which occur annually. In this talk, we specifically focus on the February to March 2016 season, and compare the results of the remotely-sensed forced model against completely independent remotely sensed measurements of AOD from MISR and AERONET.

First, the results are found to be reliable over biomass burning regions world-wind when compared against different measurements than those used to force the model or train the emissions. Second, the results show that the duration of biomass burning and the total amount of pollutant emissions are much higher than values used by other studies. Third, this new method allows reproduction of the “traditional downstream biomass burning plume” to Vietnam, Hainan, and Guangdong, to be further extended to Hong Kong, Taiwan, and the Western Pacific, as well as even more importantly, a “newly discovered downstream region” over 2000km away to Southern Thailand, Malaysia, Singapore and even further afield . Finally, the work proposes that one possible mis-match is due to the interactions between the aerosol emissions and their interaction with the energy balance, which in turn changes the meteorological fields and the ultimate destination to which the aerosols are advected.

This paper aims to explain how a more accurate albeit larger amount of aerosol emissions leads to more above the boundary layer over source regions in Southeast Asia, and how this subsequently leads to a wider effect on human health and air quality throughout regions both known and those which have never been clearly established before.