Analyzing the Spatial and Temporal Changes of Satellite Retrievals of CO and AOD in Polluted Areas of Monsoon Southeast and East Asia

This work presents a methodology and results from analyzing combined measurements of AOD from MODIS and CO from MOPITT from the past 17 years (2000-2016) over Southeast and East Asia. The results focus on those regions which are heavily influenced by large-scale biomass burning and intense urban pollution. It is observed that while there are some areas that are always polluted, there are other areas which are heavily polluted only during certain times of the year. There are other signals found in the data, corresponding to expanding urbanization, and differences on year-to-year scales.

Over the areas of significant changes, in space or time, we focus on analyzing how the changes are significantly different between the two measured datasets. Large differences are observed due to a few well known factors: different removal and in-situ atmospheric processes between the two species, leading to significantly different lifetimes; and different resolutions, with the higher resolution AOD measurements being able to replicate sudden changes more precisely. Additionally, information is obtained from the CO retrievals, which sometimes provide two vertical levels of information. When this is the case, we also observe the change of the vertical distribution, and use this piece of information to further understand the source profile.

These results are used to compare with measurements from the AERONET, NOAA, and Hong Kong government datasets, where available, and show consistent results. The results are then used to constrain model runs of WRF-CHEM to understand better the ability to fundamentally model the atmospheric loadings from first principles. We are able to conclude that presently the emissions of CO are underestimated from Southeast Asia, and further that they have a significant impact on the atmospheric loadings throughout both Southeast Asia and Southern China, as well as further afield.