Analyzing the Spatial and Temporal Changes of Satellite Retrieved Carbon Monoxide in Polluted Areas of Southeast and East Asia

This work presents a new methodology, and the unique results, based on an analysis of CO measurements from the MOPITT satellite over the past 17 years (from 2000-2016). The specifics presented here will cover Southeast and East Asia, since both regions have high levels of CO emissions, and complex underlying factors driving change in the CO loadings. We analyze the CO total column measurements, as well as the vertical mixing ratio profile (where the degree of freedom is sufficiently high), with a focus on those regions which are heavily influenced by large-scale biomass burning or intense urban pollution. The goal is to understand how the vertical, temporal and spatial distribution is changing over time, and the impacts of emissions, in-situ processing, and long-range transport, on the overall atmospheric loading.

Result indicate the biomass burning emission mainly dominate from Myanmar and Bangladesh through Thailand, Laos, and Vietnam. These regions of Southeast Asia are heavily polluted only during certain times of the year. On the other hand, urban emission mainly dominate over Northern and Eastern regions of East Asia, including Beijing, Tianjin, Hebei, Shandong, Jiangsu, Anhui, and Henan, where are always polluted. In addition to the differences in the temporal frequency, the spatial and vertical distribution of the emissions show a significant difference. Although the spatial distribution at the surface is similar to the overall column measurements throughout these regions, there are some extremely heavily polluted regions where a second maximum is found in the column. In specific, in the areas surrounding the mountains in Northeastern China, and those with intense coal burning like Taiyuan, have their heaviest CO loadings found at the 900mb and 800mb pressure levels. Additionally, the polluted regions which are dominated by biomass burning, such as Myanmar and Bangladesh, and regions downwind, have a maximum in the vertical found at the 800mb and 700mb pressure levels.

These measurements are used to train a chemical transport model. The ensuring results from the model for aerosols are then contrasted against measurements from other sources, including ground measurements from AERONET and remotely sensed AOD from MODIS (used to compare against column measurements), and CALIOP (used to compare against the vertical mixing ratio profile). It is found that the model results are surprisingly consistent with the observations, when the MOPITT CO data is used to train the model’s aerosol emissions. This gives us confidence that appropriately updating the a priori used in WRF-CHEM, greatly improves our ability to understand reproduce the atmospheric loadings, using first principles.

Our results lead to the conclusion that presently the emissions of CO are underestimated on a strongly seasonal basis over Southeast Asia, and to a lesser extent, on an annual average basis over East Asia. Further, that these underestimations have a significant impact on the atmospheric loadings both locally throughout Southeast Asia and China, as well as further afield, with Southeast Asian emissions having a sizable impact on Southern East Asia, while Northern Chinese emissions have an impact on Northern East Asia, and both impact the atmosphere over the Pacific Ocean.