Identifying Convective Transport of Carbon Monoxide Through the Intercomparison of Remote Sensing Observations and Cloud Modeling Simulations

Anthropogenic pollution impacts many of the Earth's natural processes. Therefore, understanding the mechanisms that transport pollutants from the surface to the free atmosphere is important for understanding the chemical composition of the atmosphere. This study quantifies the vertical transport of lower tropospheric carbon monoxide (CO) by deep convection associated with mesoscale convective systems. Three squall line simulations (C1-C3) based on different environmental wind shear profiles are made using the 2-D Goddard Cumulus Ensemble Model, each providing post-convection profiles. Then, the Tropospheric Emission Spectrometer (TES) instrument's ability to resolve the convectively modified CO distribution is analyzed during one of the cases (C3) using a "clear sky" retrieval scheme. Results show that environmental wind shear not only impacts the structure of squall lines, but also their transport characteristics. The squall line simulation with the strongest low-level vertical wind shear is found to transport the greatest net mass of CO, with an amount of 13,421 metric tons in the low levels and 43,916 metric tons in the middle levels of the atmosphere. However, the storm with the weakest low-level vertical wind shear and weakest environmental winds aloft has a greater mass of CO transported by the updraft and the downdraft than either of the other storms. The study finds that stronger environmental winds in the upper troposphere play an important role in the propagation speeds of the squall line, which in turn impacts the horizontal distribution of convectively lofted CO. Results also show that TES has sufficient sensitivity to resolve convectively lofted CO, as long as the retrieval scene is cloud-free. TES swaths that are located downwind of squall lines are found to have the greatest chance of sensing convective transport because the impact of clouds on retrieval quality becomes less of an issue further from the squall line.