Integrating constraints on biosphere-atmosphere exchange: from ecosystem scales to the global atmosphere

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Reliable projections of the impact of pollution on the climate system require an improved understanding of the coupling between the biosphere and the atmosphere. The proposed research program is focused on integrating the growing suite of space-based and ground-based observations of atmospheric composition to obtain a better understanding of the processes controlling the atmospheric abundances of carbon dioxide (CO2) and ozone, two important greenhouse gases. A major challenge facing the community is how to exploit the measurements of atmospheric CO2 to quantify CO2 sources and sinks on regional, policy-relevant scales. Ozone in the upper troposphere acts as a strong greenhouse gas, whereas near the surface it is a harmful pollutant that adversely impacts plants and animals. Indeed, accurate projections of atmospheric CO2 levels will require correctly accounting for the adverse impacts of increased ozone abundances on vegetation, and consequently the uptake of atmospheric CO2 by the biosphere. Reproducing the distribution of ozone is challenging, however, because it is highly variable, reflecting a balance between photochemical sources and sinks, which are spatially heterogeneous, and atmospheric transport. The specific objectives of the proposed work are to: 1) determine the conditions under which space-based CO2 observations from the Greenhouse gases Observing Satellite (GOSAT) and the Orbiting Carbon Observatory (OCO-2) can provide constraints on CO2 fluxes on regional scales, and to determine how to link the information from the satellite measurements down to ecosystem scales; 2) integrate satellite observations of ozone and NOx, HCHO, and CO, which are important ozone precursors, to better quantify surface ozone abundances, with a specific focus on better quantifying the sink of ozone associated with dry deposition, which primarily reflects the uptake of ozone by vegetation; 3) determine how climate-induced changes in the large-scale circulation of the upper troposphere and lower stratosphere will impact the distribution of upper tropospheric ozone. The program will use advanced data assimilation techniques to link the information provided by ground-based and space-based observations across a range of scales, from ecosystem scales to the global atmosphere. To bridge these scales, the work will employ the WRF regional model, the GEOS-Chem global chemical transport model, and the CESM chemistry-climate model. The proposed research program will be interdisciplinary and will provide students a unique training experience. There is increasing recognition that a more integrated and interdisciplinary approach is needed to address many of the environmental challenges that we face as a society. The research program will help ensure that the next generation of climate scientists in Canada possesses the diversity of knowledge required to address these challenges.