Coupled biosphere-atmosphere chemical data assimilation: improved understanding of the impact of biosphere-atmosphere exchange on atmospheric composition

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The terrestrial biosphere plays an important role in determining the composition of the atmosphere; and changes in atmospheric composition, in turn, can significantly impact the biosphere. Reliably predicting global climate change due to changing atmospheric abundances of greenhouse gases, such as carbon dioxide (CO2), methane (CH4), and ozone (O3), will require an improved understanding of this coupling between the biosphere and the atmosphere. The proposed research program will use a coupled biosphere-atmosphere model together with advanced data assimilation techniques to exploit newly available satellite observations and surface measurements of environmentally important trace gases to better quantify the influence of the biosphere on the composition of the troposphere. In particular, the work will develop a multi-species biosphere-atmosphere data assimilation system based on a four-dimensional variational data assimilation approach, which exploits satellite observations of atmospheric gases such CO2, CH4, and O3 to optimize the parameters that govern key ecosystem processes in the biospheric model. There has been significant effort in the land-surface modelling community using satellite observations in a data assimilation context to better model biospheric processes. Similarly, there is increasing focus in the atmospheric chemistry modelling community on exploiting the growing wealth of space-based observations of environmentally important tracer gases to better understand the global distribution of these gases. The proposed research program will link the on-going work in these communities to obtain an improved understanding of the contribution of the biosphere to the changing composition of the troposphere.