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TG-31 Abstract

Evaluation and Estimation of Surface Trace Gas Fluxes from Aircraft Measurements Above the Amazon

Luciana Vanni Gatti — IPEN - Instituto de Pesquisas Energeticas e Nucleares (USP) (SA-PI)
John Bharat Miller — NOAA/ESRL (US-PI)
Maria Assunção Faus da Silva Dias — IAG/USP (SA-PI)

The Amazon Basin accounts for ~10% of global terrestrial net primary productivity and contains one-half of the world's undisturbed tropical forest and extensive areas of tropical savanna. From the global perspective, trace gas fluxes from Amazonia, and the tropics in general, are poorly sampled by remote global observation networks. This is true not only for CO2, but also for radiatively important gases like CH4 and N2O. While global inverse models of CO2, CH4 and N2O do derive estimates for Amazonia, they are not statistically robust. From the regional, basin-wide, perspective, the situation is little better. Under the Large-scale Biosphere-atmosphere experiment in Amazonia (LBA), a large number of local scale studies throughout Amazon have been undertaken, using eddy-covariance and surface flux chambers. While these studies have contributed to a greater understanding of mechanisms that control trace gas fluxes, the disparate nature of these measurements has made extrapolation difficult.

Airborne trace gas measurements offer a remedy to this problem because of the naturally integrative properties of the atmosphere, and planetary boundary layer (PBL) in particular. Especially in the highly heterogeneous landscape of Amazonia, where large areas of the surface may be inundated at any time, atmospheric measurements offer spatially unbiased measurements, compared with eddy-flux and chamber measurements. In this proposal, we will: 1) Evaluate existing basin-wide flux estimates of CO2, CH4, and N2O, by using atmospheric transport modeling to compare simulated trace gas concentrations with those observed by aircraft above Santarem and Manaus, and 2) Directly estimate surface fluxes of CH4, N2O and other gases by using an inverse modeling approach, making use of data collected as part of the upcoming BARCA aircraft campaign over the Brazilian Amazon. Our analysis approach, in conjunction with a parallel proposal to estimate CO2 fluxes during BARCA (Steven Wofsy, PI) will allow for some of the first atmosphere-based estimates of greenhouse gas emissions in the Amazon basin. We will also estimate global scale fluxes, making using of our Amazonian vertical profiles.

In order to achieve our goals, we will be taking advantage of recent advances in both regional and global tracer transport modeling: the BRAMS (Brazilian-Regional Atmospheric Modeling System) mesoscale model, and the newly developed TM5 (Tracer Model 5) global zoom model. The combination of these two models will allow us to integrate regional Amazonian information into a global context. The significance of our proposal is two-fold: it will improve our understanding of Amazonian trace gas fluxes at the basin-scale; and it will quantitatively connect information derived from the Amazon into the global scale. Both of these outcomes are directly responsive to the primary goals of the solicitation.

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