A biogenic C02 flux adjustment scheme for the mitigation of large-scale biases in global atmospheric CO2 analyses and forecasts

TitleA biogenic C02 flux adjustment scheme for the mitigation of large-scale biases in global atmospheric CO2 analyses and forecasts
Publication TypeMiscellaneous
Year of Publication2015
AuthorsAgusti-Panareda, A, Massart, S, Chevallier, F, Balsamo, G, Boussetta, S, Dutra, E, Beljaars, A
Secondary TitleTechnical Memorandum
Number773
Abstract

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Forecasting atmospheric CO<sub>2</sub> daily at the global scale with a good accuracy like it is done for the weather is a challenging task. However, it is also one of the key areas of development to bridge the gaps between weather, air quality and climate models. The challenge stems from the fact that atmospheric CO<sub>2</sub> is largely controlled by the CO<sub>2</sub> fluxes at the surface, which are difficult to constrain with observations. In particular, the biogenic fluxes simulated by land surface models show skill in detecting synoptic and regional-scale disturbances up to sub-seasonal time-scales, but they are subject to large seasonal and annual budget errors at global scale, usually requiring a posteriori calibration. This paper presents a scheme to diagnose and mitigate model errors associated with biogenic fluxes within an atmospheric CO<sub>2</sub> forecasting system. The scheme is an adaptive calibration referred to as Biogenic Flux Adjustment Scheme (BFAS) and it can be applied automatically in real time throughout the forecast. The BFAS method improves the continental budget of CO<sub>2</sub> fluxes in the model by combining information from three sources: (1) retrospective fluxes estimated by a global flux inversion system, (2) land-use information, (3) simulated fluxes from the model. The method is shown to produce enhanced skill in the daily CO<sub>2</sub> 10-day forecasts without requiring continuous manual intervention. Therefore, it is particularly suitable for near-real-time CO<sub>2</sub> analysis and forecasting systems.</p>

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