TransCom satellite intercomparison experiment: Construction of a bias corrected atmospheric CO 2 climatology
Résumé
[1] A model-based three-dimensional (3-D) climatology of atmospheric CO 2 concentrations has been constructed for the analysis of satellite observations, as a priori information in retrieval calculations, and for preliminary evaluation of remote sensing products. The locations of ground-based instruments and the coverage of aircraft in situ measurements are limited and do not represent the full atmospheric column, which is a primary requirement for the validation of satellite data. To address this problem, we have developed a method for constructing a 3-D CO 2 climatology from the surface up to approximately 30 km by combining information from in situ measurements and several transport models. The model-simulated CO 2 concentrations have been generated in the framework of the TransCom satellite experiment. The spatial and temporal biases of the transport-model-derived data set have been corrected using in situ CO 2 measurements in the troposphere and in situ profiles of the mean age of air in the stratosphere. The constructed multimodel mean CO 2 climatology represents the seasonal cycle and the inter-hemispheric gradient better than each transport model. Our approach performs well near the surface and in regions where the observational network is relatively dense. The column-mean CO 2 of the constructed climatology was reduced by ∼1 ppm from that of a single transport models, consistent with model validation against measurements of the CO 2 total column.
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