Multispectral Retrieval Algorithm Development
The MOPITT ('Measurements of Pollution in the Troposphere') team in NESL/ACD is responsible for (1) developing and improving algorithms to determine tropospheric concentrations of carbon monoxide (CO) from raw instrument data, (2) validating the resulting products, and (3) applying those algorithms operationally to produce an archival record of tropospheric CO. MOPITT is currently the only satellite instrument equipped to observe carbon monoxide (CO) using both thermal-infrared (TIR) and reflected near-infrared (NIR) solar radiation. In principle, these complementary observations should allow space-based measurements of CO in the lower troposphere, where CO affects human health and where important sources of CO are located. Compared to currently available satellite products for CO, such 'multispectral' TIR/NIR retrievals promise better sensitivity to CO throughout the troposphere and should yield substantial improvements in estimates of CO emissions.
The MOPITT team has made great strides towards the release of MOPITT multispectral CO products in the last year. We presented the first retrieval results based on both TIR and NIR measurements and showed that the results were qualitatively reasonable. This work was recently published in the Journal of Geophysical Research (Worden, H. M., M. N. Deeter, D. P. Edwards, J. C. Gille, J. R. Drummond, and P. Nédélec, Observations of near-surface carbon monoxide from space using MOPITT multispectral retrievals, J. Geophys. Res., 115, D18314, doi:10.1029/2010JD014242, in press). The figure below demonstrates how retrievals of surface-level CO over Asia improve as the result of simultaneously exploiting MOPITT's TIR and NIR observations. The left panel shows TIR-only results, similar to the current 'Version 4 Product', whereas the right panel shows experimental TIR/NIR results. Both panels are seasonal averages for 2005-2008, September/October/November (SON) in central/east Asia. Enhanced sensitivity to surface-level CO is especially evident in central/east Asia where source regions for urban areas with high population density are clearly identifiable in the TIR/NIR results. New Version 5 retrieval products based on TIR and NIR observations will be made available to the community in 2011.