Lower-tropospheric CO2 from near-infrared ACOS-GOSAT observations
Susan S. Kulawik1, Chris O'Dell2, Vivienne H. Payne3, Le Kuai4, Helen M. Worden5, Sebastien C. Biraud6, Colm Sweeney7, Britton Stephens7, Laura T. Iraci8, Emma L. Yates1, and Tomoaki Tanaka81Bay Area Environmental Research Institute, Sonoma, CA, USA 2Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, CO, USA 3Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA 4UCLA Joint Institute for Regional Earth System Science and Engineering (JIFRESSE), Los Angeles, CA, USA 5Atmospheric Chemistry Observations & Modeling (ACOM) Laboratory National Center for Atmospheric Research, Boulder CO 80307 USA 6Lawrence Berkeley National Laboratory, Earth Science Division, Berkeley, CA, USA 7NOAA/ESRL/GMD, Boulder, CO, USA 8NASA Ames, Moffett Field, CA, USA
Received: 10 Aug 2016 – Accepted for review: 19 Sep 2016 – Discussion started: 07 Oct 2016
Abstract. We present two new products from near-infrared GOSAT observations: lower tropospheric (LMT, from 0–2.5 km) and upper tropospheric/stratospheric (U, above 2.5 km) carbon dioxide partial columns. We compare these new products to aircraft profiles and remote surface flask measurements and find that the seasonal and year-to-year variations in the new partial columns significantly improve over the ACOS-GOSAT initial guess/a priori, with distinct patterns in the LMT and U seasonal cycles which match validation data. For land monthly averages, we find errors of 1.9, 0.7, and 0.8 ppm for retrieved GOSAT LMT, U, and XCO2; for ocean monthly averages, we find errors of 0.7, 0.5, and 0.5 ppm for retrieved GOSAT LMT, U, and XCO2. In the southern hemisphere biomass burning season, the new partial columns show similar patterns to MODIS fire maps and MOPITT multispectral CO for both vertical levels, despite a flat ACOS-GOSAT prior, and CO/CO2 emission factor consistent with published values. The difference of LMT and U, useful for evaluation of model transport error, has also been validated with monthly average error of 0.8 (1.4) ppm for ocean (land). The new LMT partial column is more locally influenced than the U partial column, meaning that local fluxes can now be separated from CO2 transported from far away.
Kulawik, S. S., O'Dell, C., Payne, V. H., Kuai, L., Worden, H. M., Biraud, S. C., Sweeney, C., Stephens, B., Iraci, L. T., Yates, E. L., and Tanaka, T.: Lower-tropospheric CO2 from near-infrared ACOS-GOSAT observations, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-720, in review, 2016.