Articles | Volume 17, issue 8
Atmos. Chem. Phys., 17, 5407–5438, 2017
Atmos. Chem. Phys., 17, 5407–5438, 2017

Research article 27 Apr 2017

Research article | 27 Apr 2017

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 Tanaka8 Susan S. Kulawik et al.
  • 1Bay 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

Abstract. We present two new products from near-infrared Greenhouse Gases Observing Satellite (GOSAT) observations: lowermost tropospheric (LMT, from 0 to 2.5 km) and upper tropospheric–stratospheric (U, above 2.5 km) carbon dioxide partial column mixing ratios. 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 column mixing ratios significantly improve upon the Atmospheric CO2 Observations from Space (ACOS) and GOSAT (ACOS-GOSAT) initial guess and/or a priori, with distinct patterns in the LMT and U seasonal cycles that 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 hemispheric 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 a CO–CO2 emission factor comparable to published values. The difference of LMT and U, useful for evaluation of model transport error, has also been validated with a monthly average error of 0.8 (1.4) ppm for ocean (land). LMT is more locally influenced than U, meaning that local fluxes can now be better separated from CO2 transported from far away.

Short summary
We introduce new vertically resolved GOSAT products that better separate locally and remotely influenced CO2. Current GOSAT column results for CO2 (XCO2) are sensitive to fluxes on continental scales, whereas flux estimates from surface and tower measurements are affected by sampling bias and model transport uncertainty. These new GOSAT measurements of boundary layer CO2 are validated against aircraft and surface observations of CO2 and are compared to vertically resolved MOPITT CO.
Final-revised paper