Atmos. Chem. Phys. Discuss., 12, 6283-6329, 2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Comparison of improved Aura Tropospheric Emission Spectrometer (TES) CO2 with HIPPO and SGP aircraft profile measurements
S. S. Kulawik1, J. R. Worden1, S. C. Wofsy2, S. C. Biraud3, R. Nassar4, D. B. A. Jones5, E. T. Olsen1, and G. B. Osterman, and the TES and HIPPO teams1
1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
2Harvard University, Cambridge, MA 02138, USA
3Lawrence Berkeley National Laboratory, Earth Sciences Division, Berkeley, CA 94720, USA
4Environment Canada, Toronto, Ontario, Canada
5University of Toronto, Department of Physics, Toronto, Ontario, M5S 1A7, Canada

Abstract. Comparisons are made between mid-tropospheric Tropospheric Emission Spectrometer (TES) carbon dioxide (CO2) satellite measurements and ocean profiles from three Hiaper Pole-to-Pole Observations (HIPPO) campaigns and land aircraft profiles from the United States Southern Great Plains (SGP) Atmospheric Radiation Measurement (ARM) site over a 4-yr period. These comparisons are used to characterize the bias in the TES CO2 estimates and to assess whether calculated and actual uncertainties and sensitivities are consistent. The HIPPO dataset is one of the few datasets spanning the altitude range where TES CO2 estimates are sensitive, which is especially important for characterization of biases. We find that TES CO2 estimates capture the seasonal and latitudinal gradients observed by HIPPO CO2 measurements; actual errors range from 0.8–1.2 ppm, depending on the campaign, and are approximately 1.4 times larger than the predicted errors. The bias of TES versus HIPPO is within 0.85 ppm for each of the 3 campaigns; however several of the sub-tropical TES CO2 estimates are lower than expected based on the calculated errors. Comparisons of aircraft flask profiles, which are measured from the surface to 5 km, to TES CO2 at the SGP ARM site show good agreement with an overall bias of 0.1 ppm and rms of 1.0 ppm. We also find that the predicted sensitivity of the TES CO2 estimates is too high, which results from using a multi-step retrieval for CO2 and temperature. We find that the averaging kernel in the TES product corrected by a pressure-dependent factor accurately reflects the sensitivity of the TES CO2 product.

Citation: Kulawik, S. S., Worden, J. R., Wofsy, S. C., Biraud, S. C., Nassar, R., Jones, D. B. A., Olsen, E. T., and Osterman, and the TES and HIPPO teams, G. B.: Comparison of improved Aura Tropospheric Emission Spectrometer (TES) CO2 with HIPPO and SGP aircraft profile measurements, Atmos. Chem. Phys. Discuss., 12, 6283-6329, doi:10.5194/acpd-12-6283-2012, 2012.
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