Atmospheric Chemistry and Physics, vol. 13, issue 6 (2013) pp. 3445-3462 Published by European Geosciences Union
We present satellite based ozone profile estimates derived by combining radiances measured at thermal infrared (TIR) wavelengths from the Aura Tropospheric Emission Spectrometer (TES) and ultraviolet (UV) wavelengths mea-sured by the Aura Ozone Monitoring Instrument (OMI). The advantage of using these combined wavelengths and instru-ments for sounding ozone over either instrument alone is im-proved sensitivity near the surface as well as the capability to consistently resolve the lower troposphere, upper tropo-sphere, and lower stratosphere for scenes with varying geo-physical states. For example, the vertical resolution of ozone estimates from either TES or OMI varies strongly by sur-face albedo and temperature. Typically, TES provides 1.6 de-grees of freedom for signal (DOFS) and OMI provides less than 1 DOFS in the troposphere. The combination provides 2 DOFS in the troposphere with approximately 0.4 DOFS for near surface ozone (surface to 700 hPa). We evaluated these new ozone profile estimates with ozonesonde measure-ments and found that calculated errors for the joint TES and OMI ozone profile estimates are in reasonable agree-ment with actual errors as derived by the root-mean-square (RMS) difference between the ozonesondes and the joint TES/OMI ozone estimates. We also used a common a pri-ori profile in the retrievals in order to evaluate the capability of different retrieval approaches on capturing near-surface ozone variability. We found that the vertical resolution of the joint TES/OMI ozone profile estimates shows signifi-cant improvements on quantifying variations in near-surface ozone with RMS differences of 49.9 % and correlation coeffi-cient of R = 0.58 for the TES/OMI near-surface estimates as compared to 67.2 % RMS difference and R = 0.33 for TES and 115.8 % RMS difference and R = 0.09 for OMI. This comparison removes the impacts of using the climatologi-cal a priori in the retrievals. However, it results in artificially large sonde/retrieval differences. The TES/OMI ozone pro-files from the production code of joint retrievals will use cli-matological a priori and therefore will have more realistic ozone estimates than those from using a common a priori volume mixing ratio profile.
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