Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 3 1 2003 10.5194/acpd-3-895-2003 http://www.atmos-chem-phys-discuss.net/3/895/2003/ http://www.atmos-chem-phys-discuss.net/3/895/2003/acpd-3-895-2003.html http://www.atmos-chem-phys-discuss.net/3/895/2003/acpd-3-895-2003.pdf 895 910 2003-02-18 Averaging kernels for DOAS total-column satellite retrievals H. J. Eskes K. F. Boersma Royal Netherlands Meteorological Institute, De Bilt, The Netherlands The Differential Optical Absorption Spectroscopy (DOAS) method is used extensively to retrieve total column amounts of trace gases based on UV-visible measurements of satellite spectrometers, such as ERS-2 GOME. In practice the sensitivity of the instrument to the tracer density is strongly height dependent, especially in the troposphere. The resulting tracer profile dependence may introduce large systematic errors in the retrieved columns that are difficult to quantify without proper additional information, as provided by the averaging kernel (AK). In this paper we generalise the AK concept to total column retrievals, and derive an explicit expression for the DOAS AK. It is shown that the additional AK information corrects for the <i>a priori </i> dependence of the retrieval. The availability of averaging kernel information as part of the total column retrieval product is essential for the interpretation of the observations, and for applications like chemical data assimilation and detailed satellite validation studies.