Tropospheric column amount of ozone retrieved from SCIAMACHY limb-nadir-matching observations

Abstract

Abstract. Tropospheric ozone, O3, has two sources: transport from the stratosphere and photochemical production in the troposphere. It plays important roles in atmospheric chemistry and climate change. In this manuscript we describe the retrieval of tropospheric O3 columns from limb-nadir matching (LNM) observations of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) instrument, which flies as part of the payload onboard the European Space Agency (ESA) satellite Envisat. This retrieval technique is a residual approach that utilizes the subtraction of the stratospheric O3 columns, derived from the limb observations, from the total O3 columns, derived from the nadir observations. The technique requires accurate knowledge of the stratospheric O3 columns, the total O3 columns, tropopause height, and their associated errors. The stratospheric O3 columns were determined from the stratospheric O3 profile retrieved in the Hartley and Chappius bands, based on SCIAMACHY limb scattering measurements. The total O3 columns were also derived from SCIAMACHY measurements, in the nadir viewing mode using the Weighting Function Differential Optical Absorption Spectroscopy (WFDOAS) technique in the Huggins band. Comparisons of the tropospheric O3 columns from SCIAMACHY and collocated measurements from ozonesondes, in both hemispheres between January 2003 and December 2011 show agreement to within 2–5 DU (1 DU = 2.69 × 1016 molecules cm−2). Comparison of tropospheric O3 from SCIAMACHY with the results from ozonesondes, the Tropospheric Emission Spectrometer (TES), and the LNM method combining Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) data (hereinafter referred to as OMI/MLS), have been investigated. We find that all four retrieved data sets show agreement within the error bars and exhibit strong seasonal variation, which differs in amplitude. The spatial distribution of tropospheric ozone observed shows pollution plumes related to the release of precursors at the different seasons in both hemispheres.