Time Series of CH4 and CO2 Profiles derived from SCIAMACHY Solar Occultation Measurements with Onion Peeling DOAS
NoŽl, Stefan; Bramstedt, Klaus; Rozanov, Alexei; Liebing, Patricia; Reuter, Max; Bovensmann, Heinrich; Burrows, John P.
IUP, University of Bremen, GERMANY
In the context of the ESA GHG-CCI project the retrieval of greenhouse gas stratospheric profiles from solar occultation measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on ENVISAT has been further improved. The retrieval is performed using a method called "Onion Peeling DOAS" (ONPD) which combines an onion peeling approach with a weighting function DOAS (Differential Optical Absorption Spectroscopy) fit. The ONPD approach can in principle be applied to all gases measured by SCIAMACHY. Within the GHG-CCI project main focus was placed on the retrieval of stratospheric methane and carbon dioxide. Corresponding data sets covering the whole SCIAMACHY time series (August 2002 to April 2012) have been derived. Due to the sun-fixed orbit of ENVISAT the solar occultation measurements are restricted to the latitudinal range between about 50°N and 70°N. By use of updated pointing information and optimisations in the data selection and retrieval approach the altitude range for reasonable CH4 and CO2 data could be extended to about 15 to 45 km. As measurements of the stratospheric distribution of greenhouse gases are generally sparse, the new SCIAMACHY data sets, which cover almost ten years, can provide valuable information about changes in the middle atmosphere. In this presentation, we will describe the modifications to the retrieval and show time series of the SCIAMACHY products. Furthermore, to assess the quality of the newly derived data sets, they will be compared with independent sources.