The stratospheric aerosol retrieval for SCIAMACHY limb observations will be improved. As shown in Ernst et al. (2013), the SCIAMACHY aerosol extinction profile observations are in very good agreement with co-located SAGE II observations in a global mean sense. Systematic inter-hemispheric differences exist at mid- and high latitudes, which are most likely related to the assumed aerosol phase function that does not accurately represent the actual stratospheric aerosol phase function. As part of this project we propose to apply a novel and promising approach to improve the stratospheric aerosol retrieval from SCIAMACHY limb-scatter observations, and in particular the knowledge of the aerosol phase function:
- Use SCIAMACHY solar occultation observations in the northern hemisphere to retrieve aerosol extinction at multiple wavelengths.
- Infer the aerosol size information (mode radius and distribution) from solar occultation aerosol extinction profiles.
- Subsequently apply the method to SCIAMACHY limb-scatter measurements.
The following specific tasks are required for the successful completion of this work package:
WP 1.1 Implementation of transmission profile retrievals at suitably selected wavelengths from SCIAMACHY solar occultation measurements.
WP 1.2 Inversion of spectral dependence of derived extinction profiles to separate different constituents causing extinction by both absorption and scattering. The outcome is aerosol extinction profiles at the selected wavelengths.
WP 1.3 Using a Levenberg-Marquardt retrieval scheme driving a Mie-scattering algorithm the spectral dependence of the derived aerosol extinction profiles is used to retrieve the mode radius and width of an assumed log-normal particle size distribution. Alternatively, the effective radius may be retrieved. This routine will then be applied to both SCIAMACHY solar occultation measurements as well as the limb-scatter observations as part of WP 2.
WP 1.4 Processing of the entire SCIAMACHY solar occultation data set.
WP 1.5 Validation of the retrieved aerosol extinction profiles and particle size information with independent observations (SAGE II, OSIRIS/Odin, and possibly GOMOS/Envisat).