Stratospheric and upper tropospheric aerosol retrieval from limb scatter signals

Abstract

Solar occultation observations made by the SAGE family of space instruments have provided a record of global stratospheric and upper tropospheric aerosols that extends over 25 years. Since the demise of SAGE II and SAGE III however, there are presently no space instruments devoted to continuing this aerosol data set. The paper aims to demonstrate that aerosol extinction profiles, together with a moment of the size distribution, can be accurately retrieved from Limb Scatter measurements. The methodology is described, and retrieval examples are presented using data from a Limb Scatter instrument, namely SAGE III. The retrieved extinction profiles are compared with SAGE II and SAGE III occultation aerosol products for a series of wavelengths. It is shown that the relative retrieval accuracy is good (less than 5%), with a relative precision on the order of 25%. Once operational, it is planned to apply the retrieval method to the data collected by the two still-operating Limb Scatter instruments (namely OSIRIS and SCIAMACHY) in order to extend the aerosol data record into the present time. In the future, the OMPS Limb Profiler instrument, which is presently manifested on NPP with a launch date of September 2009, will be used for additional stratospheric aerosol research.