Stratospheric and upper tropospheric aerosol retrieval from Limb Scatter signals

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 20 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 will show that aerosol extinction profile, together with a moment of the size distribution, can be accurately retrieved from limb scatter measurements. The methodology will be described, and retrieval examples will be presented using data from two limb scatter instruments, namely SAGE III and OSIRIS. The retrieved extinction profiles will be compared with SAGE II and SAGE III occultation aerosol products for a series of wavelengths. It will be shown that the retrieval accuracy is good (less than 5%), with precision on the order of 25%. Once operational, the retrieval method will be applied to the data collected by the 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 (launch date = September 2009) will be used to update the global aerosol record.