Aerosol Retrievals from Multi-Angular Satellite Observations Using GRASP Algorithm: Achievements and Perspectives.

Based on the numerous theoretical and practical studies Multi-Angular Polarimeter (MAP) is considered as the most appropriate satellite instrument for comprehensive retrieval of properties of aerosols and a large number of advanced space polarimeters are planned to be deployed in coming years for monitoring of the atmospheric aerosols. Nevertheless, until recently practical utilization of aerosol products from polarimetry was very limited due to the relatively small amount of polarimetric observations and especially due to complexity of the polarimetric retrievals. The presentation discusses recently developed GRASP (Generalized Retrieval of Atmosphere and Surface Properties) algorithm and its utilization for generating enhanced aerosol properties from polarimetric observations.

GRASP is a new-generation algorithm developed for deriving extensive aerosol properties from all remote sensing instruments. GRASP is based on highly advanced statistically optimized fitting implemented as multi-term least-square minimization allowing use of multiple a priori constraints which had earlier been successfully implemented for aerosol retrievals from ground-based AERONET radiometers. At the same time, many new ideas were included in GRASP concept and present algorithm is highly flexible and versatile. For example, GRASP can retrieve both aerosol and underlying surface properties simultaneously from multispectral satellite observations using additional a priori constraints on the spectral variability of the land bidirectional reflection distribution function (BRDF) and can operate by relying on so-called the multi-pixel concept wherein the statistically optimized retrieval is performed simultaneously for a large group of pixels (Dubovik et al., 2011).

Several enhanced aerosol products for full archive of POLDER observation using GRASP algorithm . The results were extensively validated, analyzed and compared with conventional aerosol retrievals form MODIS observations. The presentation overviews the scope and accuracy for retrievals of diverse aerosol parameters including size distribution, refractive index, absorption, particle non-sphericity, vertical profile, etc. as well as a possibility of identifying the aerosol composition from MAP observations.

The presentation, also discusses the activities realized using GRASP in preparation of operational aerosol retrieval for future 3MI/EPS-SG and MAP/CO2M mission. In addition, the applications of GRASP algorithm to the data of recently deployed commercial polarimeter GAPMAP will be demonstrated.