GACP Projects
Cloudless Scene Identification for Aerosol Retrieval from TOMS Measurements
Omar Torres, PI
Charlie Wellemeyer, Co-I
Jay Herman, Co-I
Abstract: A method to derive aerosol optical depth over land and water surfaces using satellite based measurements in the near-UV spectral region has recently been documented. The technique can be used to retrieve information on different types of atmospheric aerosol, ranging from non- absorbing sulfates to highly UV-absorbing mineral dust. In addition to optical depth, the method provides information on aerosol absorptivity (i.e., single scattering albedo). This retrieval method can be applied to radiance measurements by the Total Ozone Mapping Spectrometer (TOMS) under cloud free conditions. The retrieval of UV-absorbing aerosol properties requires that the height of the aerosol layer be accurately known. Knowledge of aerosol height is not required for the optical depth retrieval of non-absorbing aerosols. In this project, we will combine the TOMS measurements of backscattered ultraviolet radiation and infrared observations by the THIR (1979-1985), OCTS (1996-1997) and SeaWIFS (1997-present) sensors, to identify cloud free areas where the near-UV method can be applied to retrieve optical depth of non-absorbing aerosols. We also intend to derive information on absorbing aerosols for specific events, within the same periods, for which the aerosol vertical distribution can be prescribed using lidar measurements or any other available aerosol profile information. The use of time and space collocated TOMS near-UV measurements and IR observations, will produce a multi-year aerosol optical depth data set that can be used as input in the development of a climatology of aerosol radiative forcing.
