Aerosols, Climate and Satellite Based Retrieval of Aerosol Optical Depth
Chylek, P., Henderson, B., and Davis, A.B., Los Alamos National Laboratory, Space and Remote Sensing Sciences
Fourteenth Atmospheric Radiation Measurement (ARM) Science Team Meeting
If we want to determine the top of the atmosphere aerosol radiative forcing with the accuracy of 0.5 W/m2 we need to know the aerosol optical depth (AOD) over the land with the accuracy of 0.015. None of the current operational satellite based instruments for AOD retrieval has been able to achieve this accuracy. The RMSE (Root Mean Square Error) of the AVHRR (Advanced Very High Resolution Radiometer) is typically between 0.06 and 0.15, while the RMSE of the MODIS (MOderate resolution Imaging Spectroradiometer) over the land has been estimated to be 0.05+0.2AOD, which varies between 0.07 and 0.21 for AOD between 0.1 and 0.8. Theoretical analysis suggests that the uncertainties in aerosol phase function (due to uncertainties in aerosol shape, size distribution and optical properties) are the major obstacles for accurate aerosol optical depth retrieval. These uncertainties lead to a much larger error in aerosol optical depth retrieval at large scattering angles (usually at close to nadir view), than at the off nadir views at medium scattering angles. The Department of Energy research satellite instrument, the Multispectral Thermal Imager (MTI), is capable to retrieve the aerosol optical depth with the accuracy of 0.03 using the off nadir view at medium scattering angles. Based on our theoretical analysis and on the MTI experience we suggest that to achieve the required accuracy in the AOD retrieval the future satellite instruments using single or dual-view should use off nadir views and combination of visible and near infrared spectral bands.
Note: This is the poster abstract presented at the meeting; an extended version was not provided by the author(s).
