Intercomparison between multi-angle imaging spectroradiometer (MISR) and sunphotometer aerosol optical thickness in dust source regions over China: Implications for satellite aerosol retrievals and radiative forcing calculations

Abstract

The multi-angle imaging spectroradiometer (MISR) aerosol, optical thickness (AOT) product (τ MISR) was compared with sunphotometer AOT (τ sp) at Dunhuang (40.09°N, 94.41°E), located near the Takalamakan and Gobi dust source regions in China, during March-November 2000. This study is unique because AOT measurements from the ground are not routinely available at or near dust source regions. The τ MISR and τ sp are highly correlated, with linear correlation coefficients (R) ranging from 0.85 to 0.95 depending on the different comparison criteria used to assess the MISR retrievals. With one exception where τ MISR shows large differences (>0.3) when compared with τ sp during the passage of a dust front, all other collocated τ sp/τ MISR pairs are highly correlated with R > 0.9 and with root-mean-square error of 0.06 when retrieval conditions are favourable. Overall, τ MISR systemically over-estimate τ sp by 0.05, but they all fall within the predicted uncertainties (0.05 or 20% of τ sp, whichever is larger). Due to diurnal change of AOT, the difference between daily averaged τ sp values and τ MISR reported during MISR overpass time is about 0.09. We discuss the implications of these results for satellite aerosol retrievals and radiative forcing studies. Copyright © Blackwell Munksgaard, 2004.