Desert dust observation from space - Application of measured mineral component infrared extinction spectra

Abstract

Measured extinction spectra of six different components of desert dust have been used as input for a mineral dust retrieval algorithm for the Infrared Atmospheric Sounding Interferometer IASI based on Singular Vector Decomposition. The use of measured dust component extinction spectra rather than dust sample-based optical properties widely used in thermal infrared applications improves retrieval results significantly. Correlation between IASI derived dust optical depth (at 0.5µm) and AERONET sunphotometer observations from six months over Northern Africa, the Arabian Peninsula and Asia improved from formerly 0.623 to now 0.757 while the root-mean-square difference decreased from 0.322 to now 0.174 and the bias decreased (in terms of its absolute value) from 0.181 to 0.003. The dynamically adjusted e-1 envelope of the deviation histogram between AERONETand IASI dust AOD at 0.5µm is at 0.160 while 80% of all IASI observations are within AOD0.5µm +/- 0.2 of respective AERONET values. Spatial patterns of dust observations with the retrieval based on dust components compare very well with known features in terms of monthly mean gridded Aerosol Optical Depth. Although originally being developed for Northern Africa, the Arabian Peninsula and adjacent Oceans, the retrieval method performs equally well in Asian dust source regions and downwind areas. As a further strength it provides observations at day and night overpasses of the Metop spacecraft, thus twice daily.