Utilization of O4 slant column density to derive aerosol layer height from a space-borne UV–visible hyperspectral sensor: sensitivity and case study

摘要

The sensitivities of oxygen-dimer (O) slant column densities (SCDs) tochanges in aerosol layer height are investigated using the simulatedradiances by a radiative transfer model, the linearized pseudo-sphericalvector discrete ordinate radiative transfer (VLIDORT), and the differentialoptical absorption spectroscopy (DOAS) technique. The sensitivities of theO4 index (O4I), which is definedas dividing O SCD by 10 molecules cm, to aerosol types and optical properties are alsoevaluated and compared. Among the O absorption bands at 340, 360, 380,and 477 nm, the O absorption band at 477 nm is found to be the mostsuitable to retrieve the aerosol effective height. However, the O4I at 477 nm is significantly influenced not only by the aerosol layer effectiveheight but also by aerosol vertical profiles, optical properties includingsingle scattering albedo (SSA), aerosol optical depth (AOD), particle size,and surface albedo. Overall, the error of the retrieved aerosol effectiveheight is estimated to be 1276, 846, and 739 m for dust, non-absorbing, andabsorbing aerosol, respectively, assuming knowledge on the aerosol verticaldistribution shape. Using radiance data from the Ozone Monitoring Instrument(OMI), a new algorithm is developed to derive the aerosol effective heightover East Asia after the determination of the aerosol type and AOD from theMODerate resolution Imaging Spectroradiometer (MODIS). About 80 % ofretrieved aerosol effective heights are within the error range of 1 kmcompared to those obtained from the Cloud-Aerosol Lidar with OrthogonalPolarization (CALIOP) measurements on thick aerosol layer cases.