Monday, 3 June 2002
Remote sensing of wind-blown dust at Ultraviolet wavelengths: the capability of collocated satellite and ground-based radiation measurements
The capability of detecting and quantifying mineral dust from the satellite TOMS (Total Ozone Mapping Spectrometer) observations and ground-based spectral radiation measurements at the UV wavelengths is examined by combining data and theoretical modeling. We perform the detailed analysis of the effects of aerosol optical properties and environmental conditions on TOMS radiances, TOMS Aerosol Index (AI), and surface downwelling irradiances. Calculations were done using a DISORT code which was modified to include polarized Rayleigh scattering and spectral absorption and scattering by aerosols and clouds. In particular, we explore whether a combination of collocated UV radiation ground-based measurements at Mauna Loa Observatory and TOMS satellite observations allows constraining the optical properties of aged Asian dust reaching Hawaii during the springs of 1998-2000. In addition, we analyze TOMS data in different parts of the world where mineral dust can be present. We demonstrate that, even by taking into account the composition and vertical distribution of aerosols and clouds, reliable quantification of dust properties from satellite UV-sensors such as TOMS remains an unresolved issue, though the qualitative characterization (e.g., presence of absence of UV-absorbing aerosols) are often possible.