A refinement for the Rayleigh radiance computation with variation of the atmospheric pressure
Abstract:The Rayleigh scattering radiance at the top of the atmosphere (TOA) depends on the surface atmospheric pressure. In processing the Coastal Zone Color Scanner (CZCS) imagery, Gordon et al. ( Applied Optics , 27, 862–871, 1988) developed a simple formula to account for the Rayleigh radiance changes with the variation of the surface atmospheric pressure. For the atmospheric pressure changes within ±3%, the accuracy of the Gordon et al. (1988) formula in computing the Rayleigh radiance is usually within 0.4%, 0.3%, 0.15% and 0.05% for the wavelengths 412, 443, 555 and 865 nm, respectively. This could result in up to ~3% uncertainty in the derived water-leaving radiance at the blue wavelengths for very clear atmospheres. To improve the performance, a refinement to the Gordon et al. (1988) formula is developed based on the radiative transfer simulations. The refined scheme can produce Rayleigh radiance with an uncertainty within 0.1% (often within 0.05%) at the blue, while uncertainty is within 0.05% for the green to near-infrared wavelengths. The refined algorithm has been implemented in the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data processing system. Results from the SeaWiFS data show the improved ocean colour products in the southern oceans where consistently low atmospheric pressures are usually observed. This could also significantly improve the performance of the Rayleigh radiance computations over the high altitude lakes. In addition, with the refined algorithm, the same Rayleigh radiance tables can be possibly used for the various ocean colour satellite sensors in which there are slightly different sensor spectral band characterizations.
Document Type: Research Article
Affiliations: University of Maryland Baltimore County, NASA Goddard Space Flight Center, Code 970.2, Greenbelt, Maryland 20771, USA
Publication date: December 1, 2005