On the Earth's surface energy exchange determination from ERS satellite ATSR data: Part 2. Short-wave radiation

This is the second in a series of papers which discusses determination of the Earth's surface energy exchange from ERS satellite Along-Track Scanning Radiometer (ATSR) data. The paper concentrates on short-wave radiation on sea and land surfaces. In this paper, three methods were used to determine solar irradiance by using ERS ATSR-2 data. We referred to them as `D scheme', `T scheme' and `O scheme'. Intercomparisons of the three schemes were carried out. The schemes were applied to the land and sea areas. The visible and near-infrared reflectances were derived from ERS-2 ATSR-2 spectral bands by using the atmospheric radiative transfer model developed by Xue and Cracknell. The narrowband reflectances are combined into a measure of surface albedo by use of a weighted averaged scheme. The schemes were applied to the land and sea areas in UK and deforestation area in Brazil. The D scheme can give solar spectral irradiance but can not give broadband solar irradiance because of the wavelength limit of sensor visible bands. The T scheme and O scheme can give good broadband solar irradiance but can not give solar spectral irradiance. The O scheme was developed by Oberhuber, which was used to create climatological datasets for GCMs. The O scheme also includes the effects of humidity and surface temperature. The O scheme is better used for daily or monthly averaged solar radiation. The other two schemes can also be developed to determine the hourly or daily solar irradiance. The results show that it is now possible to derive longterm surface solar irradiance from ATSR-2 data which can be useful in climate and hydrological studies. However, our current analysis is restricted to a small range of conditions and needs to be extended to a larger dataset.