Abstract
Surface solar irradiance (SW↓) was derived over the extended Amazon Basin using AVHRR observations from polar-orbiting satellites during four July months (1983–1986). Observations from the geostationary satellite GOES for July 1983 were also used to assess diurnal effects. Both satellite datasets are part of the Satellite Cloud Climatology Project (ISCCP) B3 product. It was demonstrated that it is now possible to derive long-term surface SW↓, which can be useful in climate studies, and that the accuracy of the derived fields is sufficient to detect interannual differences that can exceed at times 70 W m−2. The variability of the daily totals of SW↓ from the monthly means was similar during three of the four years investigated, yet, during the El Niño year of 1982–83, north of 10°N such variability increased drastically. This increase could be attributed to a changed pattern of convective activity as a result of higher SST off the coast of Peru. For the first time, the El Niño influence on the large-scale variability of the SW↓ was demonstrated.
