The development of a satellite‐based insolation model for the tropical western Pacific Ocean

Concurrent pyranometer and GMS (Japanese Geostationary Meteorological Satellite) data were collected for the western tropical Pacific during a 21‐month period in 1987 and 1988. Data from 10 pyranometer stations in 1987 were used to build a satellite insolation model. Such processes as surface albedo, narrow band to broad band conversion, and depletion by water vapour and aerosols were taken into account. The model was then tested with an independent pyranometer data set comprising 9 months in 1988. Results show that aerosol depletion is site‐specific, with typical long‐term values ranging from 19·8 per cent of the extraterrestrial value for Kuala Lampur, to 4·8 per cent for Willis Island. Monthly insolation may be mapped over the oceanic regions of the study area assuming that the Willis Island aerosol depletion values apply. The model gave root‐mean‐square (RMS) errors of 14·08 W m −2 when tested against all monthly average pyranometer data for 1988. Corresponding RMS errors are 11·67 W m −2 when only Willis Island data are used. Sources of errors are discussed, as are suggestions for future research.