Seasonal distributions of diabatic heating during the First GARP Global Experiment

The seasonal and annual global distributions of diabatic heating during the First GARP Global Experiment (FGGE) are estimated using the isentropic mass continuity equation. The data used are from the FGGE Level IIIa analyses generated by the United States National Meteorological Center. Spatially and temporally coherent diabatic heating distributions are obtained from the isentropic planetary scale mass circulation that is forced by large-scale heat sources and sinks. The diabatic heating in the Northern Hemisphere is closely associated with the distribution of land and ocean. While cooling prevails over Eurasia and North America and heating occurs along the east coasts of these two continents during northern winter, a contrasting situation exists during northern summer with heating over most of the continents and cooling over the oceans where subtropical anticyclonic circulations prevail. Heating in the tropics, mostly from moist convection, has considerable longitudinal variations which change seasonally. Of particular importance is the seasonal progression of the primary centre of heating within the planetary scale Asiatic monsoon which is located over the western equatorial Pacific during northern winter and near the Philippines and Southeast China during northern summer.