Using a two-layer model and mean temperature and pressure data from1954 through 1963, the authors analyse the atmospheric heat source andsink for January, April, July and October over the Northern Hemisphere.It is found that both the extent and intensity of the source and sink aregreater in winter than in summer. The strongest winter source is locatedon the Eurasian coast and a noticeable sink over the North American con-tinent, both becoming weaker in summer and the positions reversed. Situ-ations in spring and autumn are transitional with the autumnal patternmore similar to that of winter. Annual variation along 60°N and 40°N ismost prominent and least over the equatorial area and along 50°N. Data for1976 have been singled out for a seperate analysis and the trend is foundto be analogous to the long term mean with the exception that both sourceand sink’ show somewhat stronger intensity in July and October. It is also indicated that the dynamically computed source and sinkmatch quite well with the upper-air circulation, with the sources corre-sponding to troughs and sinks to ridges; the situation is reversed in sum-mer and deviation in location greater. The north-south shift of positionsof the source and sink is a significant factor in the seasonal change of thegeneral circulation.