Abstract
While Tsuchiya and Fujita (1966) were investigating mesoscale features of winter monsoon clouds over Japan by using satellite photographs and radiation data, a mesoscale upper-air disturbance was found to exist over the region of monsoon snowfall on the windward side of Hokkaido and northern Honshu as they block the strong northwesterly monsoon. A relatively dense upper-air network with an average spacing of 200km (120miles) permitted us to analyze mesosynoptically the vertical structure of the upper-air mesosystem. The system was characterized by a cold dome directly above which warm dry air descended from an eroded tropopause. Analyses of 1963 and 1964 data revealed that the upper-air mesosystem stays more or less over the regions of monsoon snowfall while high-level winds blow through it within a few hours. To explain the formation and development of this upper-air meso- system, a mechanism of mesoscale jet stream called “snowstorm mesojet ” has been proposed.
