Large-scale cross-tropopause mass fluxes are\uddiagnosed globally from 1979 to 1989 for Northern Hemisphere winter conditions\ud(December, January, and February). Results of different methods of approaches\udwith regard to the definition of the tropopause and the way to calculate the\udmass fluxes are compared and discussed. The general pattern of the mass exchange\udfrom the tropopause into the stratosphere and vice versa agrees fairly well when\udusing different methods, but the absolute values can differ up to 100%.\ud
An inspection of the temporal development of the mass fluxes\udfor solstice conditions indicates a complex picture. Whereas a permanent\udsignificant downward flux from the stratosphere into the troposphere is detected\udfor latitude regions nearly between 25°N and 40°N and\udbetween 30°S and 50°S (initiated by the poleward\udbranches of the Hadley cells), a non-uniform behaviour is observed at higher\udlatitude bands. Periods of strong mass exchange from the troposphere into the\udstratosphere are disrupted by periods of an opposite mass exchange. A comparison\udof the stratoshere-troposphere (ST) exchange with the exchange at higher\udaltitudes through surfaces, quasi-parallel to the tropopause, excludes a general\udconnection. Only a few strong upward directed ST mass exchange events have\udcounterparts at higher altitudes. The composition of the stratosphere may be\udinfluenced directly by the ST exchange only in a thin layer above the tropopause
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