Monsoon activity and coupling between low-latitude and high-latitude stratospheric activities

From a Fourier analysis of the monthly mean values of the Northern Hemispheric geopotential heights at 30- and 50-mb levels, for the period 1972-1979, the transports of momentum and of sensible heat, and the energy conversion terms, C(K sub(E) , K sub(Z) ) and C(A sub(Z) , A sub(E) ), were computed along 30 and 60 degrees N lat. The variation in these dynamic parameters at 60 degrees N, in relation to monsoon activity in low latitudes and the easterly and westerly phases of the QBO over Gan Island, suggest that a coupling may exist between the high-latitude stratospheric changes and low-latitude monsoon activity, and that the low-latitude stratospheric activity modulates high-latitude circulation, confirming the results obtained by Holton and Tan (1980) and by Labitzke (1983). The study of the low-latitude stratospheric changes in relation to the high-latitude warmings also indicates a linkage between the low- and high-latitude features.