Breaks in the Indian summer monsoon as a phenomenon of interaction between the easterly and the sub-tropical westerly jet streams

摘要: The present paper contains the results of study a synoptic situation over India during period 8 days in which normal monsoon conditions were followed by break and further return to monsoon. This has shown that breaks monsoon, trough middle latitude westerlies with jet embedded it increases considerably its amplitude gets retarded as moves into Tibetan Plateau on account entering region weaker basic current. large-amplitude weakens or destroys completely high at 500 mb level appreciably easterlies higher levels south Himalayas. Protruding Pakistan, large contributes development heavy rainfall along near foot Himalayas is characteristic conditions. southward protrusion subsequent movement eastward, also indirectly responsible for corresponding shift Iran Arabia, which, turn, seems lead formation secondary core west 80° E between 20° N 25° N. Consequent above developments, westerly had retreated north time onset reenters Indo-Pakistan sub-continent breaks. Thus we see conditions, remarkable spectacle two jets entirely different types—the easterly sub-tropical westerly—within short latitudinal distance each other dynamically interacting other. detailed study, supplemented general examination monthly mean 700 charts northern hemisphere 10 years, suggests active closely associated index circulation latitudes Asia neighbourhood, while weak low same region. DOI: 10.1111/j.2153-3490.1962.tb01346.x