Development and life cycle of the Indian monsoon: effect of the 30- 50 day oscillation

We found that the Indian monsoon circulation is portrayed by the annual cycle of the divergent circulation and develops as a classical, giant sea-breeze model. On the other hand, this monsoon system is modulated by the planetary-scale 30-50 day low-frequency mode to establish an onset-active-break-revival-retreat life cycle. The northeastward propagation of the planetary-scale 30-50 day mode over the Indian monsoon region induces transient local Hadley circulation. Through this type of circulation, the planetary-scale 30-50 day mode couples with and steers northward the low-level, 30-50 day monsoon troughs and ridges that originated around the equator. The northward migration of these low-level transient troughs and ridges cause, respectively, the deepening and filling of the monsson trough over central India. -from Authors