explain the onset and withdrawl of monsoon
The onset is defined in terms of zonal asymmetric temperature anomaly and withdrawal is defined in terms of vertical wind shear between 850 hPa and 200 hPa. The onset and withdrawal dates determined by these two indexes are also consistent with the onset/withdrawal timing of the real monsoon circulation. The onset and withdrawal day values are also reasonably correlated with the strength of the monsoon and to some of its boundary forcing over the Bay of Bengal regions.