Abstract
By data analysis, an attempt has been made to identify the associated processes which support the Pakistan Summer Monsoon (PSM) mature phase in comparison with pre-monsoon phase. We found that during pre-monsoon phase, the subsidence associated with upper level strong convergence suppresses the convective activities around Pakistan. However, during the PSM mature phase, (1) the mid-upper tropospheric warming which causes the reversal of meridional temperature gradient (MTG), further gets strengthened and expands, and (2) the subsidence significantly weakens associated with the weakening of the upper level convergence and vortex stretching around Pakistan. Simultaneously, the low level trough around Pakistan becomes stronger enough for the maturity of PSM, together with the deflected southeasterly and southwesterly moisture flux from the Bay of Bengal (BoB) and Arabian Sea (AS) increases to intrude over Pakistan. The current finding will be useful for understanding the processes associated with the anomalous tropospheric conditions during extreme PSM events.
