Journal of Earth Science & Climatic Change
Open Access

Abstract

The summer monsoon sometimes brings severe droughts and intense flooding in many parts of the world including South Asian countries like Pakistan. So, an essential question arises ?how can we contribute better to manage the water resources of the region for the societal needs?. By data analysis, the basis of the dynamical processes associated with upper tropospheric conditions during the climatological mean Pakistan Summer Monsoon (PSM) and its extreme events has been developed in the current study. During PSM mature phase, the climatological-mean structure of atmosphere favors convective activity compared to premonsoon phase, by weakening the mid-upper level subsidence together with the increasing of moisture flux in the lower troposphere from Arabian Sea and Bay of Bengal. Specifically, the upper-level convergence and subsidence observed over Pakistan during pre-monsoon phase reallocates to northwest of Pakistan during mature phase. However, PSM extreme dry (wet) events were closely related with the upper tropospheric cyclonic (anticyclonic) anomaly northwest of Pakistan and the associated cold (warm) temperature anomaly. This anomalous state of upper tropospheric cyclonic (anticyclonic) circulation is accompanied with the anomalous upper level convergence (divergence) around Pakistan, which anomalously weakens (strengthens) the climatological mean PSM trough to suppress (enhance) the PSM activities. We found two possibilities i.e. Matsuno-Gill type atmospheric response from the tropics and/or the Rossby wave train along the Asian Jet to trigger, reinforce, and maintain the upper-tropospheric cyclonic (anticyclonic) circulation. However what (i.e. source) triggers the circulation anomaly from the tropics and/or extratropics needs further investigations to reach a definite conclusion.

Biography

Shakil Ahmad has completed his PhD at the age of 37 years from the University of Tokyo and presently working as Project Researcher since October 2011 at the University of Tokyo, Japan. He has published more than 5 papers in the reputed journals and also presented his PhD research in reputed couple of international conferences, like AGU, WCRP, EGU, etc.