Case Study of a Maximum Heavy Rain Event and Its Dynamics over United Arab Emirates during 13 December 2009

Abstract:

In this study the analysis of a heavy rainfall event on 13 December 2009 over the United Arab Emirates (UAE) region is presented. This event, with daily maximum rainfall greater than 90 mm is observed with ina span of 9 hours which is very high over this region. The main aim is to understand the synoptic features and its large scale dynamics associated with this event. The favorable conditions responsible for the formation of the event have been studied using surface and upper air data sets. The relation between heavy precipitation event and the mid and low tropospheric conditions is investigated by using National Center for Environmental precipitation (NCEP) reanalysis data sets. The dynamics associated with the heavy rainfall event is studied by using composite maps. The synoptic situation with low level trough and strong south westerly wind with high equivalent potential temperatures across the baroclinic zone is one of the important patterns that favor the formation of convection or instability conditions. The existence of anti-cyclonic flow over the Arabian Peninsula causes the moisture transport from the nearby seas, which plays a major role in fueling the precipitation processes over this region. This event is characterized by the south westerly flow and eastward propagating waves, which causes wave amplification and breaking the intrusion of mid latitude upper level troughs into the subtropics that trigger storm activity or convection over this region. The combination of advected moisture, low level warm and upper level cold air causes tropospheric instability. Strong upper level divergence over the Mediterranean Sea and convergence over the southern parts of the Saudi Arabia is observed. More details will be presented during conference.