Influences of the monsoon trough and Arabian heat low on summer rainfall over the United Arab Emirates

AbstractThe factors responsible for rare summertime rainfall over portions of the United Arab Emirates (UAE), which have not been previously explored in detail, are elucidated with the Climate Forecast System Reanalysis and WRF mesoscale model simulations. The simulations show associations between active phases of the southwest Asian monsoon and intensification of the Arabian Heat Low, leading up to UAE rainfall events. Variability in location and strength of the Arabian Heat Low circulation, which differs from the static portrayal in climatological MSLP, can affect the development of deep convection over the UAE. Analysis of the vorticity equation for a two-day case study period confirms that convergence is solely responsible for spin-up and maintenance of the primary heat-low circulation. Convergence is also responsible for spin-up of a separate cyclonic circulation over the eastern UAE, which propagates offshore to the Arabian Gulf during morning hours. This cyclonic circulation advects moist air onsho...