Wednesday, 7 August 2013: 8:30 AM
Multnomah (DoubleTree by Hilton Portland)
Convection-permitting numerical experiments using the Weather Research and Forecasting (WRF) model are performed to examine the impact of a thermally-driven mountain-plains solenoid (MPS) on the diurnal variation of warm-season precipitation over Northern China. The focus of the analyses is a 15-day simulation that uses the 8-day average of the NCEP GFS gridded analyses at 0000 UTC between 17 and 24 June 2004 for the initial conditions and the 8-day averages at 0000, 0600, 1200, and 1800 UTC for the lateral boundary conditions. Despite differences in rainfall intensity and location, the control experiment captures the essence of the observed diurnal variation of warm-season precipitation in North China. Consistent with observations, the simulated local precipitation peak initiates in the afternoon on the eastern edge and the immediate lee of the mountain ranges due to the upward branch of the MPS. The peak subsequently propagates downslope and southeastward along the steering-level mean flow, reaching the central North China Plains around midnight and early morning hours resulting in a broad area of nocturnal precipitation maxima over the central plains. Sensitivity experiments show that besides the impact of the MPS, cold pool dynamics play an essential role in the propagation and maintenance of the precipitation peak over the plains.
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