Simulation of Synoptic and Sub-Synoptic Scale Phenomena Associated With the East Asian Monsoon Using a High-Resolution Gem

An assessment is made on the performance of a global atmospheric general circulation model with a horizontal resolution of approximately 55 km in reproducing various synoptic and subsynoptic scale phenomena related to the East Asian monsoon. In accord with observations, the simulated summer monsoon rains in the East Asian sector are organized about zonally elongated ‘Meiyu-Baiu’ (Plum Rain) systems. A detailed case study is performed on a prominent rainy episode in the simulation. The model is capable of reproducing the observed intense gradients in humidity and moist static stability in the vicinity of the Meiyu-Baiu front. The axis of the Meiyu-Baiu rainband in this event is aligned with the trajectory of a succession of mesoscale cyclonic vortices, which originate from southwestern China and travel northeastward over the Yangtze River Basin. Analysis of the synoptic development during a severe wintertime cold air outbreak over East Asia demonstrates the ability of this model to simulate the southeastward advance of intense cold fronts. The patterns of sea level pressure and surface temperature changes in the vicinity of these fronts on daily and hourly time scales are in accord with observations.