主讲人：Dr. Kalli Furtado
UK Met Office, Exeter, UK
题目：Convection permitting simulations of the climate of East Asia: diurnal cycle and extremes
活动号：184 757 460，密码：888888
A limited area convection permitting model (CPM) based on the Met Office Unified Model, with a 0.04 degree (4.4 km) horizontal grid spacing, is used to simulate an entire warm-season of the East Asian monsoon (from April to September. The simulations are compared to rain gauge observations, reanalysis and to a lower resolution regional model with a 0.12 degree (13.2 km) grid spacing that has a parameterization of subgrid-scale convective clouds and precipitation. The 13.2 km simulation underestimates precipitation intensity, produces rainfall too frequently, and shows evident biases in reproducing the diurnal cycle of precipitation and low-level wind fields. In comparison, the CPM shows significant improvements in the spatial distribution of precipitation intensity, although it overestimates the intensity magnitude and has a wet bias over central eastern China. The diurnal cycle of precipitation over Mei-yu region, southern China and the eastern periphery of the Tibetan Plateau, as well as the diurnal cycle of low-level winds over both the Mei-yu region and southern China are better simulated by the CPM. Over the Mei-yu region, in both simulations and observations, the local atmospheric instability in the afternoon is favorable for upward motion and rainfall. The CPM receives more sensible heat flux from the surface, has a stronger upward motion, and overestimates water vapor convergence based on moisture budget diagnosis. All these processes help explain theexcessive late afternoon rainfall over the Mei-yu region in the CPM simulation.