Abstract
A limited area convection permitting model (CPM) based on the Met Office Unified Model, with a 0.04° (4.4 km) horizontal grid spacing, is used to simulate an entire warm-season of the East Asian monsoon (from April to September 2009). The simulations are compared to rain gauge observations, reanalysis and to a lower resolution regional model with a 0.12° (13.2 km) grid spacing that has a parametrization 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 the excessive late afternoon rainfall over the Mei-yu region in the CPM simulation.
Highlights
The diurnal cycle of precipitation is an important aspect of our weather and climate
There is an evident monsoon rainband stretching from the southwest to the northeast, with several centers located in the eastern periphery of the Tibetan Plateau (TP) (100°E–107°E, 27°N–33°N), the coastal areas over southern China (110°E–120°E, 22°N–27°°N) and the Mei-yu region (112.5°E–122.5°E, 27°N–33°N)
The spatial distribution of precipitation A is obviously affected by the underlying surface and uneven regional distribution, but these phenomena are less pronounced in the results of LSM 13p2
Summary
The diurnal cycle of precipitation is an important aspect of our weather and climate. It is closely related to surface temperature, moist convection, the formation of clouds and boundary-layer development (Dai et al 1999; Yang and Slingo 2001). It is intimately connected with both regional and synoptic-scale dynamical and thermal conditions and provides a good test bed for weather and climate models (Dai and Trenberth 2004). Over inland areas of southern China, the summer rainfall peaks in the late afternoon (i.e., between 3 p.m. and 7 p.m., local solar time (LST), hereafter 1500 LST and 2000 LST; Yu et al 2007a, b; Zhou et al 2008; Jiang et al 2017). Along the Yangtze River valley, the geographical distribution of diurnal-cycle variation exhibits an eastward phase delayed in the timing of peak precipitation (Asai et al 1998; Yu et al 2007a, b; Chen et al 2010a)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
