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. Keywords Convection permitting model • Precipitation characteristics • Diurnal cycle • Moisture budget diagnosis • Water vapor transport This paper is a contribution to the special issue on Advances in Convection-Permitting Climate Modeling, consisting of papers that focus on the evaluation, climate change assessment, and feedback processes in kilometer-scale simulations and observations. The special issue is coordinated by

[1] Atmospheric sulfate aerosols have a cooling effect on the Earth's surface and can change cloud microphysics and precipitation. China has heavy loading of sulfate, but their sources and formation processes remain uncertain. In this study we characterize possible sources and formation processes of atmospheric sulfate by analyzing sulfur isotope abundances ( 32 S, 33 S, 34 S, and 36 S) and by detailed X-ray diffraction and scanning electron microscope (SEM) imaging of aerosol samples acquired at a rural site in northern China from March to August 2005. The comparison of SEM images from coal fly ash and the atmospheric aerosols suggests that direct emission from coal combustion is a substantial source of primary atmospheric sulfate in the form of CaSO 4 . Airborne gypsum (CaSO 4 ·2H 2 O) is usually attributed to eolian dust or atmospheric reactions with H 2 SO 4 . SEM imaging also reveals mineral particles with soot aggregates adhered to the surface where they could decrease the single scattering albedo of these aerosols. In summer months, heterogeneous oxidation of SO 2 , derived from coal combustion, appears to be the dominant source of atmospheric sulfate. Our analyses of aerosol sulfate show a seasonal variation in D 33 S (D 33 S describes either a 33 S excess or depletion relative to that predicted from consideration of classical mass-dependent isotope effects). Similar sulfur isotope variations have been observed in other atmospheric samples and in (homogenous) gas-phase reactions. On the basis of atmospheric sounding and satellite data as well as a possible relationship between D 33 S and Convective Available Potential Energy (CAPE) during the sampling period, we attribute the sulfur isotope anomalies (D 33 S and D 36 S) in Xianghe aerosol sulfates to another atmospheric source (upper troposphere or lower stratosphere).Citation: Guo, Z., Z. Li, J. Farquhar, A. J. Kaufman, N. Wu, C. Li, R. R. Dickerson, and P. Wang (2010), Identification of sources and formation processes of atmospheric sulfate by sulfur isotope and scanning electron microscope measurements,