No abstract

This study assesses present-day and future precipitation changes over China by using the Weather Research and Forecasting (WRF) model version 3.5.1. The WRF model was driven by the Geophysical Fluid Dynamics Laboratory Earth System Model with the Generalized Ocean Layer Dynamics component (GFDL-ESM2G) output over China at the resolution of 30 km for the present day and near future (2031)(2032)(2033)(2034)(2035)(2036)(2037)(2038)(2039)(2040)(2041)(2042)(2043)(2044)(2045)(2046)(2047)(2048)(2049)(2050) under the Representative Concentration Pathways 4.5 (RCP4.5) scenario. The results demonstrate that with improved resolution and better representation of finer-scale physical process, dynamical downscaling adds value to the regional precipitation simulation. WRF downscaling generally simulates more reliable spatial distributions of total precipitation and extreme precipitation in China with higher spatial pattern correlations and closer magnitude. It is able to successfully eliminate the artificial precipitation maximum area simulated by GFDL-ESM2G over the west of the Sichuan Basin, along the eastern edge of the Tibetan Plateau in both summer and winter. Besides, the regional annual cycle and frequencies of precipitation intensity are also well depicted by WRF. In the future projections, under the RCP4.5 scenario, both models project that summer precipitation over most parts of China will increase, especially in western and northern China, and that precipitation over some southern regions is projected to decrease. The projected increase of future extreme precipitation makes great contributions to the total precipitation increase. In southern regions, the projected larger extreme precipitation amounts accompanied with fewer extreme precipitation frequencies suggest that future daily extreme precipitation intensity is likely to increase in these regions.

The behavior of tropical extreme precipitation under changes in sea surface temperatures (SSTs) is investigated with the Weather Research and Forecasting Model (WRF) in three sets of idealized simulations: small‐domain tropical radiative‐convective equilibrium (RCE), quasi‐global “aquapatch”, and RCE with prescribed mean ascent from the tropical band in the aquapatch. We find that, across the variations introduced including SST, large‐scale circulation, domain size, horizontal resolution, and convective parameterization, the change in the degree of convective organization emerges as a robust mechanism affecting extreme precipitation. Higher ratios of change in extreme precipitation to change in mean surface water vapor are associated with increases in the degree of organization, while lower ratios correspond to decreases in the degree of organization. The spread of such changes is much larger in RCE than aquapatch tropics, suggesting that small RCE domains may be unreliable for assessing the temperature‐dependence of extreme precipitation or convective organization. When the degree of organization does not change, simulated extreme precipitation scales with surface water vapor. This slightly exceeds Clausius‐Clapeyron (CC) scaling, because the near‐surface air warms 10–25% faster than the SST in all experiments. Also for simulations analyzed here with convective parameterizations, there is an increasing trend of organization with SST.