A Long-term Regional Simulation and Observations of the Hydroclimate in China
Driven by the complex topography, inhomogeneous land surface conditions and large-scale circulation exhibiting strong variability at various time scales, the hydroclimate of China presents many unique features and poses a great challenge for climate modeling. This paper provides detailed analyses of observations and a 20-year regional climate simulation to improve our understanding of the diverse hydroclimate regimes in China. Eastern China is greatly influenced by the East Asian monsoon, leading to heavy summer rainfall that exhibits large variations at the intraseasonal and interannual time scales. The Hai River and Huaihe River basins feature the largest interannual variations in summer rainfall, with the Middle and Lower Yangtze River and Pearl River basins showing the next highest variability. In the wettest regions of the Middle and Lower Yangtze River basin and Southeast Coast, the land surface plays a comparatively passive role as evaporation is not limited by soil moisture, and boundary layer and precipitation processes are only weakly influenced by soil wetness. In contrast, northern and western China are marked by dryer and less cloudy conditions, and interannual variations in summer rainfall are typically half of that in eastern China. Precipitation is largely balanced by evapotranspiration. The land surface plays a more active role in the water cycle in these regions. This is supported by the strong correlations between soil moisture and sensible heat flux, evaporative fraction, and mixed layer depth, indicating a strong influence of soil wetness on atmospheric stability and precipitation processes. The overall spatial distribution, seasonal variations, and extreme precipitation are well simulated by the regional climate model. However, the simulation produces more rainfall associated with the lower rain rates in central and southern China. This suggests that some mechanisms responsible for heavy rainfall may not be properly simulated by the model due to insufficient spatial resolution or physical representation. A second major weakness of the regional simulation lies in its ability to capture the interannual variations of summer rainfall. The lower anomaly correlations obtained in the regional simulation compared to the global reanalysis suggest that interannual variations in the large scale circulation may not be faithfully reproduced in the regional simulation as the model solution is not highly constrained in the interior of the regional domain without some forms of nudging towards the global reanalysis.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 917214
- Report Number(s):
- PNNL-SA-51616; KP1703010; TRN: US200816%%434
- Journal Information:
- Journal of Geophysical Research. D. (Atmospheres), 112, Vol. 112
- Country of Publication:
- United States
- Language:
- English
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