Long-Term Climate Simulation of CCSM4.0 and Evaluation of Its Performance over East Asia and China
CCSM4.0的长期积分试验及其对东亚和中国气候模拟的评估

A 700-year long-term climate simulation is performed by the Community Climate System Model version 4.0 (CCSM4.0) with a low atmospheric horizontal resolution (T31, an equivalent grid spacing of about 3.75°). To systematically evaluate the capability of the model over East Asia and China, the last 100-year results of surface air temperature and precipitation in China, sea level pressure, geopotential height at 500 hPa and 100 hPa, and wind field at 850 hPa over East Asia are qualitatively compared to observation and reanalysis data, and a few statistical variables of the former three climatic elements are quantitatively examined. Results show that the model can reasonably reproduce the basic spatial patterns of the above climatic fields, though the magnitudes are somewhat different from observations. The best (worst) performance is found for surface air temperature (precipitation) as a whole. Specifically, the simulated geographical distribution of surface air temperature agrees with observations. However, it is overestimated on the Qinghai-Tibetan Plateau, and the warm center on the Tarim Basin is missed by the model throughout the year. The spatial distribution of precipitation is poorly simulated. A fake precipitation center, which is the strongest in summer, occurs over central southern China all year around except in winter. The simulation of sea level pressure is generally better in winter than in summer, though the simulated thermal contrast between the East Asian continent and adjacent oceans is larger than observations. The model can well capture the East Asia major trough and subtropical high over the western North Pacific at 500 hPa during winter and summer, though the values are larger than observations. The simulated intensity of the South Asia high at 100 hPa in summer is consistent with observations, whereas the extent and center location exhibit some deviations. The East Asian winter and summer monsoon circulations at 850 hPa are well simulated. However, the northwesterly flow is overestimated in winter. In summer, the Somalia cross-equatorial flow is underestimated, while the southwesterly flow over eastern China is overestimated. Collectively, CCSM4.0 has a reliable capability to simulate the large-scale climate features over East Asia and China, though some deficiencies still exist in a quantitative manner.