Climate Change In China As Simulated By A High Resolution Regional Climate Model

This study analyses the impacts of greenhouse warming on climate in China as simulated by a high resolution regional climate model, RegCM3. It is nested in one-way mode within the NASA/NCAR finite volume element AGCM (FvGCM). Two sets of multi-decadal simulations at 20-km grid spacing for present day (1961-1990) and future climate (2071-2100, IPCC A2 emission scenario) are conducted.Firstly the FvGCM and RegCM3's simulations of present climate in China are analyzed. Results show that both of the models can simulate well the atmospheric circulation, basically reproduce its main features and seasonal change. FvGCM is also able to reproduce some basic features of the observed mean surface climate, including surface air temperature and precipitation, over China. Comparing to FvGCM, besides the mean climate, it can reproduce more detailed structures of surface temperature distribution caused by small topography and reduce, in some extent, cold bias in the FvGCM simulations. The precipitation simulated by FvGCM gives a wrong location of the high rainfall center with its heavy rainfall belt over the east of the Tibet Plateau-Yangtze River. RegCM3 improves this, the high rainfall center in Yangtze River has already disappeared, and the other center has reduced to a reasonable extent. Furthermore, RegCM3 show more regional details than FvGCM, for example, the more rain in the northwest area and so on. Similar to the annual mean simulation, the results of RegCM3's seasonal precipitation show better than FvGCM, especially in summer.Moreover, we analyze the standard deviation (SIDE) and spatial correlation (COR) between simulated and observed seasonal mean temperature and precipitation in China. Results show that the models can simulate the distribution of temperature well, the value of COR is greater than 0.97 and give a low value of SIDE. The simulations of precipitation are worse than temperature, the value of COR is only around 0.5. So the SIDE is also high. However, compared to FvGCM, RegCM3 makes some progress in a certain extent.Results also show that by the end of the 21st century under IPCC A2 scenario the changes in 500 hpa height are all positive and the wind will appear a cyclone in the southern part and an anticyclone in the northern part. The change of sea level pressure is from -0.5 to 1.5 hpa in most area.Significant warming is simulated by FvGCM and RegCM3. The warming of annual temperature in the two models are in the range of 2.4 to 5.4oC and 2.4 to 4.5oC, with more warming in the north of the domain. The daily maximum and minimum temperature will increase obviously too. Greater warming is simulated in winter with a strong latitudinal gradient. Compared to FvGCM, RegCM3's simulations of temperature change give more regional details, and there are some differences in the range of warming. For example, the annual mean temperature increase in RegCM3 is much lower than that in FvGCM in northeast of the domain. This maybe has something to do with the difference of ice and snow's feedback.General increase in annual mean precipitation is simulated by FvGCM, most of its value is more than 10%. However, the results of RegCM3 show a big difference in different areas. In northwest, it has a strong increase, the value is more than 50%. In northeast and Huang-Huai River, the increase is between 10% and 25%. Other areas have a little change, or almost no change, or have some decrease. In Yunnan province and Tibet Plateau, the decrease value can reach 25%. There are also some differences in seasonal precipitation in the two models. In the simulations of RegCM3, higher increases in autumn and higher decreases in summer almost over the whole domain are found. But in the results of FvGCM, precipitation will increase in most area in summer, and the increase in autumn is lower than that in RegCM3. However, the results in winter and spring are similar in the two models, only some difference in the value.The monthly area mean precipitation will increase in FvGCM. The maximum value is 31.9% in December, and the minimum value appears in June. The simulation in RegCM3 will increase in general, but the precipitation in summer will decrease.The innovations in this paper are: the long time and the high resolution. Long tme simulation make the result have a real meaning in climatology. As high resolution result can provide more regional details and better distribution of different varies, we can more convinced about the result of the change in the future.