Inter-annual Climate Variability Of China And Climate Effects Of The Three Gorges Dam As Simulated By A Regional Climate Model

The using of high-resolution regional climate model,which is proved as a good tool to simulate the regional climate over China and East Asia. The main purpose is to analyse the interannual variability of climate over China region. It has an important meaning for improving the simulation ability of numerical model, investigating the local climate, and in order to enhance the climate variability prediction level of China.The ICTP (The Abdus Salam International Center for Theoretical Physics) Regional Climate Model, RegCM3 (available at http://www.ictp.it/~pubregcm) is used in the present work. The model is a development from its previous version of RegCM2.Firstly, in this paper, using regional climate model RegCM3, nesting NCEP reanalysis data from 1993 to 2002, in order to simulate the respective interannual climate variability over China and its nine sub-regions and test its ability. The abilities in reproducing the interannual variability of temperature and precipitation over each sub-region are also examined and compared, so as to investigate the predictability of climate in China, and improve the short-term climate prediction level.Our main conclusions are as follows:The overall pattern indicates that the model has a good capacity of simulating the mean climate pattern of China. To some extent, RegCM3 can reproduce the annual and summer mean temperature and precipitation distributions over China and other sub-regions. The intraannual variation of monthly temperature and precipitation are also simulated very well, and temperature is better than precipitation. The ability differences in precipitation simulation between different regions are bigger than those of temperature. Generally, the model can capture certain pattern of precipitation over most of sub-regions. The model has the abilities to do interannual temperature and precipitation variability simulation. But the biases have regional differences. It reproduces the annual mean temperature variability in these regions very well. All the correlation coefficients pass the 95% significance test, except in NE. The simulated abilities of precipitation variability in many regions are still weak, only do better in EA, NW and CC. in summer,the model has certain ability to simulate interannual temperature variability of most sub-regions. But it performs weaker in EA, CC, TB and SC than other regions. At the same time, the abilities of precipitation variability simulation are poor in summer, only a litter better in NW1, NW2 and CC.In addition, a series of simulations have been conducted by a regional climate model, the ICTP RegCM3, to simulate the climate in China and the Three Gorge Area (TGA) in 2005-2006, and to investigate the possible effects of the Three Gorge Reservoir (TGR) to climate. A 50×50 km resolution simulation with the domain covering whole China is firstly completed. Then two double nested simulations are carried out at a 10-km grid spacing over the TGA, one without the inland water coverage of TGR and one with in the TGR. Sub-grid method is employed in these two simulations to make the final model resolution to be 2×2 km (10-2 km simulations).Results show that the 50 km model reproduces the basic climatology and the anomaly of the summer temperature and precipitation over China, including the heat wave and drought over Chuanyu. The 10-2 km resolution simulation provides with more detail of local climate over TGA. Sensitivity experiments with and without the TGR showed that this had little or negligible effects except right over the TGR area. The averages of the changes over the area are very small both for temperature and precipitation. Most of the changes in the grid points are not statistically significant while most of the significant changes in temperature are found to be located over the water body of TGR. The changes show more noise than systematic effects outside the TGR. In summary, the heat wave and drought event over Chuanyu area in the summer of 2006 can be more attributed to the large-scale circulation rather than a local forcing. Contribution of the TGR is negligible.The innovation of this thesis is as follows:It investigates the simulation ability of RCM in reproducing the interannual climate variability over China and its sub-regions and tests the model performance. Meanwhile it also provides a valuable reference for regional climate predictability of China. Furthermore, the use of double nested RegCM3, model resolution has reached 10 km. And as using the SUB-BATS method, the horizontal resolution achieves the 2×2 km. Such a high-resolution topography can provide a more detailed description to the topography of Three Gorges region and the distribution of climate factors. So the simulation results are more detailed and reliable.