区域海气耦合模式对中国夏季降水的模拟

Simulation of China summer precipitation with a regional air-sea coupled model

中文关键词:  区域海气耦合模式，降水，水汽输送，海温

英文关键词:Regional air-sea coupled model, Precipitation, Moisture transport, Sea surface temperature

中文摘要:

      以区域气候模式RegCM3和普林斯顿海洋模式POM为基础，建立了一个区域海气耦合模式，对1963—2002年中国夏季气候进行模拟，重点分析该耦合模式对中国夏季降水的模拟性能以及降水模拟改进的可能原因。结果表明：耦合模式对中国夏季雨带分布的模拟明显优于控制试验（单独的大气模式），对长江流域以及华南降水的模拟性能改进尤为明显，同时耦合模式能够更为真实地刻画中国东部地区汛期雨带的移动。对降水的年际变化分析发现，耦合模式模拟的1963—2002年中国夏季降水年际变率与观测吻合，模拟的夏季长江流域降水与观测降水相关系数达到0.48，模拟的华南夏季降水与观测的相关系数达到0.61，而控制试验结果与观测降水的相关系数均较小。对中国东部长江流域夏季降水与近海海温的相关分析表明，用给定海温驱动的大气模式，并不能正确模拟出中国东部夏季降水与海温的关系，而耦合模式能够较好地模拟出长江流域与孟加拉湾、南海以及黑潮区海温的关系，与GISST(全球海冰和海表温度)和观测降水相关关系一致。对水汽输送通量的分析发现，控制试验模拟的水汽输送路径与NCEP/NCAR再分析资料相比差别较大，耦合模式模拟的来自海洋上的水汽输送强度和路径与NCEP/NCAR再分析资料一致，提高了耦合模式对水汽输送的模拟能力，从而改善了模式对华南以及长江流域降水的模拟。

英文摘要:

      A regional air-sea coupled climate model based on the regional climate model RegCM3 and the regional oceanic model POM (Princeton Ocean Model) is developed and a series of experiments are performed to verify the simulation ability of the coupled model over China in summer from 1963 to 2002. The simulation results show that the space coefficients between GISST and SST (summer sea temperature) in RegCM3 POM exceed 0.9, so the SST in RegCM3POM is reasonable and available. Compared with the uncoupled experiments, the regional air-sea coupled model RegCM3 POM has better simulation performance in simulating the mean summer (from June to August) precipitation over China, and the distribution of rainband in the coupled model is more reasonable than that in the uncoupled model. The improvement of the rainfall simulation is very remarkable over the Yangtze river valley and South China, and as for the rainbelt intraseasonal evolution over eastern China in summer, the simulation ability of RegCM3 POM is evidently improved compared with the uncoupled model. The interannual summer rainfall variation over eastern China simulated by RegCM3 POM is accordant to observation result, and the spatial pattern of the interannual summer rainfall variation in the uncoupled model is unreasonable. Further analysis indicates that the simulated correlation coefficient between the summer rainfall in uncoupled model RegCM3 and observation is 0.30 over the Yangtze river valley and 0.29 in South China, while the coefficient between the rainfall in RegCM3 POM model and observation is 0.48 over the Yangtze river valley and 0.61 in South China, which are more believable than that in the uncoupled model RegCM3. The simulation results of the relationship between SSTA (sea surface temperature anomaly) over costal oceans and summer precipitation show that the regional air sea coupled model has good performance in simulating the correlation coefficients between summer rainfall in the Yangtze river valley and SSTA of the Bay of Bengal, South China Sea and Kuroshio area, and the uncoupled model RegCM3 fails to reproduce the relationship between the rainfall over the Yangtze river valley in summer and SSTA in coastal oceans. The uncoupled model’s deficiencies are somewhat to blame that, in the uncoupled experiments, the SST is prescribed as a forcing, but in fact, SST anomaly is determined by anomalous atmosphere conditions, so the uncoupled model can not reflect the atmospheric feedback to ocean, and of course, the uncoupled model cannot reflect the air sea interaction over the sea surface. The precipitation is greatly affected by the water vapor, and a large mount of water vapor is carried from the ocean to the monsoon region by the monsoon flow. The further study shows that the monsoon circulation and the path of the moisture transport flux simulated by RegCM3-POM are in good agreement with the NCEP/NCAR data, which improves the rainfall simulation in China. Therefore, the regional air-sea coupled model is more available for China.