基于统计降尺度和CMIP5模式的泾河流域气候要素模拟与预估

    Simulation and prediction of climatic elements in Jinghe River basin using downscaling method and CMIP5

    • 摘要: 为了明确变化环境下流域未来气候要素时空变化趋势及特征,该文以泾河流域为研究对象,利用流域1960-2010的逐月降水、气温和NCEP再分析等资料,建立了流域气候要素月序列降尺度模型;然后,将模型应用于CMIP5中CNRM-CM5模式下的RCP4.5和RCP8.5情景,得到了流域未来气候要素的变化趋势。主要成果如下:1)该方法对气温的模拟效果较好,降水次之;2)RCP8.5情景下泾河流域未来年均降水量是356.41 mm,小于RCP4.5情景下的374.19 mm;除冬季外,流域未来春、夏及初秋的降水将有所减少,空间分布在南北方向呈现递减趋势;3)RCP8.5情景下泾河流域未来年均温度是9.32 ℃,高于RCP4.5情景下的8.96 ℃;流域未来气温除了深冬初春降低外,其余时期尤其是夏季将显著上升,空间分布为南高北低、西高东低。对泾河流域气候要素模拟与预估表明,泾河流域未来气候演变中存在着降水减少以及极端天气事件发生的风险,这在流域未来水资源管理运行等方面应当引起重视。

       

      Abstract: Abstract: Under the background of frequent anthropogenic activities and global environment change, it is necessary to carry out the study of future climate change, for understanding of the characteristics of temporal and spatial evolution of future climate is of great significance to agricultural production and local water resources planning and management. Located in the middle of the Loess Plateau, China, the Jinhe River basin, the second largest river in Guanzhong area, is the major base of grain production in Shaanxi Province, which has flat land and developed agriculture since ancient times. With the establishment of the Guanzhong-Tianshui economic zone, which is a national key economic development zone and will greatly promote the rapid development of the economy in the whole western region, the security of water resources in Jinhe River basin is becoming more and more important for the economic development and local peace and stability. Therefore, in this paper, we took Jinhe River basin as the research object. Then the variation characteristics of rainfall and temperature in the future were focused and analyzed by using downscaling method and CMIP5 (coupled model intercomparison project 5) global climate models, which were applied to simulate and predict climatic elements in Jinghe River basin. There were 3 steps to establish the statistical downscaling models: firstly, determinate forecast factors based on the relationship between the factors and rainfall as well as the air temperature; then normalize the forecasting factors in the NCEP (national centers for environmental prediction) reanalysis data; eventually based on the reanalysis data and historical meteorological observation data of monthly precipitation and temperature from 7 weather stations in or around the basin from 1960 to 2010, the models were set up through screening major factors by using stepwise regression. In order to evaluate the effect of the model, the fitting degree R2, the relative error of the mean Rmean and the relative error of standard deviation Rsd were selected as the evaluation index. These models were calibrated so that the results could be satisfactory. Then, on the foundation of the calibrated models, future precipitation and temperature in the Jinhe River basin were predicted by atmospheric circulation factors came from CMIP5 experiments: the RCP8.5 (highest emission of greenhouse gases) and RCP4.5 (median emission of greenhouse gases) forcing pathways under CNRM-CM5. Finally, we analyzed the characteristics of temporal and spatial of future precipitation and temperature in the basin. The results show that: (1) The statistical downscaling models function better in simulating temperature than precipitation with higher fitting degree and lower relative error in average and standard deviation; (2) Precipitation in the basin from 2011 to 2050 showed a decreasing trend from south to north direction, and would increase only in winter with different magnitudes under 2 scenarios; moreover, the annual average precipitation was 356.41 mm under the RCP8.5 scenario, which was lower than RCP4.5 forcing pathway (374.19 mm); (3) The predicted temperature in the future was much higher under RCP8.5 scenario (9.32℃) compared to RCP4.5 scenario (8.96℃) because of greenhouse gas emission with different concentration; spatial distribution of future temperature in Jinghe River basin was characterized by higher in the north and west; besides, temperature in the basin would decrease in the late winter and early spring, but significantly increase in summer, and it was inferred that there was the possibility of occurrence of extremely high temperature in summer and extremely low temperature in winter. In conclusion, there is not only a trend of decreasing in precipitation, but also a risk of extreme weather events in Jinghe River basin, which should be paid attention to in the future water resources management and planning.

       

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