GLDAS和CMIP5产品的中国土壤湿度-降水耦合分析及变化趋势

利用GLDAS同化产品和12个CMIP5模式的输出结果,从土壤湿度对降水影响的两个中间环节出发,通过分析陆面耦合指数ILH、潜热通量—抬升凝结高度耦合指数ILCL以及抬升凝结高度ZLCL间接研究中国区域土壤湿度与降水间耦合特征,并对1958~2013年及RCP4.5辐射强迫情景下50年(2006~2055年)的4个代表性区域夏季耦合强度的年代际变化特征进行分析。研究发现:1958~2013年期间,内蒙古阴山山脉附近、新疆和青海的部分地区为夏季中国土壤湿度与降水耦合的最强区域;陆面耦合指数ILH变化幅度从高到低依次出现在华北、华南、内蒙古中部和西北地区,并在20世纪70年代中到80年代中发生转折。2006~2055年的平均而言,预估内蒙古阴山山脉附近仍为耦合最强区;与历史时期(1958~2005年)比较,新疆中部和内蒙古阴山山脉附近的耦合指数ILH增大,而广西和广东地区的则减小;对于耦合指数ILH的年代际变化(2006~2055年),2026~2035年间华北最大而华南最小,西北地区变化不大,而内蒙古中部地区的耦合强度逐渐增大。

Soil Moisture-Precipitation Coupling and Trends in China, Based on GLDAS and CMIP5 Products

From the viewpoint of two intermediate processes involved in the influence of soil moisture on precipitation, and based on GLDAS data and 12 sets of CMIP5 model outputs, the characteristics of soil moisture-precipitation coupling were indirectly investigated by analyzing the land surface coupling index (I_LH), the coupling index (I_LCL) between latent heat flux and the lifting condensation level (Z_LCL), and the Z_LCL itself. Then, the decadal variations of the summer coupling indices were analyzed in four representative regions for the period 1958-2013 and-under the RCP4.5 radiative forcing scenario-the period 2006-2055. The results showed that, from 1958 to 2013, the larger summer I_LH values were located around the Yin Mountains in Inner Mongolia, and in parts of Xinjiang and Qinghai provinces. The decadal variations of the summer coupling indices decreased in the following order: North China, South China, central Inner Mongolia, and Northwest China. Abrupt change in the indices was found in the mid-1970s to mid-1980s. From 2006 to 2055, the region projected to feature larger I_LH on average was still near the Yin Mountains. Compared with the historical period (1958-2005), I_LH was projected to increase near the central region of Xinjiang Province and around the Yin Mountains, while the degree of coupling in Guangxi and Guangdong provinces was shown to reduce. In terms of decadal variation in the period 2006-2055, North China was projected to be the strongest coupling region and South China the weakest (from 2026 to 2035). Meanwhile, in Northwest China, few changes were projected to occur, and I_LH in central Inner Mongolia was shown to gradually increase.