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.