Hotspots of the sensitivity of the land surface hydrological cycle to climate change

Abstract

Due to the shortage of the global observational data of the terrestrial hydrological variables, the understanding of how surface hydrological processes respond to climate change is still limited. In this study, the Community Land Model (CLM4.0) with high resolution atmospheric forcing data is selected to simulate the global surface hydrological quantities during the period and to investigate the spatial features of these quantities in response to climate change at the regional scales. The sensitivities of evaporation and runoff with respect to the dominant climate change factors (e.g. temperature and precipitation) derived from the concept of climate elasticity are introduced. Results show that evaporation has a declining trend with a rate of 0.7 mm per decade, while runoff shows a weak increasing trend of 0.15 mm per decade over the global land surface. Analyses of the hotspots in the hydrological cycle indicate that the spatial distributions for evaporation and runoff are similar over many areas in central Asia, Australia, and southern South America, but differ largely in high latitudes. It is also found that, the evaporation hotspots in arid regions are mainly associated with the changes in precipitation. Our sensitive analysis suggests that the hydrological quantities show a rather complicated spatial dependency of response of the water cycle to the different climate factors (temperature and precipitation). The earth's climate has been warming throughout the 20th century and there is strong evidence that this warming, particularly over the last half-century, is very likely due to the increasing anthropogenic greenhouse gas concentrations [1]. One of the most direct impacts of the global warming is an accelerated hydrological cycle due to the increase of atmospheric water content associated with the warming [2]. Climate change is believed to strongly alter the global hydrological cycle [3,4]. A number of changes in the water cycle have been documented based on the observational studies. For example, Labat et al. [5] pointed out the global river flow has increased significantly during the 20th century and Roderick and Farquhar [6] found that pan evaporation has decreased in many areas of the world. Climate models also project that the frequency and intensity of extreme precipitation events will continue to increase [1]. These changes have important implications for waterresource management, agriculture, flood/drought control and many other sectors and thus the research on the changes in the global and regional water cycle has caused wide public concern all over the world.The sensitivities of the hydrological responses to climate changes have been studied recently [7][8][9]. By analyzing the hydroclimate changes in the Mississippi River, Qian et al.

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