Changes in Terrestrial Water Availability under Global Warming

Under global warming, the annual range of precipitation is widening (Chou and Lan, 2012; Chou et al., 2013) and the frequency of precipitation extreme events also increases. Due to nonlinear responses of land hydrological process to precipitation extremes, runoff can increase exponentially, and on the hard hand, soil water storage may decline. In addition, IPCC AR5 indicates that soil moisture decreases in most areas under the global warming scenario. In this study, we use NCAR Community Land Model version 4 (CLM4) to simulate changes in terrestrial available water (TAW, defined as the precipitation minus evaporation minus runoff, and then divided by the precipitation) under global warming. Preliminary results show that the TAW has clear seasonal variations. Compared to previous studies, which do not include the runoff in the calculations of the available water, our estimates on the TAW has much less available water in high latitudes through out the year, especially under extreme precipitation events.