Freshwater storage capability of global land surface across time scales

Freshwater is one of the most important renewable resources for the livelihood and stakeholders. Its main replenishment is rainfall and the rainwater can be stored in land for a period of time, which is directly affected by the land storage capability across time scales. However, quantifying global freshwater storage capability (FSC) is still a challenge due to the lack of observations and quantification index. Here we use a metric that characterizes hydrological "inertia" after rainfalls to analyze global FSC with the Gravity Recovery and Climate Experiment (GRACE) satellite observation and Community Land Model version 5 (CLM5) simulation. In the GRACE era (2003-2016), the global land surface retains 60% of the precipitation after one day, and 33% after one month, with large FSC located in arid and semi-arid regions, and small FSC over monsoonal regions. The root zone contributes to 46%-48% of the global FSC from daily to monthly time scales. As the time scale increases, the contribution of surface soil decreases from 37% to 18%, while contribution of deep soil increases from 17% to 25%. With six decades of CLM5 long-term simulation, it is found that the first three principle components that are related to the major modes of global internal climate variability, contribute to half of the global FSC decadal variability. This study suggests that FSC should receive more attentions for water resources management, specifically over arid and semiarid regions at monthly or longer time scales, where are overlooked in the past due to limited rainfall.