Quantifying the Strength of Water Cycle Variations over the US

This study aims to develop a suite of Water Cycle Intensification Indicators (WCI) to quantify the current and future change in the strength of the water cycle across the conterminous U.S. in support of the National Climate Assessment (NCA). In this regard, we estimate the water cycle trends and extremes using a wealth of observations, reanalysis and model output. Six key water cycle components are analyzed, including precipitation, evaporation, runoff, moisture convergence flux, terrestrial storage and water vapor. Our preliminary results suggest that the water cycle strength varies geographically for different variables among different datasets. For instance, MERRA-Land simulated precipitation is consistent with the CPC unified precipitation dataset in revealing positive trend over the northeastern, northwestern and west north central, but negative trend over the western and central regions. However, negative trends are observed in MERRA-land over the southern Texas and some parts of the southern coast, contrary to the positive trend detected by the unified dataset in the same area. Our future work is to aggregate the trends of annual means and extremes of these water cycle components and create a suite of spatially- and temporally-scalable indicators for quantitative assessment of changing water cycle strength over the nation.