Observed Changes in Interannual Precipitation Variability in the United States.

Characterizing changes in precipitation patterns over time is critical for hydrologically dependent fields like water resource management and agriculture. Here, we explore observed trends in interannual precipitation variability using a suite of metrics that describe changes in precipitation over time. We analyze daily in situ Global Historical Climatology Network precipitation data from 1970 to present over 17 internally consistent sub‐national United States domains using a regional Mann‐Kendall trend test. We find robustly increasing trends in annual mean precipitation and wet day frequency for most of the central and eastern U.S., but decreasing trends in the western U.S. Importantly, we identify widespread significant trends in interannual precipitation variability, with increasing variability in the southeast, decreasing variability in the far west, and mixed signals in the Rocky Mountains and north‐central U.S. Our results provide important context for water resource managers and a new observational standard for climate model performance assessments. Plain Language Summary: While many studies have examined how annual precipitation totals and precipitation frequency have changed, few examine the variability, or consistency, of year‐over‐year precipitation. We test for these trends in daily observations across 17 regions within the United States. We find changes in yearly precipitation variability for most regions, though results in the central U.S. are mixed. We also identify rising average annual precipitation and precipitation frequency for the central and eastern U.S. and falling average annual precipitation and frequency for the western U.S. Our results are important for agriculture and water resource management and can be compared against historical climate model simulations to determine how well they reproduce observations. Key Points: We find widespread robust changes in two measures of interannual precipitation variability across the United StatesWe detect increases (decreases) in annual mean precipitation and wet day frequency across the eastern (western) United StatesWe explore the interaction of changes in precipitation frequency and wet day precipitation intensity on interannual variability [ABSTRACT FROM AUTHOR]