Mar 23, 2016

Characterizing Recent Trends in U.S. Heavy Precipitation

by
Martin Hoerling, Jon Eischeid, Judith Perlwitz, Xiao-Wei Quan, Klaus Wolter, and Linyin Cheng
,
American Meteorological Society: Journal of Climate
  • Analyzes time series of U.S. daily heavy precipitation (95th percentile) to determine factors responsible for regionality and seasonality in their 1979–2013 trends
  • Characterizes contiguous U.S. trends, for annual conditions, by increases in precipitation associated with heavy daily events across the northern United States and decreases across the southern United States
  • Diagnosis of climate simulations (CCSM4 and CAM4) reveals that the evolution of observed sea surface temperatures (SSTs) was a more important factor influencing these trends than boundary condition changes linked to external radiative forcing alone
  • Finds that since 1979, boundary condition changes linked to external radiative forcing induces widespread, but mostly weak, increases in precipitation associated with heavy daily events
  • Finds that the evolution of observed sea surface temperatures (SSTs) induces a meridional pattern of northern U.S. increases and southern U.S. decreases as observed, the magnitude of which closely aligns with observed changes, especially over the south and far west
  • Analysis of model ensemble spread reveals that appreciable 35-yr trends in heavy daily precipitation can occur in the absence of forcing, thereby limiting detection of the weak anthropogenic influence at regional scales