Northeast US Rainfall: Variability versus Long-Term Change

Caroline Ummenhofer, Physical Oceanography
Ray Schmitt, Physical Oceanography
Terry Joyce, Physical Oceanography



This proposal aims to understand recent rainfall trends in the northeast US in the context of an extended analysis of interannual and decadal variability of the region's climate and links to the large-scale atmospheric circulation. Most studies exploring rainfall in relation to modes of climate variability start off from the climate driver (e.g. El Niño-Southern Oscillation, North Atlantic Oscillation), assess their impact on year-to-year variations in rainfall and circulation changes, and extrapolate from these relationships the contribution to long-term rainfall trends that are linearly congruent with trends in the climate indices. Such linear analysis techniques are limited in their utility for investigating non-linear (temporally and spatially) processes that link rainfall variability and large-scale climate anomalies. Here, we propose to use nonlinear multivariate cluster analysis to (1) identify recurrent northeast US rainfall and circulation patterns, (2) develop a physical understanding of these patterns within the region’s ocean-atmosphere system, (3) determine their variation across different timescales, and (4) assess recent northeast US rainfall trends in light of a better understanding of long-term variability. Such improved understanding of northeast US rainfall variability and trends across multiple timescales becomes crucial for water resource managers in light of significant changes to the region’s climate projected for the 21st Century.