A precipitation dipole in eastern North America

Abstract

We have identified a dipole in annual precipitation across eastern North America (ENA) east of 100°W between 30°N and 60°N. This dipole appears to create spatially coherent opposing variations in precipitation with a separation of the two regions around 45°N. Annual average precipitation over ENA appears to be stable and unimodal, suggesting that the amount of overall precipitation variability is a small fraction of the mean and is largely determined by similar large scale processes. Analysis of regional average time series at interannual (3-7 year) and decadal (10-16 year) scales indicates that the dipole over the ENA region is most clearly discernible at the decadal scale. Linear regression analysis between global sea surface temperatures (SSTs) and precipitation over the two subregions in ENA suggests that SST variations in several areas of the oceans tend to be associated with opposite precipitation anomalies in the two subregions of ENA. Copyright 2006 by the American Geophysical Union.