Climate Variability in Atmospheric River Frequencies over the North Pacific

Abstract:

Recent studies on atmospheric rivers (ARs) over the North Pacific have largely given the impression that these high impact features are cold season phenomena. This presentation briefly describes development of an objective detection algorithm based on integrated water vapor transport that can be used throughout the year and across the globe to identify AR-like features. Using output from this algorithm, we describe AR incidence over the North Pacific in terms of the long-term mean climatology, the seasonal cycle, and variability relating to El Niño-Southern Oscillation (ENSO) and the Madden-Julian oscillation (MJO). The results indicate that ARs exist throughout the year over the North Pacific, but that their preferred locations shift substantially seasonally. It is also shown that changes to the North Pacific mean-state due to ENSO and the MJO may enhance or offset the seasonal cycle of AR activity, but that such impacts also vary greatly based on location. The characteristics of high-latitude ARs in places like Alaska--events that are not well documented in peer-reviewed journals--are discussed. Finally, the relationship between Alaska and U.S. West Coast AR activity and eastern Pacific blocking is also presented