Characterizing the North Pacific Jet Stream for Understanding Historical Variability in Western United States Winter Precipitation

Abstract

We examined historical winter-season relationships among precipitation across the western United States, the northern Pacific jet stream (NPJ) across the northern Pacific Ocean basin, and the El Niño-Southern Oscillation (ENSO) phenomenon to determine if the NPJ significantly adds to the existing ENSO-based understanding of inter-annual variability in precipitation. The results indicate that the NPJ is significantly related to winter precipitation across a much larger area of the western United States than the ENSO signal. For areas where the ENSO signal is significantly related to precipitation, there generally exists a stronger or more consistent NPJ-precipitation relationship. The position of the NPJ is the most important characteristic of the jet in its relationship with precipitation across the western United States. However, winter precipitation across the northwest, especially for regions of higher elevation, is more significantly related to the strength of the NPJ. The results indicate that there is value in considering seasonal jet stream characteristics as independent variables, along with climate teleconnections, when considering seasonal precipitation variability in regions where large-scale jet stream dynamics are influential.

Keywords:

• North Pacific jet
• winter precipitation variability
• jet stream
• ENSO
• western United States