The Influence of North Pacific Jet Stream Variability on Springtime Central U.S. Hydroclimate

There is growing recognition within the subseasonal-to-seasonal (S2S) forecasting community that land surface characteristics provide a significant source of S2S predictability. Potentially the largest source regions for land-forced climate variability are elevated regions, such as the Tibetan Plateau. In this location, the land provides thermal and dynamical forcing in the middle troposphere that can modulate the characteristics of the North Pacific jet stream and downstream sensible weather conditions over North America. This Tibetan Plateau–North American teleconnection is strongest during the spring, before the North Pacific jet shifts poleward and the Pacific and Atlantic subtropical highs emerge. Collectively, this result implies that to fully harvest the potential S2S predictability embedded in the Tibetan Plateau–North American teleconnection, Earth system models must accurately represent springtime land–atmosphere interactions.

This study utilizes data from reanalysis products and a suite of long-term climate simulations to investigate the influence of Tibetan Plateau land-surface anomalies as well as long-term modes of climate variability, such as the El Niño–Southern Oscillation and the Pacific Decadal Oscillation, on springtime North Pacific jet variability. Analyses subsequently turn towards identifying North Pacific jet regimes that support enhanced low-level jet activity and precipitation across the Central U.S., and how those regimes are influenced by both land-surface characteristics over the Tibetan Plateau and sea-surface temperatures in the North Pacific. Preliminary results suggest that low-level jet activity in the Central U.S. is enhanced whenever the North Pacific jet is retracted or shifted poleward, which is most frequently observed during La Niña periods and the negative phase of the Pacific Decadal Oscillation. These results provide potential avenues for improving the S2S prediction of springtime Central U.S. precipitation based on consideration of both land-surface characteristics and synoptic-scale North Pacific jet variability.