PNNL

Abstract

Heat-dome-like stationary waves (SWs) often lead to extreme events, such as the unprecedented heatwave in Northwestern North America (NNA) during the summer of 2021. However, the future changes in summer SWs over NNA and the driving factors remain unclear. Here, we investigate the projected changes in the anticyclonic SW circulation over NNA using data from the Coupled Model Intercomparison Project Phase 6 and diagnose the circulation changes using a stationary wave model. Our findings reveal a significant 65% increase in the summer SW amplitude over NNA under the high-emission scenario in 2080~2099 relative to 1995~2014. This SW response is mainly driven by the diabatic heating changes over the tropical Pacific which induce a Rossby wave source in the northeastern tropical Pacific, and further supported by a northward expanded waveguide in North America, both enhancing wave activity flux into the NNA region. The heat-dome-like SW anomaly is expected to heighten the heatwave risk over NNA.