Empirical Orthogonal Teleconnections as a Framework for Regional Climate Analysis: Insights from Pacific Northwest Temperature Extremes

Abstract

As the climate warms, understanding whether heat waves will intensify following mean temperature trends or undergo dynamic changes in their progression leading to changes in intensity is critical for regional climate adaptation. This study investigates heat wave dynamics in Washington and Oregon using Empirical Orthogonal Teleconnections (EOT) and climate composites, with a focus on setting historical baselines for use in further study with future projections. We analyze daily 2-meter maximum temperature data during the heat wave season (May 1–September 30) from ERA5 (1951–2020) and CMIP6 (historical forcing, 1981–2010) downscaled with WRF. EOT analysis reveals distinct spatial modes of teleconnectivity of maximum temperature, and this study primarily focuses on four: the Whole Region, Northeast, Southeast, and Coastal domains, which experience heat waves distinctly from one another. The composite analysis of ERA5 fields during days in the top ten percent for 2-meter maximum temperature shows both local forcings and a degree of progression from the Coastal to Whole Region, while the Northeast and Southeast modes represent regions of remote forcing during heat waves. This is supported by the results of the heat wave selection criteria used at the defining spatial point of each mode. This work provides a novel framework for the analysis of temperature regimes on a regional scale, having implications for understanding the synoptic and mesoscale conditions necessary for heat waves in different parts of the region.