Dynamical and Thermodynamic Aspects of Long Duration Heat Extremes over the U.S. in Current and Warmer Climates

Prolonged heat extremes can lead to devastating impacts on both ecology and society –and with global warming, things are only poised to get worse. Thus, it is important to understand both the dynamical and thermodynamic processes that act to initiate and sustain persistent heat extremes over the U.S. In this work, the longest duration heat extremes over major U.S. population centers are investigated. We begin with observations, performing compositing analyses of pressure, height, winds, moisture, and near-surface temperature budget in the weeks leading up to these events as well as throughout their lifecycles. Then, these events are examined in climate model simulations for both historical and future climate projections, noting any differences found between them. We find that although the evolution of these events varies from region to region, Rossby wave dynamics and temperature advection seem to be the biggest drivers, with other mechanisms playing a more minor role depending on the region.