Abstract
Heat waves are among the deadliest natural hazards affecting the United
States (US). Therefore, understanding the physical mechanisms modulating
their occurrence is essential for improving their predictions and future
projections. Using observational data and model simulations, this study
finds that the interannual variability of the tropical Atlantic warm
pool (AWP, measured as the area enclosed by the 28.5°C sea surface
temperature isotherm) modulates heat wave occurrence over the US Great
Plains during boreal summer. For example, a larger than normal AWP
enhances atmospheric convection over the Caribbean Sea, driving an upper
tropospheric anticyclonic anomaly over the Gulf of Mexico and Great
Plains, which strengthens subsidence, reduces cloud cover, and increases
surface warming. This circulation anomaly thus weakens the Great Plains
low-level jet (GPLLJ) and associated moisture transport into the Great
Plains, leading to drought conditions and increased heat wave occurrence
for most of the US east of the Rockies.