Towards Quantifying the Risk of Compound Heat Wave Events: Projections of Frequency and Severity

Abstract

Compound heat waves, which we define as two or more individual heat wave events occurring in the same location with a break between them, pose severe ecological and economic threats to human health, agricultural production, and emergency response systems. Given the adverse impacts of compound heat waves, scientific understanding of these events is of great importance to policymakers, the insurance industry, and emergency management planning organizations. In this study, we analyze the frequency and distribution of compound and non-compound heat wave events in a high resolution coupled atmosphere and ocean general circulation model (AOGCM) developed by the Geophysical Fluid Dynamics Laboratory (GFDL), called CM2.5-FLOR. We first compare compound and non-compound heat waves to reanalysis observational datasets in order to evaluate model fidelity in simulating these events. We then evaluate these events under a future scenario with increasing radiative forcing to understand how the frequency and distribution of these events may change with global warming. We focus on the United States and Western Europe, where observation station density is high and reanalysis is reliable. We hypothesize that climate properties – such as soil moisture deficits and atmospheric blocking patterns – will cause the frequency of future compound heat waves to increase faster than we would expect given the projected increase in hot days and non-compound heat waves in the future.