Space-Time Extremes of Severe U.S. Thunderstorm Environments

原文摘要

Severe thunderstorms cause substantial economic and human losses in the United States. Simultaneoushigh values of convective available potential energy (CAPE) and storm relative helicity (SRH) are favorable tosevere weather, and both they and the composite variable PROD = √CAPE × SRH can be used as indicatorsof severe thunderstorm activity. Their extremal spatial dependence exhibits temporal non-stationarity dueto seasonality and large-scale atmospheric signals such as El Niño-Southern Oscillation (ENSO). In orderto investigate this, we introduce a space-time model based on a max-stable, Brown–Resnick, field whoserange depends on ENSO and on time through a tensor product spline. We also propose a max-stabilitytest based on empirical likelihood and the bootstrap. The marginal and dependence parameters must beestimated separately owing to the complexity of the model, and we develop a bootstrap-based modelselection criterion that accounts for the marginal uncertainty when choosing the dependence model. Inthe case study, the out-sample performance of our model is good. We find that extremes of PROD, CAPE,and SRH are generally more localized in summer and, in some regions, less localized during El Niño and LaNiña events, and give meteorological interpretations of these phenomena. Supplementary materials for thisarticle are available online, including a standardized description of the materials available for reproducingthe work.

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