Long-term Spatial Modeling for Characteristics of Extreme Heat Events
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There is increasing evidence that global warming manifests itself in more frequent warm days and that heat waves will become more frequent. Presently, a formal definition of a heat wave is not agreed upon in the literature. To avoid this debate, we consider extreme heat events, which are well-defined at local scales, as a run of consecutive days above a specified local threshold. Characteristics of EHEs are of primary interest, such as incidence and duration, as well as the magnitude of the average exceedance and maximum exceedance above the threshold during the EHE. Using approximately 60 years of time series of daily maximum temperature data collected at 18 locations in a given region, we develop a spatio-temporal model to study the behavior of EHEs over time. The model enables prediction of the behavior of EHE characteristics at unobserved locations within the region. Specifically, our approach employs a two-state space-time model for EHEs with local thresholds where one state defines above threshold daily maximum temperatures and the other below threshold temperatures. We show that our model is able to recover the EHE characteristics of interest and outperforms a traditional autoregressive model that ignores thresholds in terms of out-of-sample.
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