When record breaking heat waves should not surprise: skewness, heavy tails and implications for risk assessment | CU Experts

Extreme heat waves beset western North America during 2021, including a; 46.7°C (116°F) observation in Portland, Oregon, an astonishing 5°C above; the previous record. Using Portland as an example we provide evidence; for a latent risk of extreme heat waves in the Pacific Northwest (PNW); and along the west coast of the United States where a maritime climate; and its intrinsic variations yield a positive skewness in summertime; daily maximum temperatures. A generalized Pareto extreme value analysis; yields a heavy tailed distribution with a return period of 300-1000; years, indicating that, while rare, the event was possible, contrary to; prior claims that the event was “virtually impossible”. We demonstrate; that the extreme temperatures can be explained by the coincident extreme; values of geopotential heights, and that the relationship between; heights and extreme temperatures has not materially changed over the; observational record. The dynamical nature of the event along with; recent developments in stochastic theory justifies the use of skewed and; heavy-tailed distributions which may provide the basis for a more; proactive approach to managing the risk of future events.

VIVO