Nonstationary Temperature-Duration-Frequency curves

Abstract

Persistent extreme heat events are of growing concern in a climate change context. An increase in the intensity, frequency and duration of heat waves is observed in several regions. Temperature extremes are also influenced by global-scale modes of climate variability. Temperature-Duration-Frequency (TDF) curves, which relate the intensity of heat events of different durations to their frequencies, can be useful tools for the analysis of heat extremes. To account for climate external forcings, we develop a nonstationary approach to the TDF curves by introducing indices that account for the temporal trend and teleconnections. Nonstationary TDF modeling can find applications in adaptive management in the fields of health care, public safety and energy production. We present a one-step method, based on the maximization of the composite likelihood of observed heat extremes, to build the nonstationary TDF curves. We show the importance of integrating the information concerning climate change and climate oscillations. In an application to the province of Quebec, Canada, the influence of Atlantic Multidecadal Oscillations (AMO) on heat events is shown to be more important than the temporal trend.

Figure 1

Nonstationary TDF surfaces and 3-day maximum temperatures against the covariate at Sherbrooke and Montréal stations. Nonstationary TDF surfaces are presented for the stations at Sherbrooke (a) and Montréal (c) with the covariates Time and AMO respectively. The 3-day maximum temperatures are represented for the stations of Sherbrooke (b) and Montréal (d) against the covariates Time and AMO respectively. Red dots represent observations. (b,d) are cross sections in (a,c) respectively.

Figure 2

Comparison of the 10-year quantiles for the stationary TDF model and the nonstationary TDF models. 10-year quantiles for the stationary TDF model, the nonstationary TDF model Time for the case of the last year of record, the nonstationary TDF model AMO for the largest and lowest observed values of AMO (−0.47 and 0.51) and the nonstationary TDF model Time + AMO for the 2 years with the largest and lowest observed values of AMO (1974 and 1998) and their corresponding values.