Time-sensitive analysis of a warming climate on heat waves in Saudi Arabia: Temporal patterns and trends

The climate of the Middle East is warming and extreme hot temperature events are becoming common, as observed by the significant upwards trends in mean and extreme temperatures during the last few decades. Climate modelling studies suggest that the frequency, intensity, and duration of extreme temperature events are expected to increase as the global and local climate continues to warm. However, most of the literature about heat waves (HWs) in Saudi Arabia provides information about the duration aspect using a single index, with no detailed information about frequency and intensity aspects. To help establish a baseline for understanding past and future change, this study explored the temporal behaviour(s) of the frequency, duration, and intensity of HWs in Saudi Arabia under the observed recent climate change. Several issues are addressed including some methodological concerns associated with the commonly used heat wave index, data quality control, and statistical analysis. A new definition and method to detect HWs and their changes is proposed, considering the ongoing effects of climate warming and the subtropical arid climate. A HW event is defined as a period of two or more consecutive days (i.e., at least 48hr) with a daily maximum and minimum temperature exceeding the 90th and 85th percentiles of the maximum and minimum, respectively. Threshold percentiles were calculated monthly and adjusted for each decade of analysis. For temporal trend analyses, we consider HW events and their duration as count data using different Poisson models for analysis. HW frequency, intensity, and duration across Saudi Arabia were found to behave geographically and temporally differently across the 25 stations studied. Distinct temporal and geographical patterns were observed indicating a confounding interplay of regional and local factors, such as urbanization, elevation, latitude, and distance from a large body of water.