Recent Climatology (1991-2020) and Trends in Local Warm and Cold Season Extreme Temperature Days and Nights in Arabia.

The Arabian Peninsula (Arabia) is among the places to have experienced the greatest amount of warming during recent decades, and this trend is projected to continue. Specifics related to the characteristics (frequency, duration, and intensity) of extreme temperature events (ETEs) over Arabia as a whole are either largely outdated or limited only to specific areas. The seasonal ETE definitions commonly used in local studies are neither climatological- nor phenomenon-based. Using a novel and straightforward framework, the seasons of four extreme temperature types (extreme warm days/nights (EWDs/EWNs) and extreme cold days/nights (ECDs/ECNs)) were identified on the simultaneous basis of event occurrence and impact times. Assessments of ETE frequency, duration, and intensity and their recent changes were then provided based on the most recent climate data (1991-2020). Results showed that the use of traditional seasonal definitions (e.g., meteorological seasons) tends to assume a spatiotemporal homogeneity in the seasonality of ETEs and their potential risk levels throughout the year. The developed framework distinguished months with events that have larger potential impacts together with their local seasons. ETE seasons were found to vary at the regional and local scales and are better defined at both the local and phenomenon levels. Early extreme warm events were hotter, and those at locations with longer local warm seasons demonstrated higher intensities. ECDs tended to be more frequent at coastal locations, whereas ECNs were more frequent over southwestern Arabia. Early and late extreme cold events were much colder than those occurring mid-season. Trend analyses revealed generally increasing regional trends in the frequency of extreme warm events, whereas extreme cold events have declined. The duration (i.e., consecutive occurrences) and intensity of EWNs have been increasing at more locations, suggesting that urgent attention is needed within such an arid and hot climate type in which nighttime stress relief is already very limited.