Seasonal Rossby Wave Dynamics Driving Winter and Summer Temperature Extremes in the Arabian Peninsula

Atmospheric Rossby waves exert a strong control on the emerging pattern of summer heat and winter cold over the Arabian Peninsula, yet their regional impacts remain poorly quantified. This study uses 25 years (2000–2024) of reanalysis and observational data to assess how upper-tropospheric Rossby wave activity modulates seasonal 2 m temperature extremes over Saudi Arabia and how these responses are embedded in large-scale teleconnections linked to ENSO and Indo-Pacific variability. The analysis focuses on the evolution of warm-core structures in summer, the spatial spread of winter cold anomalies, and two recent extreme years, 2017 and 2023, that reveal the sensitivity of the Peninsula to Rossby wave regime shifts.

Results show a progressive amplification and spatial expansion of August near-surface temperatures across Saudi Arabia, with the 37–38 °C isotherms migrating northward and westward after 2010 to form a quasi-continuous warm core spanning the eastern lowlands, Rub al Khali, and central plateau. The fraction of land exceeding 39 °C in August increased from isolated spots in the early 2000s to over 20% after 2015, signifying a step-like intensification of summertime heat. Composite analyses indicate that these hot cores coincide with upper-level anticyclonic ridges and subsidence maxima, consistent with Rossby wave–induced adiabatic warming and suppressed convection.

Within this long-term warming context, 2017 stands out as a dynamical outlier. Amplified and breaking Rossby waves over the Middle East generated a quasi-stationary ridge over the Peninsula, producing exceptionally broad August heat with mean temperatures above 38 °C across central and northeastern regions. In winter 2017, enhanced wave activity drove deep trough intrusions and widespread sub‑16 °C anomalies, yielding an unusual combination of extreme summer heat and pronounced winter cooling within one year. A renewed Rossby forcing episode in 2023 accompanied one of the hottest summers on record, when the southeastern warm core intensified and spread northwestward while winter again featured strong meridional temperature gradients and broad cold coverage.

Wave activity flux diagnostics and teleconnection analyses reveal that both 2017 and 2023 extremes arose from Indo-Pacific–Eurasian Rossby wave trains. In 2017, La Niña–like conditions and a positive Indian Ocean Dipole excited a Eurasian wave train that channelled energy along the subtropical jet, reinforcing anticyclonic ridging in summer and deep winter troughs. In 2023, an ENSO phase transition under neutral IOD conditions triggered renewed Rossby dispersion from the tropical western Pacific into the Asian jet, again focusing anomalous ridging and subsidence over the Peninsula.

These results suggest that modest upstream anomalies now yield amplified regional thermal responses, implying increased dynamical gain due to background warming and altered land–atmosphere coupling. The findings point to a Rossby wave–dominated regime shift since 2017, wherein upper-level wave geometry and teleconnections increasingly control the extent of summer heat and winter cold. Saudi Arabia thus emerges as a dynamically sensitive node in the global Rossby waveguide system.