Synoptic Assessment of Climate Change and Its Impact on Rainfall Design at the Holy Site of Arafat, Makkah Al-Mukarramah, Saudi Arabia

Synoptic climatology offers a powerful lens for understanding atmospheric mechanisms that govern regional precipitation trends. In arid regions like Makkah Al-Mukarramah, subtle shifts in large-scale climate drivers can significantly alter rainfall behavior. This study evaluates the presence and impact of climate change at the Holy Site of Arafat by employing synoptic analysis based on NOAA datasets (1966–2022) focusing on geopotential height at 500 mb, sea-level pressure, and zonal wind at 250 mb. Observed changes in these parameters indicate a strengthening of high-pressure systems and a northward shift of rainfall belts, suggesting a drier regional climate with potential for more localized intense storms. To quantify how these atmospheric changes influence rainfall design, Intensity–Duration–Frequency (IDF) curves were developed using rainfall station data (9004 and J330) for two time periods: 1966–1994 and 1995–2022. A modest increase in rainfall intensity–-ranging from 5.7% to 7% for return periods of 50, 100, and 200 years–-was found. The study concludes that rainfall design calculations in Arafat should incorporate a climate change adjustment factor, and emphasizes the critical role of synoptic analysis in updating hydrological models.