Detection of Asymmetric Warming Signals and Intensification of Extreme Precipitation at the Sardasht Synoptic Station during 1986–2025

Soureh, Ehsan; Batmani, Bahareh; Rezaei Banafsheh Daragh, Majid

doi:10.30740/cccd.2026.2082548.1099

Detection of Asymmetric Warming Signals and Intensification of Extreme Precipitation at the Sardasht Synoptic Station during 1986–2025

Document Type : Original Article

Authors

Ehsan Soureh ¹

Bahareh Batmani ²

Majid Rezaei Banafsheh Daragh ³

¹ Ph.D. Student in Climatology, Faculty of Planning and Environmental Sciences, University of Tabriz, Tabriz, Iran

² PhD Candidate in Climatology, Faculty of Humanities, University of Zanjan, Zanjan, Iran

³ Department of Climatology, University of Tabriz

10.30740/cccd.2026.2082548.1099

Abstract

Changes in extreme climatic patterns, as the most prominent consequence of global warming, have created serious hydrological and ecological challenges in mountain ecosystems. This study analyzes the trends of extreme climate indices at the Sardasht synoptic station by examining downscaled temporal trends of 10 temperature and precipitation extreme indices (ETCCDI) over a 40-year period (1986–2025). After daily data quality control, the Mann–Kendall test and Sen's slope estimator were applied. The findings reveal a structural transformation in the region's climate regime, as a warming signal is observed across all temperature indices with statistical certainty (95% to 99.9%). The warm spell duration index has increased with a slope of +3.115 days/year, and tropical nights with a rate of +1.081 days/year, indicating intensified heat stress and disruption of nocturnal cooling. Conversely, frost days and ice days have decreased at rates of –1.259 and –1.059 days/year, respectively, confirming the decline of harsh winters and shortening of the cold season. Regarding precipitation, although the annual total shows no significant trend, the increase in the simple daily intensity index (+0.062 mm/day per year) suggests a shift toward short, intense downpours. Overall, the climate of Sardasht is transitioning from a temperate mountain phase toward conditions with compound extreme hazards (flash floods and heatwaves).

Keywords

Climate change

Extreme indices

Asymmetric warming

Precipitation intensity

Sardasht

Subjects