Document Type : Research/Original/Regular Article
Authors
1
B.Sc. Student in Water Science and Engineering, Department of Water Engineering, Faculty of Agricultural Engineering, Sari Agricultural Sciences and Natural Resources University (SANRU), Sari, Iran
2
Postdoctoral Researcher, Department of Water Engineering, Faculty of Agricultural Engineering, Sari Agricultural Sciences and Natural Resources University (SANRU), Sari, Iran
3
Professor of Water Engineering Department, Faculty of Agricultural Engineering, Sari Agricultural Sciences and Natural Resources University (SANRU), Sari, Iran
Abstract
Changes in temperature can have far-reaching consequences for the environment, agriculture, weather patterns, human societies, and the economy. Precipitation is another fundamental climatic variable that substantially influences both natural systems and human activities. In this study, long-term meteorological data including minimum and maximum temperatures and precipitation were used to investigate trends at 14 synoptic stations across Mazandaran Province during the baseline period (2000-2024) and the near-future period (2030-2055). Widely used climate-extreme indices were calculated, and their spatiotemporal trends were assessed using observational data for 2000-2024 and downscaled CMIP6 projections generated by the CNRM-CM6-1 model for 2030-2055 under the SSP1-2.6 and SSP5-8.5 scenarios. The climate projections were downscaled using CMHyd, and trends were analyzed using the Mann-Kendall test. Analysis of the extreme precipitation indices revealed substantial spatial heterogeneity in the occurrence and intensity of extreme precipitation events across Mazandaran Province. In general, stations in the western part of the province, particularly Ramsar, exhibited higher values of extreme precipitation indices than those in the central and eastern regions. For example, during the baseline period, RX1day reached 151.29 mm in Ramsar, compared with 65.9 mm in Galoguh, while PRCPTOT was 1,266.97 mm in Ramsar and 562.06 mm in Galoguh. These differences highlight the dominant role of moisture supplied by the Caspian Sea and the enhanced orographic uplift along the Alborz Mountains in generating intense regional precipitation. The warm-temperature indices indicate that Mazandaran Province is experiencing concurrent increases in maximum temperatures, nighttime warming, the number of tropical nights, and the frequency of extremely hot events. Although spatial differences between the mountainous and coastal areas persist, the thermal contrast between these regions is diminishing. During the baseline period, TR20 was limited to 4.00 days in Alasht and 6.22 days in Kojur. In contrast, the number of frost days in Kojur is projected to decrease from 117.43 days during the baseline period to 77.44 and 76.31 days under SSP1-2.6 and SSP5-8.5, respectively, indicating pronounced warming at higher elevations. Collectively, these patterns point to a marked climatic transition from historically temperate conditions toward more intense heat, increasingly persistent warm nights, and greater thermal stress across the province. Given the projected intensification of heat stress at both coastal and mountainous stations, coupled with longer dry spells and fewer frost days at higher elevations, adaptation strategies in Mazandaran Province should prioritize the cultivation of heat-tolerant crop varieties, adjustments to planting calendars, and the adoption of more efficient irrigation and water-allocation practices.
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