Intense industrial activity has led to an increase in greenhouse gas concentration in the Earth’s atmosphere over the past few decades, whereby the climate change phenomenon has been recognized. Increasing greenhouse gases have been changing patterns and trends of extreme climate variables that are of great importance in agriculture, water resources, and environmental hazards. In the present study, the changes and trends in climate extremes of temperature and precipitation were evaluated based on various extreme-related indices over Iran. For this purpose, both daily temperature and precipitation data of 76 synoptic stations were selected for trend analysis throughout Iran during the period 1981–2010. The nonparametric Mann-Kendall trend test and Sen’s slope estimator are used to investigate the trends in the selected data sets. The results of 11 extreme temperature-related indices showed, in general, warm indices such as the number of warm days (TX90p), warm nights (TN90p), and warm spell duration (WSDI) had an increasing trend whereas trends in cold indices such as the number of cool days (TX10p), cool nights (TN10p), and cold spell duration (CSDI) decreased. The monthly maximum value of daily maximum (TXx) and minimum (TNx) temperatures increased by 0.3 and 0.4 °C/decade on average, respectively; and the monthly minimum value of daily maximum (TXn) and minimum (TNn) temperatures increased by 0.1 and 0.3 °C/decade, respectively, on average during the study period. In the case of the extreme precipitation-related indices, the results indicated both a decreasing trend in precipitation amount and intensity, and an increasing trend in the number of consecutive dry days (CDD) at most of the selected stations. Surveys demonstrated that the western, northern, and northwestern regions of Iran were most affected by the risk of climate extremes. Thus, these extreme changes will make people more vulnerable to natural hazards and make proper management in the face of climate crises more necessary.

在过去的几十年中，激烈的工业活动导致地球大气中温室气体的浓度增加，从而认识到了气候变化现象。温室气体的增加一直在改变极端气候变量的模式和趋势，这些极端变量在农业，水资源和环境危害中具有重要意义。在本研究中，根据伊朗各地的各种极端相关指数评估了极端温度和降水的气候变化和趋势。为此目的，选择了1981年至2010年期间整个伊朗的76个天气观测站的每日温度和降水数据进行趋势分析。非参数Mann-Kendall趋势检验和Sen斜率估计器用于调查所选数据集中的趋势。11个与极端温度相关的指数的结果表明，总的来说，温暖的指数（例如，温暖的日子（TX90p），温暖的夜晚（TN90p）和温暖的持续时间（WSDI））呈上升趋势，而寒冷的指数诸如此类。随着凉爽天数（TX10p），凉爽夜数（TN10p）和寒冷拼写持续时间（CSDI）的减少。每日最高（TXx）和最低（TNx）温度的每月最大值分别平均增加了0.3和0.4°C /十年。在研究期间，每日最高（TXn）和最低（TNn）温度的每月最小值分别平均增加了0.1和0.3°C /十年。在极端降水相关指数的情况下，结果表明降水量和强度均呈下降趋势，而且大多数选定站点的连续干旱天数（CDD）呈上升趋势。调查表明，伊朗的西部，北部和西北部地区受极端气候风险的影响最大。因此，这些极端的变化将使人们更容易受到自然灾害的影响，并在面对气候危机时更加有必要进行适当的管理。