Drought monitoring is very important for water resource planning due to the impact of climate change on the frequency of drought events. The objective of this study was to evaluate the spatiotemporal characteristics of drought in Iran. Spatial and temporal distributions of drought severity were assessed using the well-accepted standardized reconnaissance drought index (RDI_st) in seasonal and annual scales in 40 synoptic meteorological stations of Iran during the years 1967–2014. Parametric and nonparametric statistical tests were further used for trend assessments. According to the results of RDI_st on an annual time scale, the trends of drought were positive in 87.5% of the stations. The results of seasonal RDI_st also indicated that the trends of drought in winter (92.5%), spring (82.5%), summer (37.5%), and fall (67.5%) were upward. In sequence series of all seasons, 90% of all stations had a negative trend in the value of their calculated RDI_st over time, which means an upward trend in drought over time. Our findings demonstrated an upward trend in drought over the study period. In 45% of the studied stations, winter had the most significant positive trend at all time scales. The results also showed that a moderate drought covered the highest portion of the study area. Generally, a positive trend was observed in coverage of extreme, severe, and moderate drought. However, a negative trend was evident in the coverage of extreme, severe, and moderate wet conditions during the time. It is suggested that the spatiotemporal distribution of the RDI_st trend can be used to identify drought and mitigate its impacts in Iran.

由于气候变化对干旱事件发生频率的影响，干旱监测对于水资源规划非常重要。这项研究的目的是评估伊朗干旱的时空特征。1967-2014年间，在伊朗的40个天气气象站中，使用公认的标准化侦察干旱指数（RDI _st）在季节和年度尺度上评估了干旱严重程度的时空分布。将参数和非参数统计检验进一步用于趋势评估。根据RDI的结果_ST上年度时间尺度，干旱的趋势是在车站的87.5％阳性。季节性RDI的结果_ST还表明，冬季（92.5％），春季（82.5％），夏季（37.5％）和秋季（67.5％）的干旱趋势呈上升趋势。在所有季节的序列系列中，所有电台的90％的RDI _st计算值均呈负趋势随着时间的推移，这意味着干旱随着时间的推移呈上升趋势。我们的发现表明，在研究期内干旱呈上升趋势。在所研究台站的45％中，冬季在所有时间尺度上都有最显着的积极趋势。结果还表明，中度干旱覆盖了研究区域的最高部分。一般而言，极端，严重和中度干旱的覆盖率呈积极趋势。但是，在这段时期内，极端，严重和中度潮湿条件的覆盖率出现了负面趋势。建议将RDI _st趋势的时空分布用于识别干旱并减轻其对伊朗的影响。