شناسایی الگوهای زمانی و مکانی خشک‌سالی در جنوب شرق ایران با رویکردی مبتنی بر روش گرافیکی تحلیل روند

ABSTRACT
Southeastern Iran, characterized by an arid climate, has recently experienced acute drought conditions and significant water scarcity. This study examines the spatiotemporal dynamics of drought and associated climatic parameters in the region. Minimum and maximum temperature and precipitation data from 20 meteorological stations (1995–2018) were obtained from the Iran Meteorological Organization. The Standardized Precipitation–Evapotranspiration Index (SPEI) was subsequently calculated, and its time series analyzed to quantify drought characteristics, including intensity, duration, severity, and frequency. Trends in climatic parameters were assessed using the Innovative Trend Analysis (ITA) method. Results show that the region experienced pronounced wet conditions until the end of 1997, followed by increasingly intense and prolonged drought events from the late 1990s onward. Within this period, the most extreme drought was observed in Chabahar in 2009 (SPEI = –4.4), while the wettest condition occurred in Anar in 1996 (SPEI = 2.5). Additionally, the greatest drought intensity was recorded at Bam (–1.48), the highest frequency in Khash (18.75%), and the most severe drought conditions in Baft, Qeshm Island, and Bam (–12.06, –11.65, and –11.35, respectively). These locations represent the most critically affected zones within the study region. The ITA results further revealed a significant upward trend in summer temperatures and a pronounced decline in precipitation during the cold season. The observed decline in SPEI values across wet categories underscores the direct influence of climate change on regional water resources.
Extended Abstract
Introduction
Drought represents one of the most persistent and insidious environmental hazards confronting arid and semi-arid regions worldwide. It develops gradually, often without a distinct onset or termination, yet generates profound and enduring socio-economic and environmental repercussions. Unlike abrupt extreme weather events such as floods or cyclones, droughts unfold silently, progressively undermining ecosystems, human livelihoods, and economic stability. According to the World Meteorological Organization (WMO), droughts accounted for 34% of all disaster-related fatalities worldwide between 1970 and 2019.
In southeastern Iran—a region marked by aridity, elevated temperatures, and highly variable rainfall—the frequency, intensity, and duration of drought events have intensified in recent decades. These changes are driven by climate change, atmospheric circulation anomalies, and insufficient water management infrastructure. Given these challenges, understanding the spatiotemporal dynamics of drought is crucial for effective resource planning, evidence-based policy formulation, and the development of robust disaster mitigation strategies.
 
Methodology
This study investigates the temporal and spatial dynamics of drought in southeastern Iran through a quantitative framework grounded in climatological and hydrometeorological analysis. The study area covers approximately one-quarter of Iran’s territory, including the provinces of Sistan and Baluchestan and Kerman, along with parts of Hormozgan, South Khorasan, Yazd, and Fars. This region is characterized by hyper-arid to semi-arid climatic zones, with mean annual precipitation ranging from 68 to 214 mm and average temperatures between 14°C and 27°C.
Climatic data—including minimum and maximum daily temperatures as well as total monthly precipitation—were obtained from 20 synoptic meteorological stations across the study area for the period 1995–2018. The Standardized Precipitation–Evapotranspiration Index (SPEI) was employed as the principal drought indicator because of its capacity to integrate precipitation and temperature anomalies. SPEI values were calculated on a 12-month timescale to represent long-term hydrological drought conditions. To examine the temporal characteristics of drought events—including severity, duration, intensity, and frequency—the study applied Run Theory, which identifies uninterrupted sequences of negative SPEI values exceeding a defined threshold.
In addition, the Innovative Trend Analysis (ITA) method was employed to detect trends in temperature, precipitation, and drought behavior. ITA offers a non-parametric graphical approach that circumvents assumptions related to data distribution, autocorrelation, and seasonality. By dividing time series into two sub-periods, independently ranking the values, and comparing their distributions against a 1:1 reference line, ITA yields nuanced insights into concealed or nonlinear trends that conventional tests (e.g., Mann–Kendall) may fail to detect.
 
Results and discussion
SPEI-based drought monitoring revealed that, until 1997, southeastern Iran experienced moderate to extreme wet conditions, particularly at stations in Kerman Province such as Anar, Shahr-e Babak, and Rafsanjan, where SPEI values exceeded +2.5 in 1996. From the late 1990s onward, however, the frequency and persistence of drought events increased markedly. The periods 1998–2002, 2006, and 2008–2012 emerged as the driest intervals within the study period. Stations in Sistan and Baluchestan—such as Zahedan, Zabol, Zahak, Iranshahr, and Khash—exhibited the greatest SPEI fluctuations, with prolonged drought durations of 5 to 7 years.
The most extreme drought was recorded at Chabahar in 2009, where SPEI dropped to −4.4, signifying an exceptional event. By contrast, Anar experienced the wettest year in 1996, with an SPEI of +2.5. Run Theory analysis further quantified drought characteristics: average intensity ranged from −1.15 to −1.48 across stations, while magnitude values extended from −4.5 to below −12, with the most severe conditions recorded in Bam, Baft, and Qeshm. Drought frequency varied between 10% and 19% across the region, with Khash, Saravan, and Zabol exhibiting the highest recurrence rates.
Spatial analysis revealed a clear pattern: lowland coastal areas, including southern Hormozgan and Sistan, exhibited the highest drought susceptibility due to elevated temperatures and intense evapotranspiration, whereas upland regions such as Kerman and its surroundings experienced comparatively more favorable moisture conditions. Seasonal maps of SPEI distribution corroborated this spatial contrast, particularly during winter and spring.
Trend analysis using ITA revealed significant increases in maximum temperatures, particularly during summer, consistent with broader global warming patterns. Minimum temperatures increased during spring, summer, and autumn, but declined significantly in winter. Winter precipitation exhibited a pronounced declining trend, particularly within the 80–120 mm range. These shifts in temperature and precipitation patterns culminated in a downward trend in SPEI values, particularly within categories denoting moderate to extreme wetness. These transitions reflect not only increasing aridity but also the weakening of historically wet periods, underscoring the intensification of drought across the study region.
 
Conclusion
This study demonstrates that southeastern Iran is experiencing pronounced climatic shifts, characterized by declining precipitation, rising temperatures, and increasingly severe and prolonged droughts. These trends pose serious risks to water availability, agricultural sustainability, and the overall resilience of the region. The findings underscore the urgent need for adaptive climate strategies and sustainable water management policies to mitigate the intensifying impacts of climate change in this highly vulnerable region.
 
Funding
There is no funding support.
 
Authors’ Contribution
Authors contributed equally to the conceptualization and writing of the article. All of the authors approved thecontent of the manuscript and agreed on all aspects of the work declaration of competing interest none.
 
Conflict of Interest
Authors declared no conflict of interest.
 
Acknowledgments
 We are grateful to all the scientific consultants of this paper.