Drought trends projection under future climate change scenarios for Iran region

and worsening drought event in the future than the last three decades for Northern Ethiopia. Monitoring drought patterns in the future climate highlighted the urgency for breeding drought-tolerant lines to secure crop productivity in rainfed regions such as Australia. Appli- cation of potential evapotranspiration (PET) in assessing influences of climate change on drought variation in the Andean high mountain basin illustrated that the evaluation of droughts in complex terrain in tropical regions should be promoted, where the representation of convection is the main limitation of global climate models [20]. In other work [15], the authors projected SPI and SPEI under adjusted outputs of global climate models in Turkey. The projections indicated fewer drought events for the near-future period of 2016–2040, with no potential extreme drought events. [21] compared indices of SPEI, SPI and Streamflow Drought Index (SDI) in identifying future drought characteristics in Cheongmicheon water- shed, Korea, under general circulation models. According to the obtained results, the SPEI showed the most robust pattern with significant increases in both drought frequency and severity. In regard to the previous investigations [22, 23], it can be inferred that drought characteris- tics alter over time due to climate changes and among regions with different climate condi- tions [24]. Accordingly, forecasting and monitoring drought would be worthwhile and beneficial in management of this phenomenon and would reduce losses due to it. Although

several studies have addressed similar topics, it should be mentioned that the vast majority of them are based on regional scales for a short period of time. Whereas, the investigation of drought for a long time in large scales considering different climatic conditions under distinct climate change scenarios has been paid less attention. This kind of study is more benefit for an area with acute water shortage such as Iran which faces long-lasting droughts for several times. Given that, the present investigation could have an advantage in terms of considering distinct climates over a large scale. Moreover, evaluating drought using the SPEI for a long term in dif- ferent climates can justify the importance of the present study. The findings of this investiga- tion could be used in managing water resources and administering sufficient policies for tackling the future water shortage crisis. 2. Material and methods Geographically, Iran is located at 25.05 to 39.78 Northern latitude and 44.08 to 63.30 Eastern longitudes. This study relied on the records of daily dataset collected from 30 synoptic stations for a 20 years period (1992–2010) for the assessment of the impacts of changes in climate con- ditions on drought. These stations were mainly considered for the quality of the data, as well as the uniformity in the period of data collection. Although some stations have data for a longer period of time, considering stations with the same time scale and no data missing matters to comparing the results under a reliable condition. There is no hesitation that any filling data

technique has an error and will affect the findings, accordingly, to avoid any error related to missing data, this period of time was considered which had no data gap. In other words, data- sets based on poor gauge coverage can produce substantial uncertainty when gaps are filled with data from different sources based on some climatology statistics [25]. Another consider- ation is that the stations are in different climatic locations which give a good sense of regional spatial distribution. Fig 1 depicts the distribution and location of the considered stations, as well as their climatic predispositions as per the Koppen system of climate classification [26]. Northern Iran is mainly the farming area of the country to the favourable weather condi- tion in the area. This necessitated the citation of several weather stations in northern Iran than the other areas of the country. The assessment of drought can be carried out by a variety of indices, however accuracy of each index changes in different regions. For instant, high PLOS ONE Drought trends projection under future climate change scenarios for Iran region PLOS ONE | https://doi.org/10.1371/journal.pone.0290698 November 9, 2023 3 / 24