Drought trends projection under future climate change scenarios for Iran region

than other scenarios. In other words, the vast area of the country will receive precipitation less than 23.6 mm per month. However, this condition under the A1B and B1 scenarios seem bet- ter. Reduction of future precipitation in Iran has been reported by [40–42], that are in line with the current results. Table 3 depicts the drought characteristics of each station in the base period. Describing drought was based on the recommendation of Edwards and McKee (1997) given in Table 1. The information of this table shows the percentage of dry and wet periods in the base period. For instance, value 1.32 percent in Ahvaz refers to the fact that the SPEI in 3 months out of 228 months (19 years) are less than -2, which refers to an extreme drought (Table 1). Overall, 17.02 percent of the studied months in the base period faced the drought, whereas 17.84 percent were in the wet condition. The most intensive drought was observed in Boshehr, by 439 per- cent. The highest number of dry months belonged to Birjand with 25.44 percent. It is notice- able that regions with high precipitation like Rasht or Gorgan have also experienced drought periods. The similar results are reported by [37], that support the present findings. For presenting the calculated SPEI values for the future period, the percentage of months that SPEI values are within each category to all the considered months (e.g., 102 years or 1224 months) was counted. The findings under each scenario are shown in Tables 4, 5, and 6. In these tables, the number of months in each category has been presented as a percentage for

each studied station. From Table 4, it can be seen that the response of each station to future climate change is completely different during the studied period. Nevertheless, for most of the stations, the per- centage of drought events in the third period (2079–2112) is more than the other periods. The average percentages of potential drought occurrences for all the stations in the next three peri- ods are 8.89, 16.58, and 27.27 respectively. These values refer that the probability of drought Fig 3. Spatial distribution of the monthly PET and precipitation in the base period and the future under the A1B, A2 and B1 scenarios. https://doi.org/10.1371/journal.pone.0290698.g003 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 9 / 24