Drought trends projection under future climate change scenarios for Iran region

will sharply increase over time. On average, about 17.74 percent of months over all the stations are likely to experience drought throughout the future years up to 2112. This finding reveals that the frequency of drought events will increase under the B1 scenario compared to the base period. Among them, the highest percentage of dry months is observed in Shiraz with 19.69%, while the lowest proportion is related to Bandarabas with 14.79 percent. Comparison of dry months demonstrates that the great number of months with extreme drought is seen in Yazd with 1.23 percent. For all stations, the number of months with moderate drought is substan- tially more than severe and extreme droughts. In contrast, the consequences of the humid events indicate that approximately 18.55 percent of months in all stations will experience wet months. Esfahan will experience the highest frequency of humid months over the upcoming period; however, the number of months with extreme wet is seen in Boshehr with 2.37%(29 months). It is remarkable that for all stations, the occurrence probability of moderate humid months is more than that of severe and extreme humid months. Although, the number of months with extreme wet or extreme drought is substantially less than others, it should be noted that losses and damages of extreme wet or drought would be considerably more than Table 3. Frequency of the SPEI based on the percentage of months in the base period. Station Extreme wet Severe wet Moderate wet Normal Moderate drought Severe drought Extreme drought

Ahvaz 0.00 11.40 3.95 72.37 3.07 7.89 1.32 Arak 0.44 5.26 14.91 64.91 6.58 6.14 1.75 Ardebil 3.07 3.51 8.77 65.79 14.04 3.51 1.32 Bandar abas 0.00 9.65 14.91 60.53 11.40 3.51 0.00 Birjand 0.00 2.19 21.93 50.44 23.68 1.75 0.00 Bojnoord 0.00 8.77 7.89 66.67 10.53 6.14 0.00 Boshehr 2.63 6.58 3.51 74.12 7.89 0.88 4.39 Esfahan 0.00 7.02 11.40 63.60 12.28 5.26 0.44 Ghazvin 0.00 8.33 10.09 64.47 10.96 5.70 0.44 Ghom 0.44 6.58 9.65 64.47 13.60 4.82 0.44 Gorgan 1.32 3.51 11.40 67.54 7.46 7.46 1.32 Hamedan 1.32 6.14 7.89 68.86 8.77 5.70 1.32 Ilam 0.00 7.89 7.89 67.11 11.40 5.70 0.00 Karaj 0.00 5.26 11.84 63.60 14.47 4.82 0.00 Kerman 0.00 9.21 9.65 64.91 11.40 4.82 0.00 Kermanshah 0.00 8.77 8.33 66.67 7.89 7.89 0.44 Khoram abad 0.44 7.02 11.40 64.47 8.77 7.02 0.88 Mashhad 0.00 9.65 6.58 67.54 9.65 6.14 0.44 Oroomie 0.00 10.53 10.09 61.84 14.47 2.19 0.88 Rasht 0.44 7.89 8.77 68.86 7.89 4.39 1.75 Sanandaj 0.44 6.58 11.84 62.28 10.96 7.89 0.00 Semnan 0.00 9.65 7.89 69.30 7.46 1.32 4.39 shahrekord 0.00 7.02 8.77 64.91 14.04 5.26 0.00 Shiraz 0.00 9.65 10.53 64.91 8.33 5.70 0.88 Tabriz 0.00 8.33 9.65 67.98 8.33 3.95 1.75 Tehran 0.00 4.82 11.40 61.84 17.54 3.95 0.44 Yasooj 0.00 3.07 14.04 63.16 13.60 5.26 0.88 Yazd 0.00 7.89 12.72 61.84 12.28 4.82 0.44 Zahedan 3.07 2.19 10.96 64.47 14.47 4.82 0.00 Zanjan 0.88 6.14 11.40 64.91 8.77 7.02 0.88

Total 0.48 7.02 10.34 65.15 11.07 5.06 0.89 https://doi.org/10.1371/journal.pone.0290698.t003 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 10 / 24