Drought trends projection under future climate change scenarios for Iran region

other situations. Thus, crisis management in each region should be designed for extreme conditions. From the data given in Table 5 it can be inferred that like the results of Table 4, for all the regions the frequency of drought in the third period is substantially more than the previous periods. This value is about 35.08 percent, which is higher than the B1 scenario, by a broad margin. As an overall trend, the results of Table 5 indicate that, the frequency of dry months in Iran over the studied period (from 2011 to 2112) will be about 18.46 percent, which is more than the observations in the B1 scenario (e.g., 17.74 percent). Thus, it can be concluded that the proportion of predicted drought under the A1B scenario is more than the B1 scenario. Subsequently, this value is far more than the number of droughts in the base period. This find- ing is in agreement with the survey of [43], who reported that the emission scenario of B1 always produces less severe extreme disasters. This is because the emission scenario of B1 assumes that the future world will be sustainable with quick variations in economic structures and more efforts in introducing clean technologies. Detailed consequences illustrate that the number of months that will be affected by moder- ate drought is considerably more than others. Arak can be introduced as a station that will face the highest number of moderate droughts over the next period, with 199 cases (16.26%). How- ever, the most proportion of months with extreme drought will be seen in Ardebil with

1.31percent, which can be a serious problem for water resources of this region. Overall, the highest frequency of dry months will belong to Shiraz, 259 months from 1224 months (21.16%). Thus, it can be mentioned that the probability of drought incidence in Shiraz would be the most among all the stations. Evaluating the results related to humid periods depict that for all stations, the number of months with moderate wet is significantly more than those with severe and extreme wet. Moreover, the number of months with extreme wet is considerably less than the severe wet. Looking in more detail, it can be seen that the highest frequency of humid months will be observed in Ghazvin with 20.10 percent, whereas the lowest frequency would be related to Hamedan, with 16.01percent. The findings of wet intensity show that the greatest number of extreme wets will occur in Boshehr, with 2.46 percent in comparison to 0.90% for Ghazvin as the lowest number. The information given in Table 6 depicts that the frequency of droughts in the third period are dramatically more than the previous periods. This difference is completely significant. This amount is about 40.81 percent in comparison to 6.72 and 10.16percent for the first and second periods respectively. It can be seen from Table 6 that the number of dry months under the A2 scenario (19.23percent) is more than the B1 and A1B scenarios (17.74 and 18.46percent). Due to the fact that the A2 scenario is introduced as a high emission scenario which describes a very het-

erogeneous world, this result seems to be reasonable and rational. Furthermore, this finding is consistent with other studies. For instance, in the survey of Akbari et al. (2016) [44], the high- est temperature, and the lowest precipitation prognosticated belonged to the A2 scenario. Fur- thermore, this result corresponds to the results of [45]. They indicated that a drought event with more intensity, duration and frequency than the base period can occur in future periods under the A2 scenario in northwest of Iran. According to the study of Modarres et al. (2018) [46], the average of the rainfall events will reduce in evaluating future extreme rainfall changes in the north of Iran as well. It can be an alarm in applying effective strategies for the future water resources in this area. An increasing trend of drought under the A2 scenario has been declared by [47], which is in line with the present forecasted consequences. The conducted research by [48] for assessing the future temperature in Iran, researchers declared that the maximum temperature changes will be increased more severely based on the A2 scenario 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 17 / 24