Point and regional analysis of drought in Northern Iran.

Here, daily precipitation depths in the period 2000–2018 were used in the 13 weather stations located in northern Iran. Three meteorological drought-related characteristics including severity (S_d), magnitude (M_d), and duration (L_d) were evaluated. The data were converted to the monthly scale by summation of the daily records for a given month. Five distinct truncation levels (TL) were selected. The maximum values of S_d, M_d, and L_d were calculated for each of the stations. Then, using the annual scale, the observed S_d and M_d series were subjected to frequency analysis. Regional droughts were analyzed using the cumulative annual precipitation depths in the stations. In each year, the area faced with drought was measured. In a monthly scale, after choosing the mean monthly precipitation ( x ¯ ) as a TL, the observed maximum value of L_d was less than 15 months. As the return period (Tr) increases, each of the drought characteristics increased as well. When the mean annual precipitation (MAP) was selected as a TL, the ratio of S_d in a 10-year to 2-year return period varied between 2.39 and 3.82, among stations. Similarly, in the case of M_d, this ratio varied in the stations between 1.88 and 3.75. Larger values of S_d and M_d were observed in western parts of the region. In the years 2008, 2010, and 2017, the study area experienced very severe regional droughts. The findings of this study may help decision-makers in better management of water in the region. [ABSTRACT FROM AUTHOR]