Flash Drought Frequency and Intensity Do Not Move Together in Iran: Scientific Reports Detects 7,044 Rapid-Onset Events, 16.9 Percent Lasting over 90 Days, in Data from 2003 to 2023
Scientific Reports published a study by Hossein Shafizadeh-Moghadam on November 11, 2026, quantifying three distinct characteristics of flash drought across the major hydrological basins of Iran. The analysis used pentad-scale, 0 to 100 centimeter depth-averaged soil-moisture percentiles derived from ERA5-Land and GLDAS-2.1, covering 2003 to 2023.
Events were detected when soil moisture declined from above the 40th to below the 20th percentile within four pentads, at a mean rate of at least five percentile points per pentad. The analysis identified 7,044 rapid-onset pixel events. Of these, 1,188, or 16.9 percent, continued beyond 90 days, and 88 right-censored candidates were excluded from completed-event persistence.
Basin means ranged from 0.004 to 0.707 events per pixel per year, from 12.33 to 17.72 percentile points per pentad for intensification rate, and from 33.56 to 54.78 days for restricted persistence. A three-group PAM typology of 13, 12 and 5 basins revealed substantive within-country heterogeneity, although its silhouette score of 0.254 and bootstrap Jaccard values of 0.591 to 0.627 indicate an exploratory rather than definitive partition.
Five basin-metric trends had raw p values below 0.05, but none remained significant after false-discovery-rate correction. The author concludes that recurrence, onset rapidity and subseasonal persistence are related but non-interchangeable dimensions of flash drought behavior. All figures follow the abstract of the paper.
Source: Scientific
Published by GSM · USA (original Chinese edition)
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