Extreme Weather Events

Floods and droughts

Iran is experiencing unprecedented climate-related problems such as drying lakes and rivers, dust storms, record-breaking temperatures, droughts, and floods. Here, we use the ensemble of five high-resolution climate models to project maximum and minimum temperatures and rainfall distribution, calculate occurrences of extreme temperatures (temperatures above and below the historical 95^th and 5th percentiles, respectively), analyze compound of precipitation and temperature extremes, and determine flooding frequencies across the country.

Compound Extreme events

We found that compared to the period of 1980-2004, during 2025-2049, Iran is likely to experience more extended periods of extreme maximum temperatures in the southern part of the country, more extended periods of dry (for ≥120 days: precipitation <2 mm, Tmax ≥30 °C) as well as wet (for ≤3 days: total precipitation ≥110 mm) conditions, and higher frequency of floods. Overall, the combination of these results projects a climate of extended dry periods interrupted by intermittent heavy rainfalls, which is a recipe for increasing the chances of floods. Without thoughtful adaptability measures, some parts of the country may face limited habitability in the future.

Extreme hot days for the historical and future periods. (A) is the 95th percentile of historical maximum daily air temperature (Tmax) (°C) (1980–2004). The shown temperatures in (A) have occurred an average of 18 days per year. (B,C) show the number of days per year in the future (2025–2049) where extreme Tmax exceeds the historical value of 18 days. Most regions in Iran may experience longer extreme hot days of up to 2 months per year.

Flood projection in Iran

Our results show that average maximum temperature may increase by 1.1 to 2.75 C across the country, while rainfall may see an annual decrease of up to 150 mm in the western parts of the country and an increase of up to 150 mm in the north and south-central regions. Except for the north and north-west, the frequency of dry periods will significantly increase in most of the country, and for some regions in the north and particularly in the west frequency of wet conditions will substantially increase. Finally, future flooding frequencies at several investigated sites showed dramatic increases of up to 27 times in the western parts of the country, while the north sees small increases. The increase in the frequency of floods and wet periods in the west, while rainfall sees a decrease, is indicative of higher frequency of convective rains of shorter durations and higher intensities in most of the country