Abstract
Scientists who want to know future climate can use multimodel ensemble (MME) methods that combine projections from individual simulation models. To predict the future changes of extreme rainfall in Iran, we examined the observations and 24 models of the Coupled Model Inter-Comparison Project Phase 6 (CMIP6) over the Middle East. We applied generalized extreme value (GEV) distribution to series of annual maximum daily precipitation (AMP1) data obtained from both of models and the observations. We also employed multivariate bias-correction under three shared socioeconomic pathway (SSP) scenarios (namely, SSP2-4.5, SSP3-7.0, and SSP5-8.5). We used a model averaging method that takes both performance and independence of model into account, which is called PI-weighting. Return levels for 20 and 50 years, as well as the return periods of the AMP1 relative to the reference years (1971–2014), were estimated for three future periods. These are period 1 (2021–2050), period 2 (2046–2075), and period 3 (2071–2100). From this study, we predict that over Iran the relative increases of 20-year return level of the AMP1 in the spatial median from the past observations to the year 2100 will be approximately 15.6% in the SSP2-4.5, 23.2% in the SSP3-7.0, and 28.7% in the SSP5-8.5 scenarios, respectively. We also realized that a 1-in-20 year (or 1-in-50 year) AMP1 observed in the reference years in Iran will likely become a 1-in-12 (1-in-26) year, a 1-in-10 (1-in-22) year, and a 1-in-9 (1-in-20) year event by 2100 under the SSP2-4.5, SSP3-7.0, and SSP5-8.5 scenarios, respectively. We project that heavy rainfall will be more prominent in the western and southwestern parts of Iran.
Highlights
Extreme rain events can result in landslides and floods, accompanied with a loss of life and the deterioration of infrastructure
A simplified and major reason for more frequent extreme rainfall is the following: when the temperature increases, the saturation specific humidity of the air is higher and the air can contain a higher amount of water vapor, as dictated by the Clausius–Clapeyron relationship [8]
Zarrin and Dadashi-Roudbari [29] concluded that the trend and slope of the intensity of extreme precipitation are increasing by the year 2100 in all zones in Iran except for some areas (BWh, BWk, and Cfa zones) for SSP1-2.6 and SSP3-7.0 scenarios
Summary
Extreme rain events can result in landslides and floods, accompanied with a loss of life and the deterioration of infrastructure. Numerous studies have reported that extreme precipitation events have become more frequent during the last century, and are occurring even more often over the 21st century ([1,2,3,4,5,6,7], for example). A simplified and major reason for more frequent extreme rainfall is the following: when the temperature increases, the saturation specific humidity of the air is higher and the air can contain a higher amount of water vapor, as dictated by the Clausius–Clapeyron relationship [8]. When rain-triggering conditions are developed, more saturated air leads to heavier rainfall [9,10]. This has been the case across some areas of the world during the last century [11]. As written by Mann and Kump [12], “While many regions are likely to become drier, scientists predict that even in those regions individual rainfall or snowfall events will become more intense, longer dry spells will separate them.”
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