Statistical analysis of extreme weather events in the Diyala River basin, Iraq

Abstract

Extreme climate and weather events have direct impacts on human life, the environment, and resources. The Diyala River basin is shared between Iraq and Iran, which makes it vulnerable not only to climate change effects but also to upstream control. Therefore, understanding and predicting extreme events is an essential step to help decision-makers make proactive plans to reduce expected damages. The pattern of extreme events has been identified using climate extreme indices developed by the World Meteorological Organization and Expert Team on Climate Change Detection Indices using ClimPACT2 software. Data were obtained from three meteorological stations in Iraq (Sulaymania, Khanakin, and Baghdad) and one in Iran (Sanandaj) over a period of 20 years (2000–2020). Results for temperature showed seven statistically significant positive trends for only three indices (annual number of days with daily maximum temperature of >35°, difference between daily maximum and daily minimum temperatures, and percentage of days with maximum temperature of >90th percentile, indicating an increase in that temperature). Baghdad station had positive temperature trends for all indices. Trends for precipitation were nearly all nonsignificant and difficult to anticipate compared with those for temperature. Percentile-based indices showed more dry and warm events than wet and cold. HIGHLIGHTS Statistical analysis was performed for the Diyala River basin to obtain information about extreme climate indices during the last 20 years.; The nonparametric Mann–Kendall test was used to detect trends at annual, seasonal, and monthly scales.; The Weibull formula was used to predict the occurrence of extreme precipitation events.; Temperature showed a more significant trend than precipitation.;

Keywords

• climate change
• diyala river basin
• extreme climate change indices
• mann–kendall test
• probability distribution