Extreme weather events related to climate change: widespread flooding in Iran, March–April 2019

Abstract

This study investigates the extreme weather pattern accompanying the widespread flash flooding in unpredicted areas during mid-March to April of 2019 in Iran. During this time, the active weather frontal system with heavy and insistent rainfalls drenched Iran (mostly north, west and southern), Iraq and Turkey (eastern part). The climatological mean and anomalies of the meteorological datasets from the National Centers for Environmental Prediction (NCEP) reanalysis model are examined, and synoptic and dynamical patterns are compared. The anomaly weather maps are created for different parameters to show the abnormal features during the study period (months of March and April 2019) presenting significant differences from the thirty-year climate normals of the period 1981–2010. This research shows an intensified pressure gradient, strong vertical motion and strengthened 500 hPa mid-tropospheric westerly currents during the study period. The relative humidity at 850 hPa shows on average ~ 4–11% higher values than the climate normal. The surface wind vector analysis reveals the intensified south flows originated from Oman sea and the Indian Ocean providing rather warmer and wet air mass encounters with an abnormal regional colder surface air mass. Upper level wind vectors at 250 hPa and vertical profile of the meridional wind anomalies exhibit a wavy jet pattern compared to the climate normal structure along with the significant vertical meridional wind shear as the sign of climate change. These abnormal atmospheric changes can contribute to forming extreme weather development over the study area during the study period. Also, understanding the recent extreme atmospheric changes in the study area may contribute to a better future forecast when such floods may happen again.