Collaborative Investigation of the Floods of Balikhlochai Watershed in Ardabil (Case Study: March 07, 2010 and December 08, 2010)

Flood as a natural disaster with the highest relative frequency of occurrence has always threatened human life. The purpose of this study was discovering the relationship between atmospheric circulation patterns and floods in the Balikhlochai watershed of Ardabil in order to prevent its dangers with an environmental approach to circulation. For this purpose, discharge data for three stations of Almas, Nir, and Gilandeh from the period 2009-2017 were obtained from the regional water department of Ardabil province. Using the ward hierarchical clustering method, two floods occurred on March 7, 2010 and December 8, 2010 were selected and analyzed. The data related to the upper levels of the atmosphere were obtained from the National Center for Environmental Prediction (NCEP-NCAR) website and combined maps of sea level pressure with geopotential height of 500 hectopascals, wind vector with precipitable water, omega with tawai and half-molar specific humidity in Gardes software were drawn. The results of the synoptic analysis showed that the dominance of the Mediterranean thermal low pressure system and the Chinese thermal high pressure system were important factors in the atmospheric disturbance, and besides that, the location of the studied area in front of the landing axis of the Eastern Mediterranean fleet resulted in rotating air movements. And the vertical air velocity of the studied area showed an unstable atmosphere. The specific humidity has also increased since the day before the flood in the lower layers of the atmosphere, and the flow of moisture from the Mediterranean Sea through the western subtropical winds on the atmosphere of the studied area has played an important role in causing torrential rains.