Sea level circulation patterns and their relationship with atmospheric rivers affecting heavy rainfall in Iran

In order to identify effective sea level circulation patterns in creating atmospheric rivers associated with heavy rainfall in Iran, sea level pressure data in 940 days of the occurrence of this phenomenon were analyzed by principal components analysis(PCA) and reduced to 13 principal components, and by applying Ward Hierarchical clustering analysis on them, 5 main patterns or circulation types with subtypes were obtained.The results showed that the establishment and expansion of eastern and western high pressures in the mid latitudes and strong low pressures of high latitudes with weak to strong low pressures of low latitudes, especially Sudanese low pressure in the study area, in all circulation types, highlights the role of moisture transfer from two sources of the northern Atlantic and the northern parts of the Indian Ocean moisture which Through the strengthening resources of the Mediterranean and Red Seas, they supplied atmospheric rivers moisture and mainly caused heavy rains on the western slopes of the Zagros and southwestern Iran.