كاربرد الگوهاي كلان مقياس جوي-اقيانوسي در تحليل نوسانات بارش (مطالعه موردي: ايستگاه اهر)

The Application of Large-scale Atmospheric-oceanic Patterns in the Analysis of Precipitation Fluctuations (Case Study of Ahar Station)

Using seasonal precipitation data of Ahar synoptic station, we have estimated a 47-year period (1960-2006) record fluctuations in this paper. The significance of seasonal changes was evaluated through Mann-Kendal test. Results indicated the significance of winter precipitation. Statistical analyses proved the significance of relationship between seasonal precipitation and tele-connection patterns. In this regard the relation of fall precipitation with atmospheric-oceanic pattern (ENSO) in warm phase causes increased precipitation while causing drought during cold phase (LANINA).The correlation between winter precipitation and tele-connection patterns of North Atlantic and Arctic Ocean fluctuations was also significant. During the negative phases of North Atlantic fluctuations, the increased amounts of entering cyclones to the area causes increased precipitation, whereas in positive phases thanks to the dominance of Azure anticyclone the precipitation reduces. The application and testing of various drought appraisal models also emphasize the fact that drought occurrence in Ahar is irreversible sometimes, and each of the utilized indexes indicate one dimension of seasonal and monthly dry and wet years.