Analysis of the Relationship between North Sea-Caspian tele-connection Pattern and Minimum Temperatures in Iran

In this study, linking between the North Sea–Caspian Pattern (NCP) and minimum temperatures fluctuation in Iran for 60 years period (1950-2010) has been investigated. The data used in this study included monthly temperature data from 17 synoptic stations in different regions of Iran, the NCP index data and upper atmospheric reanalysis data (geopotential height, zonal wind, meridional wind, temperature and thickness (1000-500 Hpa)). Pearson correlation analysis as the main method was used in this study and showed an inverse significant relationship between minimum temperatures in most selected stations and NCP index. This proves a decrease of temperature in positive phase of the NCP and increase of minimum temperature in negative phase. In terms of temporal analysis, there was a significant negative correlation between the minimum temperatures of stations and the NCP in months of January, March and February. In between stations, the monthly highest calculated correlation with -0.349 (=0.01) was computed in January. Calculated seasonal correlations show that the highest significant correlation between NCP and minimum temperatures is for winter with -0.237 (=0.01). From periodical perspective, the results indicate a strong correlation between cold period and NCP in most stations. Zahedan station had the weakest correlation with the NCP. This is probably due to its remoteness from active centers of NCP. Atmospheric patterns in 500 Hpa level in positive and negative phases of positive phase, prove the settlement of a deep trough on the Caspian Sea, Iraq, Turkey and Iran, and also the location of Iran in the eastern part of the trough axis and on the other hand, the settlement of a deep ridge on the North Sea and Europe led to the advections of cold temperature from Northern Europe near polar regions in Arctic to Iran. In negative phase placement of the study area beneath the ridge axis, led to the creation of a barotropic atmosphere with weak zonal wind and advections of warm temperatures to Iran. Therefore, with advections of warm temperatures from Africa, Arabian Pennsylvania and low latitudes, temperatures rise in Iran.