No region is independent from the point of view of climate, and the dominant climatic pattern in one region affects other regions, because there is a systematic atmospheric relationship between them in spite of climatic disparities between different regions; for instance changes occurring in tropical regions cause atmospheric differences between the areas of mid-latitude and other areas.
In general, there is always a completely distinct relationship between dominant weather conditions in high latitudes and those of low latitudes. Therefore, the earth's atmosphere works as a single system, in such a way that the change of air circulation from an area of the northern hemisphere to other parts affects the upstream or downstream of that region (Busher, translated by Qaemi, 1994).
The purpose of this paper is to present the variable state of air circulation, help provide a relative knowledge of climate change and unusual situations of pressure and air flow in the North Atlantic. The behavior of pressure systems in the Atlantic Ocean affect each other, and on the other hand they can also affect the climate of Iran directly or indirectly (Alijani, 1987).
  Hence, the knowledge of the status of these systems will be a basis for understanding the origin of some climatic behaviors in Iran. In order to understand the synoptic patterns generated from different phases of the North Atlantic oscillation, pressure distribution and abnormalities on the surface of the earth and in the Atlantic Ocean have been considered.