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Daryosh Yarahmdi, Asadollah Khoshkish, Mustafa Karampour, Ismail Ahmadi,
Volume 16, Issue 40 (3-2016)
Abstract

One of the Siberian high pressure system is the Earth climate system, atmospheric important. The purpose of this study, analysis of core changes Siberian high pressure system in the period mentioned. To identify the core spatial variations in the timeframe mentioned data, daily sea level pressure and temperature of the earth's surface with a resolution of 2.5 degrees within the space of 30 to 65 degrees north latitude and 130 degrees east longitude from the database 45 to NOAA NCEP / NCAR for the cold was extracted. The core of the GIS spatial data analysis system and two separate zones and point to output six decades was ten years old and were analyzed. To study the process of change, determine the direction of the trend, type and timing of changes in temperature and pressure of the core of the system the test of Mann-Kendal is used. Comparison between the first and sixth decades 60-year period showed that the core in January from the East to the West and in October and March from the North East to the South West from the Balkhash Lake to Baikal there has been a significant shift. Results also showed that during the same period the Siberian High central pressure was reduced in January while the land surface temperatures in January showed a significant upward trend. Unlike the months of October and January, in March the central pressure had few mutations but no trend was observed. However, during this month the Earth's surface temperature has increased significantly during thementioned period.


Mostafa Karampour, Yeganeh Khamoshian Sahneh, Zohreh Ebrahimi, Hamed Heidari,
Volume 25, Issue 78 (9-2025)
Abstract

Atmospheric rivers are one of the atmospheric phenomena that generate heavy rainfall and can lead to significant human and financial losses. Understanding the synoptic mechanisms of water vapor flux and atmospheric river formation in the country's atmosphere, as well as revealing the interaction between the NAO (North Atlantic Oscillation) zonal component and the creation and intensification of this atmospheric phenomenon, can greatly improve the predictability of torrential rainfall events. The main goal of this research is to investigate the atmospheric river phenomenon in the Iranian atmosphere and its relationship with the phases of the NAO phenomenon. In this regard, data on the zonal and meridional components of wind, specific humidity, and NAO anomalies were obtained from the NOAA database during the statistical period of 1944–2019. The results showed that during the study period, atmospheric rivers have shifted in terms of longitude and latitude, moving toward the southern half of Iran. A high correlation was observed between the NAO index and meridional flows at levels above 600 hectopascals. Additionally, a sigma value of 0.2101 indicated a strong correlation with the NAO in the area where atmospheric rivers enter the Iranian atmosphere.  High-pressure centers play an important role in directing atmospheric rivers. These rivers cannot pass through high-pressure centers and typically exhibit meridional curvature at the outer borders of these centers in the Northern Hemisphere, resulting in southwest and northeast orientations. The primary moisture source for atmospheric rivers entering Iran is the Atlantic Ocean, which is further enhanced by water bodies such as the Red Sea, the Sea of Oman, the Indian Ocean, and the Persian Gulf.


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