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Nivar

Patterning and Synoptic Analysis of Heavy Precipitation in the Cold Season in Northwest Iran

Articles in Press

Document Type : Original Article

Authors
Bromand Salahi 1
Ali Shahi 2
1 Professor of Climatology, Department of Physical Geography, Faculty of Social Sciences, University of Mohaghegh Ardabili, Ardabil, Iran.
2 PhD of climatology, Faculty of Social Sciences, University of Mohaghegh Ardabili,,
10.30467/nivar.2025.534278.1344
Abstract
This study was conducted to identify the patterns leading to generate heavy precipitation in the cold season of the northwest region of Iran. For this purpose, daily precipitation data from 19 selected synoptic meteorological stations between 2000 and 2019 were received from the Iran Meteorological Organization and upper atmosphere data for parameters effective in the occurrence of heavy precipitation, including zonal and meridional wind, specific humidity, omega, sea level pressure, and geopotential height, were received from the National Oceanic and Atmospheric Administration (NOAA). Using an environmental approach to circulation and a 99% percentile threshold along with a 30% spatial extent condition, heavy precipitation events were extracted, and then, using factor and cluster analysis, the main factors and synoptic patterns were determined. Based on the results, 16 heavy precipitation events were identified in the region and three main patterns were extracted, among which pattern number two (integration of Sudanese, Mediterranean, and Icelandic systems) was recognized as the dominant pattern. The maximum heavy rainfall in all three patterns occurred in the southwest of the study area, especially at the Piranshahr and Sardasht stations. The results also showed that the most important source of moisture for heavy rainfall in northwest Iran was the Mediterranean Sea. In the lower, middle, and upper levels of the troposphere, the land front, blicking, and jet-stream systems played a key role in the formation of heavy rainfall events, respectively. Overall, the findings indicate the completely dynamic nature of these precipitation events and the simultaneous influence of large-scale systems in their creation.
Keywords
Cluster Analysis
Factor Analysis
Heavy Rainfall
Northwest Iran
Patternning
Synoptic Analysis
Subjects
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Nivar

Articles in Press, Accepted Manuscript
Available Online from 25 November 2025

  • Receive Date 13 July 2025
  • Revise Date 14 November 2025
  • Accept Date 25 November 2025
  • Publish Date 25 November 2025