Synoptic analysis of atmospheric circulation patterns affecting the precipitation of Farvardin 2024 in Yazd Province

Document Type : Research Paper

Authors

1 Professor, Department of Geography, Faculty of Humanities and Social Sciences, Yazd University, Yazd, Iran.

2 PhD Student, Department of Geography, Faculty of Humanities and Social Sciences, Yazd University, Yazd, Iran.

10.29252/aridbiom.2026.4149

Abstract

Heavy and torrential rainfall, as one of the most important climatic hazards, always plays an effective role in the occurrence of flash floods and inflicting extensive damage to the infrastructure, construction and agricultural sectors. The aim of this research is to synoptically analyze the atmospheric circulation patterns affecting the torrential rainfall event of Farvardin 2024 in Yazd province. In order to examine the spatial distribution pattern of precipitation, CHIRPS satellite precipitation data was used. Also, to analyze the synoptic conditions governing this event, maps of the land surface pressure, the middle level of 500 hectopascals and maps of moisture, omega and circulation at the level of 850 hectopascals were analyzed during two days of Farvardin 6 and 28, 1403. In order to investigate the state of atmospheric instability, the instability indices SI, KI, TTI and LI were calculated using the thermodynamic diagram of the Shiraz station, which confirms the existence of unstable atmospheric conditions on the days of precipitation. The results of the synoptic analysis showed that the establishment of a truncated low on both days of the study led to the formation of a deep trough with a southwest-northeast extension, such that the Red Sea, the Persian Gulf and the eastern Mediterranean were located along the axis of the trough, and conditions were provided for air ascent and the penetration of low-pressure systems into the central regions of the country. On these two days, the omega index reached a significant and extreme value of about -0.2 Pascal/second at the level of 850 hectopascals, which indicates strong air ascent. In terms of moisture supply, the results showed that the main moisture sources at the level of 850 hectopascals included the Red Sea, the Persian Gulf, and the Sea of ​​Oman, and the specific humidity in the region reached about 8 to 10 grams per kilogram of dry air. The simultaneous movement of the constant-speed wind blades with a southwest-northeast direction and the maximum relative humidity cores located over the Red Sea and the Persian Gulf played an important role in injecting moisture and intensifying the phrenic precipitation in Yazd province. In general, the combination of strong dynamic conditions, adequate moisture supply, and severe atmospheric instability was the main factor in the occurrence of the phrenic precipitation in Farvardin 2024 in the study area.

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References

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Journal of Arid Biome
Volume 15, Issue 2
September 2025
Pages 37-55

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