Spatiotemporal Reconstruction and analysis of under -15 Degree Celsius Extreme Temperature in Iran

Aalijahan, Mehdi and Salahi, Broumand and Ghavidel Rahimi, Yousef and Farajzadeh Asl, Manuchehr (2018) Spatiotemporal Reconstruction and analysis of under -15 Degree Celsius Extreme Temperature in Iran. Doctoral thesis, University of Mohaghegh Ardabili.

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Abstract

This research has been carried out for reconstruction the spatiotemporal of -15 degree Celsius and colder extreme temperature in the region of Iran. To do this research, NASA organization 20th century surface and upper-level data were used in 143 years (1871 – 2012) period of time. In order to achieve research aims and extraction the upper and surface level of the atmosphere patterns, were used of factor analysis and hierarchical clustering methods. The results of this study showed that during the 142 years of the period of study time in total 948 days were identified that the -15 degree Celsius temperature occurred in them, finally in order to synoptic analysis and extraction of atmospheric patterns was used of 304 days that the desired temperature extensively observed in the region. The occurrence of these temperatures depends on the northern of the Iran, which occurred either in the northwest or northeast or simultaneously in both of them northwest – northeast. According to the results, it can be said that the pressure system on the surface in the northeast of Iran leads to lower extreme temperature in most of the cases is Siberian anticyclone and in the northwest of Iran is the Ararat anticyclone. The referred pressure systems, either individually or in combination with another atmospheric systems, affected the study area. Also, in upper levels of the atmosphere, atmospheric blocking and trough formation and its spread over the studied area, and the placement of these regions on the axis and west of the trough and east of the ridge, is the main cause of the occurrence of ultra-cold temperature in the studied area.

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