نوع مقاله : علمی -پژوهشی
نویسندگان
1 استادیار، دانشکده علوم زمین، دانشگاه شهید بهشتی
2 استادیار، معاون فنی و شبکه ایستگاههای هواشناسی کشور، تهران
3 دانش آموخته کارشناسیارشد آب و هواشناسی دانشکده علوم زمین، دانشگاه شهید بهشتی
چکیده
کلیدواژهها
عنوان مقاله [English]
Central Iran hasn't the extent resources such as water bodies and dense plant cover that can modify temperature challenges. It is known as arid and semi-arid land that is frost-prone especially during winter. In this research we try to determine the atmosphere level of cold air flows from the basin of Siberian High toward Central Iran. Thus we extracted the zero and under zero temperatures as daily maximum temperatures from 8 weather stations including Shahrood, Tehran, Semnan, Kashan, Isfahan, Yazd, Kerman, and Bam Cities during 1980 to 2012. Therefore, we determined 47 CAWs and we used two index including ≥ 2 days duration and observing CAW in ≥ 2 stations and finally it was determined 17 CAWs as critical colds over central Iran. Converting the data of up level filed from compact format (.nc) to text one (.txt) and air mapping finalized to synoptic pattern. Our principal results appeared in 1000HPA isobaric surface as the ideal surface for the modeling of pressure changes in low atmosphere. The pattern of outermost and closed contour and so, the pattern of outermost and effective one showed respectively the apparent and non-apparent presence of Siberian High during in the most critical colds of Central Iran. For some critical colds, we found migrant highs over Europe and north of Caspian Sea in 750, 500 and 300 HPA isobaric surfaces. Therefore, it seems Central Iran is the confluence of horizontal cold air flows from northeastern and vertical ones from northwestern
کلیدواژهها [English]