نوع مقاله : مقاله پژوهشی

نویسنده

استادیار دانشکدۀ جغرافیا، دانشگاه تهران، ایران.

چکیده

روند رو به رشد طوفان‌های گرد و غبار در سال‌های اخیر و تعیین تعداد وقوع این رخداد در سال‌های گذشته و جواب به این سوال که آیا این دفعات وقوع تغییری داشته یا خیر باعث شد، بررسی جامعی در مورد روند و وضعیت طوفان‌های گرد و غبار در سال‌‌های گذشته انجام گیرد. در این پژوهش بر اساس داده‌های مشاهده‌ای 112 ایستگاه هواشناسی از سال 1364- 1384 به بررسی روند این طوفان‌ها پرداخته شده است. نتایج نشان می­دهد کل روز‌های غبارناک در این دوره در مناطق مختلف از ۱۱ روز تا 3833 روز متغیر می­باشد. برای بررسی بهتر، تعداد روز­های کل غبارناکی با استفاده از روش خوشه­بندی K-means و نرم‌افزار SPSS به 5 دسته به شرح ذیل تقسیم شده­اند. 1-کمتر از 492 روز، 2-588 روز تا 1153 روز، 3-1243 روز تا 1757 روز، 4-از 2007روز تا ۲۲۳۹ روز
۵- بیش از 3832 روز و سپس هر دسته به صورت مجزا مورد بررسی قرار گرفته است. سرانجام خوشه‌ها با استفاده از آنالیز واریانس مورد بررسی قرار گرفتند و مشخص گردید با درستی 99 درصد خوشه­بندی انجام شده صحیح می­باشد. خوشه­های به دست آمده با تبخیر و تعرق، دما، بارش، ژئومورفولوژی و ارتفاع مقایسه شدند. نتایج مؤید آن است که به ترتیب با تبخیر، دما و بارش دارای همبستگی می­باشند ولی با ژئومورفولوژی و ارتفاع دارای همبستگی نمی­باشند. دلیل این امر را می‌توان در منشاء خارجی ریزگرد­ها، ارتفاع بالای حرکت آن­ها و نقش رطوبت در نشست آن­ها جستجو کرد.

کلیدواژه‌ها

عنوان مقاله [English]

Status and trends of dust storms in Iran from 1364 to 1384

نویسنده [English]

  • Shirin Mohammadkhan

Azin Av. Enghelab Av. Tehran Iran

چکیده [English]

The phenomenon of dust storm causes a number of damages such as aggravation of heart or lung disease, air and land traffic. Occurrence of dust storm has been growing inrecent years and has created many problems in some cities of Iran. Dust storms of Iran arise either from internal or external sources. In this paper, Climatology of dust storms in Iran is compiled based on observational data of 112 meteorological stations from 1985 to 2005. Results show that the total number of dust stormy days varies from 11 to 3833. Accordingly, we have identified five types of cities; 1- less than 492 days;  2- from 588 to 1153 days; 3- from 1243 to 1757 4 days;  from 2007 to 2239 5 days; 5- more than 3832 days. Afterwards, we examined each of them separately. The first group is fixed. Cities of this group are located mostly in North, East and Center of Iran.  The second group contains three parts:First, an ascending trend to 1992 and then a descending part to 1998 and again,an ascending part to 2005. Cities of second group are located in the southern pasrt of the country. The third group contains four parts: First, a down trend to 1990 and then an ascending part to 1993 and again, a descending part to 1998 and finally, a branch of the ascending to 2005.  Cities of the third group are located almost in the southwest. The cities of the fourth group are located in Sistan&Baloochestan province and are affected by the120-day wind. The occurrence of dust storm in the fourth group is ascending. Finally, using GIS and interpolation systems, we have plotted dust storm zone classification map of Iran from 1998 to 2005.

کلیدواژه‌ها [English]

  • Dust
  • trend line
  • K- means clustering
  • Iran
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