نوع مقاله : مقاله پژوهشی
نویسندگان
ندارد
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
In order to understand the mechanism governing the solar activities and it’s relation to
the Earth’s climate, physical characteristics of the Sun and it’s activities, characteristics
and structure of sunspots and the relation between solar variability- specially sunspots
cycle- and the Earth’s climate were investigated. In this case, Iran-Middle East,
Northern Africa and Mediterranean regions selected as a sample of subtropical region. It
was done in two stages. First, some of the synoptic stations of Iran and adjacent
subtropical regions were investigated and rainfall and temperature data of 16 stations
with 61 years (1930-1990) and 50 years (1951-2000) were chosen respectively.
Summertime average temperature (July, August and September) and wintertime average
temperature (January, February and March) were used. In the second stage, the Iran-
Middle East, northern Africa and Mediterranean region were divided into four sectors
and average geopotential height of 500hpa and 50hpa levels for a 53 years period (1948-
2000) were calculated for the winter and summer. Also, the average position and speed
of subtropical jet stream in 200hpa level were derived for the above regions, periods and
seasons and then their relation with the solar activity were investigated. For determining
the relation between solar variability and climatic variables and regional atmospheric
circulation components, sunspot numbers, solar radio flux and a solar geomagnetic
activity index (AA) were used.
The results did not show a considerable significant correlation between sunspot
numbers and solar radio flux with winter rainfall and extreme seasons average
temperature of those selected stations. However, the low correlation indicates that in the
years with maximum solar activity, the average winter temperature in the Middle East
and Iran relatively decreases. The result of investigating the relation between 500hpa
and 50hpa average geopotential height with solar activity indices for the extreme
seasons have had positive correlation. The maximum correlation was seen in 50hpa
level (lower stratosphere) as there was a significant positive correlation between this
level and solar activity indices. Also, there has been a low negative correlation between
the position and speed of subtropical jet stream and sunspot numbers and the other solar
activity indices.
کلیدواژهها [English]
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