Variability of Solar Activity and it’s Influenceon the Earth’s ClimateCase Study: Climate of Middle East and Iran

In order to understand the mechanism governing the solar activities and it’s relation tothe Earth’s climate, physical characteristics of the Sun and it’s activities, characteristicsand structure of sunspots and the relation between solar variability- specially sunspotscycle- 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. Itwas done in two stages. First, some of the synoptic stations of Iran and adjacentsubtropical regions were investigated and rainfall and temperature data of 16 stationswith 61 years (1930-1990) and 50 years (1951-2000) were chosen respectively.Summertime average temperature (July, August and September) and wintertime averagetemperature (January, February and March) were used. In the second stage, the Iran-Middle East, northern Africa and Mediterranean region were divided into four sectorsand 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 speedof subtropical jet stream in 200hpa level were derived for the above regions, periods andseasons and then their relation with the solar activity were investigated. For determiningthe relation between solar variability and climatic variables and regional atmosphericcirculation components, sunspot numbers, solar radio flux and a solar geomagneticactivity index (AA) were used.The results did not show a considerable significant correlation between sunspotnumbers and solar radio flux with winter rainfall and extreme seasons averagetemperature of those selected stations. However, the low correlation indicates that in theyears with maximum solar activity, the average winter temperature in the Middle Eastand Iran relatively decreases. The result of investigating the relation between 500hpaand 50hpa average geopotential height with solar activity indices for the extremeseasons have had positive correlation. The maximum correlation was seen in 50hpalevel (lower stratosphere) as there was a significant positive correlation between thislevel and solar activity indices. Also, there has been a low negative correlation betweenthe position and speed of subtropical jet stream and sunspot numbers and the other solaractivity indices.