dr saeid movahedi

In this study, we aimed to reconstruct the mean, maximum mean and ‎minimum mean temperature from the chronology of tree rings width of two ‎Quercus Persica sites in Dena region, where efficient climatic data have a ‎short period (1982-2011). The duration of common chronology of the sites ‎is 131 years (1881-2011).Considering the strong correlation between ‎climatic data and growth rings width (P < 0.01), with positive coefficient, ‎we attempted to reconstruct the variables using combined linear and ‎quadratic regression analysis and ring growth width from 1881 to ‎‎2011.Accordingly, the highest maximum temperature was in 2001-2011 ‎decade and the lowest minimum temperature was during the decade 1981-‎‎1991.Over the recent three decades, the average and the annual maximum ‎mean temperature had an increase of 0.5°c and 1°c in comparison to the ‎previous century and the average annual minimum temperature has had a ‎decrease of 0.2°c.‎

In this research، for synchronization analysis of Black Sea high pressure with daily precipitation in IRAN data base have been created with using the sea level pressure data in Reanalysis II database in National Centers for Environmental Prediction (NCEP) /National Center for Atmospheric Research (NCAR). Temporal resolution of data is daily and spatial resolution is 2. 5 × 2. 5 degrees of arc. Framework covers the areas including of 20 -70 degrees east longitude and 20-70 degrees north latitude، consisting of 441 pixels. Second database is daily precipitation in 235 synoptic stations in IRAN. Study period is 45-year (1961 to 2004 AD) and includes 16071 days. In this matrix، rows are time and the columns are stations. The result shown that most relevant between precipitation in Iran and Black Sea high pressure is %66 in March and Lowest is %30 in August. Range of spatial in March is located in east، North East، North West and West South West of Iran. But in July، only the southern coast of Caspian Sea has precipitation associated with high pressure system in the Black Sea. Also Most of seasonal percent is %60 in winter season and Lowest is in summer with %38. Overall، more than 50 percent of the precipitation occurs at time of occur Black Sea high pressure system.

Iran country due to laying in the desert belt on the northern hemisphere، are dry and desert climate of many parts of it Predominate. Due to the same location in the atmospheric loss of human life and animal life and it has an important role. And according to the moisture sources in the country and located outside of the atmospheric loss from year to year fluctuations have other roles pluvial systems are more bold. One of the important mechanisms that cause instability and density will be cyclones. Therefore recognition of cyclonic centers and cyclogenesis can in environmental studies، planning and management of water resources and natural disasters، weather forecasts and the country sociol-economic development is necessary and important. Therefore، for identify and positioning cyclonic action is used from reanalysis data geo-potential height NCEP/NCAR with 6-hour time resolution (00، 06، 12، 18 z) and spatial resolution 2. 5× 2. 5 degree for the 1371 Solar year (93-1992). for Cyclone identification in six levels 1000، 925، 850، 700، 600، 500 hecto pascal Two conditions are considered Which include the: 1- geo-potential height pixel resurvey than every eight neighboring surrounds is low. 2- Large gradient geo-potential height on the Cornell Equal to or greater than 100 meters is 1000 km. In this study، first cyclonic centers according to the provisions are intended Identify and then monthly، seasonal and annual plans، drawn and cases were analyzed. According to the calculations performed were determined The maximum cyclone frequency in the first nine months in The 500 hpa level and three months in winter in level 1000 hpa and low they in the levels both 850 and 700 hpa Occurred. Also cyclogenesis centers of the cyclones they affect the country are include Genoa cyclogenesis area، Italy southern، Sicily and Sardinia Islands، southern Greece، Adriatic Sea، West Spain، Libya and Algeria، Iceland and are Pakistan. Finally، a correlation between frequency percentage cyclone monthly with an average monthly precipitation country established Shows that The highest correlation is in hpa 1000 level and in other levels correlation value decreases. finally، Can be said that there is between frequency percentage cyclones with rainfall average country a positive correlation.