| چکیده انگلیسی مقاله |
 The study of the lowest temperature changes in Iran    F. Khoshakhlagh. E. Gharibi. Z. Shafiei.  Received: 30 October 2009 / Accepted: 14 December 2010, 41-44 P          Extended abstract  1- Intro duction  The temperature is the most important climate of parameters.a more factors causes to tempo â spatial the temperaturecomplex.its Based on the maps of thetemperatureof existence , the Northwest and the south in Iran are to disciplinethe coldest and the warmestof areas .also the mountain of regions are more cold than low ones. Buttemperature trend is ascendedin all of the stations.this research studies the lowest temperature data in Iran the period of statistical duration (1956- 2005). The research goal is spread and intense the lowest of temperature in difference areas in Iran by ways of the temperature time series, isotherm plots and temperature distribution plots.    2- Methodology  This research studies the lowest temperatureof data and a number of days of less temperature than 4ºCelsius for 21    stations atthe period of statistical duration (1956-2005).  The temperature data wereanalysed by the softwares of SPSS and Surfer.The results were described by charts and used thelowest temperature time series.In order toprovide the temperature maps, at first were made the maps any years, season, month and then was calculated the average of this maps by software SURFER for the statistical period and became the base of analysis in this research.   3- Discussion  3-1- the lowest temperature of Annual, seasonal and monthly in Iran  The lowest temperature has experiencedat the duration of the statistical periods short term oscillations that caused more variation at the time series, also illustrate ascend trend it. thelowest temperature exhibit fourshort term periods at time series that end periods haveoccuredat higher level than average and caused ascend trend it.theFunction of autocorrelation approve this issue.The lowest temperature illustrated four or three short term periods of temperature at winter and spring,the coldest temperature has occurred at winter and then spring to along high variations. Winter temperature average was -6.8º Celsius and spring 8.3º Celsius. Thistwo seasons illustrated ascend trend. At the summer was increased the lowest temperature and the variations were decreased that result of to moderate trend.The lowest temperature averagewas at the summer 13.2º Celsius. Theautumn include both low and high temperatures related to average thatis the most important characteristic it that didn't look at other seasons and variations have reduced it too.alsothe lowest temperature average was -1º Celsius.general trend of the lowest temperature of monthly is increased all months except March. The coldest months were onNovember until March that those include the most changes. Other warm months exhibit low changes. January and July were to discipline the coldest and the warmest months.theaverage and trend lines of temperature in1979 and 1980 years have crossed together that it exhibit climate change the stations of in Iran.Therefor we can say the climate of in Inran has became warmer than before decades and it had contemporary to world warming.   3-2- the Days with maximum temperature equal 0 and below.  The stations of Hamadan and Zanjan have the most frequencycold days that those average are to discipline 80.9 and 68 days.the stations of Arak, Sanandaj, Kerman and Tabriz have experienced 50 dayscold, the stations at above were mentioned almost located the northwest in Iran except kerman. cold days average are 26.3 days in whole country while those are 55 days in the northwest country that illustrated spatial intense changes of the cold days distribution in Iran.also south stations don't have cold days. The cold days in the northwest have caused an occurrence cold temperatures in one that themselves are at result of invade northern cold air masses.   3-3. the lowest Temperature spatial distribution in Iran  The country based on maps divided to fourareas.the firthof the northwest stations havethe coldest temperature to range -25 to -35º Celsius and to the most intense variations. Second thermalarea include the northwest ofmargin areas and also the northeast and east stations to temperature -15 to -25º Celsius.The thirdarea that is the most spread involve majority of stations such as Tehran, Isfahan, Shiraz, Zahedan, Kermanshah, Khoramabad, Ilam and Semnan to temperature range -5 to -10ºCelsius. The fourthregion is the southcoasts that exhibit the warmest temperature in Iran.It seem the temperature changes have occurred in Iran at toward latitude. The most spread of country is belonging to the third area to temperature range -15 to -25º Celsius. The range of temperature changes is 40ºCelsius in Iran that this amount is the most intense of changes at statisticalperiodduration. It can be at result of the difference of air masses invade that they enter to country of differences directions and it don't inherent this region.     4- Conclusion  This research illustrated intense changes at the lowest temperature the statistical of periodduration for recent decades, particular at cold areas such as the northwest. Also time series has experienced increase trend on seasons and months difference that it exhibit high and low variations. The Lowest temperature spatial distribution illustrated at least thermal fourareas in country that the northwest and the northeast were the coldest areas and other areas were more warm than those.generally the northwest and margin areas particular stations of hamedan and zanjanexperienced the most of cold days and the southcoastshave had at least ones. Look at cold areas were causedby the northren air mass aspreadthat have increased a number of cold days at this areas. The years of middle time series all the stations occurred climate change so thattrend line has crossedaverage line and movement to higher than it. Generally the lowest temperature exhibit tempo â spatial intense changes in Iran so that the range of temperature changes reached 40ºCelsius in Iran.  Key words: temperature lowest, time series, trend, variance, statistical periods, moving average.    References  Kaviany, Mohammad reza. And Alijani. Bohlool. (2001). the foundations of climatology, samt, eighth publication, Tehran.  Azizi.Ghasem. (2004). Climate change, ghoomes, firth publication, Tehran.  Asakereh, Hossein. (2007). Climate change, Zanjan University, firth publication, zanjan.  Azizi.Ghasem, (2000), El Nino and drought â rainy periods in Iran, geographical researches, tome38, Tehran.  Asakereh. Hossein. (2004). 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Gharibi, M. A. of Climatology, University of Tehran, Tehran, Iran.    Z. Shafiei, M. A. of Climatology, University of Tehran, Tehran, Iran. |