بررسی تغییرات دما و بارندگی در سواحل جنوبی دریای خزر و مقایسه آن با تغییرات درمقیاس جهانی و نیمکره شمالی

  In this research, an investigation on the changes of two major climatic parameters i.e., temperature and precipitation is done in the Mazandaran Province and west of Golestan Province with emphasi s on part of coastal line of Caspian Sea and its comparison with changes of these two parameters in scales of northern hemisphere and global. For this purpose, the time series of annual precipitation and mean, maximum and minimum temperature in three the Gorgan, Babolsar and Ramsar sites, were analyzed during statistical period of 1956-2005 and in five decades and also nine other sites with various statistical periods from 19 years to 36 years. In this research, used from non-parametric tests of Mann-Kendall and sen ׳ s estimator of slope to detect trend qualify and quantity respectively. Results indicates that Changes in mean of five decades than long mean and also relationship of temperature and precipitation changes in three sites of Gorgan, Babolsar and Ramsar is observed that with decrease in temperature, is seen a decrease in precipitation and with increase of temperature, an increase in precipitation is observed. This concept, only in five the 10-year periods is seen as separate and trend in these two parameters during the 50-year period is to the other form and in three stations is different so that average temperature is increased and precipitation is decreased in Ramsar site and regional average, and in two Babolsar and Gorgan sites is observed increase and decrease of these two parameters respectively . Also in two global and northern hemisphere scales, is observed increase of average temperature and decrease of precipitation that take place opposite of each other and is similar to changes in these two parameters in Ramsar site and regional average. Also investigation of minimum and maximum temperature in these three stations, in general, showed stronger increase in minimum temperature than maximum temperature, and it can be in relation to increase in greenhouse gases that has more impact on increase of minimum temperature. Generally, increase in temperature is observed in all of case study sites with the exception of the Gorgan site and also precipitation in different sites has various changes that this condition can be result of increase in greenhouse gases in local, regional and global scal e s and also distance from voluminous reservoir of Caspian Sea.