عنوان مقاله [English]
نویسنده [English]چکیده [English]
In this paper, the correlation between total ozone and upper air meteorological parameters such as heights of geopotential surfaces and temperatures for three stations of Tehran, Ankara and Bet Dagan located in the Middle East, in cold period (Jan, Feb and March) of years of 2005, 2007 and 2008 has been investigated. Data for upper air is taken from Wyoming University and ozone data is from satellite data.
The amounts of daily total ozone in selected stations have been nearly close to each other and with increasing latitude, the average of period has also increased. The maximum of period average is for the Ankara station. During the survey period, the range of changes of daily total ozone for the Ankara station has been between 249 and 447 DU, for the Tehran station between 253 and 420 DU and for Bet Dagan between 252 and 429 DU.
The results from investigating coefficients of correlation between total ozone and meteorological parameters of upper air shows that in all of the examined stations, there is a significant negative correlation between total ozone and heights of the 500, 300, 200 and 100 hPa geopotential surfaces.
Comparing the correlation coefficient of ozone and heights of geopotential surfaces at different stations shows that, at all, correlation 300 hPa level is stronger than 100 and 500 hPa levels. In other words, the correlation between ozone and meteorological parameters in the upper troposphere is stronger than the middle troposphere and stratosphere, and with decreasing latitude in stations, the stratospheric correlation (100hPa) increases. The greatest correlation coefficient is for 200 hPa level.
The investigation of the relation between changes of different geopotential surfaces of the troposphere and stratosphere shows that pressure changes of the troposphere and stratosphere have been coherent and in accordance with each other.
Also there is a good coordination between changes in 200 hPa and 500 hPa during cold times of the year and the range of changes in heights of geopotential surfaces in stratosphere is less than the upper troposphere.
There is positive correlation between total ozone and stratospheric temperature and negative correlation between total ozone and the temperature of the middle and upper troposphere.
The main reason for these correlations between total ozone and heights of geopotential surfaces and temperature may be related to the atmosphere dynamics and rising and falling air currents. In other words, in lower stratosphere where ozone increases with height, during decrease of heights of geopotential surfaces ,ozone convergence occurs in high altitudes and causes an increase in atmosphere total ozone column and the opposite, with an increase in heights of geopotential surfaces, divergence of ozone in high latitudes occurs and atmosphere total ozone column decreases.
In the Tehran station, an increase of 10 meter in the heights of the 200 hPa geopotential surface, corresponds to total ozone decrease by 1.7 DU.