عنوان مقاله [English]
نویسنده [English]چکیده [English]
One of the most important components of the extent of pollutants mixing and air quality at near the Earth''s surface is the height of boundary layer. Many variables involved in determining the height of the boundary layer of atmosphere. Researchers have used of these variables to estimate and determine of the height and the roof of the boundary layer. The primary aim of this study is to approximate the height or the ceiling of boundary layer on Mehrabad station by vertical sounding of atmosphere. The analysis of vertical profiles of the potential temperature and the inversion Critical have used. In this respect, the vertical sounding data of the atmosphere of Tehran’s Mehrabad station from the database of Wyoming University was used. By drawing and analysis of Skew-T graphs based on Heffer critical inversion, one day per month was chosen as a day with the critical inversion. So the inversion roofing of those days was considered as the roof of the boundary layer of atmosphere. The results show that the cold air subsidence is the permanent type of the critical inversions in both February and December. Also the lapse rates of the potential temperature are 0.024 and 0.026 Kelvin respectively in meters. In these months the height of boundary layer (1482 and 1267 meters) is in the lowest situation. The maximum height of the boundary layer has seen in July and August which is equal to 3060 and 3312 meters, respectively, and the kind of these critical inversions is air subsidence. The study also showed that the most frequent type of the critical inversions is radiation inversions and also in days with these types of inversions the lapse rate of the potential temperature are lower than days with subsidence and frontal inversions. Also the results shows that the thickness of inversion layer in the radiation inversions is higher than others inversions.