This study is based on 3 years daily observations of upper air of Tehran (35No) during 1964-66. The author identifies the characteristics of Tehran tropopause and investigates the relationships of Some, of these characteristics with the temperature and pressure of the surface. The altitude of the tropopause changed between 5.7 and 19.2 km; in 57 percent of the cases the tropopause altitude was between 10-13 km. Average daily change of tropopause altitude was about 1 km. The fluctuation of the

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... titude was more in summer than in winter. In 50 percent of the cases, the tropopause has a mean temperature of –600 with an approximation of 50C. The average of tropopause pressure was 183 mb. The temperature of the Tehran tropopause in January and July was quite different from that estimated for the Lat. 350N. There existed a postive correlation between the altitude of tropopause and the surface temperature on the one hand, and a negative correlation between the temperature of tropopause and the surface temperature on the other hand. No significant correlation was found between tropopuase pressure and the surface pressures.