A Statistical Analysis of the Tropopause Characteristic over Tehran and Shiraz in January and July (2000-2022)

This paper analyses the characteristics of the tropical tropopause, mid-latitude, and polar tropopause based on the sounding temperature data at Mehrabad and Shiraz airport stations in January and July in the statistical period of 2000-2022. The results showed that the observed frequency of the tropical tropopause in Iran in January (41 and 59 present in Mehrabad and Shiraz, respectively) is less than in July January (95 and 94 present in Mehrabad and Shiraz, respectively), and the frequency of the observed tropical tropopause in July is more than that of the mid-latitudes. The reason for this difference can be found in the increased thermal energy of the atmosphere in the warm seasons. In July, due to the development of thermal low pressure over Iran, the thermal energy, the air temperature, and the thickness of the atmosphere increased. As a result, the tropopause elevates and approaches the level of the tropical tropopause. It was also found that the tropical and mid-latitude tropopauses have a higher height in the warm month and are placed in lower pressure levels. For this reason, the temperature of these two tropopauses in the warm month is lower than the corresponding value in the cold month. Based on the results, the average height and temperature in tropical tropopause levels were estimated between 16.5 to 17.4 kilometers and -65 to -78 degree Celsius, respectively, in different regions of Iran. Also, these parameters for mid-latitude tropopause level were estimated from 11.5 to 12.8 kilometers and -52 to -59 degree Celsius, respectively