Analysis of the trend of long-term changes in the tropopause height on the Iranian atmosphere in the transition seasons

In this study, the trend of tropopause changes in the Iranian atmosphere in the spring and autumn months was analyzed using ECMWF database data from 1979 to 2018. The results of studying the trend of tropopause changes in spring and autumn showed that in large parts of the country the observed trend was without statistical significance and only in March in parts of the west and northwest of the country and in September in the Zagros Mountains was positive and statistically significant. The results of studying the temperature trend of two levels around the tropopause also showed that in all months of spring and the first two months of autumn, except for very limited areas of the country, the observed trend is without statistical significance. The two-level temperature trend around the tropopause in November was significantly different from other months under the study; this month, large parts of the country were statistically significant in the two levels around the tropopause. Examination of the temperature difference trend of the two levels around the tropopause also showed that in areas with a significant trend, the trend of the difference between the two levels of high and low tropopause was negative. Analysis of Variance, Skewness and Kurtosis Tropopause trends also showed that in the three months of spring in most areas the observed trend is not statistically significant, but in autumn (especially September) in some parts of the country, the observed trend is significant. According to the results, it can be said that during the last forty years, the effect of climate change on the tropopause layer on the Iranian atmosphere in spring and autumn has been very small and changes in spring have been much more limited than in autumn.