Introduction: Tropopause is the transitional layer between the troposphere and stratosphere. This layer determines the upper limit of the troposphere and somehow expresses the spatial and temporal variations in the thickness of the layers and the layer indicated his thermodynamic variability. This is the layer that short-term and long-term atmospheric phenomena occur in. In other words, this layer determines the thickness and upper limit of the troposphere layer. Iran in terms of geographical location is on the northern side of the Hadley cells in the general circulation. That’ s why when handling the extremely cells, we observe changes in the climate of this country. That's why the country is in the range of atmospheric systems of important effects such as (Arabian subtropical high pressure, Siberian high pressure, Azores high pressure, Mediterranean cyclones and Sudan low).....

ABSTRACT 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 Extended Abstract Introduction The tropopause is usually defined as the transition region separating the stably stratified and turbulent troposphere. These two atmospheric regions differ in numerous dynamic and chemical constituents. Depending on season and latitude, the tropopause is typically found at around 18 km in the tropics and around 8 km at high latitudes. Tropopause is defined based on up to three different definitions. The conventional tropopause is the thermal one which is usually characterized by an abrupt change in temperature lapse rate. Its definition is based on the fact that the stratosphere is much more stably stratified than the troposphere. The thermal tropopause is defined as the lowest level above 500hPa at which the lapse rate decreases to 2 K/km or less, provided that also the average lapse rate between this level and all higher levels within 2 km does not exceed 2 K/km. The dynamical tropopause is defined in terms of sharp changes in the potential vorticity, which measures the stratification and wind shears in air masses. The original concept of the dynamical tropopause is based on the isentropic gradient of potential vorticity. It is typically determined in a thin layer with absolute potential vorticity values within 1 and 4 potential vorticity units. The chemical tropopause is another type defined based on the vertical concentrations of trace gases such as ozone and water vapor. In this paper, the tropical, mid-latitudes, and the polar tropopause are defined based on latitude and geographical characteristics. The characteristics of the different tropopauses are analyzed regarding the temperature profiles from radiosonde data of the Mehrabad and Shiraz airport stations in January and July on the statistical period of 2000-2022.   Materials and methods The radiosonde data are obtained from the Integrated Global Radiosonde Archive of the NOAA National Climatic Data Center. The temperature data in January and July 2000-2022 are taken from the two radiosonde stations in the central and southern regions of Iran, including Mehrabad (51.31°E, 35.56°N) and the Shiraz airport stations (52.60°E, 29.53°N). The individual sounding profiles are exerted to determine the location and analyze the lowest tropopause and, if present, the second or the third tropopause based on the definition of the Commission for Aerology of World Meteorological Organization.  In former studies, the data of the 200-hPa pressure surface were often used to measure the mid-latitude tropopause and that of the 100-hPa for the tropical tropopause. However, sounding measurements confirm that a constant pressure surface is a flawed assumption for detecting tropopauses. In this study, the lower tropical tropopause, the mid-latitude tropopause, and the polar tropopause levels data are used (based on the mean pressure of thermal tropopause) in the 0-30°N, 30-60°N, 60-90°N regions to analysis their characteristics.     Results and discussion Comparing the frequency of tropopauses detected in Mehrabad and Shiraz airport stations shows that the frequency of days with two tropopauses detected over Mehrabad airport is lower than in Shiraz station in January. However, the number of days with three and four tropopauses at Mehrabad airport is more meanwhile the not detected tropopause, i.e. the break-down ones is more frequent in Mehrabad station. The days with one tropopause are more frequent in Mehrabad airport in January, but the number of days with two tropopauses is the same. The significantly elevated tropopause of the subtropical region in the warm season is the reason for the detected differences in which the radiosonde may not pass over the tropopause levels. Comparing the frequency of tropical and mid-latitude tropopause shows that at Mehrabad airport (Shiraz station) in January, the number of detected mid-latitude tropopauses is more (less) than that of tropical ones. This difference is related to the combined geographical-latitudinal characteristics of the two stations. The tropical tropopause in July is the most frequent in both stations. 5 up to 6 percent of them are due to subsidence inversion.   Investigations also showed that the average temperature of the tropical tropopause in Shiraz station is lower than Mehrabad airport in January. Mid-latitudinal tropopause temperature is almost the same in both stations, but the mean polar tropopause temperature in January over Mehrabad airport station is lower than in Shiraz station. The analysis of the January precipitation variability of these stations (in the 2000-2022 statistical period) shows that Shiraz is much greater than that of Mehrabad airport, so the average precipitation in this month in Mehrabad airport is 34 mm and in Shiraz station is 70 mm. It seems that in January, the release of latent heat caused by the condensation process in the upper parts of the troposphere and the frequency of the turbulent pressure systems over the Shiraz station was more than that of the Mehrabad airport, which caused the higher polar tropopause temperature in Shiraz station than the Mehrabad airport.   Conclusion 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 is less than in July, 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, pressure, temperature, and potential temperature in tropical tropopause levels were estimated between 16.5 to 17.4 kilometers, 92 to 96hPa, -65 to -78 degree Celsius, and 386 to 411 Kelvin, respectively, in different regions of Iran. Also, these parameters for mid-latitude tropopause level were estimated from 11.5 to 12.8 kilometers, 200 to 213hPa, -52 to -59 degree Celsius, and 335 to 386 Kelvin, respectively.   Funding There is no funding support.   Authors’ Contribution All of the authors approved thecontent of the manuscript and agreed on all aspects of the work.   Conflict of Interest Authors declared no conflict of interest.   Acknowledgments We are grateful to all the scientific consultants of this paper.

The behavior of the oceans and the atmosphere in mid-latitudes may be considered as a small departure from the background rotation of the Earth as a solid body. This provides a ground for the quasigeostrophic (QG) approximation, which is obtained by a formal expansion of the primitive equations in Rossby number that measures the intensity of such departures from the background rotation. The resulting equations, though much simpler than the full set, are still complex enough that it is not always clear what they imply about the nature of their solutions. Therefore, further simplifications have been sought in particular contexts, looking for more tractable models. A model of this kind constructed based on the assumption of a uniform interior QG potential vorticity is discussed in this paper. A further simplification may be obtained by assuming uniform stratification in the atmosphere/ocean. This model has been proposed for explaining some aspects of instability in the atmosphere by Charney and Eady and is used in this paper for studying some effects of wind shear on baroclinic instability.In the Eady model, the wind shear on the lower (ground surface) and upper (tropopause surface) boundaries plays a determining role in the occurrence of instability. However, in the classic form of the baroclinic instability theory of Charney and Eady, wind shear is considered constant with height, and therefore the effect of variations in wind shear on the ground and tropopause surfaces are not covered.According to the Charney–Stern–Pedlosky theorem, with uniform interior potential vorticity, for instability to occur, the wind shear at the upper and lower boundaries must be of the same sign. This theorem provides the necessary condition for instability but gives no further information on the effect of the wind shear at the two boundaries.Then here, the objective is to assess the effects of the wind shear on Eady-like models, that is, models with uniform interior QG potential vorticity. After examining a quadratic vertical zonal wind profile for the basic state as a special case, the arbitrary variation of the wind shear at the two boundaries is studied in an Eady-like model. It is shown that for each wavenumber, there are upper and lower bounds, respectively denoted by g1 and g2, for the ratio of the tropopause wind shear `uzH to the earth's surface wind shearuz `uz0, beyond which instability cannot occur. That is, for instability the ratio must be in the interval g1>`uzH/`uz0>g2 which serves as an additional necessary condition for instability. Considering all the wavenumbers, the lowest value for g2 is found to be 0.3. With nondimensional wavenumbers k*=(2p/L) LR in which L and LR are respectively the dimensional wavelength and Rossby deformation radius, for k*>2.4, instability occurs provided that the wind shear at the lower boundary is greater than that at the upper boundary. For k* between 1 and 1.4, g1 tends to infinity which means that for instability there is no restriction on the magnitude of the wind shear at the upper boundary.

Introduction: Monitoring the tropopause features over a geographic area is important for a number of interrelated reasons. From a climatological point of view, it is important to investigate the behaviour of the tropopause charactreristics for a long term, so that to detect any increased or decreased trends. From a dynamic point of view, it is essential to define the tropopause hieght, in order to explore the stratosphere— troposphere exchange taking place over a geographic area that may be responsible for changes in the chemical composition of the atmosphere. Over the past two decades, there has been growing interest in the tropopause charactreristics among the atmospheric scientific community. It is now broadly accepted that the tropopause plays a key role in a variety of atmospheric and climatic phenomena. Materials and methods: Compared to studies performed globally, in Iran a limited number of studies concerning the tropopause have been conducted. Moreover, the methods have been used and the length of the dataset were often inadequate. Therefore, in the present study, for the detection of tropopause, the daily data of Temperature, and Geopotential Height from the European Centre for Medium-Range Weather Forecasts (ECMWF) for 700 to 50 hpa with a spatial resolution of 0. 25 × 0. 25 longitude/latitude from 1979 to 2018 was adopted. Accordingly, 2491 cells have been covered across Iran. The LRT was used to detect tropopause. the tropopause is defined as ‘ ‘ the lowest level at which the lapse-rate decreases to 2 /km or less, provided that the average lapse-rate between this level and all higher levels within 2 km does not exceed 2C/km. In this study, in addition to the tropopause pressure level, the tropopause height (m) was also evaluated during this period. To obtain better cognitive knowledge about tropopause, the factors that were likely to be related to the spatial changes in height of tropopause were investigated. To achieve this goal, the relationship between tropopause pressure and spatial variables (e. g. longitude, latitude, and elevation) was assessed by general and partial linear correlation ceofeicents. In addition to the characteristics of temperature at the lower and upper levels of the tropopause, the difference in temperature between these two levels on the atmosphere of Iran and the characteristics of the minimum, maximum, average, as well as the temperature range of the earth's surface were evaluated and their relationship with tropopause pressure levels and height levels was assessed. Results and discussion: Investigating the characteristics of tropopause on the atmosphere of the studied area in the under investigation period (1979 to 2018) and its related factors in the autumn and spring months showed that in the months of these two seasons, various factors affecting height and pressure levels of tropopause are diffrnt and in both seasons have different characteristics. In all spring and autumn except for September, the height of the tropopause is decreasing as the latitude increases, but in October and November, the rate of change was greater than in the other months. In all the months of these two seasons (except September), the highest level of the tropopause taking place in the south-east of the country, whilst the lowest level of pressure occured in the north-west of the country. Investigating the changes in tropopause height and tropopause pressure levels also showed that they were not consistent in the under investigation seasons, so that in places with similar pressure levels, observed elevations were different. the tropopause pressure levels have a strong relation with the latitude, but changes in the tropopause height did not show a regular relationship with latitude. Tropopause height changes are mostly irregular in spring and autumn, and in parts of the country, it is almost dependent on longitude. In the spring and autumn periods, the high and low tropopause levels are among the most influential factors on tropopause. Among the cases that were related to the tropopause were surface temperatures and their characteristics in the spring and autumn seasons. During these two seasons, it was found that the potantial relationship of surface temperatures with tropopause pressure and elevation levels, especially at high latitudes, is low, but in lower latitudes, due to limited variation in the surface temperature, the potantial connection of tropopause and surface temperatures are higher than other parts of the country. In the months of the spring and October and November, it was revealed that the potantial correlation between tropopause pressure and elevation levels with local factors was low, but in September in parts of the country, the effects of surface elevations on the levels of tropopause pressure is much more significent. Conclusion: The results of the study of the tropopause and its related factors showed that the trend of tropopause pressure changes in the vicinity of latitude is decreasing with increasing the latitude. But the tropopause height is not aligned with its pressure levels, and in most areas, it is in the vicinity of Longitude. Among the studied factors, the low and high levels of tropopause have the highest impact on the tropopause, and the effects of surface temperature and other examined cases have not a noticable impact. he results of the study of the tropopause and its related factors showed that the trend of tropopause pressure changes in the vicinity of latitude is decreasing with increasing the latitude. But the tropopause height is not aligned with its pressure levels, and in most areas, it is in the vicinity of Longitude. Among the studied factors, the low and high levels of tropopause have the highest impact on the tropopause, and the effects of surface temperature and other examined cases have not a noticable impact. he results of the study of the tropopause and its related factors showed that the trend of tropopause pressure changes in the vicinity of latitude is decreasing with increasing the latitude. But the tropopause height is not aligned with its pressure levels, and in most areas, it is in the vicinity of Longitude. Among the studied factors, the low and high levels of tropopause have the highest impact on the tropopause, and the effects of surface temperature and other examined cases have not a noticable impact.

Introduction: The tropopause is a thin layer separating the stratosphere from the troposphere and is often characterized by a large change in the thermal, mass and chemical structure of the atmosphere. Compared to global studies on the tropopause and its various features, studies conducted in Iran are very few and the methods used are often less inclusive or the length of the statistical period is limited. For this reason, and considering the importance of the tropopause and its effect on exchanges between the troposphere and the stratosphere, and also due to the lack of information about it in Iran, accurate knowledge of the height of the tropopause in the country using more reliable data sources is a fundamental necessity. To calculate the tropopause, we used daily temperatures of ECMWF reanalysis datasets from January 1979 until December 2018. Gridded data witha spatial resolution of 0. 25*0. 25 were used. In vertical levels, we used 10 standard isobaric surfaces from 700 to 50 hPa. Methods: The location of the tropopause thermally and dynamically was defined. According to the WMO (World Meteorological Organization), the tropopause is defined as the lowest level at which the lapse rate decreases to 2° C/km or less, provided that the average lapse rate between this level and all higher levels within 2 km does not exceed 2° C/km. In this study, this index was used to identify the tropopause. In this study, to identify the factors affecting the tropopause, the relationship between the tropopause and spatial variables (latitude and longitude) and altitude was evaluated by general and partial correlations. Results & Discussion: The results of this study showed that in the months of cold season, the tropopause pressure level on Iran is followed by latitude, and the tropopause height decreases with increasing latitude, but in the months of the warm season (June, July, and August), the tropopause pressure level is different from the months of the winter season. In these months, the changes in the tropopause pressure levels do not follow the latitude; on the Zagros and Kerman heights, the tropopause height is at its lowest, while the highest tropopause elevation is in these months at higher latitudes than in other months. The temperature of the upper and lower levels of tropopause also showed that the temperature of the lower levels of the tropopause in all seasons was below the temperature of the upper levels of the tropopause and the temperature of the two levels changed with the changes in the levels of tropopause pressure in different months. The study of low and high levels of tropopause showed that during the cold season, the temperature of the two levels around the tropopause, following the tropopause pressure levels, follows the latitude, and with increasing latitude, temperature increases in the two levels around the tropopause. In two studied seasons, the lowest temperature of the two levels of the tropopause is consistent with the highest level of the tropopause, but the highest two-level temperature is only consistent with the lowest tropopause pressure level during the warm season months, and in other months, this observation coordination failed. Investigating the thermal difference between two levels of tropopause showed that the temperature difference between the two levels of the tropopause in the warm season is more significant than that of the cold season, while in the cold season, the temperature difference in most regions of the latitude is obeyed. Slowly, the difference in temperature decreases with increasing latitude. Conclusion: Examination of the characteristics of the tropopause and its related factors for summer and winter showed that in each season due to local conditions and changes in large-scale factors, the height of the tropopause changes, and therefore the tropopause in each season has completely different characteristics from the other season. Examination of the characteristics of the tropopause and its related factors for summer and winter showed that in each season due to local conditions and changes in large-scale factors, the height of the tropopause changes, and therefore the tropopause in each season has completely different characteristics from the other season.

in this research, their effects on the flight of airplanes were investigated. The study area is the country of Iran, and the flight routes of Kermanshah, Ahvaz and BandarAbbas to Tehran. The research data includes maps of the Vertical Transect (profile) of the jet stream, the daily average of the Zonal wind (U-Wind) and meridional wind (V-Wind) components for the winter period of 2018 through NOAA/NCEP environmental databases. Also, flight route information was received from FlightRadar24 and Flightaware systems. First, by using Vertical Transect maps, the days containing strong U-Wind were extracted, and the average position of the core of the Jet Streams in the Zonal and meridional wind components, the Tropospheric level of 200 HP was detected. The list of flights was prepared, and the Zonal Wind maps were produced. Finally, the height of the flights was compared with the level of the currents of the Jet Streams, and the influence or lack of influence of the Jet Streams on the flights was studied. According to the results of the research, all the Jet Streams caused turbulence for all flights, and they caused a decrease in the speed of flights between Ahvaz and BandarAbbas to Tehran and an increase in the speed of flights between Kermanshah and Tehran according to the direction and type of Jet Streams. It was also found that all the Jet Streams had a speed of more than 90 knots, so the capacity to create tension and turbulence such as CAT was seen in them

In general, the southwest Asia is one of the regions with positive anomalous values of tropopause folding frequency compared to the annual average of the northern hemisphere. The frequency of folding in this region in warm seasons is higher than in cold seasons. This research was carried out with the aim of statistical and dynamical analysis of the atmospheric processes associated with the tropopause folds in the southwest Asia during 2000– 2015. Identification of tropopause folding is based on the algorithm developed by Sprenger et al. (2003) and Gray (2003) and refined by Š kerlak et al. (2014). The detected folds are divided into three categories as shallow, medium, and deep based on their vertical extensions. The time series analysis of all types of tropopause folds shows that the frequency of folding events has an increasing trend during the period of study. The most frequent folding type is as shallow or medium in the summer season but as deep in the winter. The geographical distribution of the correlation coefficients between the monthly mean folding frequencies and some relevant dynamical quantities indicates that baroclinic instability mechanism plays the main role in the occurrences of tropopause foldings in the winter, while the effects of thermodynamic factors are dominant in the summer. Dynamical study of tropopause folds in both winter and summer seasons was conducted using January 2001 and 2004 as well as June 2007 and 2015 data sets. Results show that the winter tropopause foldings are associated with the formation of intense baroclinic waves in mid-levels of troposphere, strengthening of jet streams in upper levels and subsequently the formation of surface cyclones. Also, together with the seasonal displacement of the jet, the positions of tropopause folds are moving about 10 to 15 degrees latitudinally. The analysis of horizontal wave activity flux in January 2004, reveals the presence of a strong wave source (divergence of wave activity flux) in the Western Mediterranean and, at the same time, a wave sink (convergence of flux) over Europe. In January 2001, the wave activity flux was weakened and divided into two branches, one located in middle latitudes and the other in subtropical regions that transmitted wave energy to the southwest Asia. Furthermore, the strong equatorward wave propagation in this month indicates the anticyclonic wave breaking. In the two June months, as the baroclinic waves were weakened, the intensities of wave activity flux as well as the convergence and divergence centers in the southwest Asia were decreased compared to the January cases. Comparing the above results, it can be deduced that in winter, intense baroclinic wave packets in middle latitudes cause the strength of the subtropical jet, and consequently intensification of wave breaking which are associated with the occurrences of deep tropopause folds in the southwest Asia. In summer, the weakening of baroclinic activities leads to the reduction of deep folding frequency and the folds are formed mainly as shallow type at high levels.

This research is aimed to study the global distribution of tropopause folding frequency and its seasonal changes, emphasizing the ones over the Southwest Asia, for a 3-year period from Jan. 2013 up to Dec. 2015. For this purpose, the European Centre for Medium-Range Weather Forecasts (ECMWF) (ERA-Interim) reanalysis data set including wind, temperature and geopotential height were used. The horizontal resolution of the initial fields is 1×1 degrees in longitudinal and latitudinal directions prepared operationally every six hours at 60 levels. Applying the initial fields, the secondary fields, such as potential vorticity and potential temperature were calculated. From the 60 vertical levels, about 19 levels extending from 600 to 100 hPa cover the depth of all tropopause folding events studied here. In this research, we define the 2PVU potential vorticity surface as the dynamical tropopause (1PVU corresponds to 10-6 m2s-1Kkg-1). Identification of tropopause folding is based on the algorithm developed by Sprenger et al. (2003) and Gray (2003) and refined by Š kerlak et al. (2014) using pseudosoundings in each of the grid points. A 3-D labeling algorithm is used to distinguish between stratospheric and tropospheric air masses and labeling them according the PV values. After labeling, the tropopause folds are identified at every grid points from the vertical profiles of the label field as areas of multiple crossings of dynamical tropopause. The frequency of folds at each grid point over a chosen period is calculated from the number of folding divided by the total 6-hourly instances corresponding to the season, and finally expressed as a percentage. According to this algorithm, tropopause folds are classified into three categories as shallow, medium and deep. The analysis of spatio– temporal distributions of tropopause folds shows that the frequency of folding events over subtropical and mid latitude regions (between 20° to 40° north and south latitudes) is higher than the other latitudes in both the Northern and Southern Hemispheres and their frequency is increased remarkably in the winter season. Tropopause foldings in the Northern Hemisphere winter are seen as a relatively narrow band located in the subtropical latitude that surrounds zonally the whole Hemisphere, while in the summer season, foldings are concentrated in the subtropical region of the Eastern Hemisphere. Also, tropopause foldings occur mainly as shallow type in the subtropical region but as medium or deep ones in higher latitudes. Foldings in high latitudes are attributed to large-scale deformation fields, as noted by Holton and Hakim (2013), that are confirmed with water vapor satellite images, while the ageostrophic frontal circulations affect the tropopause deformation in mid latitudes. The other noticeable point is that the Southwest Asia region has positive anomalous values of tropopause folding frequency annually, relative to the Northern Hemisphere mean. This can be partly due to the Rossby wave breaking as pointed out by Martius et al. (2007) and Gabriel and Peters (2008). These anomalous values of folding frequency change in different seasons and obtain their maximum amounts in the summer time. Two regions with the maximum value of the folding frequency more than 5 times the Northern Hemisphere mean, seen over Iran– Afghanistan and the eastern of the Mediterranean Sea that occurred in June. The increase of folding frequency in the Southwest Asia during the summer season can be related mainly to the formation and existence of the monsoon anticyclone over the subtropical region of the Indian Ocean (Tyrlis et al., 2013) and partly to the baroclinic instability events. Results of the case study relevant to tropopause foldings in June 2015 show the existence of two strong jet streams in the aforementioned regions. Also, in the meridional cross-sections of wind and PV fields two principal areas of tropopause folding are seen in the west and downward of the jet streams locations. As expected, the potential temperature maps indicate the existence of marked baroclinic regions associated with the tropopause foldings.

showed different results with pressure level. During the winter months, the trend was positive in all regions, and in January and February, this trend was significant in many areas, while the summer months did not exhibit a significant tropopause. The results of examining the trend of the low temperature of the tropopause in summer and winter months showed that the observed trend was not statistically significant in December, but in other months, a positive and significant trend was detected. Examination of the temperature trend in the high level of tropopause also showed that the temperature trend in this part of the atmosphere, like the low level of the tropopause in large parts of the country in the studied seasons, lacked statistical significance. Examination of the trend of the temperature difference between high and low levels also showed that the trend of the temperature difference between these two levels was statistically insignificant at the majority of cases. The temperature difference trend of the two levels studied in the summer months was negative and significant at most regions. In other words, the decrease in the temperature difference between low and high tropopause in these two seasons and in some areas indicates a strong decrease in tropopause. Examination of the trend of variance, kurtosis and skewness also showed that the observed trend lacked statistical significance in the two studied chapters at most areas. There was also no relationship between the surface temperature trend and changes in tropopause height. Conclusion: The results of this study showed that tropopause had no statistically significant trend in most areas and months. Moreover, the significant trend was not related to the two temperatures around tropopause and surface temperatures.

The growing need to know the temporal and spatial structure of meteorological parameters in the tropopause transition zone caused the temporal changes of the temperature and height of this layer to be investigated during the last two decades (2002-2022) using the reanalyzed data of the Atmospheric Infrared Sounder (Aqua, MODIS, ARIS). Also, the relationship between the changes in tropopause characteristics and climate change of temperature and precipitation in Iran was studied using daily precipitation data of GPCP (2000-2022) and minimum, maximum and average daily temperature data of MERRA-2 model (1980-2022). In this regard, Pearson's correlation tests and regression analysis were used to investigate the relationship between research variables, and Kendall's seasonal time series and Mann-Kendall's ordinal tests were used to analyze regional mean daily and monthly trends. The results showed that the variables of tropopause temperature and height (TTH) have a negative correlation of 0.93 with each other (R2=0.85). On the other hand, the variable of the regional mean of daily tropopause height (TH) has a significant positive correlation with the variables of the daily earth's surface temperature (with correlation coefficients exceeding 0.8). Also, R2 values higher than 0.6 indicate a completely significant correlation of total monthly precipitation data with changes in monthly mean of TTH, which makes it possible to predict the rainfall anomaly in Iran by monitoring the tropopause characteristics. Time series analysis of the research variables using Kendall's seasonal and ordinal tests showed that the TH variable and the surface temperature variables are respectively with statistical values (τ). 0.18, 0.22, 0.27 and 0.32 have shown significant increasing trends in the last few decades. Finally, by introducing the TH as an indicator of climate change in Iran, the necessity of conducting more research in this field is emphasized.