Analysis of the long - term trend of the tropopause pressure levels over the atmosphere of Iran in the warm and the cold seasons

آب و خاک

Article 13, Volume 34, Issue 5 - Serial Number 73, November 2020, Pages 1189-1202   

Document Type: Research Article

DOI: 10.22067/jsw.v34i5.86196

Authors

H. Asakereh¹; S.A. Masoodian²; M. Darand³; S. Zandkarimi^{* 4}

¹Professor of Climatology, University of Zanjan, Zanjan, Iran

²Professor of Climatology, University of Isfahan, Isfahan, Iran

³Associate Professor at Climatology, University of Kurdistan, Iran and Board Member of Department of Zrebar Lake Environmental Research, Kurdistan Studies Institute, University of Kurdistan

⁴Ph.D. Candidate of Climatology (Climate Change), University of Zanjan, Zanjan, Iran

Abstract

Introduction: Studies of the atmosphere over the last hundred years have shown that human activities have caused changes in the atmosphere. The tropopause is one of the layers of the atmosphere whose changes have recently been introduced as a sign of a human impact on climate change. The height of the tropopause is affected by its upper and lower layers (the stratosphere and troposphere). The results of the studies conducted by various researchers have shown that different factors affect the height of tropopause and its changes, which can be divided into two groups. The first group of natural factors (such as changes in solar radiation and weather due to volcanoes, etc.) and the second one is human factors (including changes in greenhouse gases, human-induced changes affecting the ozone of the stratosphere and the production of air vents from human resources, etc.). Thus, altitude tropopause is naturally influenced by spatial characteristics (e.g. latitude and altitude), time (such as the time of year and hours of the day) as well as the frequency of atmospheric actions that determine climatic conditions.
Materials and Methods: Compared to the studies performed globally, a limited number of studies concerning the tropopause have been conducted in Iran. Moreover, the applied methods and the length of the dataset were often inadequate. Therefore, in the present study, 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 were applied from 1979 to 2018 for the detection of tropopause. Accordingly, 2491 cells 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 ºC/km or less, provided that the average lapse-rate between this level and all higher levels within 2 km does not exceed 2 ºC /km”. In the present study, in addition to changing the position, changing the scale (variance) as well as the shape of the frequency distribution (skewness and elongation) of the tropopause pressure level in each of the pixels on Iran was investigated. To calculate skewness, and kurtosis, daily tropopause height data were used. For each of the months studied, diffraction, skewness, and elongation were extracted using daily data and finally using data during the 40 years. The extracted trends of variance, skewness, and kurtosis were examined for each month. To track the synchronicity and conformity of changes in altitude and trend of tropopause pressure level with the trend of changes in mean monthly temperature in the lower and upper levels of the tropopause and the trend of the temperature difference between the two layers around tropopause was also evaluated over 40 years. In order to evaluate the long-term trend of each of the studied indices (mean, variance, skewness, and kurtosis) in relation to the height and pressure level of the tropopause, linear regression method with least-squares error method was used.
Results and Discussion: The results of the study of altitude trend and tropopause pressure level showed that in most of the months studied and in most parts of the country, the trend of changes in tropopause pressure level was not significant at the level of 95% confidence. According to the results obtained for the winter months, it was found that the trend of a tropopause pressure level in December had no statistical significance over Iran at a 95% confidence level. In January and February, the obtained trend was not statistically significant except for southeastern areas. In the summer months, unlike the winter months, the trend of tropopause pressure levels was significant in most regions. During the summer months, in areas where the trend was significant, the trend of tropopause pressure levels was positive. Examination of the trend of tropopause height in terms of meters 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.

Keywords

Cold season; Iran; Tropopause pressure level; Tropopause; Warm season

References

1-       Asakereh H. 2008. Application of linear regression in analysis of Tabriz annual temperature trend. Geographical Research Journal 22(4): 3-26. (In Persian with English abstract)

2-       Asakereh H. 2011. Fundamentals of statistical climatology. Zanjan University. (In Persian)

3-       Asakereh H. 2012. Analysis of Heavy Precipitation Trends in Zanjan City. Journal of Geograohy and Planning 16(4): 73-88. (In Persian with English abstract)

4-       Asakereh H. 2017. Fundamentals of Research in Climatology. Zanjan University. (In Persian)

5-       Azarakhshi M., Farzad M. J., Eslah  M., and Sahabih H. 2013. An investigation on trends of annual and seasonal rainfall and temperature in different. Climatologically Regions of Iran 1-16. (In Persian with English abstract)

6-       Keikhosravi G. 2015. Synoptic analysis-statistical height of the tropopause layer as a profile of climate change in Khorasan Razavi. Journal of Applied Climatology 2(2): 33-48. (In Persian with English abstract)

7-       Khosravi M., Hamidianpour  M., and Kurdi Tamin S. 2016. A Study of Tempo Spatial Variation of Pakistan Low Pressure. Climatological Research 27: 25-42. (In Persian with English abstract)

8-       Masoodian S.A., Ebrahimi R., and Yarahmadi E. 2015. Time-space Analysis of the Monthly Heating Degree Days in Iran. Journal of Geography and Regional Development 12(23). (In Persian with English abstract)

9-       Masoodian S.A. 2004. temperature trends in iran during the last half century. Geography and Development 2(3): 89-106. (In Persian with English abstract)

10-   Sabziparvar A.A., Mirgaloybayat  R., and Shamami F.G. 2011. Evaluation of the possible changes in diurnal temperature range (DTR) trend in some arid climates of Iran since last five decades. Iranian Journal of Physics Research 11(1). (In Persian with English abstract)

11-   Sharifi M.A., and Khaniani A. 2011. Using GPS Radio Occultation Technique to Study Climate Change, Geomatics Conference 90. Tehran. National Mapping Organization, https://www.civilica.com/Paper-GEO90-GEO90_146.html. (In Persian)

12-   Butchart N., Scaife A.A., Bourqui M., De Grandpré J., Hare S.H.E., Kettleborough J., and Shindell D. 2006. Simulations of anthropogenic change in the strength of the Brewer–Dobson circulation: ClimateDynamics 27(7-8): 727-741.

13-   Cai W., Cowan T., and Sullivan A. 2009. Recent unprecedented skewness towards positive Indian Ocean Dipole occurrences and its impact on Australian rainfall. Geophysical Research Letters 36(11).

14-   Cao X., Liang Y., Zhao L., and Le H. 2013. Mobility of Pb, Cu, and Zn in the phosphorus-amended contaminated soils under simulated landfill and rainfall conditions. Environmental Science and Pollution Research 20(9): 5913-5921.

15-   Chapman S.C., Stainforth D.A., and Watkins N.W. 2013. On estimating local long-term climate trends. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 371(1991): 20120287.

16-   Gettelman A., Hoor P., Pan L.L., Randel W., Hegglin M.I., and Birner T. 2011. The extratropical upper troposphere and lower stratosphere: Reviews of Geophysics 49(3).

17-   Highwood E.J., Hoskins B.J., and Berrisford P. 2000. Properties of the Arctic tropopause. Quarterly Journal of the Royal Meteorological Society 126(565): 1515-1532.

18-   Holton J.R., Haynes P.H., McIntyre M.E., Douglass A.R., Rood R.B., and Pfister L. 1995. Stratosphere‐troposphere exchange. Reviews of Geophysics 33(4): 403-439.

19-   Homeyer C.R., Pan L.L., Dorsi S.W., Avallone L.M., Weinheimer A.J., O'Brien A.S., and Campos T.L. 2014. Convective transport of water vapor into the lower stratosphere observed during double‐tropopause events. Journal of Geophysical Research, Atmospheres 119(18).

20-   Makowski K., Wild M., and Ohmura A. 2008. Diurnal temperature range over Europe between 1950 and 2005. Atmospheric Chemistry and Physics 8(21): 6483-6498.

21-   Mikkonen S., Laine M., Mäkelä H. M., Gregow H., Tuomenvirta H., Lahtinen M., and Laaksonen A. 2015. Trends in the average temperature in Finland, 1847–2013. Stochastic Environmental Research and Risk Assessment 29(6): 1521-1529.

22-   Mohanakumar K. 2008. Stratosphere troposphere interactions: an introduction: Springer Science & Business Media.

23-   Mote P.W., Rosenlof K.H., McIntyre M.E., Carr E.S., Gille J.C., Holton J.R., and Waters J.W. 1996. An atmospheric tape recorder: The imprint of tropical tropopause temperatures on stratospheric water vapor. Journal of Geophysical Research: Atmospheres 101(D2): 3989-4006.

24-   Oberländer‐Hayn S., Gerber E. P., Abalichin J., Akiyoshi H., Kerschbaumer A., Kubin A., and Morgenstern O. 2016. Is the Brewer‐Dobson circulation increasing or moving upward?. Geophysical Research Letters 43(4): 1772-1779.

25-   Randel W.J., and Jensen E.J. 2013. Physical processes in the tropical tropopause layer and their roles in a changing climate. Nature Geoscience 6(3): 169.

26-   Rebetez M., and Reinhard M. 2008. "Monthly air temperature trends in Switzerland 1901–2000 and 1975–2004." Theoretical and Applied Climatology 91(1-4): 27-34.

27-   Reichler T., Dameris M., and Sausen R. 2003. Determining the tropopause height from gridded data, Geophysical.

28-   Santer B.D., Sausen R., Wigley T.M.L., Boyle J.S., AchutaRao K., Doutriaux C., and Schmidt G. 2003. Behavior of tropopause height and atmospheric temperature in models, reanalyses, and observations: Decadal changes. Journal of Geophysical Research: Atmospheres 108(D1): ACL-1.

29-   Sausen R., and Santer B.D. 2003. Use of changes in tropopause height to detect human influences on climate. Meteorologische Zeitschrift 12(3): 131-136.

30-   Schmidt T., Wickert J., Beyerle G., and Heise S. 2008. Global tropopause height trends estimated from GPS radio occultation data. Geophysical Research Letters 35(11).

31-   Seidel D.J., and Randel W.J. 2006. Variability and trends in the global tropopause estimated from radiosonde data. Journal of Geophysical Research: Atmospheres 111(D21).

32-   Seidel D.J., and Randel W.J. 2006. Variability and trends in the global tropopause estimated from radiosonde data. Journal of Geophysical Research: Atmospheres 111(D21).

33-   Seidel D.J., Ross R.J., Angell J.K., and Reid G.C. 2001. Climatological characteristics of the tropical tropopause as revealed by radiosondes. Journal of Geophysical Research: Atmospheres 106(D8): 7857-7878.

34-   Shapiro M.A. 1980. Turbulent mixing within tropopause folds as a mechanism for the exchange of chemical constituents between the stratosphere and troposphere: Journal of the Atmospheric Sciences 37(5): 994-1004.

35-   Shepherd Theodore G. 2002. "Issues in stratosphere-troposphere coupling." Journal of the Meteorological Society of Japan 769-792.

36-   Škerlak B., Sprenger M., and Wernli H. 2014. A global climatology of stratosphere-troposphere exchange using the ERA-Interim data set from 1979 to 2011. Atmospheric Chemistry & Physics 14(2).