Variation of Iran’s air temperature from Earth surface to lower stratosphere as an index of climate change during 1979-2014


Assistant Professor, Department of Climatology, Faculty of Natural Recourses, University of Kurdistan, Iran


Radiation input from the Sun is the source of energy for the Earth’s climate system (Hartmann, 1994). Most of the solar radiation absorbed at the surface, the rest is absorbed by the atmosphere. The global temperature profile of the atmosphere reflects a balance between the radiative, convective, and dynamical heating/cooling of the surface-atmosphere system. Understanding of the climate change in recent decades is important for the prediction of the future climate. Observed modifications in the vertical temperature structure of the atmosphere have been proposed as a primary indicator of climate change (Marshal, 2002). Radiosonde data are the primary source for monitoring changes in upper-air parameters. The second source is satellite-derived data from the microwave-sounding unit (MSU). Third source of ‘‘observed’’ upper-air data are the reanalysis projects as NCEP/NCAR and ECMWF.  In this study, we attempt to estimate trends in the Irans surface and upper atmosphere temperature as an index of climate change on the basis of ECMWF data, which offer substantially higher vertical resolution than radiosounds and the microwave sounding unit (MSU), thus allowing a more accurate identification of the upper atmosphere and possible multiple upper atmosphere levels. In addition, the tempo-spatial resolution of applied data is higher than other data sources.
The monthly surface and upper atmospheric air temperature data of Iran during 1/1979 to 4/2014 extracted from European Centre for Medium-Range Weather Forecasts (ECMWF). The spatial resolution 0.125 degree has been applied. Based on selected spatial resolution, 9965 pixels located on the Iran political boundry. The variation of spatial mean air temperature over Iran from surface to 10 hPa was analyzied. The radiosonds recorded air temperature from 11 upper stations over Iran compared to the ECMWF data to evaluate accuracy of applied data. Two non parametric tests of Mann-Kendal and Sen,s estimatotor used to decide about significancy of trend and slope of trend respectively.
The results of this study show that using ECMWF data to evaluate varation of surface and upper atmospheric air temperature is useful. The tempo-spatial resolution of applied data is very high in horizontal and vertical. This implies that the ECMWF data do a reasonable job of capturing the variability of upper atmospheric temperature and are more adequate rather than Microwave Sounding Unit (MSU) and radiosounds data. The results also show that trend of surface and upper atmospheric air tempertre is significant at 95% confidence level. The observed trend near the earth surface and low and high troposphere is positive while is negative in the stratosphere. Althoght the trend of Iran’s middle troposphere layer temperature is not significant statistically at the 95% but fitting regression line on the standardized air temperature time series show that trend is positive. The slope rate of Iran’s surface temperature is 0.65°C per decades and is higher that other levels. The observed warming rate in the lower troposphere is higher than upper troposphere. The spatial distribution of the trend slope near the surface show that the highest warimimg observed between 34 to 37 latitudes.  In the southern parts of Alborz and eastern parts of Zagros, the slope rate of surface temperature rate is 1.3 to 1.6 degrees C per decade.  
The obsereved increased tropospheric temperature and cooling of stratosphere is in good agreement with previous studies findings. The temperature change near the surface and lower troposphere is high in the semi northern parts of the country. The rate of upper troposphere temperature is not significant in the semi northern parts. The increase of upper troposphere temperature in the southern parts results in change tropopouse height. The depletion of ozone in the stratosphere (upper atmosphere) maybe contributing to the cooling of the stratosphere layer. The increased man made pollutants, green house gases and ozone in troposphere is also contributing to the warming of the troposphere. In temporal view from 1998, a positive anomay in temperature is observed near the surface and lower troposphere. The highest warming occurred in 2010 and 2001. According to other researchers finding warming of troposphere results in the displacement of Hadley cells and subtropical jet streams towards north and changes in tropical circulation patterns.


Main Subjects

علیجانی، ب.، محمودی، پ.، سلیقه، م. و ریگی بخش، ا.ب.، 1390، بررسی تغییرات کمینه و بیشینه‌های سالانه دما در ایران، فصلنامۀ تحقیقات جغرافیایی، 102، 122-101.
مسعودیان، س.ا.، 1384، بررسی روند دمای ایران در نیم سدة گذشته، مجلة پژوهش‌های جغرافیایی، 54، 45-29.
Allen, R.J., Sherwood, S.C., Norris, J.R. and Zender, C.S., 2012, Recent Northern Hemisphere tropical expansion primarily driven by black carbon and tropospheric ozone. Nature., 485, 350-354.
Andrews, D. G., Holton, J. R. and Leovy, C. B., 1987, Middle Atmosphere Dynamics, 498 pp., Academic, San Diego, Calif.
Barnett, T. P., and Schlesinger, M. E., 1987, Detecting changes in global climate induced by greenhouse gases. J. Geophys. Res., 92, 14 772–14 780.
Bengtsson, L., and Hodges, K. I., 2011, On the evaluation of temperature trends in the tropical troposphere, Clim. Dyn., 36, 419–430.
Butler, A. H., Thompson, D. W. J. and Heikes, R., 2010, The steady‐state atmospheric circulation response to climate change‐like thermal forcings in a simple general circulation model, J. Clim., 23, 3474–3496.
Christy J. R., W. B. Norris, R. W. Spencer, J. J. Hnilo, 2007: Tropospheric temperature change since 1979 from tropical radiosonde and satellite measurements. Journal of Geophysical Research-Atmospheres, 112: D06102, DOI:10.1029/2005JD006881.
Colman, R. A., 2001, On the vertical extent of atmospheric feedbacks,Clim. Dyn., 17, 391–405,
Fu, Q. and Lin, P., 2011a, Poleward Shift of Subtropical Jets Inferred from Satellite-ObservedLower-Stratospheric Temperatures, J. Clim., 24, 5597-5603.
Fu, Q., Johanson, C. M. Wallace, J. M. and Reichler, T., 2006, Enhanced mid-latitude tropospheric warming in satellite measurements, Science., 312, 1179.
Fu, Q., Manabe, S. and Johanson, C. M., 2011b, On the warming in the tropical upper troposphere: Models versus observations, Geophys. Res. Lett.,38, L15704, doi:10.1029/2011GL04810.
Fu, Q., Solomon, S. and Lin, P., 2010, On the seasonal dependence of tropical lower-stratospheric temperature trends. Atmos. Chem. Phys., 10, 2643–2653.
Gaffen, D.J., Santer, B.D., Boyle, J.S., Christy, J.R., Grahan, N.E and Ross, R.J., 2000, Multidecadal changes in the vertical temperature structure of the tropica troposphere, Science, 287, 1242-1245.
Goody, R.M. and Yung, Y.L., 1995, Atmospheric radiation: Theoritical basis, Second edition, Oxford University Press.
Hartmann, D. L., and Larson, K., 2002, An important constraint on tropical cloud‐climate feedback, Geophys. Res. Lett., 29, 1951, doi:10.1029/2002GL015835.
Holton, J. R., 1979, An Introduction to Dynamic Meteorology, Second Edition. Academic Press, New York, 416 pp.
Held, I. M., 1982, On the Height of the Tropopause and the Static Stability of the Troposphere. J. Atmos. Sci., 39, 412–417.
Held, I. M., 1993, Large‐scale dynamics and global warming, Bull. Am. Meteorol. Soc., 74, 228–241
Hudson, R. D., Andrade, M. F.,  Follette, M. B. Frolov, D., 2006, The total ozone field separated into meteorological regimes.Part II: Northern Hemisphere mid-latitude total ozone trends. Atmos. Chem. Phys., 6, 5183–5191.
Hurrell, J. W. and Trenberth, K. E., 1998, Difficulties in obtaining reliable temperature trends: Reconciling the surface and satellite microwave sounding unit records.J. Climate., 11, 945–967.
Karl T. R., Hassol, S. J., Miller,  C. D. and Murray , W. L., 2006, Temperature Trends in the Lower Atmosphere: Steps for Understanding and Reconciling Differences. A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. National Oceanic and Atmospheric Administration, National Climatic Data Center: Asheville, NC; 164.
Kiehl, J.T., 1992, Atmospheric general circulation modeling. Cambridge University Press, Cambreidge.
Marshall, G.J., 2002, Trends in Antarctic geopotential height and temperature: A comparison between Radiosonde and NCEP–NCAR reanalysis data, J. Climate., 15, 659-674.
Randel, W. J., and Wu, F., 1999, Cooling of the Arctic and Antarctic polar stratospheres due to ozone depletion.J. Climate., 12,1467–1479.
Randel, W. J., and Wu, F., and Gaffen, D. J., 2000, Interannual variability of the tropical tropopause derived from radiosonde data and NCEP reanalyses. J. Geophys. Res., 105, 509–15 523.
Reichler, T., 2009, Changes in the Atmospheric Circulation as Indicator of Climate Change. In Trevor M. Letcher, editor: Climate Change: Changes in the Atmospheric Circulation as Indicator of Climate Change, Elsevier, pp. 145-164.
Santer, B. D., Taylor, K.E., Wigley, T.M.L., Johns., T.C., Jones, P.D., Karoly, D.J., Mitchell, J.F.B., Oort, A.H., Penner, J.E., Ramaswamy, V., Schwarzkopf, M.D., Stouffer, R.J. and Tett, S., 1996, A search for human influences on the thermal structure of the atmosphere. Nature., 382, 39–46.
Santer, B.D., Hnilo, J.J., Boyle, J.S.,  Doutriaux, C., Fiorino, M., Parker, D.E., Taylor, K.E. and Wigley,  T.M.L., 1999, Uncertainties in observationally-based estimates of temperature change in the free atmosphere. J. Geophys. Res., 104, 6305-6333.
Santer, B. D., Wigley, T. M. L., Boyle,  J. S., Gaffen, D. J., Hnilo,  J. J., Nychka,  D.,  Parker,  D. E. and Taylor, K. E., 2000, Statistical significance of trends and trend differences in layer-average atmospheric temperature time series, J. Geophys. Res., 105, 7337– 7356.
Shah, K. P., and Rind, D., 1998, Comparing upper tropospheric and lower stratospheric temperatures: Microwave sounding unit, radiosonde, COSPAR International Reference Atmosphere, and National Center for Environmental Prediction/National Center for Atmospheric Research reanalysis monthly mean climatologies. J. Geophys. Res., 103, 31569–31591.
Seidel, D.J. and Randel, W.J., 2006, Variability and trends in the global tropopause estimated from radiosonde data, J. Geophys. Res., 111, D21101, doi:10.1029/2006JD007363.
Seidel, D. J., Fu, Q., Randel, W. J. and Reichler, T. J., 2008, Widening of the tropical belt in a changing climate, Nat. Geosci., 1, 21– 24.
Seidel, D.J., Free, M and Wang, J.S., 2012, Reexamining the warming in the tropical upper troposphere: Models versus radiosonde observations. J. Geophys. Res., 39, 1-5.
Stephens, G. L. and Webster, P. J., 1981, Clouds and Climate: Sensitivity of Simple Systems. J. Atmos. Sci., 38, 235-245.
Stouffer., R.J. and Manabe, S., 1999, Response of a Coupled Ocean–Atmosphere Model to Increasing Atmospheric Carbon Dioxide: Sensitivity to the Rate of Increase, J. Clim., 12, 224-2237.
Struthwolf, M.E., 1995, Forecasting maximum temperatures through use of an adjusted 850- to 700-mb thickness technique, Weather and forecasting., 10, 160-171.
Tett, S.F.B., Mitchell, F.B., Parker, D.E and Allen, M.R., 1996, Human Influence on the Atmospheric Vertical Temperature Structure: Detection and Observations, Scince., 274, 1170-1173.
Trenberth, K.E. and Stepaniak, D.P., 2003, Covariability of Components of Poleward Atmospheric Energy Transports on Seasonal and Interannual Timescales. J. Climate, 16, 3691–3705.
Wallace, J.M., Fu, Q., Smoliak, B.V., Lin, P. and Johanson, C.M., 2012, Simulated versus observed patterns of warming over the extratropical Northern Hemisphere continents during the cold season, PNAS., 109, 14337–14342.
Wentz, F. J., and  Schabel, M., 1998, Effects of orbital decay on sat-ellite-derived lower-tropospheric temperature trends. Nature., 394, 661–664.