Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 7 10 2007 10.5194/acp-7-2631-2007 http://www.atmos-chem-phys.net/7/2631/2007/ http://www.atmos-chem-phys.net/7/2631/2007/acp-7-2631-2007.html http://www.atmos-chem-phys.net/7/2631/2007/acp-7-2631-2007.pdf 2631 2642 2007-05-21 A study on natural and manmade global interannual fluctuations of cirrus cloud cover for the period 1984–2004 K. Eleftheratos kelef@geol.uoa.gr C. S. Zerefos P. Zanis D. S. Balis G. Tselioudis K. Gierens R. Sausen Laboratory of Climatology & Atmospheric Environment, University of Athens, Greece Foundation for Biomedical Research, Academy of Athens, Greece National Observatory of Athens, Greece Department of Meteorology and Climatology, Aristotle University of Thessaloniki, Greece Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, Greece Goddard Institute for Space Studies, National Aeronautics and Space Administration, USA Institute of Atmospheric Physics, DLR, Germany The seasonal variability and the interannual variance explained by ENSO and NAO to cirrus cloud cover (CCC) are examined during the twenty-year period 1984–2004. CCC was found to be significantly correlated with vertical velocities and relative humidity from ECMWF/ERA40 in the tropics (correlations up to −0.7 and +0.7 at some locations, respectively) suggesting that variations in large-scale vertical winds and relative humidity fields can be the origin of up to half of the local variability in CCC over these regions. These correlations reflect mostly the seasonal cycle. Although the annual cycle is dominant in all latitudes and longitudes, peaking over the tropics and subtropics, its amplitude can be exceeded during strong El Nino/La Nina events. Over the eastern tropical Pacific Ocean the interannual variance of CCC which can be explained by ENSO is about 6.8% and it is ~2.3 times larger than the amplitude of the annual cycle. Natural long-term trends in the tropics are generally small (about −0.3% cloud cover per decade) and possible manmade trends in those regions are also small. The contributions of NAO and QBO to the variance of CCC in the tropics are also small. In the northern mid-latitudes, on the other hand, the effect of NAO is more significant and can be very important regionally. Over northern Europe and the eastern part of the North Atlantic Flight Corridor (NAFC) there is a small positive correlation between CCC and NAO index during the wintertime of about 0.3. In this region, the interannual variance of CCC explained by NAO is 2.6% and the amplitude of the annual cycle is 3.1%. Long-term trends over this region are about +1.6% cloud cover per decade and compare well with the observed manmade trends over congested air traffic regions in Europe and the North Atlantic as have been evidenced from earlier findings. Bourassa, A. E., Degenstein, D. A., and Llewellyn, E. J.: Climatology of the subvisual cirrus clouds as seen by OSIRIS on Odin, Adv. Space Res., 36, 807–812, 2005. Cess, R. D., Zhang, M., Wang, P.-H., and Wielicki, B. A.: Cloud structure anomalies over the tropical Pacific during the 1997/98 El Nino, Geophys. Res. Lett., 28, 4547–4550, 2001. Chen, B. and Liu, X.: Seasonal migration of cirrus clouds over the Asian Monsoon regions and the Tibetan Plateau measured from MODIS/Terra, Geophys. Res. Lett., 32, L01804, doi:10.1029/2004GL020868, 2005. Dessler, A. E. and Yang, P.: The Distribution of Tropical Thin Cirrus Clouds Inferred from Terra MODIS Data, J. Climate, 16, 1241–1247, 2003. Gierens, K., Schumann, U., Helten, M., Smit, H. G. J., and Marenco, A.: A distribution law for relative humidity in the upper troposphere and lower troposphere derived from three years of MOZAIC measurements, Ann. Geophys., 17, 1218–1226, 1999. Gierens, K., Schumann, U., Helten, M., Smit, H., and Wang, P. H.: Ice–saturated regions and subvisible cirrus in the northern midlatitude upper troposphere, J. Geophys. Res, 105, 22 743–22 754, 2000. Jensen, E. J., Toon, O. B., Selkirk, H. B., Spinhirne, J. D., and Schoeberl, M. R.: On the formation and persistence of subvisible cirrus clouds near the tropical tropopause, J. Geophys. Res., 101(D16), 21 361–21 375, 1996. Liao, X, Rossow, W. B., and Rind, D.: Comparison between SAGE II and ISCCP high-level clouds, 1. Global and zonal mean cloud amounts, J. Geophys. Res., 100(D1), 1121–1135, 1995. Liou, K. N.: Influence of cirrus clouds on weather and climate processes: a global perspective, Mon. Wea. Rev., 114, 1167–1199, 1986. Lohmann, U. and Feichter, J.: Global indirect aerosol effects: a review, Atmos. Chem. Phys., 5, 715–737, 2005. Luo, Z., Rossow, W. B., Inoue, T., and Stubenrauch, C. J.: Did the Eruption of the Mt. Pinatubo Volcano Affect Cirrus Properties?, J. Climate, 17, 2806–2820, 2002. Lynch, D. K.: Cirrus clouds: Their role in climate and global change, Acta Astronautica, 38(11), 859–863, 1996. Massie, S., Lowe, P., Tie, X., Hervig, M., Thomas, G., and Russell III, J.: Effect of the 1997 El Nino on the distribution of upper tropospheric cirrus, J. Geophys. Res., 105(D18), 22 725–22 741, 2000. Mergenthaler, J. L., Roche, A. E., Kumer, J. B., and Ely, G. A.: Cryogenic Limb Array Etalon Spectrometer observations of tropical cirrus, J. Geophys. Res., 104, 22 183–22 194, 1999. Minnis, P., Ayers, J. K., Palikonda, R., and Phan, D.: Contrails, Cirrus Trends, and Climate, J. Climate, 17, 1671–1685, 2004. Rossow, W. B. and Schiffer, R. A.: ISCCP Cloud data products, Bull. Amer. Meteorol. Soc., 72, 2–20, 1991. Rossow, W. B., Walker, A. W., Beuschel, D. E., and Roiter, M. D.: International Satellite Cloud Climatology Project (ISCCP) Documentation of New Cloud Datasets, WMO/TD 737, World Climate Research Programme, Geneva, Switzerland, 1996. Rossow, W. B. and Schiffer, R. A.: Advances in understanding clouds from ISCCP, Bull. Amer. Meteorol. Soc., 80, 2261–2287, 1999. Sandor, B. J., Jensen, E. J., Stone, E. M., Read, W. G., Waters, J. W., and Mergenthaler, J. L.: Upper tropospheric humidity and thin cirrus, Geophys. Res. Lett., 27(17), 2645–2648, 2000. Sassen, K. and Campbell, J. R.: A Midlatitude Cirrus Cloud Climatology from the Facility for Atmospheric Remote Sensing. Part I: Macrophysical and Synoptic Properties, J. Atmos. Sci., 58, 481–496, 2001. Sausen, R., Gierens, K., Ponater, M., and Schumann, U.: A diagnostic study of the global distribution of contrails, part I: present day climate, Theor. Appl. Climatol., 61, 127–141, 1998. Sausen, R., Isaksen, I., Grewe, V., Hauglustaine, D., Lee, D. S., Myhre, G., Köhler, M. O., Pitari, G., Schumann, U., Stordal, F., and Zerefos, C.: Aviation radiative forcing in 2000: An update on IPCC (1999), Meteorol. Z., 14(4), 555–561, 2005. Schumann, U.: Formation, properties and climate effects of contrails, C. R. Physique, 6, 549–565, 2005. Spichtinger, P., Gierens, K., and Read, W.: The global distribution of ice-supersaturated regions as seen by the microwave limb sounder, Quart. J. Roy. Meteorol. Soc., 129, 3391–3410, 2003. Spichtinger, P., Gierens, K., and Dörnbrack, A.: Formation of ice supersaturation by mesoscale gravity waves, Atmos. Chem. Phys., 5, 1243–1255, 2005. Stordal, F., Myhre, G., Stordal, E. J. G., Rossow, W. B., Lee, D. S., Arlander, D. W., and Svendby, T.: Is there a trend in cirrus clouds cover due to aircraft traffic?, Atmos. Chem. Phys., 5, 2155–2162, 2005. Stubenrauch, C. J. and Schumann, U.: Impact of air traffic on cirrus coverage, Geophys. Res. Lett., 32, L14813, doi:10.1029/2005GL022707, 2005. Tselioudis, G. and Jakob, C.: Evaluation of midlatitude cloud properties in a weather and a climate model: dependence on dynamic regime and spatial resolution, J. Geophys. Res., 107(D24), AAC–14, 2002. Wang, P.-H., Minnis, P., McCormick, M. P., Kent, G. S., and Skeens, K. M.: A 6-year climatology of cloud occurrence frequency from Stratospheric Aerosol and Gas Experiment II observations (1985–1990), J. Geophys. Res., 101, 29 407–29 429, 1996. Wang, P. H., Minnis, P., Wielicki, B. A., Wong, T., and Vann, L. B.: Satellite observations of long-term changes in tropical cloud and outgoing longwave radiation from 1985 to 1998, Geophys. Res. Lett., 29, 1397, doi:10.1029/2001GL014264, 2002. Wang, P.-H., Minnis, P., Wielicki, B. A., Wong, T., Cess, R. D., Zhang, M., Vann, L. B., and Kent, G. S.: Characteristics of the 1997/1998 El Nino cloud distributions from SAGE II observations, J. Geophys. Res., 108(D1), 4009, doi:10.1029/2002JD002501, 2003. Woodbury G. E. and McCormick, M. P.: Zonal and Geographical Distributions of Cirrus Clouds Determined From SAGE Data, J. Geophys. Res., 91(D2), 2775–2785, 1986. Wylie, D. P. and Menzel, W. P.: Eight Years of High Cloud Statistics Using HIRS, J. Climate, 12, 170–184, 1999. Zerefos, C. S., Tourpali, K., and Bais, A. F.: Further studies on possible volcanic signal to the ozone layer, J. Geophys. Res., 99, 25 741–25 746, 1994. Zerefos, C. S., Eleftheratos, K., Balis, D. S., Zanis, P., Tselioudis, G., and Meleti, C.: Evidence of impact of aviation on cirrus cloud formation, Atmos. Chem. Phys., 3, 1633–1644, 2003. Zerefos, C. S., Eleftheratos, K., Zanis, P., Balis, D. S., and Tselioudis, G.: Search for manmade cirrus-contrails over Southeast Asia, Special Issue of East Asia Climate and Environment (EACE) in TAO, in press, 2007.