ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-10-10273-2010 Dynamics of the Antarctic and Arctic mesosphere and lower thermosphere – Part 1: Mean winds Sandford D. J. 1 Beldon C. L. 1 Hibbins R. E. 2 Mitchell N. J. 1 Department of Electronic and Electrical Engineering, University of Bath, Bath, UK British Antarctic Survey, Cambridge, UK 04 11 2010 10 21 10273 10289 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/10/10273/2010/acp-10-10273-2010.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/10/10273/2010/acp-10-10273-2010.pdf

Zonal and meridional winds have been measured in the upper mesosphere and lower thermosphere at polar latitudes using two ground-based meteor radars. One radar is located at Rothera (68° S, 68° W) in the Antarctic and has been operational since February 2005. The second radar is located at Esrange (68° N, 21° E) in the Arctic and has been operational since October 1999. Both radars have produced relatively continuous measurements. Here we consider measurements made up to the end of 2009. Both radars are of similar design and at conjugate geographical latitudes, making the results directly comparable and thus allowing investigation of the differences in the mean winds of the Antarctic and Arctic regions. The data from each radar have been used to construct climatologies of monthly-mean zonal and meridional winds at heights between 80 and 100 km. Both Antarctic and Arctic data sets reveal seasonally varying zonal and meridional winds in which the broad pattern repeats from year to year. In particular, the zonal winds display a strong shear in summer associated with the upper part of the westward summertime zonal jet. The winds generally reverse to eastward flow at heights of ~90 km. The zonal winds are eastward throughout the rest of the year. The meridional winds are generally equatorward over both sites, although brief episodes of poleward flow are often evident near the equinoxes and during winter. The strongest equatorward flows occur at heights of ~90 km during summer. <br><br> There are significant differences between the mean winds observed in the Antarctic and Arctic. In particular, the westward winds in summer are stronger and occur earlier in the season in the Antarctic compared with the Arctic. The eastward winds evident above the summertime zonal wind reversal are significantly stronger in the Arctic. The summertime equatorward flow in the Antarctic is slightly weaker, but occurs over a greater depth than is the case in the Arctic. <br><br> Comparisons of these observations with those of the URAP and HWM-07 empirical models reveal a number of significant differences. In particular, the zonal winds observed in the Antarctic during wintertime are significantly weaker than those of URAP. However, the URAP zonal winds are a good match to the observations of the Arctic. Significant differences are evident between the observations and HWM-07. In particular, the strong wintertime zonal winds of the Arctic in HWM-07 are not evident in the observations and the summertime zonal winds in HWM-07 are systematically stronger than observed. The agreement with meridional winds is generally poor. <br><br> There is a significant amount of inter-annual variability in the observed zonal and meridional winds. Particularly high variability is observed in the Arctic zonal winds in spring and is probably associated with stratospheric warmings.

 References Alexander,~M J. and Teitelbaum,~H.: Observation and analysis of a~large amplitude mountain wave event over the Antarctic Peninsula, J. Geophys. Res., 112, D21103, \doi10.1029/2006JD008368, 2007. Alexander,~M J., Gille,~J., Cavanaugh,~C., Coffey,~M., Craig,~C., Eden,~T., Francis,~G., Halvorson,~C., Hannigan,~J., Khosravi,~R., Kinnison,~D., Lee,~H., Massie,~S., Nardi,~B., Barnett,~J., Hepplewhite,~C., Lambert,~A., and Dean,~V.: Global estimates of gravity wave momentum flux from High Resolution Dynamics Limb Sounder observations, J. Geophys. Res., 113, D15S18, \doi10.1029/2007JD008807, 2008. Baumgaertner,~A J G., McDonald,~A J., Fraser,~G J., and Plank,~G E.: Long-term observations of mean winds and tides in the upper mesosphere and lower thermosphere above Scott Base, Antarctica, J. Atmos. Sol.-Terr. Phys., 67(16), 1480–1496, 2005. Baumgaertner,~A J G. and McDonald,~A J.: A gravity wave climatology for Antarctica compiled from Challenging Minisatellite Payload/Global Positioning System (CHAMP/GPS) radio occultations, J. Geophys. Res., 112, D05103, \doi10.1029/2006JD007504, 2007. Becker,~E., and Fritts,~D C.: Enhanced gravity-wave activity and interhemispheric coupling during the MaCWAVE/MIDAS morthern summer program 2002, Ann. Geophys., 24, 1175–1188, 2006. Beldon,~C L., and Mitchell,~N J.: Gravity waves in the mesopause region observed by meteor radar, 2: Climatologies of gravity waves in the Antarctic and Arctic, J. Atmos. Sol.-Terr. Phys., 71, 875–884, 2009. Cervera,~M A. and Reid,~I M.: Comparison of simultaneous wind measurements using collocated VHF meteor radar and MF spaced antenna radar systems, Radio Sci., 30(4), 1245–1261, 1995. Dowdy,~A J., Vincent,~R A., Igarashi,~K., Murayama,~Y., and Murphy,~D J.: A~comparison of mean winds and gravity wave activity in the northern and southern polar MLT, Geophys. Res. Lett., 28(8), 1475–1478, 2001. Dowdy,~A J., Vincent,~R A., Tsutsumi,~M., Igarashi,~K., Murayama,~Y., Singer,~W., and Murphy,~D J.: Polar mesosphere and lower thermosphere dynamics: 1. Mean wind and gravity wave climatologies, J. Geophys. Res., 112, D17104, \doi10.1029/2006JD008126, 2007a. Dowdy,~A J., Vincent,~R A., Tsutsumi,~M., Igarashi,~K., Murayama,~Y., Singer,~W., Murphy,~D J., and Riggin,~D M.: Polar mesosphere and lower thermosphere dynamics: 2. Response to sudden stratospheric warmings, J. Geophys. Res., 112, D17105, \doi10.1029/2006JD008127, 2007b. Drob,~D P., Emmert,~J T., Crowley,~G., Piconem~J M., Shepherd,~G G., Skinner,~W., Hays,~P., Niciejewski,~R J., Larsen,~M., She,~C Y., Meriwether,~J W., Hernandez,~G., Jarvis,~M J., Sipler,~D P., Tepley,~C A., O'Brien,~M S., Bowman,~J R., Wu,~Q., Murayama,~Y., Kawamura,~S., Reid,~I M., and Vincent,~R A.: An empirical model of the Earth's horizontal wind fields: HWM07, J. Geophys. Res., 113, A12304, \doi10.1029/2008JA013668, 2008. Engler,~N., Singer,~W., Latteck,~R., and Strelnikov,~B.: Comparison of wind measurements in the troposphere and mesosphere by VHF/MF radars and in-situ techniques, Ann. Geophys., 26, 3693–3705, \doi10.5194/angeo-26-3693-2008, 2008. %%%ok Hall,~C M., Aso,~T., Manson,~A H., Meek,~C E., Nozawa,~S., and Tsutsumi,~M.: High-latitude mesospheric mean winds: a~comparison between Troms\o (69\degree N) and Svalbard (78\degree N), J. Geophys. Res., 108(D19), 4598, \doi10.1029/2003JD003509, 2003. Hedin,~A E., Fleming,~E L., Manson,~A H., Schmidlin,~F J., Avery,~S K., Clark,~R R., Franke,~S J., Fraser,~G J., Tsuda,~T., Vial,~F., and Vincent,~R A.: Empirical wind model for the upper, middle and lower atmosphere, J. Atmos. Terr. Phys., 58(13), 1421–1447, 1996. Hibbins, R. E., Shanklin, J. D., Espy, P. J., Jarvis, M. J., Riggin, D. M., Fritts, D. C., and Lübken, F.-J.: Seasonal variations in the horizontal wind structure from 0–100 km above Rothera station, Antarctica (67° S, 68° W), Atmos. Chem. Phys., 5, 2973–2980, doi:10.5194/acp-5-2973-2005, 2005. %%%ok Hocking,~W K. and Thyaparan,~T.: Simultaneous and collocated observations of winds and tides by MF and meteor radars over London, Canada (43\degree N, 81\degree W), during 1994–1996, Radio. Sci., 32(2), 833–865, 1997. Hocking,~W K., Fuller~B., and Vandepeer,~B.: Real-time determination of meteor-related parameters utilizing modem digital technology, J. Atmos. Sol.-Terr. Phys., 63, 155–169, 2001. Hocking,~W K.: Middle atmosphere dynamical studies at Resolute Bay over a~full representative year: mean winds, tides, and special oscillations, Radio. Sci., 36(6), 1795–1822, 2001. Hoffmann,~P., Singer,~W., Keuer,~D., Hocking,~W K., Kunze,~M., and Murayama,~Y.: Latitudinal and longitudinal variability of mesosphere winds and temperatures during stratospheric warming events, J. Atmos. Sol.-Terr. Phys., 69, 2355–2366, 2007. Holton,~J R., Curry,~J A., and Pyle,~J A.: Encyclopedia of Atmospheric Sciences, Volumes~1–6, Elsevier, 2003. Jacobi, C., Arras,~C., Kürschner,~D., Singer,~W., Hoffmann,~P., and Keuer,~D.: Comparison of mesopause region meteor radar winds, medium frequency radar winds and low frequency drifts over Germany, Adv. Space Res., 43, 247–252, 2009. Karlsson,~B., McLandress,~C., and Shepherd,~T G.: Inter-hemispheric mesospheric coupling in a comprehensive middle atmosphere model, J. Atmos. Sol.-Terr. Phys., 71, 518-530, 2009. Kishore,~P., Namboothiri,~S P., Igarashi,~K., and Murayama,~Y.: Further evidence of hemispheric differences in the MLT mean wind climatology: simultaneous MF radar observations at Poker Flat (65\degree N, 147\degree W) and Davis (69\degree S, 78\degree E), Geo. Res. Lett., 30(6), 1336, \doi10.1029/2002GL016750, 2003. Lieberman,~R S.: The gradient wind in the mesosphere and lower thermosphere, Earth Planets Space, 51, 751–761, 1999. Lübken,~F J., Müllemann,~A., and Jarvis,~M J.: Temperatures and horizontal winds in the Antarctic summer mesopause, J. Geophys. Res., 109, D24112, \doi10.1029/2004JD005133, 2004. Manson,~A H., Meek,~C E., Hall,~C M., Nozawa,~S., Mitchell,~N J., Pancheva,~D., Singer,~W., and Hoffmann,~P.: Mesopause dynamics from the scandinavian triangle ofradars within the PSMOS-DATAR Project, Ann. Geophys., 22, 367–386, \doi10.5194/angeo-22-367-2004, 2004. %%%ok McIntyre,~M E.: On dynamics and transport near the polar mesopause in summer, J. Geophys. Res., 94(D12), 14617–14628, 1989. McLandress,~C., and McFarlane,~N A.: Interactions between Orographic Gravity Wave Drag and Forced Stationary Planetary Waves in the Winter Northern Hemisphere Middle Atmosphere, J. Atmos. Sci., 50, 1966-1990, 1993. Merzlyakov,~E G., Murphy,~D J., Vincent,~R A., and Portnyagin,~Y I.: Long-term tendencies in the MLT prevailing winds and tides over Antarctica as observed by radar at Molodezhnaya, Mawson and Davis, J. Atmos. Sol.-Terr. Phys., 71, 21–32, 2009. Mitchell,~N J., Pancheva,~D., Middleton,~H R., and Hagan,~M E.: Mean winds and tides in the Arctic mesosphere and lower thermosphere, J. Geophys. Res., 107(A1), 1004, \doi10.1029/2001JA900127, 2002. Müllemann,~A. and Lübken,~F J.: Horizontal winds in the mesosphere at high latitudes, Adv. Space Res., 35, 1890–1894, 2005. Pogoreltsev,~A.: Simulation of the influence of stationary planetary waves on the zonally averaged circulation of the mesosphere lower thermosphere region, J. Atmos. Terr. Phys., 58, 901–909, 1996. Portnyagin,~Y I., Forbes,~J M., Fraser,~G J., Vincent,~R A., Lysenko,~I A., and Makarov,~N M.: Dynamics of the Antarctic and Arctic mesosphere/lower thermosphere regions, Adv. Space Res., 12(10), 89–96, 1992. Portnyagin,~Y I., Forbes~J M., Fraser~G J., Vincent~R A., Avery~S K., Lysenko~I A., and Makarov~N A.: Dynamics of the Antarctic and Arctic mesosphere and lower thermosphere regions – I. The prevailing wind, J. Atmos. Terr. Phys., 55, 827–841, 1993. Portnyagin,~Y I., Solovjova,~T V., Makarov,~N A., Merzlyakov,~E G., Manson,~A H., Meek,~C E., Hocking,~W., Mitchell,~N., Pancheva,~D., Hoffmann,~P., Singer,~W., Murayama,~Y., Igarashi,~K., Forbes,~J M., Palo,~S., Hall,~C., and Nozawa,~S.: Monthly mean climatology of the prevailing winds and tides in the Arctic mesosphere/lower thermosphere, Ann. Geophys., 22, 3395–3410, \doi10.5194/angeo-22-3395-2004, 2004. %%%ok Portnyagin,~Y I., Merzlyakov,~E G., Solov'eva,~T V., and Makarov,~N A.: Interhemispheric distinctions in wind-regime parameters in the polar mesosphere-lower thermosphere, Izv. Atmos. Ocean. Phys., 42(1), 93–104, 2006. Plane,~J M C., Cox,~R M., and Rollason,~R J.: Metallic layers in the mesopause and low thermosphere region, Adv. Space Res., 24, 1559–1570, 1999. Smith,~A K.: Physics and chemistry of the mesopause region, J. Atmos. Sol.-Terr. Phys., 66, 839–857, 2004. Stubbs,~T J.: The measurement of winds in the D-region of the ionosphere by the use of partially reflected radio waves, J. Atmos. Terr. Phys., 35, 909–919, 1973. Swinbank,~R. and Ortland,~D A.: Compilation of wind data for the Upper Atmospheric Research Satellite (UARS) reference atmosphere project, J. Geophys. Res., 108(D19), 4615, \doi10.1029/2002JD003135, 2003. Vincent,~R A.: Gravity-wave motions in the mesosphere and lower thermosphere observed at Mawson, Antarctica, J. Atmos. Terr. Phys., 56(5), 593–602, 1994. Wu,~D L., and Jiang,~J H.: MLS observations of atmospheric gravity waves over Antarctica, J. Geophys. Res., 107(D24), 4773, \doi10.1029/2002JD002390, 2002. Younger,~P T., Astin,~I., Sandford,~D J., and Mitchell,~N J.: The sporadic radiant and distribution of meteors in the atmosphere as observed by VHF radar at Arctic, Antarctic and equatorial latitudes, Ann. Geophys., 27, 2831–2841, \doi10.5194/angeo-27-2831-2009, 2009. %%%ok