Cover Journal of the Atmospheric Sciences
Journal of the Atmospheric Sciences

  • Barnes, R., R. Hide, A. White, and C. Wilson, 1983: Atmospheric angular momentum fluxes, length-of-day changes and polar motion. Proc. Roy. Soc. London,387A, 31–73.

  • Bell, M., 1994: Oscillations in the equatorial components of the atmosphere’s angular momentum and torques on the earth’s bulge. Quart. J. Roy. Meteor. Soc.,120, 195–212.

  • ——, R. Hide, and G. Sakellarides, 1991: Atmospheric angular momentum forecasts as novel tests of globalnumerical weather-prediction models. Philos. Trans. Roy. Soc. London,1334, 55–92.

  • Bougeault, P., and Coauthors, 1993: The atmospheric momentum budget over a major mountain range: First results of the PYREX field program. Ann. Geophys.,11, 395–418.

  • Brzezinski, A., 1987: Statistical investigations of atmospheric angular momentum functions and of their effect on polar motion. Manuscr. Geodaetica,12, 268–281.

  • Chao, B., 1993: Excitation of earth’s polar motion by atmospheric angular momentum. Geophys. Res. Lett.,20, 253–256, 1980–1990.

  • Chapman, S., and R. Lindzen, 1970: Atmospheric Tides. Reidel, 200 pp.

  • Davies, H., and D. Phillips, 1985: Mountain drag along the Gotthardt section during ALPEX. J. Atmos. Sci.,42, 2093–2109.

  • Dickey, J., and T. Eubanks, 1986: The application of space geodesy to earth orientation studies. Space Geodesy and Geodynamics, A. Anderson and A. Cazenave, Ed., Academic Press, 221–267.

  • Egger, J., and W. Metz, 1981: On the mountain torque in barotropic planetary flow. Quart. J. Roy. Meteor. Soc.,107, 299–312.

  • ——, and K. P. Hoinka, 1999: The equatorial bulge, angular momentum and planetary wave motion. Tellus,51, 786–802.

  • Eubanks, T., J. Steppe, J. Dickey, R. Rosen, and D. Salstein, 1988: Causes of rapid motions of the Earth’s pole. Nature,134, 115–119.

  • Exner, F., 1925: Dynamische Meteorologie. Springer, 421 pp.

  • Frederiksen, J., 1982: Eastward and westward flows over the topography in nonlinear and linear barotropic models. J. Atmos. Sci.,39, 2478–2489.

  • Furuya, M., Y. Hamano, and I. Naito, 1996: Quasi-periodic wind signal as a possible excitation of Chandler wobble. J. Geophys. Res.,101 (B11), 25 537–25 546.

  • Gibson, R., P. Kållberg, S. Uppala, A. Hernandez, A. Nomura, and E. Serrano, 1997: ERA description. ECMWF Reanalysis Project Report Series, Vol. 1, 86 pp. [Available from ECMWF, Shinfield Park, Reading RG2 9AX, United Kingdom.].

  • Hide, R., 1984: Rotation of the atmospheres of the earth and planets. Philos. Trans. Roy. Soc. London,313A, 107–121.

  • ——, and J. Dickey, 1991: Earth’s variable rotation. Science,253, 629–637.

  • Hoinka, K. P., 1998: Mean global surface pressure series evaluated from ECMWF reanalysis data. Quart. J. Roy. Meteor. Soc.,124, 2291–2297.

  • Iskenderian, H., and D. Salstein, 1998: Regional sources of mountain torque variability and high-frequency fluctuations in atmospheric angular momentum. Mon. Wea. Rev.,126, 1681–1694.

  • Kang, I.-S., and K.-M. Lau, 1994: Principal modes of atmospheric circulation anomalies associated with global angular momentum fluctuations. J. Atmos. Sci.,51, 1194–1205.

  • Newton, C., 1971: Mountain torques in the global angular momentum balance. J. Atmos. Sci.,28, 623–627.

  • Peixoto, J., and A. Oort, 1992: Physics of Climate. American Institute of Physics, 520 pp.

  • Ponte, R., D. Stammer, and J. Marshall, 1998: Oceanic signals in observed motions of the Earth’s pole of rotation. Nature,391, 476–479.

  • Salstein, D., and R. Rosen, 1989: Regional contribution to the atmospheric excitation of rapid polar motion. J. Geophys. Res.,94 (D7), 9971–9978.

  • Sawford, B., and J. Frederiksen, 1983: Mountain torque and angular momentum in barotropic planetary flows: Equilibrium solutions. Quart. J. Roy. Meteor. Soc.,109, 309–324.

  • U.S. Weather Bureau, 1962: U.S. Standard Atmosphere. NASA, 276 pp.

  • Volland, H., 1996: Atmosphere and earth’s rotation. Surv. Geophys.,17, 101–144.

  • von Ficker, H., 1910: Die Ausbreitung kalter Luft in Rußland und Nordasien. Sitzungsber. Kaiserl. Akad. Wissensch. Math. Naturwiss. Klasse,69, 1769–1837.

  • Weickmann, K., G. Kiladis, and P. Sardeshmukh, 1997: The dynamics of intraseasonal atmospheric angular momentum oscillations. J. Atmos. Sci.,54, 1334–1461.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 94 94 1
PDF Downloads 6 6 1
Editorial Type:
Article

Mountain Torques and the Equatorial Components of Global Angular Momentum

Joseph Egger1 and Klaus-P. Hoinka2
View More View Less
  • 1 Meteorologisches Institut, Universität München, Munich, Germany
  • | 2 Institut für Physik der Atmosphäre, DLR, Oberpfaffenhofen, Germany
Print Publication:
01 Jul 2000
DOI:
https://doi.org/10.1175/1520-0469(2000)057<2319:MTATEC>2.0.CO;2
Page(s):
2319–2331
© Get Permissions Rent on DeepDyve
Restricted access

Abstract

The atmosphere induces changes of the earth’s angular momentum via orographic and frictional torques and, in particular, via torques exerted by the equatorial bulge. While the torques leading to fluctuations of the axial component of angular momentum and to corresponding changes of the length of the day have been investigated intensively in the past, this is not so for the torques linked to the equatorial components of global angular momentum. Here, the orographic torques that affect the equatorial components of global angular momentum and contribute to polar motion are discussed. The torques linked to the equatorial bulge are considered as well. European Centre for Medium-Range Weather Forecasts reanalysis data are used to investigate the torques both in an inertial and an earth fixed frame. The basic statistical characteristics of the mountain torques are derived for various regions on the globe. It is found that a large fraction of the torque exerted by the bulge is due to the presence of orography. Moreover, mountain torques are not negligible when compared to those exerted by the bulge. Examples of atmospheric flow patterns linked to large torques at the Tibetan plateau are given.

Corresponding author address: Dr. Joseph Egger, Meteorologisches Institut, Universitat München, Theresienstrasse 37, D-80333 Munich, Germany.

Email: J.Egger@lrz.uni-muenchen.de

Abstract

The atmosphere induces changes of the earth’s angular momentum via orographic and frictional torques and, in particular, via torques exerted by the equatorial bulge. While the torques leading to fluctuations of the axial component of angular momentum and to corresponding changes of the length of the day have been investigated intensively in the past, this is not so for the torques linked to the equatorial components of global angular momentum. Here, the orographic torques that affect the equatorial components of global angular momentum and contribute to polar motion are discussed. The torques linked to the equatorial bulge are considered as well. European Centre for Medium-Range Weather Forecasts reanalysis data are used to investigate the torques both in an inertial and an earth fixed frame. The basic statistical characteristics of the mountain torques are derived for various regions on the globe. It is found that a large fraction of the torque exerted by the bulge is due to the presence of orography. Moreover, mountain torques are not negligible when compared to those exerted by the bulge. Examples of atmospheric flow patterns linked to large torques at the Tibetan plateau are given.

Corresponding author address: Dr. Joseph Egger, Meteorologisches Institut, Universitat München, Theresienstrasse 37, D-80333 Munich, Germany.

Email: J.Egger@lrz.uni-muenchen.de

Save