ssg5173

Special Study Group 5.173 Interaction of the Atmosphere and Oceans with the Earth’s Rotational Dynamics Chairman: Clark R. Wilson University of Texas Department of Geological Sciences PO Box 1085 Austin, TX-78712 USA

Members and Corresponding Members:

Jean O. Dickey (United States), Richard Gross (United States), Marshall Eubanks (United States), Jim Ray (United States), Frank Bryan (United States) Roland Madden (United States), Steve Dickman (United States), David Salstein (United States), Richard Rosen (United States), Clark R. Wilson (United States), Richard Eanes (United States), Tom Johnson (United States), John Kuehne (United States), Jianli Chen (United States), C.K. Shum (United States), R.S. Nerem (United States), Byron Tapley (United States), Bob Schutz (United States), Daniel Gambis (France), Martine Feissel (France), Ben Chao (United States), Richard Ray (United States), Chopo Ma (United States), Tom Herring (United States), Masato Furuya (Japan), Shailen Desai (United States), John Wahr (United States), Olivier de Viron (Belgium), Veronique Dehant (Belgium), Aleksander Brzezinski (Poland), Barbara Kolaczek (Poland), Jolanta Nastula (Poland), Wieslaw Kosek (Poland), Sergei Petrov (Russia), Dawai Zheng (China), Shigeo Yoshida (Japan), K. Kuma (Japan), H. Itoh (Japan), Klaus Weickmann (United States), Dick Peltier (Canada), Jim Merriam (Canada), Isao Naito (Japan), Peter Brosche (Germany), Pascal Gegout (France), Prof. Dr. J. Sunderman (Germany), Douglas S. Luther (United States)

1. Missions

International Association of Geodesy Special Study Group 5.173, 'Interaction of the Atmosphere and Oceans with the Earth's Rotational Dynamics' was established to coordinate studies related to understanding the causes of observed rotational variations and their relationships with oceanic and atmospheric variability over the range of time scales from hours to decades. Understanding these rotational variations requires a combined effort of theory, observation, and numerical modeling of geodetic, oceanographic, and atmospheric processes.

2. Organization

SSG members organized a great variety of special sessions at scientific meetings as noted under the bibliography section, below. Several SSG meetings of opportunity were held at these meetings, and a world wide web site was developed to organize the SSG during its formative year.

As a result of recommendations from the October 1996 workshop, the IERS issued a call for coordinating centers for various geophysical fluids. The extension of IERS missions to include geophysical fluids is directly an effort of members of SSG5.173, and puts in place an organization to advance the study of the interaction of the oceans and atmosphere with the earth’s rotation. In effect, the formal development of these geophysical fluid centers is a statement of the success of this SSG, which builds on the work of several related SSG’s over the past decade.

The study of the gravity field is the focus of IAG Section III, and the study of the time variations in the gravity field is the subject of Special Study Group 5.174. However, it has become clear that the geophysical sources that change the gravity field also affect the rotation of the earth, and are dominated by the atmosphere and oceans. Thus, forthcoming satellite missions (Germany-CHAMP; NASA-GRACE; ESA-GOCE) that will be capable of observing the gravity field have great importance for the study of Earth rotation changes. They are closely coupled problems, with the focus of earth rotation being the Degree 2 spherical harmonics that influence polar motion and Length of Day. As a means of monitoring variations in mass distribution, earth rotation will retain the advantage of high temporal sampling rates for a limited number of harmonics, and the disadvantage that earth rotation changes measure the sum of mass redistribution and relative angular momentum (wind and current) effects.

Recognizing that earth rotation and gravitational potential problems are closely linked, it is worth noting that members of this SSG have also been engaged in the study of the Earth’s geopotential fields, both gravity and magnetic. The principal tool for whole-earth observations is satellite measurement.. Recognition of the next decade (starting in 1999) as the geopotential field decade was proposed at the IAG Assembly in Rio de Janeiro, in September, 1997. The Executive Committee of IAG has adopted a proposal for the declaration of an International Decade of Geopotential Fields Research, similar to the one adopted earlier by IAGA. The activity related to the time variable gravity field will naturally improve the estimates of the degree 2 spherical harmonic components which are important in the study of earth rotation.

3. Results

The studies of previous Special Study Groups in related areas had established that the atmosphere provides significant forcing of changes in polar motion and length of day, but that there are observable, often large variations in these rotation elements which cannot be explained by the atmosphere. Additionally, it was recongized that the atmosphere and oceans may contribute some influences that would appear as changes in nutation and precession. With improved ability to model and observe the atmosphere, the calculation of atmospheric angular momentum changes has improved steadily within th emeteorological community. Global atmospheric general circulation calculations obtained routinely (every few hours) for weather forecasting purposes are now available, as are reanalysis time series, where the numerical model is held fixed. These atmospheric calculations also provide an estimate of the winds acting on the oceans, and it has become possible to numerically produce time series of oceanic angular momentum variations. Such time series cannot be obtained from observations because the oceans are too poorly observed, but the evidence is that ocean models can be quite effective in estimating changes in earth rotation. The full bibliography below shows the breadth of efforts in this area for both the atmosphere and oceans, and related problems.

Two papers in the bibliography nicely summarize the conclusion that the oceans explain a large part of the remaining variations in the earth’s rotation, at periods of a year and less. The paper by Marcus et al (1998) clearly shows that residual non-atmospheric Length of Day changes are of oceanic origin. Similarly, Ponte et al (1998) show a similar result for the case of polar motion. Of course there is a contribution from the storage of water mass on land and in ice, but this appears to be less important at short periods (less than a year), and is probably more important at longer periods. The geophysical fluid centers are organized to address this issue, and others as well. As the bibliography shows, there has also been progress in understanding tidal influences on Earth rotation, and atmospheric and oceanic effects that contribute to apparent nutations.

Overall, the activity of this SSG has made the ocean and atmospheric sciences communities aware of the importance of angular momentum as a diagnostic tool, and the ability of earth rotation observations to determine these quantities for the oceans and atmospheres with high accuracy.

4. Recommendations

The establishment of the Geophysical Fluid Centers activity under the IERS, in 1997, now provides a structure to provide data and to further stimulate research in this area. The SSG recommends that time series which reflect atmospheric, oceanic and other influences on the rotation of the earth be reported in the most fundamental SI units of torques and angular momenta.

Continued study of the effects of the oceans on earth rotation is called for, because the oceans are poorly observed. There is common ground with other important geodetic problems, notably the study of time variable gravity from space, variations in the geocenter, and the study of nutation and precession. These topics span the full range of time scales from hours to decades. Development of a Special Study Group which engages geodetic and oceanographic communities, while strengthening the efforts of the Geophysical Fluid Center for the oceans, is appropriate.

It is clear that there remain some important earth rotation changes that are not fully understood, both in polar motion and length of day, particularly at long periods, beyond a year. Further study of these is warranted. The core is implicated in these longer term variations in LOD, and hydrological mass balance is a suspected contributor to longer term polar motion changes. The data provided by the various Geophysical Fluid Centers working under the IERS should enable further research in these areas.

5. Bibliography
Bizouard Ch., Brzezinski A. and Petrov S. (1997). Variability of nutations: can it be driven by the atmosphere?, Proceedings Journees Systemes de Reference Spatio-Temporels 1997, Astronomical Institute, Academy of Sciences of the Czech R., pp. 73-76.
Bizouard Ch., Brzezinski A. and Petrov S. (1998). Diurnal atmospheric forcing and temporal variations of the nutation amplitudes, Journal of Geodesy, Vol. 72, pp. 561-577.
Black, R.X., D.A. Salstein, and R.D. Rosen, 1996: Interannual modes of variability in atmospheric angular momentum. J. Climate, 9, 2834-2849.
Brosche, P., J. Wünsch, E. Maier-Reimer, J. Segschneider, J. Sündermann. The axial angular momentum of the general circulation of the oceans. Astron. Nachr. 318, 193-199, 1997
Brzezinski A. (1995a). On the interpretation of maximum entropy power spectrum and cross-power spectrum in earth rotation investigations,manuscripta geodaetica, Vol.20, pp. 248-264.
Brzezinski A. (1996a). "Broad band" Liouville equation of polar motion, Publ. Inst. Geophys. Pol. Acad. Sc., Vol. M-18 (273), pp. 173-181.
Brzezinski A. and Petrov S. (1998). Observational evidence of the free core nutation and its geophysical excitation. Proceedings Journees Systemes de Reference Spatio-Temporels 1998, Paris Observatory, in press.
Celaya, M., J. Wahr, and F.O. Bryan, 1999. Climate Driven Polar Motion, J. Geophs. Res., 104, 12813-12830.
Chen, J.L., C.R. Wilson, R.J. Eanes, and R.S. Nerem, Geophysical Interpretation of Observed Geocenter Variations, J. Geophys. Res., Vol. 104, No. B2, 2683 - 2690, 1999.
Chen, J.L., C. R. Wilson, D.P. Chambers, R.S. Nerem, and B.D. Tapley, Seasonal global water mass budget and mean sea level variations, Geophysical Research Letters, 25, 19, 3555-3558, October 1, 1998
Chao, B. F., R. D. Ray, and G. D. Egbert, Diurnal/semidiurnal oceanic tidalangular momentum: Topex/Poseidon models in comparison with Earth's rotation rate, Geophys. Res. Lett., 22, 1993-1996, 1995.
Chao, B. F., J. B. Merriam, and Y. Tamura, Geophysical analysis of zonal tidalsignals in length of day, Geophys. J. Int., 122, 765-775, 1995.
Chao, B. F., Anthropogenic impact on global geodynamics due to water impoundment in major reservoirs, Geophys. Res. Lett., 22, 3533-3536, 1995.
Chao, B. F., R. D. Ray, J. M. Gipson, G. D. Egbert, and C. Ma,Diurnal/semidiurnal polar motion excited by variations in oceanic tidal angular momentum, J. Geophys. Res., 101, 20,151-20,163, 1996.
Chao, B. F., and R. D. Ray, Oceanic tidal angular momentum and Earth's rotation variations, Prog. in Oceanog., 40, 399-421, 1998.
Chao, B. F., and Y. H. Zhou, Meteorological excitation of interannual polar motion by the North Atlantic Oscillation, J. Geodynamics, 27, 61-79, 1998.
Clark, T. A., C. Ma, J. W. Ryan, B. F. Chao, J. M. Gipson, D. S. MacMillan, N.R. Vandenberg, T. M. Eubanks, A. E. Niell, Earth rotation measurement yields valuable information about the dynamics of the Earth system, EOS, Trans. Amer. Geophys. Union, 79, 205-209, 1998.
Dehant, V., Wilson, C. Salstein, D., Chao, B., Gross, R., LeProvost, C, Ponte, R., Study of Earth’s Rotation and Geophysical Fluids Progresses, EOS, Transactions of the American Geophysical Union, 78, 34, p. 357, August 26, 1997.
Dehant V., Bizouard Ch., Legros H., Lefftz M. et Hinderer J., 1996,"The effects of on atmospheric pressure perturbations precession and nutations.", Phys. Earth planet. Inter., 96, 1, pp. 25-40.
Dehant V., C. Wilson, B. Fong Chao, R. Gross, Ch. Le Provost, R. Ponte, et D.Salstein, 1997, "Earth rotation dynamics and geophysical fluids." Report concerning Topic 6 of Workshop of the International Earth Rotation Service,Paris, France, octobre 1996, in: IERS Technical Note, eds. C. Reigberg et N. Capitaine, 22, pp. 31-40.
Dehant V., Feissel M., Defraigne P., Roosbeek F. et Souchay J., 1997,"Could the energy near the FCN and the FICN be explained by luni-solar or atmospheric forcing?", Geophys. J. Int., 130, pp. 535-546.
Desai, S. and J. Wahr, 1995 Empirical Ocean Tide Models Estimated from TOPEX/POSEIDON Altimetry, J. Geophys. Res., 100 (C12), 25205-25228.
Desai, S., J. Wahr, and Y. Chao, 1997.Error Analysis of Empirical Ocean Tide Models Estimated from TOPEX/POSEIDON Altimetry, J. Geophys. Res., 102 (C11), 25157-25172.
Desai, S., and J. Wahr, 1999.Monthly and fortnightly tidal variations of the earth's rotation rate predicted by a TOPEX/POSEIDON empirical ocean tide model",Geophys. Res. Lett., 26, 1035-1038.
DeViron,O., C. Bizouard, D.A. Salstein, and V. Dehant, 1999: Atmospheric torque on the Earth and comparison with atmospheric angular momentum variations, J. Geophys. Res., 104, 4861-4875.
De Viron O., Bizouard Ch. et Dehant V., 1997, "Calcul des moments de force produits par l'atmosphere sur la Terre solide, effets correspondents sur la nutation annuelle.", in: Proc. Journees Systemes de Reference Spatio-temporels 1996, septembre 1996, Paris, France, ed. N. Capitaine, pp. 189-190.
Dickman, S.R. and Y.-S. Nam, 1995. Revised predictions of long-period ocean tidal effects on Earth's rotation rate, J. Geophys. Res., 100, 8233-8243.
Dickman, S.R. and Y.-S. Nam, 1998. Constraints on Q at long periods from Earth's rotation, Geophys. Res. Lett., 25, 211-214.
Dickman, S.R., 1998. Determination of oceanic dynamic barometer corrections to atmospheric excitation of Earth rotation, J. Geophys. Res., 103, 15127-15143.
Furuya, M., and B. F. Chao, Estimation of period and Q of the Chandler wobble,Geophys. J. Int. 127, 693-702, 1996.
Furuya, M., Hamano, Y., and Naito, I., Quasi-Periodic Wind Signal As a Possible Excitation of Chandler Wobble, J.Geophys.Res., 101,25537-25546, 1996.
Furuya, M., Hamano, Y., and Naito, I., Importance of Wind for the Excitation of Chandler Wobble As Inferred From Wobble Domain Analysis, J. Phys.Earth. 47, 177-188, 1997.
Furuya, M. and Hamano, Y., Effect of the Pacific Ocean on the Earth's seasonal wobble inferred from National Center for Environmental Prediction ocean analysis data}, J. Geophys.Res., 103,10131-10140, 1998.
Gaspar, P., and R.M. Ponte, 1997. Relation between sea level and barometric pressure determined from altimeter data and mode simulations. Journal of Geophysical Research, 102, 961-971.
Gegout P., Hinderer J., Legros, H., Greff M. et Dehant V., 1998, "Influence of atmospheric pressure on the Free Core Nutation, precession and some forced nutational motions of the Earth.", Phys. Earth planet. Inter., 106, pp. 337-351.
Gross, R. S., B. F. Chao, and S. Desai, Effect of long-period ocean tides on the Earth's polar motion, Prog. Oceanogr., 40, 385ˆ397, 1998.
Gross, R. S., S. L. Marcus, T. M. Eubanks, J. O. Dickey, and C. L. Keppenne, Detection of an ENSO signal in seasonal length-of-day variations, Geophys. Res. Lett., 23, 3373ˆ3376, 1996.
Gross, R. S., K. H. Hamdan, and D. H. Boggs, Evidence for excitation of polar motion by fortnightly ocean tides, Geophys. Res. Lett., 23, 1809ˆ1812, 1996
Hide, R., J.O. Dickey, S.L Marcus, R.D. Rosen, and D.A. Salstein, 1997: Atmospheric angular momentum fluctuations in global circulation models during the period 1979-1988. J. Geophys. Res., 102, 16423-16438.
Hinderer J., Legros, H., Gegout P., Greff M., Dehant V. et Bizouard Ch., 1996, "L'atmosphere peut-elle perturber la pr'ecession de la Terre?", Comptes-rendus de l'Academie des Sciences, Paris, France, Serie Geophysique, Geodynamique, T. 323, Serie IIa, pp. 205-211.
Iskenderian, H., and D.A. Salstein, 1998: Regional Sources of Mountain Torque Variability and High-Frequency Fluctuations in Atmospheric Angular Momentum, Mon. Wea. Rev, 126, 1681-1694.
Johnson, T.J., C.R. Wilson, B.F. Chao. Oceanic Angular Momentum Variability Estimated From The Parallel Ocean Climate Model, 1988-1998, J. Geophysical Res., in press.
Kagan, B.A. and J. Sündermann. Dissipation of tidal energy paleotides and evolution of the Earth-Moon system. Adv. in Geoph. 38, 179-266, 1996
Klosko, S. M., and B. F. Chao, The use of satellite laser ranging and long duration orbital changes to constrain geophysical models, in Dynamics of the Ice Age Earth: A Modern Perspective, ed. P. Wu, Trans Tech Pub., 533-556, 1998
Klosko, S. M., and B. F. Chao, Secular variations of the zonal gravity field,global sea level, and polar motion as geophysical constraints, Physics and Chemistry of the Earth, 23, 1091-1102, 1998.
Kuehne, J., Wilson, C., and Johnson, S., 1996. Estimates of the Chandler Wobble Frequency and Q., Journal of Geophysical Research v. 101, B6, 13573-13580.
Lejenas,h., r.a. madden, and J.J.. Hack,1997: global atmospheric angular momentum and earth-atmosphere exchange of angular momentum simulated in a general circulation model. j.geophys.res.,v102,p1931-1941
Madden,r.a., and P. Speth, 1995: estimates of atmospheric angular momentum,friction, and mountain torques during 1987-1988. j. atmos. sci., v 52, p3681-3694
Madden,r.a., h. lejenas, and j.j. hack,1998: semidiurnal variation in the budget of angular momentum in a general circulation model and in the real atmosphere. j.atos.sci., v55, p2561-2575
Madden, r.a., t.j. Hoar, and r.f. Milliff, 1999: scatterometer winds composited according to the phase of tropical intraseasonal oscillations. tellus, v51a, p 263-272
Marcus, S.L., Y. Chao, J.O. Dickey, P.Gegout, Detection and Modeling of Nontidal Oceanic Effects on Earth’s Rotation Rate, Science 281, 1656-1659.
Mireault, Y., J. Kouba, and J. Ray, IGS Earth Rotation Parameters, GPS Solutions, in press 1999.
Nastula, J., and D. A. Salstein, 1999: Regional atmospheric angular momentum contributions to polar motion excitation, J. Geophys. Res., 104, 7347-7358.
Nastula, J., and R.M. Ponte, 1999. Further evidence for oceanic excitation of polar motion, Geophysical Journal International, in press.
Nastula J.,Short periodic variations of polar motion and hemispheric atmospheric angular momentum excitation functions in the period 1984-1992, Ann. Geophysiace, 13, 217-225, 1995.
Nastula J. , Analysis of the EAAM regional contributions to the polar motion excitation, proceedings of the international conference Journees 1995, Systemes de reference spatio-temporels, Warsaw, Poland, 155 - 158, 1995.
Kolaczek B., M. Nuzhdina, J. Nastula & W. Kosek, El Nino impact on atmospheric and geodetic excitation of polar motion, in printing in JGR-Solid Earth.
Kosek W., J. Nastula & B. Kolaczek, Variability of polar motion oscillations with periods from 20 to 150 days in 1979 -1991, Bulletin Geodesique, 30, 1, 27 - 43, 1995.
Nastula J., W. Kosek and B. Kolaczek, analyses of zonal atmospheric excitation functions nd their correlation with polar motion excitation functions, Annales Geophysicae, Vol. 15, 439 -1446, 1997.
Nastula J. & S. Manabe, Influence of the shallow seas on the pressure terms of the EAAM functions, IAG Symposia, Vol. 117; Segawa et al. (eds.), Gravity, Geoid and Marine Geodesy, Springer-Verlag, 273 - 280, 1997.
Nastula J., The regional atmospheric contributions to the polar motion and EAAM exciatation functions, IAG Symposia, Vol. 117; Segawa et al. (eds.), Gravity, Geoid and Marine Geodesy,Springer-Verlag, 281 - 288, 1997.
Nastula J. & D. A. Salstein, Regional atmospheric angular momentum contributions to the polar motion excitation, IAG Symposia, Vol. 119; Forsberg et al. (eds.), Geodesy an the Move,Gravity, Springer-Verlag, 333 - 338., 1998.
Nastula J., O. Kotreleva, B. Kolaczek, & W. Kosek, Time-frequency characteristics of the pressure term of the EAAM excitation, IAG Symposia, Vol.119; Forsberg et al. (eds.) Geodesy on the Move, Springer-Verlag, 339 -334, 1998. .
Kolaczek B., M. Nuzhdina, J. Nastula & W. Kosek, El Nino impact on atmospheric and geodetic excitation of polar motion, in printing IERS Technical Notes No 26, Paris France.
Petrov S. D., A. Brzezinski & J. Nastula, First estimation of the non-tidal oceanic effect on nutation poceedings of the international conference Journees 1998, Systemes de reference spatio-temporels; Conceptual,conventional and practical studies related to Earth rotation; september 21 - 23, France, Paris, in press.
Petrov S., Brzezinski A., and Gubanov V. (1995). On application of the Kalman filter and the least squares collocation in earth rotation investigations, Proceedings Journees Systemes de Reference Spatio-Temporels 1995, Space Res. Centre, Polish Acad. of Sciences, pp. 125-128.
Petrov S. and Brzezinski A. (1996). On the contribution of the atmospheric normal modes to the polar motion excitation, Proc. of the Russian Conference "Modern Problems and Methods of Astrometry and Geodynamics", 23 – 28 September 1996, St. Petersburg, pp. 308-313.
Petrov S., Brzezinski A. and Gubanov V. (1996). A stochastic model for polar motion with application to smoothing, prediction, and combining, Artificial Satellites, Planetary Geodesy No 26, Vol. 31, pp. 51-70.
Petrov S., Brzezinski A. and Bizouard Ch. (1997). Time domain comparison of the VLBI nutation series and observed changes of the atmospheric angular momentum. Proceedings Journees Systemes de Reference Spatio-Temporels 1997, Astronomical Institute, Academy of Sciences of the Czech R., p. 107.
Petrov S. (1998). Modeling geophysical excitation of Earth rotation: stochastic and nonlinear approaches. Ph.D. Thesis, Polish Academy of Sciences, Space Res. Centre, Warsaw, Poland, 121 pages.
Petrov S., Brzezinski A. and Bizouard Ch. (1998a). Diurnal and semidiurnal variations of the atmospheric angular momentum and Earth orientation parameters, Trudy IPA RAN, wyp.3 "Astrometria i geodinamika", St.Petersburg, pp. 24 - 35, in Russian.
Petrov S., Brzezinski A. and Nastula J. (1998b). First estimation of the non-tidal oceanic effect on nutation. Proceedings Journees Systemes de Reference Spatio-Temporels 1998, Paris Observatory, in press.
Ponte, R.M., 1997. Oceanic excitation of daily to seasonal signals in Earth rotation: results from a constant-density numerical model. Geophysical Journal International, 130, 469--474.
Ponte, R.M., 1997. Nonequilibrium response of the global ocean to the 5-day Rossby-Haurwitz wave in atmospheric surface pressure. Journal of Physical Oceanography, 27}, 2158--2168.
Ponte, R.M., D. Stammer, and J. Marshall, 1998. Oceanic signals in observed motions of the Earth's pole of rotation. Nature, 391, 476--479.
Ponte, R.M., 1999. A preliminary model study of the large-scale seasonal cycle in bottom pressure over the global ocean, Journal of Geophysical Research, 104, 1289-1300.
Ponte, R.M., and P. Gaspar, 1999. Regional analysis of the inverted barometer over the global ocean using TOPEX/POSEIDON data and model results, Journal of Geophysical Research, in press.
Ponte, R.M., and R.D. Rosen, 1999. Torques responsible for evolution of atmospheric angular momentum during the 1982--83 El Nino, Journal of Atmospheric Sciences, in press.
Ponte, R.M., and D. Stammer, 1999. Role of ocean currents and bottom pressure variability on seasonal polar motion, Journal of Geophysical Research, accepted.
Ray, R. D., B. F. Chao, Z. Kowalik, and A. Proshutinsky, Angular momentum of Arctic Ocean tides, J. Geodesy, 71, 344-350, 1997.
Salstein, D.A., 1995: Atmospheric angular momentum and Earth Rotation, Journees 1995, Systemes de reference statio-temporels, Space Research Center, Warsaw, Poland, 139-146.
Salstein, D.A. and R.D. Rosen, 1998: Global Momentum and Energy Parameters from Reanalyses, Proceedings of the first WCRP International Conference on Reanalyses, Silver Spring, MD, 286-289.
Salstein, D. A., 1999: Angular momentum and during the 1997-98 El Niño event., IERS Technical note 26, on the Impact Of El Nino And Other Low-Frequency Signals On Earth Rotation And Global Earth System Parameters., in press.
Segschneider, J. and J. Sündermann. Response of a global ocean circulation model to real time forcing and implications to Earth's rotation. J. Phys. Oc. 27, 2370-2380, 1997
Stieglitz, T.C and S.R. Dickman, 1999. Refined correlations between atmospheric and rapid polar motion excitations, Geophys. J. Int., in press.
Thomas, M. and J. Sündermann. Tides and tidal torques of the world ocean since the last glacial maximum. J. Geoph. Res. 104, C2, 3159-3183, 1999
vanDam, T.M., J. Wahr, Y. Chao, and E. Leuliette, 1997.Predictions of Crustal Deformation and of Geoid and Sea Level Variability Caused by Oceanic and Atmospheric Loading, Geophys. J. Int., 129, 507-517.
Vicente, R., and Wilson, C., 1997, On the Variability of Earth Rotation Parameters, Journal of Geophysical Research, 102, B9, 20439-20445.
Wilson, C., and Chen, J., 1996. Discrete Polar Motion Equations for High Frequencies. Journal of Geodesy. v. 70, no. 9.
Wilson, C.R., Oceanic Effects on Earth’s Rotation Rate, Science, 281, 5383, September 11, 1998, 1623-1624.
Xie, L. and S.R. Dickman, 1995. North Sea pole tide dynamics, Geophys. J. Int., 121, 117-135.
Xie, L. and S.R. Dickman, 1996. Tide gauge data analysis of the pole tide in the North Sea, Geophys. J. Int., 126, 863-870.
Xie, B.Q., Zheng, D.W., High frequency excitation of Earth rotation parameter (ERP) from atmosphere, Acta Astronomica Sinica, 37, 2,113-123, 1996
Yu, N.H., Zheng, D.W., Oceanic angular momentum and its excitation tothe Earth rotation variations, Progress in Astronomy, 16, 1, 35-40, 1998
Yu, N.H., Zheng, D.W., and Wu, H.Q., Contribution of new AAM data source change to LOD excitation, Journal of Geodesy, 1998, accepted
Yu, N.H., Zheng, D.W., Earth rotation and it's relations to geophysical phenomena: I. The changes of length of day, Progress in Geophysics,11, 3, 70-81, 1996
Zharkov V. N., S. M. Molodensky, A. Brzezinski, E. Groten and P. Varga (1996). The Earth and its Rotation: Low Frequency Geodynamics, Herbert Wichman Verlag, H¸thig GmbH, Heidelberg, 501 pages.
Zheng, D.W., Y. H. Zhou, N. H. Yu, and B. F. Chao, Improvement of edge effect of the wavelet time-frequency spectrum: Application to the length of day series, in press, J. Geod., 1999.
Zheng, D.W., Chen, J.L., Hua, Y.M., Xiao, N.Y., Preliminary research of the influence of Earth rotation rate on latitude wards changes of sea level, Acta Astronomica Sinica, 37, 1, 97-104, 1996
Zheng, D.W., Zhou, Y.H., Chao, B.F., Variation in NAO and polar motionon decadal time scale, Acta Astronomica Sinica, 38, 2, 204-208, 1997
Zheng, D.W., Yu, N.H., Earth rotation and it's relations to geophysical phenomena: I. The changes of length of day, Progress in Geophysics,11, 2,81-104, 1996
Zhou, Y., D. Zheng, M. Zhao, and B. F. Chao, Interannual polar motion with relation to the North Atlantic Oscillation, Global and Planetary Change, 18,79-84, 1998.
Zhou, Y.H., Zheng, D.W., Application of LSTAR model to improvement of wavelet transform of LOD variation series, Annuals of Shanghai Observatory Academia Sinica, 18, 13-17, 1997
Zhou, Y.H., Zheng, D.W., Wavelet analysis of interannual length-of-dayvariation, El Nino-Southern Oscillation and atmospheric Quasi-Biennial Oscillation, Acta Astronomica Sinica, 38, 2, 209-214, 1997

Scientific Sessions and Meetings List
Fall 1995 AGU, San Francisco, December, 1995 Session G51A: Geodetic and Geophysical Evidence of Global Change; The Interdisciplinary Impact of Earth Rotation Studies: A Tricentennial Commemoration;
Spring 1996 AGU, Baltimore, May, 1996 Session G1: Geodetic Measurements of Past and Present Climate Change Session U41A: Earth System Dynamics From High Frequency to Global Change Time Scales I Session U51A Earth System Dynamics From High Frequency to Global Change Time Scales II;
Spring European Geophysical Society Meeting, The Hague, June 1996 Session SE5/G8 Earth’s Rotation Variabilities at Different Time Scales and Tidal Deformations in memory of Keith Runcorn, Convened by J. Hinderer
IERS Workshop: Future Directions, Paris Observatory, October, 1996 Session on Topic 6: Geophysical Fluids.
VLBI/CORE Workshop, College Park Maryland, November, 1996 Special workshop convened by NASA
Fall 1996 AGU, San Francisco, December, 1996 Session G11A Paleogeodesy: Ice Sheets, Oceans and the Earth's Shape; Session G12C Static and Time-Varying Gravity Field Modeling and Their Application to Climate Change Studies; Session G31B Earth System Dynamics: Insights from Earth Rotation Studies
Spring 1997 European Geophysical Society, Vienna, April 1997Session G13/SE12 Variations in Earth Rotation
Spring 1997 AGU, Baltimore, May, 1997 Session G42B Earth Rotation: Measurements and Models II Posters; Session G42C Earth Rotation: Measurements and Models I
July 1997 IAPSO General Assembly, Melbourne, Australia Session on Angular Momentum Variations in the Oceans
Fall 1997 AGU, San Francisco, California, December 1997; Session G31A Insights Into Earth System Science: Variations in Earth's Rotation and Its Gravitational Field I Posters; Session G41D Insights Into Earth System Science: Variations in Earth's Rotation and Its Gravitational Field II
Spring 1998 European Geophysical Society, Nice, France, April 1998 Session G7 Joint EGS/AGU symposium on geodetic observation and geophysical interpretation of mass movements in the Earth system Part 1 Solid Earth and core, Part 2 Ocean and hydrosphere Part 3 Cryosphere Part 4 Atmosphere Part 5 Interactions between the components of the Earth system
Spring 1998 AGU, Boston, May 1998 Session G21A The Impact of El Nino and Other Low-Frequency Signals on Earth Rotation and Global Earth System Parameters. Session G22A The Impact of El Nino and Other Low-Frequency Signals on Earth Rotation and GlobalEarth System Parameters Posters Session G22BThe Impact of El Nino and Other Low-Frequency Signals on Earth Rotation and Global Earth System Parameters
Western Pacific Geosciences Meeting, Taipei, Taiwan, July, 1998 Session G31A Measuring Global Geodynamics and Mass Transports in Geophysical Fluids
Fall 1998 AGU, San Francisco, California Session G71I Polar Motions From Hours to Decades I; Session G41A Polar Motions From Hours to Decades II Posters
Spring 1999 London Workshop on Ocean Bottom Pressure changes and ocean contributions to time variable gravity;
Spring 1999 EGS Meeting, The Hague, April 1999 Session G16 The impact of global fluids on Earth rotation. Session G16 The impact of global fluids on Earth rotation - Poster Session; Session G18 High frequency and subseasonal oscillations of Earth rotation I and II.
Spring 1999 AGU Meeting, Boston, June, 1999 Session U32 Geodetic Monitoring of the Earth System
IUGG Birmingham Symposium JSG14 July, 1999. Insights into Earth System Science: Variations in the Earth’s Rotation and its Gravitational Field.