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Revised Atmospheric Angular Momentum Series Related to Earth's Variable Rotation under Consideration of Surface TopographyThe atmospheric angular momentum is closely related to variations in the Earth rotation. The atmospheric excitation function (AEF), or namely atmospheric effective angular momentum function, is introduced in studying the atmospheric excitation of the Earth's variable rotation. It may be separated into two portions, i.e, the "wind" terms due to the atmospheric motion relative to the mantle and the "pressure" terms due to the variations of atmospheric mass distribution evident through surface pressure changes. The AEF wind terms during the period of 1948-2004 are re-processed from the NCEP/NCAR (National Centers for Environmental Prediction-National Center for Atmospheric Research) reanalysis 6-hourly wind and pressure fields. Some previous calculations were approximate, in that the wind terms were integrated from an isobaric lower boundary of 1000 hPa. To consider the surface topography effect, however, the AEF is computed by integration using the winds from the Earth's surface to 10 hPa, the top atmospheric model level, instead of from 1000 hPa. For these two cases, only a minor difference, equivalent to approx. 0.004 milliseconds in length-of-day variation, exists with respect to the axial wind term. However, considerable differences, equivalent to 5-6 milliarcseconds in polar motion, are found regarding equatorial wind terms. We further compare the total equatorial AEF (with and without the topographic effect) with the polar motion excitation function (PMEF) during the period of 1980-2003. The equatorial AEF gets generally closer to the PMEF, and improved coherences are found between them when the topography effect is included. Keywords: Atmospheric angular momentum, Atmospheric excitation function, Earth rotation, Topography, Wind, Pressure.
Document ID
20080014846
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Zhou, Y. H.
(Shanghai Astronomical Observatory China)
Salstein, D. A.
(Atmospheric and Environmental Research, Inc. Lexington, MA, United States)
Chen, J. L.
(Texas Univ. Austin, TX, United States)
Date Acquired
August 24, 2013
Publication Date
June 29, 2006
Publication Information
Publication: Journal of Geophysical Research
Volume: 111
Subject Category
Meteorology And Climatology
Funding Number(s)
CONTRACT_GRANT: NNG04GF93G
Distribution Limits
Public
Copyright
Other

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