Atmospheric angular momentum and length of day
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Authors
Benedict, William L.
Subjects
Length of Day
Atmospheric Angular Momentum
Atmospheric Angular Momentum
Advisors
Haney, Robert Lee
Date of Issue
1988-03
Date
Publisher
Monterey, California. Naval Postgraduate School
Language
en_US
Abstract
Changes in the globally integrated absolute angular momentum of the atmosphere
were computed from the Fleet Numerical Oceanography Center NOGAPS wind analyses
and compared to astronomically measured changes in length of day [LOD) obtained
from the U.S. \aval Observatory, Washington D.C. The two time series were subjected
to both time and frequency domain analysis. In the time domain, digital filters were used
to isolate seasonal and subseasonal components. In the frequency domain, energy density,
coherence and phase were computed over periods from 2 days to 1000 days. Over
90°o of the total variance in astronomically determined LOD can be explained by
meteorological phenomena. Fluctuations in LOD are coherent and in phase with lluctuations
in the globally integrated angular momentum of the Earth's shell (crust, mantle
and oceans; liquid core is excluded) at almost all periods less than 365 days. Annual
fluctuations in LOD appear to originate in the midlatitudes and propagate equatorward.
Subseasonal fluctuations (30 to 100 day periods) appear to be a tropical phenomena.
Type
Thesis
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Distribution Statement
Approved for public release; distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.