NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Atmospheric Angular Momentum Fluctuations During 1979-1988 Simulated by Global Circulation ModelsChanges in major global dynamical phenomena in the Earth's atmosphere are manifested in the time series of atmospheric angular momentum (AAM), as determined directly from meteorological observations and indirectly from geodetic observations of small fluctuations in the rotation of the solid Earth which are proportional to length of day. AAM fluctuations are intimately linked with energetic processes throughout the whole atmosphere and also with the stresses at the Earth's surface produced largely by turbulent momentum transport in the oceanic and continental boundary layers and by the action of normal pressure forces on orographic features. A stringent test of any numerical global circulation model (GCM) is therefore provided by a quantitative assessment of its ability to represent AAM fluctuations on all relevant timescales, ranging from months to several years. From monthly data provided by the Atmospheric Model Intercomparison Project (AMIP) of the World Climate Research Programme, we have investigated seasonal and interannual fluctuations and the decadal mean in the axial component of AAM in 23 AMIP GCMs over the period 1979-1988. The decadal means are generally well simulated, with the model median value (1.58 x 10(exp 26) kg sq m/s) being only 3.5% larger than the observed mean and with 10 of the models being within 5% of the observed. The seasonal cycle is well reproduced, with the median amplitude of the models seasonal standard deviations being only 2.4% larger than observed. Half the seasonal amplitudes lie within 15% of the observed, and the median correlation found between the observed and model seasonal cycles is 0.95. The dominant seasonal error is an underestimation of AAM during northern hemisphere winter associated with errors in the position of subtropical jets. Less robust are the modeled interannual variations, although the median correlation of 0.61 between model simulations and observed AAM is statistically significant. The two El Nino-Southem Oscillation events that occurred during the AMIP decade 1979-1988 have the expected positive AAM anomalies, although the AAM signature of the 1982-1983 event tends to be underestimated and that of the 1986-1987 event overestimated.
Document ID
19990018983
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Hide, R.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Dickey, J. O.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Marcus, S. L.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Rosen, R. D.
(Atmospheric and Environmental Research, Inc. Cambridge, MA United States)
Salstein, D. A.
(Atmospheric and Environmental Research, Inc. Cambridge, MA United States)
Date Acquired
August 19, 2013
Publication Date
July 27, 1997
Publication Information
Publication: Journal of Geophysical Research
Publisher: American Geophysical Union
Volume: 102
Issue: D14
ISSN: 0148-0227
Subject Category
Geophysics
Report/Patent Number
Paper-97JD00699
Funding Number(s)
CONTRACT_GRANT: NSF ATM-92-23164
CONTRACT_GRANT: NSF ATM-96-32559
CONTRACT_GRANT: NAG5-32861
CONTRACT_GRANT: NAGw-2615
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available