Dynamical analysis of the atmospheric angular momentum short-term fluctuations. Comparison with the Earth

2000 ◽  
Vol 73 (12) ◽  
pp. 660-670
Author(s):  
V. Frede
Keyword(s):  
Angular Momentum ◽  
Atmospheric Angular Momentum ◽  
Dynamical Analysis ◽  
Short Term ◽  
The Earth

The short-term prediction of universal time and length of day using atmospheric angular momentum

1994 ◽  
Vol 99 (B4) ◽  
pp. 6981 ◽  
Author(s):  
A. P. Freedman ◽  
J. A. Steppe ◽  
J. O. Dickey ◽  
T. M. Eubanks ◽  
L.-Y. Sung
Keyword(s):  
Angular Momentum ◽  
Universal Time ◽  
Atmospheric Angular Momentum ◽  
Length Of Day ◽  
Short Term ◽  
Term Prediction ◽  
Short Term Prediction

scholarly journals Atmospheric torque on the Earth and comparison with atmospheric angular momentum variations

1999 ◽  
Vol 104 (B3) ◽  
pp. 4861-4875 ◽  
Author(s):  
O. de Viron ◽  
C. Bizouard ◽  
D. Salstein ◽  
V. Dehant
Keyword(s):  
Angular Momentum ◽  
Atmospheric Angular Momentum ◽  
The Earth ◽  
Atmospheric Torque

Axial Atmospheric Angular Momentum Budget at Diurnal and Subdiurnal Periodicities

2008 ◽  
Vol 65 (1) ◽  
pp. 156-171 ◽  
Author(s):  
François Lott ◽  
Olivier de Viron ◽  
Pedro Viterbo ◽  
François Vial
Keyword(s):  
Boundary Layer ◽  
Angular Momentum ◽  
Surface Pressure ◽  
Vertical Direction ◽  
Zonal Flow ◽  
Atmospheric Angular Momentum ◽  
Model Driven ◽  
The Earth ◽  
Momentum Budget ◽  
Diurnal Period

Abstract The diurnal and subdiurnal variations of the mass and wind terms of the axial atmospheric angular momentum (AAM) are explored using a 1-yr integration of the Laboratoire de Météorologie Dynamique (LMDz) GCM, twelve 10-day ECMWF forecasts, and some ECMWF analysis products. In these datasets, the wind and mass AAMs present diurnal and semidiurnal oscillations for which tendencies far exceed the total torque. In the LMDz GCM, these diurnal and semidiurnal oscillations are associated with axisymmetric (s = 0) and barotropic circulation modes that resemble the second gravest (n = 2) eigensolution of Laplace’s tidal equations. This mode induces a Coriolis conversion from the wind AAM toward the mass AAM that far exceeds the total torque. At the semidiurnal period, this mode dominates the axisymmetric and barotropic circulation. At the diurnal period, this n = 2 mode is also present, but the barotropic circulation also presents a mode resembling the first gravest n = 1 eigensolution of the tidal equations. This last mode does not produce anomalies in the mass and wind AAMs. A shallow-water axisymmetric model driven by zonal mean zonal forces, for which the vertical integral equals the zonal mean zonal stresses issued from the GCM, is then used to interpret these results. This model reproduces well the semidiurnal oscillations in mass and wind AAM, and the semidiurnal mode resembling the n = 2 eigensolution that produces them, when the forcing is distributed barotropically in the vertical direction. This model also reproduces diurnal modes resembling the n = 1 and n = 2 eigensolutions when the forcings are distributed more baroclinically. Among the dynamical forcings that produce these modes of motion, it is found that the mountain forcing and the divergence of the AAM flux are equally important and are more efficient than the boundary layer friction. In geodesy, the large but opposite signals in the mass and wind AAM due to the n = 2 modes can lead to large errors in the evaluation of the AAM budget. The n = 2 responses in surface pressure can affect the earth ellipcity, and the n = 1 diurnal response can affect the geocenter position. For the surface pressure tide, the results suggest that the dynamical forcings of the zonal-mean zonal flow are a potential cause for its s = 0 component.

scholarly journals Short-term variation of the Earth's rotation and the solar activity

1988 ◽  
Vol 128 ◽  
pp. 353-358 ◽  
Author(s):  
D. Djurovic ◽  
P. Paquet
Keyword(s):  
Spectral Analysis ◽  
Angular Momentum ◽  
Solar Activity ◽  
Earth Rotation ◽  
Cyclic Variation ◽  
The Sun ◽  
Physical Processes ◽  
Short Term ◽  
The Earth ◽  
Term Variation

In 1980, Feissel et al. identified a quasi–cyclic variation of 55 days in the irregularities of the Earth Rotation (ER) later detected in the Atmospheric Angular Momentum (AAM) (Langley et al., 1981). The purpose of this work is to analyse whether the causes of this cycle could lie in the physical processes of the Sun. The Wolf Numbers (WN) are used as parameters of the solar activity. Their spectral analysis over the period 1967–1985 shows such a component at 51 days. Analysis of three other periods, among which is the MERIT campaign, confirms it as well as during low or increasing solar activity periods.

scholarly journals Interdecadal oscillations in Atmospheric Angular Momentum variations

2012 ◽  
Vol 2 (1) ◽  
pp. 42-52 ◽  
Author(s):  
R. Abarca-del-Rio ◽  
D. Gambis ◽  
D. Salstein
Keyword(s):  
Angular Momentum ◽  
Time Scales ◽  
Secular Trend ◽  
Atmospheric Angular Momentum ◽  
Positive Trend ◽  
Short Term ◽  
The Pacific ◽  
Time Signals

Interdecadal oscillations in Atmospheric Angular Momentum variationsGlobal Atmospheric Angular Momentum (AAM) is an intrinsic index for describing processes that affect the atmospheric circulation on time scales ranging from intraseasonal to secular. It is associated with length-of-day (LOD) variability through conservation of global angular momentum in planet Earth and thus is of considerable importance for quantifying how the Earth acts as a system. The availability of lengthy AAM time series computed from the recent 20th Century atmospheric reanalyses (1870-2008), complemented by the NCAR-NCEP reanalysis in the overlapping period of 1948-2008 allows the investigation of the role of decadal and interdecadal cycles as well as the recent overall trend in AAM. Thus, we extend to the entire 20th century (and prior, back to 1870) results concerning decadal time scales and a secular positive trend detected over recent decades by different authors. In addition, we also note that AAM has features of interdecadal time scales that modulate the lower frequency variability. These interdecadal time signals oscillate with periods of about 30-50 years, and we found an indication of an 80-90 year period. Short term signals interact with the long-term (secular) trend. Particularly over the years 1950-1985 the global positive trend in AAM appears to result from a conjunction of constructive positive slopes from all lower frequency signals (interdecadal short-term trends and the long-term positive secular trend). Since the mid 1980s, however, the interdecadal oscillation short-term trend contribution decreases, as does the total signal in global AAM. These oscillations appear as two interdecadal modes originating within the Pacific (associated principally with the Pacific Decadal Oscillation and also ENSO) from which they propagate poleward, with differing characteristics in each hemisphere.

Global propagation of interannual fluctuations in atmospheric angular momentum

Nature ◽  
1992 ◽  
Vol 357 (6378) ◽  
pp. 484-488 ◽  
Author(s):  
J. O. Dickey ◽  
S. L. Marcus ◽  
R. Hide
Keyword(s):  
Angular Momentum ◽  
Atmospheric Angular Momentum ◽  
Interannual Fluctuations
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