Grenoble, France.

The zonal toroidal t_1^0 and t_3^0 components of a fully time-dependent
geostrophic flow constructed under the frozen flux hypothesis are used to
estimate the core angular momentum (CAM) using the hypothesis of Jault Gire and
Le Mouel (1988). The CAM is then transformed into an equivalent change in the
length of day as seen on the solid Earth by conservation of angular
momentum. The predictions only give relative changes in the lod, therefore an
arbitrary offset should be chosen in order that the predictions agree reasonably
well with the lod series from astronomical observations. A value of 3.25
milliseconds has been added to the predictions to give the values presented
here.

* Description of the data used for model computation* :

__Column '1'__

Date

__Column '2' and '3'__

Zonal toroidal coefficients of the surface angular velocity respectively of degree
one and three of an expansion in Legendre Polynomials (unit = degree / year).

__Column '4'__

Integrated angular velocity of the Earth core (unit = degree / year) in a frame of
reference rotating at the (variable) mantle angular spin rate. The surface velocity
field has been derived from different secular variation models calculated with different
truncations and regularizations.

* References to be mentioned when data are used* :

Jault D., Gire C., and Le Mouël J.-L., 'Westward drift, core motions and exchanges of angular momentum between core and mantle',

* Related references* :

1969 |
-0.073 |
+0.014 |
-0.049 |

1970 |
-0.074 |
+0.015 |
-0.048 |

1970 |
-0.064 |
+0.011 |
-0.045 |

1975 |
-0.069 |
+0.009 |
-0.052 |

1980 |
-0.089 |
+0.018 |
-0.057 |

1980 |
-0.094 |
+0.015 |
-0.068 |

1982 |
-0.098 |
+0.018 |
-0.067 |

1982 |
-0.117 |
+0.027 |
-0.072 |

1982 |
-0.098 |
+0.018 |
-0.067 |

1982 |
-0.128 |
+0.027 |
-0.082 |

1985 |
-0.116 |
+0.030 |
-0.064 |

1987 |
-0.16 |
+0.047 |
-0.079 |

1987 |
-0.159 |
+0.048 |
-0.077 |