Atmospheric tides (both thermal and tidal) cause diurnal and semidiurnal components in the lenght of day or UT1. Most important contributions (diurnal wave S1 and semidiurnal wave S2) have been computed by Brzezinski,Bizouard and Petrov (2002) ["Influence of the atmosphere on Earth Rotation : what new can be learned from the recent atmospheric angular momentum estimates?"
, Surveys in Geophysics, 23
, 33-69, 2002] from NCEP/NCAR Angular Atmospheric Momentum data. Herebelow we present updated estimates for the AAM data spanning the period from 1990 to 2002
. Corresponding model is put under the form :
ΔUT1 = Σj aj cos(ARGj) + bj sin(ARGj)
ΔLOD = Σj cj cos(ARGj) + dj sin(ARGj)
is integer linear combination of Delaunay
, GMST + &$pi;
= a1 l + a2 l' + a3 D + a4 F + a5 Ω + a6 (GMST + π).
N.B.: the values here-below should be taken with caution because AAM remain poorly
estimated at diurnal scales.