UT1 & LENGTH OF DAY VARIATIONS INDUCED
BY THE NON-TIDAL VARIATIONS
IN OCEANIC ANGULAR MOMENTUM


Non-tidal fluctuations in water heigh and currents (partly caused by atmospheric wind and pressure variations) induce variation of the axial oceanic angular momentum (OAM). de Viron, Goosse, Bizouard and Lambert have derived such an OAM series spanning 1997.0-2002.0, and computed the associated perturbations on nutation, diurnal and subdiurnal polar motion, and UT1 (communication done at EGS General Assembly 2002) for the span 1997.0-2002.0. The atmospheric perturbations, as derived from Atmospheric Angular Momentum (AAM) series of the NCEP/NCAR reanalyis project, were considered additionaly. We present both OAM, AAM and cumulated effects for UT1 and length of day. The model is put under the form :

DUT1 = Sj aj cos(ARGj) + bj sin(ARGj)

DLOD = Sj cj cos(ARGj) + dj sin(ARGj)


where ARGj is integer linear combination of Delaunay arguments, GMST + p :
ARGj = a1 l + a2 l' + a3 D + a4 F + a5 W + a6 (GMST +p) .

N.B.: the values here-below should be taken with caution because AAM and OAM remain poorly estimated at diurnal scales. 
                  
      l   l'  F   D   W  GMST + p     PERIOD              aj       bj        cj        dj       
                                      (hours)             (mus)    (mus)    (mus)     (mus)                
S1    0  -1   0   0   0     1         24.000                                   
                                                OAM       -0.5     -0.4      2.4       -3  																								
                                                AAM        0.1      0.8     -4.8        0.4
                                                -------------------------------------------	
                                                total     -0.4      0.4     -2.4       -2.6
												

Delaunay arguments 
(IERS Conventions 2000, from Simon et al., 1994, Astron. Astrophys. 282, 663-683):
     
 Mean anomaly of the Moon :
   l = 134°.963 402 51 + 1 717 915 923.2178" t + 31".879 2 t
2 + 0".051 635 t3 - 0".000 244 70 t4
 
 Mean anomaly of the Sun  : 
   l'= 357°.529 109 18 +   129 596 581.0481" t - 0".553 2 t2 -  0".000 136 t3 - 0".000 011 49 t4
 
 F = L -W  with L mean longitude of the Moon  
   F =  93°.272 090 62 + 1 739 527 262.8478" t - 12".751 2 t2 - 0".001 037 t3 + 0".000 004 17 t4
 
 Mean elongation of the Moon from the Sun :
   D = 297°.850 195 47 + 1 602 961 601.2090" t -  6".370 6 t2 + 0".006 593 t3 - 0".000 031 69 t4

 Mean longitude of the ascending node of the Moon :
   W = 125°.044 555 01  - 6 962 890.543 1" t + 7".472 2 t2 + 0".007 702 t3 - 0".000 059 39 t4

where t is measured un Julian Centuries of 36525 days of 86400 seconds of Dynamical Time since J2000.0.          

Rotation angle in arcseconds : Greenwich Mean Sidereal Time + 180°

   GMST + p = (67310.54841 + (876600d0*3600 + 8640184.812866) t 
             + 0.093104 t2 - 6.2 10-6 t3 )*15 + 648000.0


where t is measured un Julian Centuries of 36525 days of 86400 seconds of Dynamical Time since J2000.0.