Sub-Diurnal Earth Rotation Variations Observed by VLBI

We analyse sub-diurnal Earth rotation variations obtained from the continuous VLBI experiments CONT02, CONT05, and CONT08. We find that the Earth rotation parameters estimated from these campaigns contain signals with periods ±12 hours, +24 hours, and in CONT02 also -8 hours, which cannot be explained by the current IERS sub-diurnal pole model. We investigate if these signals could be caused by atmospheric excitations, but find that these excitations are too small.