Monitoring high frequency Earth rotation by ring laser: on modeling the local tilts

Horizontally mounted large ring laser gyroscope (RLG) is sensitive to changes of the instantaneous Earth rotation vector, variations in the orientation of an instrument and variations in the laser operation. In the previous study concerning potential usage of RLG data for monitoring high-frequency signals in Earth rotation parameters (ERP) (Tercjak and Brzeziński, IUGG GA 2015) we shown how diurnal and subdiurnal signals in polar motion (PM) and length of day (LOD) reflect in the Sagnac frequency which is the observable of the RLG. Continuing our investigation, we focus here on global and local diurnal and subdiurnal effects impacting orientation of an instrument. We consider influence of both tidal and non-tidal effects, including atmosphere loading, on the RLG observations at the Wettzell Observatory as well as on simulated observations at other geographic locations. We take into account both known and publicly available models and also our own solutions. Preliminary results show that those effects are comparable in size with the ERP-induced signals and should be taken into account when processing of RLG data.