The Effect of Meteorological Input Data on the VLBI Reference Frames

Abstract

Atmosphere pressure and air temperature are input quantities for corrections applied to the observables of space geodetic techniques, such as Very Long Baseline Interferometry (VLBI) and Global Navigation Satellite Systems (GNSS). A priori troposphere zenith delay and atmosphere loading models are directly connected with the atmosphere pressure and thermal deformations of the antennas depend on temperature variations. In this study effects on the VLBI terrestrial and celestial reference frames (TRF, CRF) are investigated using atmosphere pressure and temperature from various sources: the numerical weather model (NWM) of the European Centre for Medium-Range Weather Forecasts (ECMWF), the empirical global pressure and temperature model (GPT), the Berg atmosphere model and meteorological observations acquired in-situ or in the vicinity of the site. While Vienna Mapping Functions 1 and atmosphere loading corrections are applied and kept constant during the analysis, zenith delay and thermal deformation models are considered separately. Comparing the Helmert parameters estimated between the different TRF solutions, the rotations and translations do not significantly differ when applying pressure data of various sources, but the scale varies up to 0.32 ppb. The time series of vertical station positions can show significant variations in the range of ± 5 mm. Antenna thermal deformations driven by temperature cause annual scale variations of up to 0.6 ppb. Source position differences stay at the 0.1 mas level. We recommend the application of homogeneous in-situ meteorological observations, for the determination of the TRF and in particular, zenith delay and vertical station position time series.