Troposphere Delay Modeling Based on Numerical Weather Models

Modern troposphere delay models like the Vienna Mapping Functions (VMF1) are based on data from Numerical Weather Models (NWM) with a time resolution of typically 6 hours. Different from purely analytical formulations like the Global Mapping Functions, the VMF1 can account for real weather phenomena like changing high and low pressure systems and are thus more accurate. Additionally, the zenith hydrostatic delays can also be derived from NWM if pressure values recorded at the sites are not available. We compare the VMF1 and zenith delays as derived from data of the European Centre for Medium-range Weather Forecasts (ECMWF) with those parameters derived from data of the National Centers for Environmental Prediction (NCEP), and we find a good agreement between those two realizations with station height differences at the few-millimeter level.