Refined Tropospheric Delay Models for CONT11

Abstract

For the period of CONT11, a continuous VLBI campaign which lasted from September 15 through September 29, 2011, new a coefficients for the Vienna Mapping Functions 1 (VMF1; Böhm et al., J Geophys Res 111:B02406, 2006) and an extended calculation strategy for horizontal gradients were applied. The a coefficients of the mapping functions are usually calculated by ray-tracing through numerical weather models (NWM) from the European Centre for Medium-Range Weather Forecasts (ECMWF) with a spatial resolution of 0.25^∘ × 0.25^∘ every 6 h. By enhancing the spatial resolution to 0.125^∘ × 0.125^∘ and using a new ray-tracing program called RADIATE, the actual refractivities are described in more detail. Moreover, existing equations for the calculation of the azimuth-dependent part of the slant delay by means of horizontal gradients were extended in order to achieve better accordance with the data from ray-tracing, which improves the resulting baseline length repeatabilities.