6. Multi-technique comparison of troposphere zenith delays and gradients during IVS-CONT08

摘要

In this chapter, VLBI estimates of troposphere zenith total delays (ZTD) and gradients during IVS-CONT08 were compared with those derived from observations with the Global Positioning System (GPS), Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and water vapor radiometers (WVR) co-located with the VLBI radio telescopes. Space geodetic techniques derived ZTD and gradients were also compared to those determined by ray-tracing through the profiles of various Numerical Weather Models (NWM) i.e. the European Centre for Medium-Range Weather Forecasts (ECMWF) (all sites), the Japan Meteorological Agency (JMA) and Cloud Resolving Storm Simulator (CReSS) (Tsukuba in Japan), and the High Resolution Limited Area Model (HIRLAM) (European sites). It should be noted that all comparisons and validation tests presented within this section contribute important information to the planned combination and integration of various observing techniques. In fact, such a multitude of different methods to simultaneously determine troposphere parameters from space geodetic techniques and other sources have never been available for comparison before. Thus, the data taken during the IVS-CONT08 campaign will contribute to combination studies in the framework of the Global Geodetic Observing System (GGOS) (Rummel et al., 2005) of the International Association of Geodesy (IAG).