A simple geometric'' mapping function for the hydrostatic delay at radio frequencies and assessment of its performance

[1] The hydrostatic mapping function, m(epsilon), describes the dependence of the hydrostatic path delay on the elevation angle e. We have developed a simple mapping function, where the only free parameter is an effective height'' of the atmosphere, H-atm, corresponding to about the first two scale heights above the surface. The value of m(epsilon) is given by the ratio of the straight-line ray path length within height Hatm to height Hatm itself. We used simulated delays at GPS (Global Positioning System) frequencies derived from high resolution ECMWF (European Centre for Medium-Range Weather Forecasts) atmospheric analysis fields to assess the performance of the geometric'' mapping function relative to well established ones (the Davis, Niell, and Herring mapping functions, respectively). At elevations >6degrees the new function generally exhibits, based on a single parameter, a performance comparable to or better than the other mapping functions.