Coupling numerical weather prediction and radiative transfer models for applications in tropospheric radiocommunications

Modelling atmospheric processes is a crucial point for several radiocommunication applications. For satellite-to-Earth links, for example, the atmospheric radiopropagation parameters (i.e., atmospheric brightness temperature and attenuation) are basic information for the optimum design of the link in order to minimize the data-loss during the transmission. In microwave radiometry contexts, the goal is the knowledge of both atmospheric brightness temperature (measured by the radiometer) and attenuation (retrieved through suitable retrieval algorithms or models) for receiver calibration, liquid water path and integrated water vapor retrievals, temperature profiles, tipping curve calibrations, propagation channel characterization, and so on. In this work we combine numerical weather prediction and radiative transfer models to characterize the atmosphere at microwave frequencies in specific geographical areas. The numerical weather prediction model that we adopt is the weather research and forecasting model (WRF) with a spatial resolution of 4 km and a release time of 1 hour. WRF provides a meteorological characterization of the atmosphere in terms thermodynamic variables (e.g., pressure, temperature, humidity, wind velocity and orientation) and microphysical variables (e.g., atmospheric particle concentration of water clouds and aerosol dispersions). These meteorological quantities are converted into radiopropagation parameters by a radiative transfer model: the Goddard satellite data simulator unit (Matsui et al. JGR 2014). The latter simulates the radiopropagation parameters, corresponding to the input meteorological scenario, as measured by a ground-based microwave radiometer at different elevation angles and frequencies. In this work we verify our weather-forecast based chain exploiting a Sun-tracking microwave radiometer that provides simultaneous measurements of both atmospheric brightness temperature and attenuation in all-weather conditions using the Sun as a reference signal-source. This weather-forecast based atmospheric channel description can be exploited for several purposes such as the optimization of satellite-to-Earth links on the basis of the forecasted atmospheric conditions or the set-up and verification of atmospheric models.