Spin-up Time Research on the Weather Research and Forecasting Model for Atmospheric Delay Mitigations of Electromagnetic Waves

Kurzfassung

Atmosphere causes distortions in the geometry and phases of synthetic aperture radar images denoted by the atmospheric phase screen (APS). Numerical weather models are beneficial in correcting these disturbances. After initialization, the models need time to derive a physical valid state. This is called the spin-up time and it affects delay predictions. The positive impact of a 12-hour spin-up time on delay mitigation has not yet been reported and is the objective of this paper. Hence, four independent experiments are considered revealing the best accuracy in case of the 12-hour predictions and showing best consistency of spatial frequencies. First, global positioning system zenith path delay (ZPD) series are compared with model-predicted ZPD series, which reports a 28% reduction of the root mean squared error. Second, the absolute ranging technique as an application of the delay prediction reports a 21% standard deviation decrease of position estimates. Third, a comparison of spatial frequencies between APS predictions and interferograms shows a closer consistency by using a 12-hour rather than a 6-hour spin-up time. Fourth, the APS mitigation in interferograms as an application of the APS prediction is twice as good with respect to the 12-hour spin-up time than with the 6-hour spin-up time.