Static Pressure from Aircraft Trailing-Cone Measurements and Numerical Weather-Prediction Analysis

Abstract

Accurate static pressure measurements are a prerequisite for safe navigation and precise air data measurements on aircraft. Pressure is also fundamental for wind and air temperature analysis in meteorology. Static pressure measurement by aircraft is disturbed by aerodynamics and needs to be corrected using calibration. In this paper we compare static pressure measured by means of a trailing cone (TC) in the atmosphere behind two different jet aircraft at flight levels up to 450 with data from numerical weather predictions (NWP). The height is derived from differential Global Navigation Satellite System (GNSS) measurements. The GNSS height is compared to NWP geopotential height. The NWP data were provided by the Integrated Forecast System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). When computing the geopotential with latitude/height dependent gravity the pressure/height differences are -0.01+-0.15 hPa and 0.6+-2.8 m. This pressure accuracy implies NWP temperature errors <0.1 K on average below 10 km altitude. The TC measurements provide a first quantification of the case-specific accuracy of NWP pressure-geopotential relationships. The method of comparing operational pressure/GNSS measurements on aircraft with NWP analysis or predictions can be used to test the height keeping performance of aircraft after or during operation.