Articles | Volume 9, issue 8
Research article
30 Aug 2016
Research article |  | 30 Aug 2016

Estimates of Mode-S EHS aircraft-derived wind observation errors using triple collocation

Siebren de Haan

Abstract. Information on the accuracy of meteorological observation is essential to assess the applicability of the measurements. In general, accuracy information is difficult to obtain in operational situations, since the truth is unknown. One method to determine this accuracy is by comparison with the model equivalent of the observation. The advantage of this method is that all measured parameters can be evaluated, from 2 m temperature observation to satellite radiances. The drawback is that these comparisons also contain the (unknown) model error. By applying the so-called triple-collocation method (Stoffelen, 1998), on two independent observations at the same location in space and time, combined with model output, and assuming uncorrelated observations, the three error variances can be estimated. This method is applied in this study to estimate wind observation errors from aircraft, obtained utilizing information from air traffic control surveillance radar with Selective Mode Enhanced Surveillance capabilities (Mode-S EHS, see de Haan, 2011). Radial wind measurements from Doppler weather radar and wind vector measurements from sodar, together with equivalents from a non-hydrostatic numerical weather prediction model, are used to assess the accuracy of the Mode-S EHS wind observations. The Mode-S EHS wind (zonal and meridional) observation error is estimated to be less than 1.4±0.1 m s−1 near the surface and around 1.1 ± 0.3 m s−1 at 500 hPa.

Short summary
The paper presents estimates of aircraft-derived wind observations obtained using Mode-S EHS method by applying the triple-collocation technique. Triple-collocated data sets were constructed using sodar (at Schiphol airport) and Doppler radar wind observation (from two radars in the Netherlands) in combination with numerical weather model data. It was found that the wind error near the surface is around 1.4 m s−1, while at 500 hPa the error is estimated to be around 1.1 m s−1.