Abstract
AbstractWe present a detailed evaluation of the turbulence forecast product eddy dissipation parameter (EDP) used at the Deutscher Wetterdienst (DWD). It is based on the turbulence parameterization scheme TURBDIFF, which is operational within the Icosahedral Nonhydrostatic (ICON) numerical weather prediction model used operationally by DWD. For aviation purposes, the procedure provides the cubic root of the eddy dissipation rate ε1/3 as an overall turbulence index. This quantity is a widely used measure for turbulence intensity as experienced by aircraft. The scheme includes additional sources of turbulent kinetic energy with particular relevance to aviation, which are briefly introduced. These sources describe turbulence generation by the subgrid-scale action of wake eddies, mountain waves, and convection, as well as horizontal shear as found close to fronts or the jet stream. Furthermore, we introduce a postprocessing calibration to an empirical EDR distribution, and we demonstrate the potential as well as limitations of the final EDP-based turbulence forecast by considering several case studies of typical turbulence events. Finally, we reveal the forecasting capability of this product by verifying the model results against one year of aircraft in situ EDR measurements from commercial aircraft. We find that the forecasted EDP performs favorably when compared to the Ellrod index. In particular, the turbulence signal from deep convection, which is accounted for in the EDP product, is advantageous when spatial nonlocality is allowed in the verification procedure.
Highlights
Aviation turbulence is a major cause of injuries on commercial aircraft, sometimes causing even structural damage
To gain insight into the role played by the different turbulent kinetic energy (TKE) source terms, as well as the post processing steps, including the calibration procedure, we evaluate several versions of the eddy dissipation parameter (EDP) product
We investigate the influence of the spatial uncertainty scale in greater detail using the receiver operating characteristic (ROC) area, where larger area under the curve is indicative of better forecasts
Summary
Aviation turbulence is a major cause of injuries on commercial aircraft, sometimes causing even structural damage. Sources of TKE have been introduced that contribute in the upper atmosphere, such as horizontal shear, convection and subgrid-scale orography (Raschendorfer 2011) In addition to this extension of the model, a related postprocessing has been developed during this phase, which improves the quality of the final EDP product. The turbulence parameterization that underlies the EDP product will be used in the ICON-D2 domain over Germany with Dx ’ 2 km This domain is currently too small to be of big interest for aviation so this aspect has not yet been investigated. We investigate several typical situations where turbulence often occurs, including mountain waves, deep convection and horizontal wind shear These cases help to expose the behavior of the particular additional TKE source terms, which are shown to be able to represent the relevant events quite well.
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