Verification of NWP turbulence intensity guidance using eddy dissipation rate from aircraft data

This paper discusses the use of eddy dissipation rate (EDR) from commercial jets to verify the performance of NWP turbulence intensity products from the World Area Forecast Centres (WAFC). Wind measurements recorded by flight data recorder are pre-processed by a band-pass filter algorithm to generate EDR. Contingency table approach is adopted to determine the hit, miss and false alarm of the clear air turbulence (CAT) potential from NWP models under different EDR thresholds. To assess the performance of model guidance, relative operating characteristic (ROC) curves are produced using different model CAT potential thresholds to determine the hit rate and false alarms. With a 12 month period of aircraft data, it is found that both US and UK WAFC turbulence guidance products demonstrate skills in predicting light and moderate turbulence. In terms of the areas under the ROC curve, a slightly better performance can be seen in the US WAFC model guidance. Additionally, the verification is applied to the turbulence intensity guidance from the Non-Hydrostatic Model (NHM), a new operational mesoscale NWP system in the Observatory. It is found that similar level of forecast skill on the moderate turbulence can also be obtained from NHM.