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Turbulence algorithm intercomparison: winter 2000 results
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2000
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[PDF-51.41 MB]
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Description:This report summarizes basic results of a second intercomparison of the capabilities of a number of clear-air turbulence (CAT) forecasting algorithms to predict the locations of CAT. The algorithms considered in the study include most of the algorithms that were included in the first intercomparison, which took place during winter 1998-99, as well as two additional algorithms. The algorithm forecasts are based on output of the Rapid Update Cycle (RUC-2) numerical weather prediction model during the period 10 January through 31 March 2000. Forecasts issued at 1200, 1500, 1800, and 2100 UTC, with 3-, 6-, 9-, and 12-h lead times were included in the study. The evaluation also includes the turbulence AIRMETs, the operational turbulence forecast product that is issued by the NWS Aviation Weather Center (AWC) and is limited to the continental United States and to altitudes above 20,000 ft. The forecasts were verified using Yes and No turbulence observations from pilot reports (PIREPs), as well as No observations based on automated vertical accelerometer (AVAR) data that were obtained from a number of aircraft. The algorithms were evaluated as Yes/No turbulence forecasts by applying a threshold to convert the output of each algorithm to a Yes or No value. A variety of thresholds were applied to each algorithm. The verification analyses were primarily based on the algorithms’ ability to discriminate between Yes and No observations, as well as the extent of their coverage. The study was comprised of two components. First, the algorithms were evaluated in near real time by the Real-Time Verification System (RTVS) of the NOAA Forecast Systems Laboratory (FSL), with results displayed through a graphical user interface on the World Wide Web (http://www-ad.fsl.noaa.gov/afra/rtvs/RTVS-proiect des.html). Second, the verification results were re-evaluated in greater depth in post-analysis, using a post-analysis verification system at the National Center for Atmospheric Research (NCAR), with additional thresholds applied to each algorithm to provide a more complete depiction of algorithm quality. Results of the intercomparison suggest that a few of the algorithms (e.g., DTF3, ITFA, Ellrod) have somewhat better overall forecasting performance than the others. In particular, these algorithms have somewhat larger values of the True Skill Statistic (TSS) for comparable thresholds, and they have a slightly larger overall discrimination skill statistic. However, the best algorithms have very similar performance characteristics. In some (but not all) cases the algorithm performance is approximately the same as the performance of the AIRMETs. Results of the study are consistent with the results obtained from the 1998-1999 Turbulence Algorithm Intercomparison study.
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Rights Information:CC0 Public Domain
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