FORECASTING AIRCRAFT ICING IN COMPLEX TERRAIN

摘要

Through verification of different aircraft icing forecasts for the period from December 2000-April 2001, it appears that forecasts of aircraft icing over the complex terrain could be improved. No forecasting method produced accuracies higher than 72% for the study period as a whole. However, there were many differences noted in each of the forecasts examined. The NNICE forecast produced high accuracy percentages, although it overpredicts icing occurrences. On the other hand, WICE tended to underpredict icing events, with accuracies on average around the 50% mark. The AFWA MM5-based forecasts and AWSP algorithm both produced forecasts that had a very high ratio of false negatives to false positives. The AFWA algorithm did not produce a significantly improved forecast when grid spacing was reduced from 45km to 15km. AFWA accuracy percentages were in general higher than AWC. The AWSP algorithm was generally more accurate than either the AWC or AFWA methods. Using ETA soundings interpolated for KMWN as input data produced forecasts of higher accuracy than using nearby GYX radiosonde data. There is potential for manipulation of this forecasting algorithm for improvement in regions of complex terrain. Initial research shows that adaptation of the algorithm by adjusting the input data is a way to improve forecasts. Additional work is underway to evaluate the icing severity predictions of the various forecast methods. These results will be reported in a future paper and/or report. Further research over more than a single season is needed to study the adaptation of icing forecasting methods over complex terrain. It is shown that there is potential for an algorithm to be developed that can incorporate the atmospheric dynamics over terrain regions more successfully than current methods. With input data coming from the ETA model, forecasts can be made at 6-hour intervals out to 60 hours. Advanced warning and accurate icing forecasts over topographic regions has widespread importance, and there appears to be room for improvement.