Verification and Comparison of Polar MM5 and AFWA MM5 Forecasts Over Alaska

摘要

The Mesoscale Model 5th Generation (MM5) is used for operational support to Air Force missions in the Alaskan Theater. The 11th Operational Weather squadron has identified problems with the MM5 producing excessively warm surface temperatures. The Polar MM5 (PMM5), developed by the Byrd Polar Research Center for high latitude ice sheets, is tested over the Alaskan domains used by the Air Force Weather Agency to determine the utility in replacing the MM5 with the PMM5. The verification ofsurface temperature, pressure and wind as well as upper-air temperature, geopotential height, and relative humidity of 27-hour PMM5 forecasts are compared to the MM5 forecasts to assess the differences between the models accuracies. A grid-to-station technique is used to compare model output to surface observation for 68 locations and to radiosonde upper-air observations for 7 locations. The MM5 outperformed the PMM5 in root mean square error of all surface and upper-air parameters, while the PMM5 exhibited smaller biases in all fields. The differences between the models fell within the measurement accuracies of all parameters expect temperature. The analysis of horizontal features and comparison of domain biases alludes to a more physically realistic solution of the PMM5. The bottom line of site forecast accuracy precludes replacing the MM5 with the PMM5 at this time.