Climatological Evaluation of Supercooled Liquid Water Content Forecasts from the Mesoscale model
Steadman, D.
A climatology archive has been produced (for March 1999) based on supercooled liquid water content (SLWC) and ice water content (IWC) prognostic variables extracted from operational mesoscale model output. Fields at model "wet" levels were extracted from 1 forecast run per day (00Z) at 3 hourly lead time intervals (T+3, T+6, etc.) and data relevant to the forecast presence of SLW were stored for future processing. Analysis of the climatology archive revealed no unrealistic characteristics with respect to the relationship between SLWC and temperature. Comparisons made between the climatology archive data and parameterizatio?ns derived in Special Investigations Memorandum 112 (for stratiform cloud) show consistency. The limited comparisons which are possible between the climatology archive data and the FAR/JAR icing atmosphere also show good agreement. The use of the model SLWC output as an indicator of moderate/severe icing is unlikely to result in overforecasting of moderate/severe icing compared with the present schemes in use, provided that suitable choices of SLWC value are made for the thresholds of moderate and severe icing. However, the likely accuracy of an individual forecast cannot be inferred from the climatological study.
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