Assessment of the low visibility predictions at Schiphol Airport

Performance of the Terminal Aerodrome Forecast Guidance

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Airport operations are highly dependent on safe weather conditions for their daily operations. Especially the visibility conditions are crucial. Low Visibility Procedures (LVP phase M, A, B and C) are defined at Schiphol Airport, resulting in capacity and runway use restrictions. These Low Visibility Pro­cedures are based on a post­processing model of a Numerical Weather Prediction (NWP): the Terminal Aerodrome Forecast Guidance (TAFG). This model provides a probability for the occurrence of a given LVP phase, based on thresholds of the Runway Visual Range (visibility including back luminescence at airports) and the ceiling (cloud base height). Currently, the TAFG is operational for three NWP models (HARMONIE, HIRLAM and ECMWF). This research found that the HIRLAM TAFG has a better performance than the HARMONIE TAFG. This result is caused by the larger training data­set that is used for the HIRLAM TAFG (20 years) compared the training data­set of for the HARMONIE TAFG (3 years). The ECMWF TAFG has a better performance for the severe LVP phases B and C. This is remarkable, since ECMWF is not often used for airport operations. However, the standard error of the performance indicator of the ECMWF TAFG is higher compared to the other models and, therefore, a larger data­set should be studied to confirm these findings.