Fog prediction using a very high resolution numerical weather prediction model forced with a single profile

Fog and low level Cloud forecasting is crucial for aviation, land transport and shipping, Current numerical weather prediction (NWP) models call give a broad indication of fog formation and dissipation oil scales of a few tells of kilometres, but can provide little detail especially in areas of complex terrain. One-dimensional models for specific locations taking into account the impact of the surrounding orography oil the flow have been developed as a cheap Solution, but they are unable to treat complex three dimensional flows. A full NWP model running at a horizontal resolution of around 1 km (or better) may be required to address the three-dimensional fog forecasting problem in full. Enhancement of the model resolution to Such a scale is restrained by available computing power and is not presently feasible for general coverage. However, in the weakly forced Situations leading to fog formation, the use of it small, local area (e.g. 50 km x 50 km), high resolution NWP model may be a viable alternative. In this study, the local area NWP model approach is explored, initializing and forcing the model with a time series of single forcing profiles from either a low resolution NWP model, or from a local radiosonde profile. This method of homogeneous single-profile forcing (SPF) allows the model to be run locally with a small volume Of input data. The UK Met Office Unified Model (UM) is set-up for a 50 km by 50 km horizontal domain, with real orography and a grid spacing of 1 km and 76 vertical levels. The model is initialized and forced with temperature, humidity and wind profiles front a 12 km coarse resolution model. Some typical results from it single-profile forcing (SPF) model run will be shown and compared with the Output from a full NWP model with 1 km resolution and with observational data. (C) Crown Copyright 2008. Reproduced with the permission of the Controller of HMSO. Published by John Wiley & Sons, Ltd