1-DEFOP (1-Dimensional Ensemble Fog Prediction in Complex (Terrain)

• Research unit: COST
• Project number: C03.0024

Key words (English)

Fog; visibility; 1-D model; 3-D model; airport; ensemble prediction; complex terrain; boundary layer

Research programs (English)

COST-Action 722 - Nowcasting of fog, visibility and low clouds

Short description (English)

A one-dimensional weather prediction model (COBEL) is used to forecast fog. The use of COBEL will be set up in two ways: a) by implementing a 1-d ensemble prediction scheme; b) by implementing different 3-d NWP models as initial boundary conditions.

Further information (English)

Full name of research-institution/enterprise: Bundesamt für Meteorologie und Klimatologie MeteoSchweiz Flugwetterzentrale

Partners and International Organizations (English)

AT, BG, CH, CY, DE, DK, ES, FI, FR, HU, NO, PL, SE, UK

Abstract (English)

Two high resolution numerical 1D models, namely COBEL and PAFOG, have been adapted to compute a probabilistic fog forecast. Major modifications were made to the COBEL model. It was coupled to the NOAH land surface model to take into account the effects of soil and vegetation and furthermore a parameterization of precipitation was added. To deal with the large uncertainty inherent to fog forecasts, a whole ensemble of 1D runs is computed using the two different numerical models and a set of different initial conditions in combination with distinct boundary conditions. Initial conditions are obtained from variational data assimilation, which optimally combines observations with a first guess taken from operational 3D models. The design of the ensemble scheme computes members that should fairly well represent the uncertainty of the current meteorological regime. Verification reveals that the probabilistic forecast shows some potential to improve the current information records used for fog forecasting. Due to the importance of advection and the complexity of topography around Zürich airport, a three-dimensional modelling approach was also pursued. With droplet number concentration as a new prognostic variable it is possible to better represent the gravitational settling as well as condensation and evaporation of cloud water. Several case studies outline the good performance of the 3D fog model and also the potential of sophisticated satellite cloud products, which can be used for verification purposes. However, for conclusive skill assessment a whole season needs to be simulated and analyzed, which will be part of future research.

References in databases (English)

Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. [phone] Swiss Project-Number: C03.0024