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Forecasting in the Vertical with a Local Dynamical Interpretation Method

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  • 1 Direction de la Meteorologie Nationale SCEM/D/Es&sol, Paris, France
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Abstract

A one-dimensional (I-D) planetary boundary-layer model, including a complete set of simple physical parameterizations, has been used since July 1986 to predict daily soundings at Trappes in the suburbs of Paris. This model is coupled to the French operational spectral hemispheric model, representing the large-scale atmospheric environment by means of horizontal gradients and vertical velocity in the advective terms, and geostrophic wind. The study of the statistical scores (mean absolute error and mean error) for 220 cases during the year 1986–87 provides good accuracy for the 12-h forecast (as compared to fine mesh modeling and statistical interpretation methods) but exhibits a loss of accuracy for periods longer than 12 h. Improvement in the results through adjustment of some of the model parameters with the help of a file containing 22 test situations appreciably reduces the mean absolute error, this method would thus be useful for local forecasts of sensitive weather elements. Further improvement could be obtained by coupling this I-D model with a three-dimensional, fine mesh model and by refining cloudy turbulence and soil evaporation schemes.

Abstract

A one-dimensional (I-D) planetary boundary-layer model, including a complete set of simple physical parameterizations, has been used since July 1986 to predict daily soundings at Trappes in the suburbs of Paris. This model is coupled to the French operational spectral hemispheric model, representing the large-scale atmospheric environment by means of horizontal gradients and vertical velocity in the advective terms, and geostrophic wind. The study of the statistical scores (mean absolute error and mean error) for 220 cases during the year 1986–87 provides good accuracy for the 12-h forecast (as compared to fine mesh modeling and statistical interpretation methods) but exhibits a loss of accuracy for periods longer than 12 h. Improvement in the results through adjustment of some of the model parameters with the help of a file containing 22 test situations appreciably reduces the mean absolute error, this method would thus be useful for local forecasts of sensitive weather elements. Further improvement could be obtained by coupling this I-D model with a three-dimensional, fine mesh model and by refining cloudy turbulence and soil evaporation schemes.

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