A Field Case Study and Numerical Simulation of Mountain Flows with Weak Ambient Winds

E. Hernández Department of Atmospheric Sciences, Complutense University, Ciudad Universitaria, Madrid, Spain

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J. de las Parras Department of Atmospheric Sciences, Complutense University, Ciudad Universitaria, Madrid, Spain

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I. Martín Department of Atmospheric Sciences, Complutense University, Ciudad Universitaria, Madrid, Spain

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A. Rúa Department of Atmospheric Sciences, Complutense University, Ciudad Universitaria, Madrid, Spain

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L. Gimeno Center of Meteorological Training, Spanish National Meteorology Institute, Ciudad Universitaria, Madrid, Spain

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Abstract

Wind data collected by two ground stations in a mountainous area are used to investigate the mean properties of the flow on two typical summer days when the wind at the ridgetop had a perpendicular component to the ridge. The study area is located in the Central Range in the center of the Iberian Peninsula, Spain. The overall objective of the study is to develop a wind model. Its main application will be to supply surface wind fields to a forest fire simulator, although it could be used for the whole emergency response community. This model has been developed with the premise that in mountainous terrain the wind on a given point can be considered as the result of vector addition of a large-scale flow modified by the local topography and the different components of the wind generated by the subgrid-scale inhomogeneities of the ground surface. Functions that include the topographic effects of sheltering and deflecting and the generation of slope flows have been formulated. The model is considered a physical–mathematical model coupled to the output of a mesoscale prediction model. The model outputs are presented and compared with the experimental data. This discussion is restricted to the weak ambient wind conditions in which the thermal stratifications in the planetary boundary layer are significant and thermally induced circulations are meaningful.

Corresponding author address: Dr. Emiliano Hernández, Departamento de Fisica del Aire, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, Ciudad Universitaria, 28040 Madrid, Spain.

imartin@6000.aire.fis.ucm.es

Abstract

Wind data collected by two ground stations in a mountainous area are used to investigate the mean properties of the flow on two typical summer days when the wind at the ridgetop had a perpendicular component to the ridge. The study area is located in the Central Range in the center of the Iberian Peninsula, Spain. The overall objective of the study is to develop a wind model. Its main application will be to supply surface wind fields to a forest fire simulator, although it could be used for the whole emergency response community. This model has been developed with the premise that in mountainous terrain the wind on a given point can be considered as the result of vector addition of a large-scale flow modified by the local topography and the different components of the wind generated by the subgrid-scale inhomogeneities of the ground surface. Functions that include the topographic effects of sheltering and deflecting and the generation of slope flows have been formulated. The model is considered a physical–mathematical model coupled to the output of a mesoscale prediction model. The model outputs are presented and compared with the experimental data. This discussion is restricted to the weak ambient wind conditions in which the thermal stratifications in the planetary boundary layer are significant and thermally induced circulations are meaningful.

Corresponding author address: Dr. Emiliano Hernández, Departamento de Fisica del Aire, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, Ciudad Universitaria, 28040 Madrid, Spain.

imartin@6000.aire.fis.ucm.es

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