Publication: Radiation fog, gravity waves and their interactions with turbulence in the atmospheric boundary layer
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2016-02-16
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Universidad Complutense de Madrid
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Abstract
Esta tesis aborda el estudio de dos fenómenos atmosféricos que aparecen normalmente en la capa límite estable (SBL): nieblas radiativas y ondas de gravedad (GWs). Estos procesos no están bien comprendidos y por lo tanto su representación en los modelos numéricos es uno de los desafíos a los que se enfrenta la modelización meteorológica futura. De esta forma, el principal objetivo de esta tesis es ampliar el conocimiento sobre estos fenómenos, con un enfoque especial a sus interacciones con la turbulencia en la SBL. El trabajo comienza con experimentos de sensibilidad del modelo WRF (Weather Research and Forecasting) para la determinación de las opciones físicas más apropiadas para la predicción de nieblas. Posteriormente, se aborda la predicción de nieblas a través de dos enfoques diferentes: modelización numérica directa (WRF) y métodos estadísticos (M14, Menut et al. (2014)). Estos dos métodos son evaluados y comparados en dos centros experimentales diferentes. Por otro lado, se presenta una climatología estadística robusta con el objetivo de señalar las diferencias más importantes entre las nieblas radiativas en ambos sitios. Finalmente, se ofrecen nuevos métodos para la estimación de la altura del tope de la niebla. Esta variable es normalmente desconocida o está sujeta a la disponibilidad de datos de difícil adquisición. La estimación que se ofrece en esta tesis se basa en medidas superficiales de turbulencia (velocidad de fricción y flujo de calor). Con respecto a las GWs, por un lado se presenta un análisis observacional único de GWs casi monocromáticas propagadas en un canal, siendo difícil tener la oportunidad de analizar observacionalmente un caso como éste. Por otro lado, se muestran los mecanismos físicos que gobiernan GWs de menor escala y flujos de drenaje, analizando en detalle las interacciones de estos fenómenos con la turbulencia en la SBL, tema que es uno de los actuales desafíos de los estudios micrometeorológicos.
This thesis deals with the study of two atmospheric phenomena that normally appear in the stable boundary layer (SBL): radiation fog and gravity waves (GWs), processes that are still not well understood. Therefore, their representation in the numerical weather prediction (NWP) models is one of the current challenges for the meteorological modelling. Thus, the main objective of this thesis is to gain knowledge about these phenomena, with especial emphasis to their interactions with turbulence in the SBL. The work starts with sensitivity experiments of the WRF (Weather Research and Forecasting) mesoscale model, in order to determine the most appropriate physical options for the simulation of fog. Subsequently, radiationfog forecasting is addressed through two different approaches: numerical modelling (WRF) and statistical methods (M14, Menut et al. (2014)). These two methods are evaluated and compared at two contrasting experimental sites. Finally, new methods for the fog-top height estimation are presented. This variable is usually unknown or subjected to expensive or not-always accessible data. The estimation offered in this thesis is based on turbulent surface measurements (friction velocity and heat flux). Regarding GWs, on the one hand, a comprehensive observational analysis of near-monochromatic GWs propagated in a duct layer is presented, being difficult to have the chance of analysing a case like this in the real atmosphere. On the other hand, the physical mechanisms governing smaller-scale GWs and drainage flows are elucidated, analysing in detail the interactions of these phenomena with the turbulence in the SBL, which is one of the main current challenges in micrometeorological studies
This thesis deals with the study of two atmospheric phenomena that normally appear in the stable boundary layer (SBL): radiation fog and gravity waves (GWs), processes that are still not well understood. Therefore, their representation in the numerical weather prediction (NWP) models is one of the current challenges for the meteorological modelling. Thus, the main objective of this thesis is to gain knowledge about these phenomena, with especial emphasis to their interactions with turbulence in the SBL. The work starts with sensitivity experiments of the WRF (Weather Research and Forecasting) mesoscale model, in order to determine the most appropriate physical options for the simulation of fog. Subsequently, radiationfog forecasting is addressed through two different approaches: numerical modelling (WRF) and statistical methods (M14, Menut et al. (2014)). These two methods are evaluated and compared at two contrasting experimental sites. Finally, new methods for the fog-top height estimation are presented. This variable is usually unknown or subjected to expensive or not-always accessible data. The estimation offered in this thesis is based on turbulent surface measurements (friction velocity and heat flux). Regarding GWs, on the one hand, a comprehensive observational analysis of near-monochromatic GWs propagated in a duct layer is presented, being difficult to have the chance of analysing a case like this in the real atmosphere. On the other hand, the physical mechanisms governing smaller-scale GWs and drainage flows are elucidated, analysing in detail the interactions of these phenomena with the turbulence in the SBL, which is one of the main current challenges in micrometeorological studies
Description
Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física de la Tierra, Astronomía y Astrofísica I, leída el 17-12-2015