(Nieblas radiactivas, ondas de gravedad y sus interacciones con la turbulencia en la capa límite atmosférica)

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física de la Tierra, Astronomía y Astrofísica I, leída el 17-12-2015Esta 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 studiesDepto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEunpu

Characterization of evening atmospheric boundary layer transitions from a sonic anemometer and an array of microbarometers during the BLLAST field campaign

Póster elaborado para la European Geosciences Union General Assembly celebrada los días 22-27 de abril de 2012 en Viena.This research has been funded by the Spanish Ministry of Science and Innovation (projects CGL2009-12797-C03-03 and CGL2011-13477-E). The GR35/10 program (supported by Banco Santander and UCM) has also partially financed this work through the Research Group “Micrometeorology and Climate Variability” (nº 910437). M. Sastre is supported by a FPI-UCM fellowship (BE45/10)

Verification of fog and low cloud simulations using an object oriented method

Póster presentado en: EGU General Assembly celebrada del 7 al 12 de abril de 2013 en Viena, Austria

Study of the interaction between fog and turbulence

Póster elaborado para la European Geosciences Union General Assembly, celebrada en Viena del 3 al 8 de abril de 2011.This researchh as been funded by the Spanish Ministry of Education and Science (projects CGL2006-12474-C03-03 and CGL2009-12797-C03-03).The GR58/08 program (supported by BSCH and UCM) has also partially financed whis work through the Research Group “Micrometeorology and Climate Variability” (nº910437)

Evening transitions of the atmospheric boundary layer: characterization, case studies and WRF simulations

Micrometeorological observations from two months (July–August 2009) at the CIBA site (Northern Spanish plateau) have been used to evaluate the evolution of atmospheric stability and turbulence parameters along the evening transition to a Nocturnal Boundary Layer. Turbulent Kinetic Energy thresholds have been established to distinguish between diverse case studies. Three different types of transitions are found, whose distinctive characteristics are shown. Simulations with the Weather Research and Forecasting-Advanced Research WRF (WRF-ARW) mesoscale model of selected transitions, using three different PBL parameterizations, have been carried out for comparison with observed data. Depending on the atmospheric conditions, different PBL schemes appear to be advantageous over others in forecasting the transitions.This research has been funded by the Spanish Ministry of Science and Innovation (projects CGL 2006-12474-C03-03 and CGL2009-12797-C03-03). The GR58/08 program (supported by BSCH and UCM) has also partially financed this work through the Research Group “Micrometeorology and Climate Variability” (No 910437). M. Sastre is supported by a FPI-UCM fellowship (reference BE45/10)

Observations and WRF simulations of fog events at the Spanish Northern Plateau

The prediction of fogs is one of the processes not well reproduced by the Numerical Weather Prediction (NWP) models. In particular, the role of turbulence in the formation or dissipation of fogs is one of the physical processed not well understood, and therefore, not well parameterized by the NWP models. Observational analysis of three different periods with fogs at the Spanish Northern Plateau has been carried out. These periods have also been simulated with the Weather Research and Forecasting (WRF) numerical model and their results have been compared to observations. The study includes a comparison of the skill of different planetary boundary layer (PBL) parameterizations, surface layer schemes and a test of the gravitational settling of clouds/fogs droplets option. A statistical analysis of this comparison has been evaluated in order to study differences between the periods and between the various parameterizations used. The model results for each PBL parameterization were different, depending on the studied period, due to differences in the features of each fog. This fact made it difficult to obtain generalized conclusions, but allowed us to determine which parameterization performed better for each case. In general, judging from the models results of liquid water content (LWC), none of the PBL schemes were able to correctly simulate the fogs, being Mellor-Yamada Nakanishi and Niino (MYNN) 2.5 level PBL scheme the best one in most of the cases. This conclusion is also supported by the root mean square error (RMSE) calculated for different meteorological variables.This research has been funded by the Spanish Ministry of Science and Innovation (project CGL2009-12797-C03-03). The GR35/10 program (supported by BSCH and UCM) has also partially financed this work through the Research Group “Micrometeorology and Climate Variability” (No 910437)

Evaluación de las características de la brisa marina en la costa cantábrica oriental mediante observaciones y simulaciones con el modelo WRF

Ponencia presentada en: XXXIV Jornadas Científicas de la AME y el XVII Encuentro Hispano Luso de Meteorología celebrado en Teruel, del 29 de febrero al 2 de marzo de 2016.Proyectos Nacionales CGL2012-37416-C04-02 y CGL2015-65627-C3-3-R y el programa GR3/14 (Nº 910437)

Near-monochromatic ducted gravity waves associated with a convective system close to the Pyrenees

Near-monochromatic gravity waves (GWs) associated with a mesoscale convective system (MCS) were detected during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field campaign in Lannemezan (France) on 21 June 2011. These GWs are analyzed using available instrumental data (e.g. an array of microbarometers, a microwave system Humidity And Temperature PROfiler (HATPRO) and an ultra-high-frequency (UHF) wind profiler). Pressure oscillations of up to 0.5 hPa were recorded after a pronounced pressure drop of 1.4 hPa, identified as the MCS weak low. Wavelet analysis and evaluated wave parameters confirm the occurrence of such GWs (period ∼9 min, horizontal wavelength ∼7 km), which propagated from southwest to northeast, i.e. in the same direction of propagation as the MCS. Observational evidence suggests the downdraughts associated with the rear-inflow jet at the weak low zone of the MCS as the most likely generator mechanism of the GWs. However, the complex orography and proximity of the Pyrenees to the field campaign could also play an important role. Wave propagation was possible through the ducting mechanism, favoured by the existence of a critical level in a wind-sheared environment around 2000 m above ground level. Wave-like motions related to the passage of the GWs were also observed in other atmospheric parameters close to the surface and within the lower troposphere. The effects of GWs on the surface fluxes have also been analyzed through Multi-Resolution Flux Decomposition (MRFD) methods.This research has been funded by the Spanish Government (projects CGL2009-12797- C03-03, CGL2011-13477-E and CGL2012-37416-C04-02). The tower equipment and UHF radar have been supported by CNRS, University of Toulouse and European POCTEFA FluxPyr program and FEDER program (Contract 34172 – IRENEA – ESPOIR). The edge-site measurements were financed by the DFG (Deutsche Forschungsgemeinschaft) project GR2687/3-1 and SCHU2350/2-1

A case study of shallow radiation fogs over CIBA: observations and simulations (WRF and HARMONIE models)

Póster presentado en: EGU General Assembly celebrada del 7 al 12 de abril de 2013 en Viena, Austria.This research has been funded by the Spanish Government (projects CGL2009-12797-C03-03, CGL2011-13477-E and CGL2012-37416-C04-02)