Estructura térmica y dinámica de un ciclón subtropical típico en el Atlántico Norte

Los ciclones subtropicales son sistemas atmosféricos de baja presión que se caracterizan por tener una estructura térmica híbrida, a medio camino entre los ciclonestropicales y extratropicales. Debido, tanto al interés científico, como a los impactos socio-económicos que provocan, estos sistemas han propiciado un auge en la investigación para la mejora de su modelización numérica, lo que ha repercutido en la precisión de la predicción. Esta tesis tiene como objetivo profundizar en los procesos dinámicos y térmicos que se llevan a cabo durante la génesis e intensificación de este tipo de ciclones, así como las características que los definen. Los diversos estudios que componen esta memoria se han centrado en el análisis de un ciclón subtropical típico, concretamente el desarrollado en octubre de 2014 en las inmediaciones de las Islas Canarias. De este ciclón se tiene información muy detallada debido a los daños provocados por el mismo en la isla de Tenerife, siendo ampliamente reflejados en los medios de comunicación. Así mismo la AEMET (Agencia Estatal de Meteorología) ha proporcionado herramientas y campos de diagnóstico convectivo para caracterizar este fenómeno..

Assessing the performance of the HARMONIE-AROME and WRF-ARW numerical models in North Atlantic Tropical Transitions

Producción CientíficaTropical cyclones (TCs) can develop as a result of the tropical transition (TT) process, which occurs when an extratropical cyclone (EC) begins to exhibit tropical characteristics, forming a TC. In this study, four TT processes that lead to a hurricane structure [Delta (2005), Ophelia (2017), Leslie (2018), and Theta (2020)] are evaluated using two high-resolution numerical models (WRF and HARMONIE-AROME). Both tracks and intensities of the cyclones are assessed by comparing the simulated minimum sea level pressure and maximum wind speed to an observational dataset. Moreover, a spatial verification is performed by comparing the MSG-SEVIRI brightness temperature (BT) and accumulated precipitation (IMERG) to the corresponding simulations accomplished by both models. Analyzing the track results, the WRF model, on average, outstands HARMONIE-AROME. However, it is the HARMONIE-AROME model that performs better than WRF when reproducing the intensity of these cyclones. Concerning the BT spatial validation, HARMONIE-AROME slightly outperformed WRF when reproducing the cyclone's structure but failed when simulating the BT amplitude. Besides, both models achieved a nearly perfect cyclone location. In terms of accumulated precipitation results, the HARMONIE-AROME model overestimates the larger structures while underestimating the smaller ones, whereas the WRF model underestimates the bigger structures, being poorly located by both models. Although it is difficult to establish which numerical model performs better, the overall results show an outstanding of the HARMONIE-AROME model over the WRF model when simulating TT processes.IBERCANES (Project PID2019-105306RB-I00/AEI/10.13039/501100011033)Ministerio de Ciencia e Innovación de España - FPI program (PRE2020-092343

Assessment of HARMONIE-AROME in the simulation of the convective activity associated to a subtropical transition using satellite data

Producción CientíficaSubtropical transition events (STT) are a challenge for forecasting and research due to the hybrid characteristics they give to the cyclones. The ability and skillfulness of the HARMONIE-AROME model to reproduce the cloud structure and convection associated to the October 2014 STT is here evaluated. Brightness temperature, cloud top height and accumulated precipitation are assessed against satellite data using traditional skill scores and object-based techniques specific to forecasting spatial evaluation. The results present differences in the simulation of the cyclone between the periods before and after the transition. They also show a very good performance of the model in the location of the events and a good simulation of the intensity of the variables. The performance is sub-optimal for the estimation of the sizes of the convective objects. Brightness temperature and cloud top heights yield very good results in general, with a slight overestimation in both cases. However, the model struggles to capture the accumulated precipitation. There is scarce work evaluating the HARMONIE-AROME model in this type of events; nevertheless, the results are in line with those produced by the simulations with other numerical models. The overall performance of the model is very adequate, although it might be hindered by the internal stability of the model produced by the deep-convection computation.Agencia Estatal de Investigación (PID2019-105306RB-I00/AEI/10.13039/501100011033)Ministerio de Ciencia e Innovación de España - FPI program (PRE2020-092343

Subtropical cyclone formation via warm seclusion development: the importance of surface fluxes

Subtropical cyclones (STCs) are characterized by a thermal hybrid structure with tropical and extratropical features. STCs are considered a numerical modeling challenge because of their rapid intensification. A fundamental part of their strength is derived from diabatic processes associated with convection and heat fluxes from the ocean. This study evaluates the importance of surface turbulent heat fluxes during the transition of an extratropical precursor into a STC. This cyclone evolved embedded within a strong meridional flow, having a Shapiro‐Keyser structure and undergoing a warm seclusion process. To assess the importance of those heat fluxes, two Weather Research and Forecasting simulations were defined considering the presence and absence of those fluxes. Results of both simulations reveal a warm seclusion process, which weakened in absence of the heat fluxes. During the system genesis and in absence of heat fluxes, the wind and rainfall values were increased due to the remarkably intense area of frontogenesis to the northwest. Given these results and the lack of transition in the absence of heat fluxes, the frontal nature of the system was verified. Considering the heat fluxes, the obtained potential vorticity values diminished, reducing wind shear and intensifying convection in the system, which favored its transition into an STC. This study is groundbreaking in that no STC has been linked to a warm seclusion process in the Eastern North Atlantic. Additionally, simulated wind field shows an underestimation in comparison with Atmospheric Motion Vectors, used as observational data so as to give a weight to the wind analysis.This work was partially supported by research projects PCIN-2014-013-C07-04, PCIN2016-080 (UE ERA-NET Plus NEWA Project), CGL2016-78702-C2-1-R, CGL2016-78702-C2-2-R, and CGL2016-81828-REDT and the ECMWF special projects (SPESMART and SPESVALE)

Análisis de la temperatura en un ciclón subtropical mediante el modelo WRF: uso de diferentes parametrizaciones

Ponencia presentada en: XXXV Jornadas Científicas de la AME y el XIX Encuentro Hispano Luso de Meteorología celebrado en León, del 5 al 7 de marzo de 2018.Debido a la compleja dinámica y rápida intensificación de los ciclones subtropicales (STCs), estos sistemas siguen siendo un fenómeno de interés, además, de constituir un reto su predicción. Es por ello, que resulta conveniente conocer y analizar los esquemas de parametrización que mejor simulan este tipo de fenómenos. En este trabajo se realizan diversas simulaciones usando el modelo numérico WRF con el fin de llevar a cabo un análisis de la temperatura en el ciclón a distintos niveles atmosféricos a partir de diferentes combinaciones de parametrizaciones. Estos sistemas se caracterizan por poseer una estructura térmica híbrida, por lo que este estudio se lleva a cabo durante el desarrollo e intensificación del sistema. De esta forma, se pretende analizar la evolución de la estructura térmica del sistema desde que comienza siendo un ciclón extratropical hasta que adquiere características subtropicales. Así mismo, dicho análisis se desarrolla tanto desde un punto de vista determinista como probabilista. De este modo, se pretende obtener mayor información sobre estos fenómenos extremos con el fin de poder mejorar su simulación y, con ello, conseguir realizar predicciones más precisas en un futuro. Finalmente, se exponen, para los diferentes niveles atmosféricos, las combinaciones de parametrizaciones que mejor simulan la temperatura para este tipo de fenómenos

Comparison of the WRF and HARMONIE models ability for mountain wave warnings

Mountain lee waves usually involve aircraft icing and turbulence events. These weather phenomena, in turn, are a threat to aviation safety. For this reason, mountain lee waves are an interesting subject of study for the scientific community. This paper analyses several mountain lee waves events in the south-east of the Guadarrama mountain range, near the Adolfo Suarez Madrid-Barajas airport (Spain), using the Weather Research and Forecasting (WRF) and the HARMONIE-AROME high-resolution numerical models. For this work, simulated brightness temperature from the optimum WRF parametrization schemes and from the HARMONIE are validated using satellite observations to evaluate the performance of the models in reproducing the lenticular clouds associated to mountain lee waves. The brightness temperature probability density shows interesting differences between both models. Following, a mountain wave characterization is performed simulating some atmospheric variables (wind direction, wind speed, atmospheric stability, liquid water content and temperature) in several grid points located in the leeward, windward and over the summit of the mountains. The characterization results are compared for both numerical models and a decision tree is developed for each to forecast and warn the mountain lee waves, lenticular clouds and icing events with a 24 to 48 h lead time. These warnings are validated using several skill scores, revealing similar results for both models.This work was partially supported by research projects: PID2019- 105306RB-I00, CGL2016-78702-C2-1-R and CGL2016-78702-C2-2-R (SAFEFLIGHT project), FEI-EU-17-16 and SPESMART AND SPESVALE (ECMWF Special Projects). J. Díaz-Fernández acknowledges the grant supported from the MINECO-FPI program (BES-2017)

Analysis of the October 2014 subtropical cyclone using the WRF and the HARMONIE-AROME numerical models: Assessment against observations

Subtropical cyclones (STCs) are low-pressure systems characterized by having a thermal hybrid structure and sharing tropical and extratropical characteristics. These cyclones are widely studied due to their harmful impacts, in some cases, similar to those caused by hurricanes or tropical storms. From a numerical modeling point of view, they are considered a challenge on account of their rapid intensification. That is the reason why this paper analyzes the simulations of the STC that occurred in October 2014 near the Canary Islands through two highresolution numerical models: Weather Research and Forecasting (WRF) and HARMONIE-AROME. In this study, the simulations obtained with both models of this STC are analyzed versus different observational data. METAR data are used to validate some surface simulated variables throughout the STC life while soundings are chosen to study the tropospheric behavior. Finally, MSG-SEVIRI satellite brightness temperature is used to be compared to those brightness temperatures simulated by both models to give information of the cloud top spatial structure of this atmospheric system. The 2 m temperature, 2 m dew-point temperature, and 10 m wind speed variables do not show significant deviations when carrying out the validation of both models against the available METAR data. It is outstanding the good results found for the HARMONIE-AROME model when analyzing the temperature sounding for both analyzed dates. Additionally, regarding the wind speed sounding, better results are presented in general by the HARMONIE-AROME model, being the WRF model slightly better during the pre-STC stage. Moreover, the skillfulness of the HARMONIE-AROME model is highlighted when simulating the infrared brightness temperature and cloud distribution compared to the WRF model.This work was partially supported by research projects: PID2019- 105306RB-I00, PCIN-2014-013-C07-04, and PCIN2016-080 (UE ERANET Plus NEWA Project), CGL2016-78702-C2-1-R and CGL2016- 78702-C2-2-R (SAFEFLIGHT project), FEI-EU-17-16 and the two ECMWF Special Projects (SPESMART and SPESVALE). JJGA is supported by the FJC2018-035821 grant and JDF acknowledges the grant supported from the MINECO-FPI program (BES-2017)

Wind kinetic energy climatology and effective resolution for the ERA5 reanalysis

Producción CientíficaERA5 represents the state of the art for atmospheric reanalyses and is widely used in meteorological and climatological research. In this work, this dataset is evaluated using the wind kinetic energy spectrum. Seasonal climatologies are generated for 30° latitudinal bands in the Northern Hemisphere (periodic domain) and over the North Atlantic area (limited-area domain). The spectra are also assessed to determine the effective resolution of the reanalysis. The results present notable differences between the latitudinal domains, indicating that ERA5 is properly capturing the synoptic conditions. The seasonal variability is adequate too, being winter the most energetic, and summer the least energetic season. The limited area domain results introduce a larger energy density and range. Despite the good results for the synoptic scales, the reanalysis’ spectra are not able to properly reproduce the dissipation rates at mesoscale. This is a source of uncertainties which needs to be taken into account when using the dataset. Finally, a cyclone tropical transition is presented as a case study. The spectrum generated shows a clear difference in energy density at every wavelength, as expected for a highly-energetic status of the atmosphere.Ministerio de Asuntos Económicos y Transformación Digital y Universidad Complutense de Madrid (projects: (PID2019-105306RB-I00 (IBER - CANES), CGL2016-78702 (SAFEFLIGHT), PCIN-2016-080 and FEI-EU-17-16)Publicación en abierto financiada por el Consorcio de Bibliotecas Universitarias de Castilla y León (BUCLE), con cargo al Programa Operativo 2014ES16RFOP009 FEDER 2014-2020 DE CASTILLA Y LEÓN, Actuación:20007-CL - Apoyo Consorcio BUCL

Aircraft icing: in‐cloud measurements and sensitivity to physical parameterizations

The prediction of supercooled cloud drops in the atmosphere is a basic tool for aviation safety, owing to their contact with and instant freezing on sensitive locations of the aircraft. One of the main disadvantages for predicting atmospheric icing conditions is the acquisition of observational data. In this study, we used in‐cloud microphysics measurements taken during 10 flights of a C‐212 research aircraft under winter conditions, during which we encountered 37 regions containing supercooled liquid water. To investigate the capability of the Weather Research and Forecasting model to detect regions containing supercooled cloud drops, we propose a multiphysics ensemble approach. We used four microphysics and two planetary boundary layer schemes. The Morrison parameterization yielded superior results, whereas the planetary boundary layer schemes were essential in evaluating the presence of liquid water content. The Goddard microphysics scheme best detected the presence of ice water content but tended to underestimate liquid water content.This research was carried out in the framework of the SAFEFLIGHT project, financed by MINECO (CGL2016‐78702) and LE240P18 project (Junta de Castilla y León)

Climatología de ondas de montaña en la Sierra de Guadarrama: caracterización con el modelo meteorológico de alta resolución WRF

Ponencia presentada en: XII Congreso de la Asociación Española de Climatología celebrado en Santiago de Compostela entre el 19 y el 21 de octubre de 2022.[ES]Las ondas de montaña se forman a sotavento de una barrera orográfica y son un tipo de ondas de gravedad a menudo asociadas con fenómenos meteorológicos adversos. Un ejemplo de ellos es la turbulencia, que afecta a la seguridad aérea y ha aparecido en numerosos informes como causa de accidentes aéreos. Por ello, el estudio de las ondas de montaña es un tema importante para prevenir sus efectos en la aviación. En este trabajo se simulan y analizan 68 eventos de ondas de montaña utilizando el modelo numérico de predicción meteorológica de alta resolución Weather Research and Forecasting (WRF). Debido a la frecuencia de estos eventos y al interés socioeconómico, el área de estudio se centra en las inmediaciones del principal aeropuerto de España (Adolfo Suárez Madrid-Barajas). La temperatura de brillo del satélite Meteosat Second Generation ha sido seleccionada como variable observacional para validar las simulaciones de la nubosidad asociada a las ondas de montaña. Se ha comprobado que el WRF es capaz de simular las ondas de montaña incluso sin nubosidad asociada. Además, se ha elaborado una caracterización de los eventos de ondas de montaña en la zona de estudio mediante el análisis de las variables atmosféricas que intervienen en la formación de las ondas de montaña. Los resultados obtenidos muestran diferencias significativas entre los eventos de ondas de montaña con nubosidad asociada y sin ella en las variables de velocidad de viento y de contenido de agua líquida.[EN]Mountain lee waves form in the leeward of an orographic barrier and are a type of gravity wave often associated with adverse meteorological conditions. One example is turbulence, which affects aviation safety and has been reported in several reports as a cause of aircraft accidents. Therefore, the study of mountain lee waves is an important topic in order to prevent their effects on aviation. In this paper, 68 mountain lee wave events are simulated and analyzed using the high-resolution numerical weather prediction model Weather Research and Forecasting (WRF). Due to the frequency of these events and the socio-economic interest, the study area is focused on the vicinity of the main airport in Spain (Adolfo Suárez Madrid-Barajas). The brightness temperature of the Meteosat Second Generation satellite has been selected as an observational data to validate the simulations of the cloudiness associated with mountain lee waves. The results show the ability of WRF to simulate mountain lee waves even without cloudiness associated. In addition, a characterization of mountain lee wave events in the study area has been developed by analyzing the atmospheric variables involved in mountain lee wave formation. The results obtained show significant differences between mountain lee wave events with and without associated cloudiness in the wind speed and liquid water content variables.Este trabajo está respaldado por los siguientes proyectos de investigación: PID2019- 105306RB-I00, CGL2016-78702-C2-1-R y CGL2016-78702-C2-2-R (proyecto SAFEFLIGHT), FEI-EU-17-16 y SPESMART AND SPESVALE (Proyectos Especiales del ECMWF)