Díaz Fernández, Javier

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First Name
Last Name
Díaz Fernández
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Física de la Tierra y Astrofísica
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Search Results

Now showing 1 - 7 of 7
  • Publication
    Mountain waves analysis in the vicinity of the Madrid-Barajas airport using the WRF model
    (Hindawi Ltd, 2020-12-18) Díaz Fernández, Javier; Quitián Hernández, L.; Bolgiani, Pedro; Santos Muñoz, Daniel; García Gago, Ángel; Fernández González, Sergio; Valero Rodríguez, Francisco; Merino, Andrés; García Ortega, Eduardo; Sánchez, José Luis; Sastre Marugán, Mariano; Martín, María Luisa
    Turbulence and aircraft icing associated with mountain waves are weather phenomena potentially affecting aviation safety. In this paper, these weather phenomena are analysed in the vicinity of the Adolfo Su´arez Madrid-Barajas Airport (Spain). Mountain waves are formed in this area due to the proximity of the Guadarrama mountain range. Twenty different weather research and forecasting (WRF) model configurations are evaluated in an initial analysis. .is shows the incompetence of some experiments to capture the phenomenon. .e two experiments showing the best results are used to simulate thirteen episodes with observed mountain waves. Simulated pseudosatellite images are validated using satellite observations, and an analysis is performed through several skill scores applied to brightness temperature. Few differences are found among the different skill scores. Nevertheless, the .ompson microphysics scheme combined with the Yonsei university PBL scheme shows the best results. .e simulations produced by this scheme are used to evaluate the characteristic variables of the mountain wave episodes at windward and leeward and over the mountain. .e results show that north-northwest wind directions, moderate wind velocities, and neutral or slightly stable conditions are the main features for the episodes evaluated. In addition, a case study is analysed to evidence the WRF ability to properly detect turbulence and icing associated with mountain waves, even when there is no visual evidence available.
  • Publication
    Analysis of the October 2014 subtropical cyclone using the WRF and the HARMONIE-AROME numerical models: Assessment against observations
    (Elsevier Science INC, 2021-10-01) Quitián Hernández, L.; Bolgiani, P.; Santos Muñoz, D.; Sastre Marugán, Mariano; Díaz Fernández, Javier; González Alemán, Juan Jesús; Farrán, J.I.; López, L.; Valero Rodríguez, Francisco; Martín, M.L.
    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.
  • Publication
    Comparison of the WRF and HARMONIE models ability for mountain wave warnings
    (Elsevier, 2021-10-27) Díaz Fernández, Javier; Bolgiani, P.; Santos Muñoz, D.; Quitián Hernández, L.; Sastre Marugán, Mariano; Valero, F.; Farrán, J.I.; González Alemán, J.J.; Martín, M.L.
    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.
  • Publication
    Ability of the WRF-ARW and HARMONIE-AROME models to detect turbulence related to mountain waves over Central Iberia
    (Elsevier, 2022-03-11) Díaz Fernández, Javier; Bolgiani, P.; Sastre Marugán, Mariano; Santos-Muñoz, D.; Valero Rodríguez, Francisco; Farrán, J.I.; Martín, M.L.
    Aircraft turbulence is one of the most dangerous meteorological phenomena that can affect aviation safety. This study is focused on the turbulence associated to mountain lee waves in the vicinity of Adolfo Suárez Madrid-Barajas airport (Spain). Sixty-eight mountain lee waves events are selected to simulate the turbulence with the Weather Research and Forecasting (WRF-ARW) and the HARMONIE-AROME numerical weather prediction models. To study and characterize the turbulence associated, the vertical wind speeds are selected as an important variable and the Eddy Dissipation Rate is estimated. Both models have properly simulated the turbulence and the clear air turbulence, obtaining higher values of turbulence intensity by WRF-ARW than HARMONIE-AROME in the mountain lee waves events. Finally, these results are used to enhance a mountain wave warning decision tree, including the turbulence warning which is validated through several turbulence reports.
  • Publication
    The impact of the summer 2003 heat wave in Iberia: how should we measure it?
    (Springer, 2006-01) Díaz Fernández, Javier; García Herrera, Ricardo; Trigo, R.M.; Linares, C.; Valente, M.A.; De Miguel, J.M.; Hernández, E.
    We present a new approach to improve the reliability of quantifying the impact of a heat wave on mortality rates. We show, for the recent European summer 2003 heat wave, that the use of absolute maximum temperature values, or number of days above a given threshold, can be misleading. Here, we have assessed the impact of the heat wave on Iberian mortality by applying a four step procedure: (1) calculating, for each observatory, the local maximum temperature (T_(max)) distributions, (2) calculating the corresponding 95th percentile values (T_(threshold)), (3) locally defining extremely hot days (EHD) as those days on which the local threshold of the 95th percentile of the series is exceeded, and (4) calculating the total degrees-days (DD) of exceedance, by calculating the difference T_(max)− T_(threshold) and summing these values for all days above T_(threshold). We show that the relationship between summer mortality rates and the DD index is non-linear and can be described by a logarithmic function, with a correlation coefficient of 0.78, which explains 60.6% of the mortality variance (F value of 24.64, significant at P<0.0001). Using maximum temperatures, no significant relationship is found with mortality, whereas the EHD frequency shows a significant association with mortality, albeit weaker than that obtained with DD.
  • Publication
    Wind kinetic energy climatology and effective resolution for the ERA5 reanalysis
    (Springer Nature, 2022-01-29) Bolgiani, Pedro; Calvo Sancho, C.; Díaz Fernández, Javier; Quitián Hernández, Lara; Sastre Marugan, Mariano; Santos Muñoz, D.; Farrán, J. I.; González Alemán, Juan Jesús; Valero Rodríguez, Francisco; Martín, M. L.
    ERA5 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 degrees 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.
  • Publication
    Modelos meteorológicos de alta resolución aplicados a la predicción de ondas de montaña y condiciones de engelamiento para la mejora de la seguridad aérea
    (Universidad Complutense de Madrid, 2022-03-21) Díaz Fernández, Javier; Martín Pérez, María Luisa; Valero Rodríguez, Francisco
    Las ondas de montaña son un tipo de ondas de gravedad que se forman a sotavento de los principales sistemas montañosos en determinadas condiciones. La turbulencia y el engelamiento son fenómenos meteorológicos adversos asociados a este tipo de ondas que pueden comprometer a la seguridad aérea. No en vano, la turbulencia asociada a ondas de montaña y el engelamiento han sido citados como la causa de numerosos accidentes de aviación. Actualmente aún existe bastante incertidumbre en el pronóstico de eventos de ondas de montaña, lo que dificulta la anticipación a los mismos. La disponibilidad de datos observacionales directos es el mayor hándicap en el estudio de las ondas de montaña, ya que es muy difícil obtener mediciones fiables en su zona de formación. Consecuentemente, para el estudio de este fenómeno en esta tesis doctoral se ha utilizado la nubosidad asociada a ondas de montaña como método observacional...