Person:
González Alemán, Juan Jesús

First Name

Juan Jesús

Last Name

González Alemán

URI

https://hdl.handle.net/20.500.14352/87048

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Físicas

Department

Física de la Tierra y Astrofísica

Area

Física de la Tierra

Identifiers

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Now showing 1 - 8 of 8

Analysis of the October 2014 subtropical cyclone using the WRF and the HARMONIE-AROME numerical models: Assessment against observations
(Atmospheric research, 2021) 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.
Comparison of the WRF and HARMONIE models ability for mountain wave warnings
(Atmospheric research, 2021) Díaz Fernández, Javier; Bolgiani, P.; Santos Muñoz, D.; Quitián Hernández, L.; Sastre Marugán, Mariano; Valero, F.; Farrán, J.I.; González Alemán, Juan Jesús; 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.
On the atmospheric conditions leading to mountain lee waves in central Iberia under CMIP6 projections
(Atmosphere, 2024) Díaz Fernández, Javier; Calvo-Sancho, Carlos; Bolgiani, Pedro Mariano; González Alemán, Juan Jesús; Farrán, José Ignacio; Sastre Marugán, Mariano; Martín, M.L.
Mountain lee waves present significant hazards to aviation, often inducing turbulence and aircraft icing. The current study focuses on understanding the potential impact of global climate change on the precursor environments to mountain lee wave cloud episodes over central Iberia. We examine the suitability of several Global Climate Models (GCMs) from CMIP6 in predicting these environments using the ERA5 reanalysis as a benchmark for performance. The dataset is divided into two periods: historical data (2001–2014) and projections for the SSP5–8.5 future climate scenario (2015–2100). The variations and trends in precursor environments between historical data and future climate scenarios are exposed, with a particular focus on the expansion of the Azores High towards the Iberian Peninsula, resulting in increased zonal winds throughout the Iberian Peninsula in the future. However, the increase in zonal wind is insufficient to modify the wind pattern, so future mountain lee wave cloud events will not vary significantly. The relative humidity trends reveal no significant changes. Moreover, the risk of icing precursor environments connected with mountain lee wave clouds is expected to decrease in the future, due to rising temperatures. Our results highlight that the EC-EARTH3 GCM reveals the closest alignment with ERA5 data, and statistically significant differences between the historical and future climate scenario periods are presented, making ECEARTH3 a robust candidate for conducting future studies on the precursor environments to mountain lee wave cloud events.
On the impact of initial conditions in the forecast of Hurricane Leslie extratropical transition
(Atmospheric Research, 2023) López Reyes, Mauricio; González Alemán, Juan Jesús; Sastre Marugán, Mariano; Insua Costa, Damián; Bolgiani, Pedro Mariano; Martín, M.L.
Hurricane Leslie (2018) was a non-tropical system that lasted for a long time undergoing several transitions between tropical and extratropical states. Its trajectory was highly uncertain and difficult to predict. Here the extratropical transition of Leslie is simulated using the Model for Prediction Across Scales (MPAS) with two different sets of initial conditions (IC): the operational analysis of the Integrate Forecast System (IFS) and the Global Forecast System (GFS). Discrepancies in Leslie position are found in the IC patterns, and in the intensity and amplitude of the dorsaltrough system in which Leslie is found. Differences are identified both in the geopotential height at 300 hPa and the geopotential thickness. Potential temperature in the dynamic tropopause shows a broader, more intense trough displaced western when using the IC-IFS. The IC-IFS simulation shows lesser trajectory errors but wind speed overestimation than the IC-GFS one. The complex situation of the extratropical transition, where Leslie interacts with a trough, increases the uncertainty associated with the intensification process. The disparities observed in the simulations are attributed to inaccuracies in generating the ICs. Both ICs generate different atmospheric configurations when propagated in time. Results suggest that during an extratropical transition in a highly baroclinic atmosphere, the IFS model’s data assimilation method produced a more precise analysis than GFS due to the greater number of observations assimilated by the IFS, the greater spatial resolution of the model and the continuous adjustment of the simulations with the field of observations.
Major role of marine heatwave and anthropogenic climate change on a giant hail event in Spain
(Geophysical Research Letters, 2024) Martín, M.L.; Calvo-Sancho, Carlos; Taszarek, M.; González Alemán, Juan Jesús; Montoro-Mendoza, Ana; Díaz Fernández, Javier; Bolgiani, Pedro Mariano; Sastre Marugán, Mariano; Martín, Yago
A severe hailstorm that occurred in Spain on 30 August 2022, caused material and human damage, including one fatality due to giant hailstones up to 12 cm in diameter. By applying a pseudo‐global warming approach, here we evaluate how a simultaneous marine heatwave (and anthropogenic climate change) affected a unique environment conductive to such giant hailstones. The main results show that the supercell development was influenced by an unprecedented amount of convective available energy, with significant contributions from thermodynamic factors. Numerical simulations where the marine heatwave is not present show a notable reduction in the hail‐favorable environments, related mainly to modifications in thermodynamic environment. Our simulations also indicate that the environment in a preindustrial‐like climate would be less favorable for convective hazards and thus the hailstorm event would likely not have been as severe as the observed one, being possible to perform a novel attribution of such kind.
Horizontal kinetic energy analysis of tropical transition simulations with the WRF and HARMONIE-AROME models
(Quarterly Journal of the Royal Meteorological Society, 2023) Calvo Sancho, Carlos; Bolgiani, Pedro Mariano; Subías, Álvaro; Sastre Marugán, Mariano; González Alemán, Juan Jesús; Martín, M.L.
Four tropical transition (TT) events in the North Atlantic basin are simulated with the Weather Research and Forecasting (WRF) and the HARMONIE-AROME (HAR) models to study the main features of the horizontal kinetic energy (HKE) spectra of these kinds of high-energetic atmospheric system. Though most of the times similar results are obtained with both models, HAR shows a more intense filtering and numerical dissipation, whereas WRF tends to represent overenergized spectra in the synoptic scale and especially at smaller wavelengths. Predictability is dissimilar for the four TTs studied due to the different spectral curve slope obtained for each case, ranging from unlimited to very poor predictability at synoptic scale. Additionally, an increased HKE is presented in the middle–upper troposphere spectra. A deep analysis of the different terms involved in the equation of the spectral energy budget is presented through a detailed study of one of these TTs. The role of all of them is studied, connecting the energy spectra and the meteorological processes involved. The energy budget terms related to the nonlinear spectral transfer, the three-dimensional divergence, and diabatic process tendencies are identified as the key ones, whereas the potential and kinetic conversion terms and the vertical flux HKE and pressure divergence terms play a secondary role on modulating the spectrum behaviour. The major energetic contributions are found at the synoptic scale, but results show that a two-dimensional energy cascade does not fully capture the whole spectrum of a TT. The role of convection, latent heat release, and moist convection outbursts is sketched and a link within different vertical levels is found. Results show that a high-energetic system, such as a TT, can effectively alter the atmospheric energy behaviour.
Supercell convective environments in Spain based on ERA5: hail and non-hail differences
(Weather and Climate Dynamics, 2022) Calvo Sancho, Carlos; Díaz Fernández, Javier; Martín, Yago; Bolgiani, Pedro Mariano; Sastre Marugán, Mariano; González Alemán, Juan Jesús; Santos Muñoz, Daniel; Farrán, José Ignacio; Martín, M.L.
Severe convective storms, in particular supercells, are occasionally responsible for a large number of property losses and damage in Spain. This paper aims to study the synoptic configurations and pre-convective environments in a dataset of 262 supercells during 2011–2020 in Spain. The events are grouped into supercells with hail (diameter larger than 5 cm) and without hail and the results are compared. ERA5 reanalysis is used to study the synoptic configurations and proximity atmospheric profiles related to the supercell events at the initial time. In addition, temperature, convective available potential energy, convective inhibition, lifting condensation level, level of free convection, height of freezing level, wind shear and storm-relative helicity are obtained for each event. Results show that supercells are more frequent on the Mediterranean coast during the warm season. Some of the variables analyzed present statistically significant differences between hail and non-hail events. In particular, supercells with hail are characterized by higher median values of most-unstable convective available potential energy than supercells without hail.
Subtropical Cyclone Formation via Warm Seclusion Development: The Importance of Surface Fluxes
(Journal of geophysical research-atmospheres, 2020) Quitián Hernández, L.; González Alemán, Juan Jesús; Santos Muñoz, D.; Fernández González, S.; Valero Rodríguez, Francisco; Martín, M.L.
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.