Spectral variability in high frequency in sea level and atmospheric pressure on Buenos Aires Coast, Argentina

Existem evidências observacionais que apoiam a ideia de que as ondas de gravidade atmosféricas são um forçante eficiente para os tsunamis meteorológicos (meteotsunamis) na região da costa da província de Buenos Aires, Argentina. Os meteotsunamis e as ondas de gravidade atmosférica que se propagam simultaneamente na superfície do mar e na atmosfera, respectivamente, são exemplos típicos de sinais geofísicos não estacionários. Neste trabalho investiga-se a variabilidade de meteotsunamis e de ondas de gravidade atmosférica medidas em Mar del Plata. Os resultados obtidos mostram que os ondeletas para os meteotsunamis e as ondas de gravidade são relativamente semelhantes. Isso reforça a ideia da relação causa (ondas de gravidade atmosférica) efeito (meteotsunamis) entre ambos. No entanto, vários episódios muito curtos de moderada a baixa atividade de ondas de gravidade atmosféricas foram detectados sem detectar atividade meteotsunami. Por outro lado, encontrou-se que a energia espectral das ondas de gravidade atmosférica pode aparecer nos ondeletas como uma simples ou múltipla irrupção, como eventos irregulares relativamente longos, ou como pacotes de ondas regulares. Os resultados obtidos neste trabalho proporcionam informação espectral sobre as ondas de gravidade atmosférica na região costeira da província de Buenos Aires. Esta informação poderia ser útil para incluí-la em modelos numéricos realistas, com o objetivo de investigar a gênese desta complexa interação oceano-atmosfera.There are some observational evidences which support that atmospheric gravity waves constitute an efficient forcing for meteorological tsunamis (meteotsunamis) along the coast of Buenos Aires, Argentina. Meteotsunamis and atmospheric gravity waves, which propagate simultaneously on the sea surface and the atmosphere, respectively, are typical examples of non-stationary geophysical signals. The variability of meteotsunamis and atmospheric gravity waves recorded at Mar del Plata was investigated in this paper. Results obtained in this work reinforce the idea of a cause (atmospheric gravity waves) effect (meteotsunami) relationship, because wavelet spectra obtained from both signals resulted quite similar. However, several very short episodes of mod-erate/low activity of atmospheric gravity waves were detected without detecting meteotsunami activity. On the other hand, it was found that atmospheric gravity wave spectral energy can appear in the wavelets as a single or multiple burst as relatively long and irregular events or as regular wave packets. Results obtained in this paper provide original spectral data about atmospheric gravity waves along the coast of Buenos Aires. This information is useful to be included in realistic numerical models in order to investigate the genesis of this complex atmosphere-ocean interaction

Description of atmospheric gravity waves in the Buenos Aires coast, Argentina

En este trabajo se estudiaron las perturbaciones de la presión atmosférica en alta frecuencia (ondas de gravedad atmosféricas, OGA) registradas en Mar del Plata durante 2013. Mediante el análisis realizado con el método espectral wavelets se obtuvo que las duraciones de los lapsos de actividad, la estructura espectral, la intensidad energética y las amplitudes de las OGA son diferentes para cada evento. En general, los eventos activos duran entre 5 y 20 h y las máximas fluctuaciones de presión están comprendidas entre 0.5 y 2 hPa, con periodicidades típicas entre 30 y 150 min. De los 37 casos de OGA detectados se encontró que 24 están asociado a frentes fríos, 9 a frentes cálidos, y 4 están relacionados con otros forzantes sinópticos. Se encontró que la mayoría de los eventos ocurren cuando la zona frontal se ubica al N de la Patagonia y se desplaza hacia el E o NE. Se utilizó el modelo Weather Research and Forecasting (WRF) para simular dos casos. En el primero se observó un frente frío y un ciclón en superficie al S de la provincia de Buenos Aires y sobre el océano mientras que en el segundo, un frente cálido al S de Buenos Aires que luego se desplazó hacia el NO como frente frío. Los resultados obtenidos con el modelo WRF indicarían que la dirección predominante de propagación de OGA en la región costera bonaerense sería hacia el E-NE, discrepando con los escasos antecedentes disponibles para la región que indican que la dirección de propagación sería hacia el ESE-SE.High-frequency perturbations of the atmospheric pressure (atmospheric gravity waves, AGW) measured at Mar del Plata in 2013 are studied in the present paper. Implementing the wavelet spectral method it was obtained that the duration of the active lapses, the spectral structure, the energy and the amplitudes of AGW are different for each event. It was found that, in general, active events last between 5 and 20 h and that the maximum pressure fluctuations range between 0.5 and 2 hPa, with typical oscillations between 30 and 150 min. From the 37 active cases of AGW, it was established that 24 are associated with cold fronts, 9 with warm fronts, and 4 are related to other synoptic systems. It was found that most of the events occur when the frontal zone is located at the northern Patagonia and moves towards the E or NE. The Weather Research and Forecasting (WRF) model was implemented and two cases were simulated. In the first case, a cold front and a cyclone located at the southern Buenos Aires Province and on the ocean were observed. In contrast, in the second case, a warm front was observed at the southern Buenos Aires Province, which then moved towards the NW as a cold front. The results achieved with the WRF model indicate that the predominant direction of propagation in the coastal region of Buenos Aires could be towards E-NE, in disagreement with the available scarce background for the region indicating that the direction of propagation could be towards the ESE-SE.Fil: Perez, Iael. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Dragani, Walter Cesar. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Saucedo, Marcos Adolfo. Ministerio de Defensa. Secretaria de Planeamiento. Servicio Meteorológico Nacional; ArgentinaFil: Godoy, Alejandro Anibal. Ministerio de Defensa. Secretaria de Planeamiento. Servicio Meteorológico Nacional; Argentina. Universidad Nacional de La Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cerne, Silvia Bibiana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos; ArgentinaFil: Martin, Paula Beatriz. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Universidad de Buenos Aires. Facultad de Filosofía y Letras. Departamento de Geografía. Cátedra de Geografía Argentina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Genesis, propagation, and impact of meteorogical tsunamis on the Buenos Aires Province Coast, Argentina

Los tsunamis meteorológicos (meteotsunamis) son oscilaciones forzadas por perturbaciones atmosféricas que se propagan sobre la superficie del mar, con períodos comprendidos entre unos pocos minutos hasta casi 3 h, y alturas típicamente inferiores a 1 m. Los mismos han sido frecuentemente observados en la costa bonaerense entre Mar de Ajó y Necochea. El objetivo de esta Tesis es, por un lado, profundizar el conocimiento sobre la génesis y física de los meteotsunamis y, por el otro, evaluar su posible impacto en la erosión de playas del nordeste bonaerense. Se analizaron series simultáneas en alta resolución (5 min) de niveles del mar y de presión atmosférica para la región costera bonaerense, obtenidas en Mar del Plata durante el 2013. Para ambas series se obtuvieron espectros de energía, wavelets, espectro de coherencia y de diferencia de fase. Se estudiaron eventos energéticos registrados simultáneamente en el mar (meteotsunamis) y en la atmósfera (ondas de gravedad atmosféricas, OGA) y se investigó la génesis y propagación de los meteotsunamis en la costa bonaerense mediante el modelado atmosférico y oceánico. Con el modelo WRF se simularon OGA y éstas se utilizaron como forzante de un modelo oceánico de aguas someras (TAWIC). Los resultados del WRF mostraron que las OGA se propagan preponderantemente desde el SW hacia el NE, con celeridades comprendidas entre 10 y 20 m/s. Se compararon espectralmente los resultados modelados y observados concluyéndose que WRF logra captar la estructura espectral de las OGA. Si bien el WRF también logra captar temporalmente la actividad de las OGA, se obtuvo que el mismo subestima en aproximadamente 2 hPa el pico de la máxima fluctuación atmosférica. El modelo TAWIC reproduce bien la actividad de los meteotsunamis indicando que los mismos se propagan de SW a NE, a lo largo de la costa bonaerense, y que sus amplitudes decaen hacia el mar (“off-shore”). A partir de estas simulaciones se estimó la velocidad de propagación de los meteotsunamis obteniéndose un valor de 10 m/s, aproximadamente. El modelo oceánico también logra captar adecuadamente los lapsos de actividad de los meteotsunamis y es eficiente para reproducir su estructura espectral. Sobre la base de los resultados se concluyó que los meteotsunamis de la costa bonaerense pueden ser descriptos como ondas de borde. Se analizaron posibles mecanismos de amplificación y se concluyó que el más realista es el de resonancia de Greenspan. Finalmente, se implementó el modelo X-BEACH para estudiar el posible impacto de los meteotsunamis sobre playas arenosas en condiciones de tormenta moderada. Se concluyó que los patrones de erosión sobre las playas dependen de la posición del meteotsunami en el ciclo de marea.Meteorological tsunamis (meteotsunamis) are oscillations forced by atmospheric disturbances that propagate over the sea level surface, with periods ranging from a few min to almost 3 h, and heights typically lower than 1 m. They have been frequently observed on the Buenos Aires coast, between Mar de Ajó and Necochea. The aim of this Thesis is, on the one hand, to deepen the knowledge about the genesis and physics of meteotsunamis and, on the other hand, to evaluate its possible impact on the beach erosion, in the Northeast coast of Buenos Aires. Simultaneous high resolution (5 min) data series of sea level and atmospheric pressure obtained in Mar del Plata during 2013 were analyzed. For both series, energy spectra, wavelets, coherence and phase difference spectra were calculated and studied. Energetic events recorded simultaneously for the sea level (meteotsunamis) and for the atmosphere (gravity waves) were investigated. Moreover, the genesis and propagation of meteotsunamis on the Buenos Aires coast was analyzed by means of atmospheric and ocean models. Atmospheric gravity waves (AGW) were simulated using WRF model, and these results were implementing as forcing of a shallow ocean model (TAWIC). The results of the WRF showed that the AGW propagate mainly from SW to NE, with celerities between 10 and 20 m/s. The simulated and observed results were spectrally compared, concluding that WRF achieves to reproduce the spectral structure of the AGW. While WRF is also able to capture temporarily the activity of the AGW, it was obtained that the model underestimates the peak of the maximum atmospheric fluctuation by approximately 2 hPa. The activity of the meteotsunamis is well reproduced by the TAWIC model, and it indicated that meteotsunamis propagate from SW to NE, along the Buenos Aires coast, and their amplitudes decay towards the sea ("off-shore"). From these simulations, the propagation speed of meteotsunamis was estimated, obtaining a value of approximately 10 m/s. The ocean model is also able to reproduce the activity lapses of meteotsunamis and it is efficient to reproduce their spectral structure. Based on the results it was concluded that meteotsunamis of the Buenos Aires coast can be described as edge waves. Possible amplification mechanisms were analyzed and it was determined that the Greenspan resonance is the most realistic. Finally, the X-BEACH model was implemented to study the possible impact of meteotsunamis on sandy beaches in moderate storm conditions. It was concluded that the erosion patterns on the beaches depend on the position of the meteotsunami in the tidal cycle.Fil: Perez, Iael. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentin

Spectral variability in high frequency in sea level and atmospheric pressure on Buenos Aires Coast, Argentina

Abstract There are some observational evidences which support that atmospheric gravity waves constitute an efficient forcing for meteorological tsunamis (meteotsunamis) along the coast of Buenos Aires, Argentina. Meteotsunamis and atmospheric gravity waves, which propagate simultaneously on the sea surface and the atmosphere, respectively, are typical examples of non-stationary geophysical signals. The variability of meteotsunamis and atmospheric gravity waves recorded at Mar del Plata was investigated in this paper. Results obtained in this work reinforce the idea of a cause (atmospheric gravity waves) effect (meteotsunami) relationship, because wavelet spectra obtained from both signals resulted quite similar. However, several very short episodes of mod-erate/low activity of atmospheric gravity waves were detected without detecting meteotsunami activity. On the other hand, it was found that atmospheric gravity wave spectral energy can appear in the wavelets as a single or multiple burst as relatively long and irregular events or as regular wave packets. Results obtained in this paper provide original spectral data about atmospheric gravity waves along the coast of Buenos Aires. This information is useful to be included in realistic numerical models in order to investigate the genesis of this complex atmosphere-ocean interaction

The role of meteorological tsunamis on beach erosion in the Buenos Aires coast: some numerical experiments

Meteorological tsunamis (meteotsunamis) are very similar to ordinary tsunamis but are produced by atmospheric processes. In this work, some numerical experiments are performed using XBeach numerical model investigate the role of moderate meteorological tsunamis on a sandy beach. The model was forced using tide, a moderate storm surge event, wave height data series and a meteorological tsunami event recorded in the Buenos Aires coast, Argentina. Several numerical experiments were carried out considering different time lags between the peak level of the meteotsunami event and the highest sea level (storm surge and tide). In these experiments, the volumes of moved sand were quite similar, although different erosion patterns on the beach were appreciated. Numerical experiments presented in this work constitute the first indication that the occurrence of regular meteotsunamis during moderate storm conditions could change the erosion pattern on sandy beaches in the coast of Buenos Aires.Fil: Alonso, Guadalupe. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Dragani, Walter Cesar. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; ArgentinaFil: Perez, Iael. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Meteotsunamis at the Río de la Plata estuary

A recent numerical study showed that low-amplitude meteotsunamis could be detected at the Río de la Plata (RDP) estuary. In this work, eight sea level series (one year long, 2018) were analyzed: six measured within the RDP estuary and two at the adjacent continental shelf. All meteotsunami events during 2018 were identified and analyzed at the RDP estuary, and the maximum wave height observed was 0.78 m. The atmospheric conditions during the analyzed events were investigated, showing that the presence of atmospheric cold fronts and atmospheric gravity waves seem to happen simultaneously with meteotsunami events. From sea-level observations gathered at the estuary it was inferred that the meteotsunamis could be driven by atmospheric forcings propagating (i) mainly from SE to NW (the meteotsunami would be driven along the estuary from the outer to the upper RDP, and the Proudman resonance mechanism could explain its amplification), (ii) predominantly from SW to NE (the meteotsunami would be simultaneously generated at different locations of the RDP estuary), or (iii) the meteotsunami could be generated in waters of the continental shelf, to get into the RDP estuary, and then freely propagates from the outer to the upper RDP (in this case the Proudman resonance mechanism would not explain the amplification within the estuary). It is important to mention that the results of the present investigation are biased to the high-period band of meteotsunamis because the sampling interval (20 min, for most locations) is rather large to allow the study of the whole meteotsunami frequency band.Fil: Perez, Iael. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; ArgentinaFil: Dragani, Walter Cesar. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Franco-argentino Sobre Estudios del Clima y Sus Impactos.; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; ArgentinaFil: Oreiro, Fernando Ariel. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería; ArgentinaFil: Fiore, Mónica. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería; Argentin

Meteorite impacts in the ocean: the danger of tsunamis on the coast of Buenos Aires Province, Argentina

Comets, meteorites, or asteroids impacting against the Earth are not unusual events. Such impacts on the ocean could produce tsunamis which can reach coastal areas. This paper aimed to analyze the tsunami wave heights on the coast of Buenos Aires Province produced by a meteorite impact in the South Atlantic Ocean. This subject is carried out using a simplified analytical model based on the energy flux conservation. The worst scenario was obtained in the case of the meteorite falling at the deepest continental slope edge, on a transect orientated normally to Mar del Plata coast (around 42° S–54° W). The hazard would quickly decrease if the meteorite impacted farther this location. It was also inferred that, if the meteorite fell on the Patagonian or Brazilian continental shelves, or in the Pacific, Indian or North Atlantic oceans the dangerousness would be drastically reduced. Finally, the possible implementation of this simple analytical model is analyzed in different regions of the World Ocean.Fil: Perez, Iael. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Wörner, Stefania. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Dragani, Walter Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos; ArgentinaFil: Bacino, Guido Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; ArgentinaFil: Medina, Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentin