On the distortions in calculated GW parameters during slanted atmospheric soundings

The significant distortions introduced in the measured atmospheric gravity wavelengths by soundings other than those in vertical and horizontal directions, are discussed as a function of the elevation angle of the sounding path and the gravity wave aspect ratio. Under- or overestimation of real vertical wavelengths during the measurement process depends on the value of these two parameters. The consequences of these distortions on the calculation of the energy and the vertical flux of horizontal momentum are analyzed and discussed in the context of two experimental limb satellite setups: GPS-LEO radio occultations and TIMED/SABER ((Atmosphere using Broadband Emission Radiometry/Thermosphere-Ionosphere-Mesosphere-Energetics and Dynamics)) measurements. Possible discrepancies previously found between the momentum flux calculated from satellite temperature profiles, on site and from model simulations, may to a certain degree be attributed to these distortions. A recalculation of previous momentum flux climatologies based on these considerations seems to be a difficult goal.Fil: de la Torre, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería; ArgentinaFil: Alexander, Pedro Manfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Schmidt, Torsten. German Research Centre for Geosciences; AlemaniaFil: Llamedo Soria, Pablo Martin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería; ArgentinaFil: Hierro, Rodrigo Federico. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Orographic and convective gravity waves above the Alps and Andes mountains during GPS radio occultation events – a case study

The significant distortions introduced in the measured atmospheric gravity wavelengths by soundings other than in vertical and horizontal directions, are discussed as a function of elevation angle of the sounding path and the gravity waves aspect ratio. Under- or overestimation of real vertical wavelengths during the measurement process depends basically on the value of these two parameters. The consequences of these distortions on the calculation of the energy and vertical flux of horizontal momentum are analyzed and discussed in the context of two experimental limb satellite setups: GPS-LEO radio occultations and TIMED/SABER measurements. Possible discrepancies previously found between the momentum flux calculated from satellite temperature profiles, on site and from model simulations, may, to a certain degree, be attributed to these distortions. A recalculation of previous momentum flux climatologies based on these considerations seems to be a difficult goal.Fil: Hierro, Rodrigo Federico. Universidad Austral. Facultad de Ingeniería. Departamento de Ciencias Básicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Steiner, Andrea K.. Universidad de Graz; AustriaFil: de la Torre, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería. Departamento de Ciencias Básicas; ArgentinaFil: Alexander, Pedro Manfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Llamedo Soria, Pablo Martin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería. Departamento de Ciencias Básicas; ArgentinaFil: Cremades, Pablo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; Argentin

Precision estimation in temperature and refractivity profiles retrieved by GPS radio occultations

The Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) is a six-satellite Global Positioning System (GPS) radio occultation (RO) mission that started in April 2006. The close proximity of these satellites during some months after launch provided a unique opportunity to evaluate the precision of GPS RO temperature and refractivity profile retrievals in the neutral atmosphere from nearly collocated and simultaneous observations. In order to work with nearly homogeneous sets, data are divided into five groups according to latitude bands during 20 days of July. For all latitude bands and variables, the best precision values (about 0.1%) are found somewhere between 8 and 25 km height. In general, we find that precision degrades significantly with height above 30 km and its performance becomes there worse than 1%. Temperature precision assessment has been generally excluded in previous studies. Refractivity has here, in general, a precision similar to dry temperature but worse than wet temperature in the lower atmosphere and above 30 km. However, it has been shown that the better performance of wet temperature is an artificial effect produced by the use of the same background information in nearly collocated wet retrievals. Performance in refractivity around 1% is found in the Northern Hemisphere at the lowest heights and significantly worse in the southern polar zone above 30 km. There is no strong dependence of the estimated precision in terms of height on day and night, on latitude, on season, or on the homogeneity degree of each group of profiles. This reinforces the usual claim that GPS RO precision is independent of the atmospheric conditions. The roughly 0.1% precision in the 8–25 km height interval should suffice to distinguish between day and night average values, but no significant differences are found through a Student t test for both populations at all heights in each latitude band. It was then shown that the present spatial density of GPS RO does not allow to analyze smaller latitudinal bands, which could lead to smaller dispersions associated with the day and night means, where it would then be potentially possible to detect significant statistical differences among both categories. We studied the uncertainties associated with the background conditions used in the retrievals and found that their contribution is negligible at all latitudes and heights. However, they force an artificial improvement of wet temperature precision as compared to the dry counterpart at the lowest and highest altitudes studied. In addition, we showed that there is no detectable dubious behavior of COSMIC data prior to day 194 of year 2006 as warned by the data providers, but our result applies only to the precision issue and cannot be extended to other features of data quality. Regarding accuracy, we estimated an average bias of 0.1 K for GPS RO temperature between about 10 and 30 km height and somewhat larger at lower altitudes. We expect a roughly −0.5 K bias above 35 km altitude. Regarding refractivity, a −0.2% bias of the measurements was estimated below about 8 km height.Fil: Alexander, Pedro Manfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: de la Torre, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería; ArgentinaFil: Llamedo Soria, Pablo Martin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería; ArgentinaFil: Hierro, Rodrigo Federico. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería; Argentin

Assessment of precision in ionospheric electron density profiles retrieved by GPS radio occultations

The Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) is a six satellite radio occultation mission that was launched in April 2006. The close proximity of these satellites during some months after launch provides a unique opportunity to evaluate the precision of Global Positioning System (GPS) radio occultation (RO) retrievals of ionospheric electron density from nearly collocated and simultaneous observations. RO data from 30 consecutive days during July and August 2006 are divided into ten groups in terms of daytime or nighttime and latitude. In all cases, the best precision values (about 1%) are found at the F peak height and they slightly degrade upwards. For all daytime groups, it is seen that electron density profiles above about 120 km height exhibit a substantial improvement in precision. Nighttime groups are rather diverse: in particular, the precision becomes better than 10% above different levels between 120 and 200 km height. Our overall results show that up to 100?200 km (depending on each group), the uncertainty associated with the precision is in the order of the measured electron density values. Even worse, the retrieved values tend sometimes to be negative. Although we cannot rely directly on electron density values at these altitudes, the shape of the profiles could be indicative of some ionospheric features (e.g. waves and sporadic E layers). Above 200 km, the profiles of precision are qualitatively quite independent from daytime or latitude. From all the nearly collocated pairs studied, only 49 exhibited a difference between line of sight angles of both RO at the F peak height larger than 10. After analyzing them we find no clear indications of a significant representativeness error in electron density profiles due to the spherical assumption above 120 km height. Differences in precision between setting and rising GPS RO may be attributed to the modification of the processing algorithms applied to rising cases during the initial period of the COSMIC mission.Fil: Alexander, Pedro Manfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: de la Torre, Alejandro. Universidad Austral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Hierro, Rodrigo Federico. Universidad Austral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Llamedo Soria, Pablo Martin. Universidad Austral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Oscillation modes of humidity over the Amazon basin derived from GPS RO profiles

The Global Positioning System radio occultation (GPS RO) technique provides vertical profiles of refractivity from which water vapor can be derived. It is possible to reproduce global, synoptic, and regional climatological patterns. From Formosa Satellite 3/Constellation Observing System for Meteorology Ionosphere and Climate mission data (2006?2013), the variability of the moistest region of Southern Hemisphere as the Amazon basin is analyzed. Applying different spatial and temporal filters, oscillation modes of the integrated specific humidity (Q) are found. A slight decreasing trend in Q is found during the studied period. Zonal variability of this variable averagedin time between Amazon basin latitudes presents a main mode of oscillation of a wavelength of one quarter of the Earth (T4). A secondary mode of wavelength at around T6 wavelength is also found after high-pass filtering the original signal. In turn, temporal variability averaged over Amazon basin latitudes shows a wavelength at around 12 months, while secondary modes of 6 months are found.Fil: Hierro, Rodrigo Federico. Universidad Austral; Argentina;Fil: Llamedo Soria, Pablo Martin. Universidad Austral; Argentina;Fil: de la Torre, Alejandro. Universidad Austral; Argentina;Fil: Alexander, Pedro Manfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires; Argentina

The Amazon basin as a moisture source for an Atlantic Walker-type Circulation

The Amazon basin constitutes the most developed rainforest in the world, accounting for 15-20% of the global freshwater input into the oceans. The low level flow over this region is climatologically dominated by the Atlantic anticycslone and the trade winds. This yields an incoming oceanic moist air to the continent from the East, which is forced to lift up over the Andes range at the West. The confluence of the entrance of humidity, heat, evaporation and strong rainfall results in an accumulation of water vapor in this region. There is a statistically significant surplus of humidity over land as compared to over ocean (the largest difference is found during austral summer). This turns the Amazon basin into one of the most important heat sources for the tropical atmosphere, feeding a global pattern like the Atlantic Walker-type circulation, where the ascent stage is not over ocean but over land. The Global Positioning System radio occultation data show to be an excellent tool to observe the accumulated water vapor above the Amazon basin.Fil: Hierro, Rodrigo Federico. Universidad Austral. Facultad de Ingeniería. Laboratorio de Investigación Desarrollo y Transferencia - Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Laboratorio de Investigación Desarrollo y Transferencia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Llamedo Soria, Pablo Martin. Universidad Austral. Facultad de Ingeniería. Laboratorio de Investigación Desarrollo y Transferencia - Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Laboratorio de Investigación Desarrollo y Transferencia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: de la Torre, Alejandro. Universidad Austral. Facultad de Ingeniería. Laboratorio de Investigación Desarrollo y Transferencia - Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Laboratorio de Investigación Desarrollo y Transferencia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alexander, Pedro Manfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin

Some recent applications of radio occultationtechnique in atmospheric proceses

En los últimos años, el uso del principio de radio ocultamiento (RO) satelital para observar la atmósfera terrestre y el clima aprovecha los ocultamientos bajo el horizonte del sol, de la luna, de las estrellas y principalmente de satélites artificiales de baja altura (LEO). En este último caso, se utilizan señales cruzadas entre satélites LEO y satélites de gran altura GPS. La aplicación de la técnica de RO usando transmisores del sistema de GPS en órbitas altas y receptores a bordo de satélites de baja órbita, ha provisto perfiles de refractividad atmosférica muy precisos. La idea básica de un RO es observar como las ondas de radio emitidas por los GPS se propagan en la atmósfera. La trayectoria del rayo asociado a una onda de radio entre un LEO y un satélite GPS, mientras se están ocultando mutuamente por interponerse la Tierra entre ambos, atraviesa la atmósfera desviándose debido a gradientes de refractividad. El ángulo de desviación del rayo se obtiene a partir de un cambio en el retraso de la fase (corrimiento Doppler) de la señal GPS recibida por el LEO. Suponiendo simetría esférica, la información de la desviación puede ser invertida mediante una transformación de Abel, y así obtener un perfil vertical del índice de refracción. A partir de perfiles atmosféricos verticales de refractividad y de un modelo atmosférico, se obtienen diversos parámetros indirectamente: desde temperatura (T), presión, altura geopotencial y vapor de agua, hasta especies minoritarias como aerosoles, agua líquida de las nubes y densidad electrónica ionosférica. La enorme ventaja ofrecida por la cobertura en todo el planeta, tanto sobre los territorios continentales como oceánicos, la resolución en T menor que 1 K, la estabilidad a largo plazo y fundamentalmente la ausencia de cualquier limitación impuesta por posibles condiciones climáticas, hace a la técnica de RO GPS única dentro de los diferentes sistemas de sensado remoto de la atmósfera. Hasta la actualidad ha sido obtenida y procesada una base de datos con varios cientos de miles de sondeos de este tipo, recogidos por los primeros satélites LEO y posteriores (SAC-C, CHAMP, GRACE, COSMIC, TerraSAR-X, MetOp). En el presente trabajo, se mostrarán ejemplos de resultados, a escala global y regional de la distribución de vapor de agua y de energía asociada a ondas atmosféricas, mediante datos de RO GPS. Se pondrá especial énfasis sobre las regiones montañosas de la cordillera de los Andes a latitudes medias y de la península antártica, para lo cual se analizarán individualmente eventos de RO de interés, a partir de las excepcionales características observables de OIG en dicha región. Dicho análisis será complementado con simulaciones numéricas con el modelo de mesoescala WRF, versión 3.2. y con perfiles de T de RO disponibles en las regiones de interés. En particular, se mostrará: i) la distribución espacial de ondas internas de gravedad (OIG) estacionarias, ii) su propagación en las atmósferas baja y media y iii) la posible importancia relativa de las ondas de montaña como mecanismo de detonación de procesos de convección profunda con generación de granizo.In the last years, the use of radio occultation (RO) technique to observe the terrestrial atmosphere and the climate takes advantage of the occultation of the Sun, the Moon, the stars and principally of artificial satellites of low height (LEO). In the latter case, crossed signs between LEO and GPS satellites are used. The application of RO's technology using transmitters of the GPS system in high orbits and recipients on board of low orbit satellites, has provided profiles of atmospheric refractivity very precise. The basic idea of a RO is to observe how waves emitted by a GPS are propagated in the atmosphere. The ray trajectory associated to a radio wave between a GPS and a LEO, while these are hiding themselves mutually due to the interposition of the Earth, is deviated due to refractivity gradients. The ray bending angle is obtained from a change in the phase (Doppler shift) of the signal received by the LEO. Assuming spherical symmetry, the deviation information may be inverted by an Abel transformation to obtain a vertical profile of the index of refraction. From atmospheric profiles of refractivity and an atmospheric model, several parameters are obtained: from temperature (T), pressure, geopotential height and water vapor to minor species as aerosols, cloud liquid water and ionospheric electron density. The enormous advantage offered by the coverage in the whole planet, above the continental and oceanic territories, the 1K T resolution, the long term stability and mainly the absence of any restriction imposed by climatic conditions, makes the GPS RO technique unique among different remote sensing atmospheric systems. Up to now, hundreds of thousands of soundings have been processed, from the first satellites to recent (SAC-C, CHAMP, GRACE, COSMIC, TerraSAR-X, MetOp). In the present work, examples of global and regional water vapor and atmospheric wave energy distributions will be shown. It will be put on special emphasis on the mountainous regions of the Andes Range at middle latitudes and the Antarctic Peninsula and case studies will be analyzed. This analysis will be complemented by WRF model simulations and with measured T profiles in the regions of interest. In particular it will be shown: i) the spatial distribution of stationary gravity waves, ii) their propagation in the lower and middle atmospheres, and iii) the possible relevance of mountain waves as a triggering mechanism of seep convection processes with hail production. Key words: satellite radio occultation, gravity waves.Fil: de la Torre, Alejandro. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Provincia de Mendoza. Subsecretaría de Agricultura; ArgentinaFil: Alexander, Pedro Manfredo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Llamedo Soria, Pablo Martin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería; ArgentinaFil: Hierro, Rodrigo Federico. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pessano, Horacio. Provincia de Mendoza. Subsecretaría de Agricultura; Argentina. Universidad Tecnologica Nacional; ArgentinaFil: Odiard, Andrés. Provincia de Mendoza. Subsecretaría de Agricultura; Argentin

The influence of topography on vertical velocity of air in relation to severe storms near the Southern Andes Mountains

On the basis of 180 storms which took place between 2004 and 2011 over the province of Mendoza (Argentina) near to the Andes Range at southern mid-latitudes, we consider those registered in the northern and central crop areas (oases). The regions affected by these storms are currently protected by an operational hail mitigation project. Differences with previously reported storms detected in the southern oasis are highlighted. Mendoza is a semiarid region situated roughly between 32S and 37S at the east of the highest Andes top. It forms a natural laboratory where different sources of gravity waves, mainly mountain waves, occur. In this work, we analyze the effects of flow over topography generating mountain waves and favoring deep convection. The joint occurrence of storms with hail production and mountain waves is determined from mesoscale numerical simulations, radar and radiosounding data. In particular, two case studies that properly represent diverse structures observed in the region are considered in detail. A continuous wavelet transform is applied to each variable and profile to detect the main oscillation modes present. Simulated temperature profiles are validated and compared with radiosounding data. Each first radar echo, time and location are determined. The necessary energy to lift a parcel to its level of free convection is tested from the Convective Available Potential Energy and Convection Inhibition. This last parameter is compared against the mountain waves' vertical kinetic energy. The time evolution and vertical structure of vertical velocity and equivalent potential temperature suggest in both cases that the detected mountain wave amplitudes are able to provide the necessary energy to lift the air parcel and trigger convection. A simple conceptual scheme linking the dynamical factors taking place before and during storm development is proposed.Fil: de la Torre, Alejandro. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pessano, H.. Universidad Tecnologica Nacional. Facultad Regional San Rafael; ArgentinaFil: Hierro, Rodrigo Federico. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Santos, J. R.. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Llamedo Soria, Pablo Martin. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alexander, Pedro Manfredo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Comparison between GNSS ground-based and GPS radio occultation precipitable water observations over ocean-dominated regions

Precipitable water (PW) inferred from GPS (Global Positioning System) radio occultation (RO) and ground-based (GB) Global Navigation Satellite System (GNSS) observations are compared between years 2007 and 2014. As previous studies were mainly performed over continental areas we now focus over ocean-dominated geographical areas. Our analysis is done in order to find out how the reliability level of RO results over oceanic areas compares to land. As RO soundings usually miss some information close to the ground, we also assess different methods to complete the lacking data. We found 47 terrestrial stations that lie in islands small and far away from continental areas where the weather might be governed by the sea conditions. From comparisons of almost 5000 collocated samples, PW from RO and GB exhibit a global mean difference around 1 mm, root-mean-square deviation about 5 mm and a correlation above 0.9. The 2007–2014 timeseries and the monthly mean RO and GB PW were also compared to reanalyses per hemisphere, latitude regions and oceans. In each zone it was found that PW from RO, GB and reanalyses all exhibit in general consistent seasonal qualitative behavior. However, quantitative differences exist between reanalyses on one side and RO and GB on the other side. It is shown that PW from reanalyses lacks reliability in areas where the island topography is poorly represented by them. We also conclude that RO and GB seem to be more sensitive for the detection of features that depart from the regular annual cycle.Fil: Burgos Fonseca, Yuditsabet. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Alexander, Pedro Manfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: de la Torre, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería; ArgentinaFil: Hierro, Rodrigo Federico. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Austral. Facultad de Ingeniería; ArgentinaFil: Llamedo Soria, Pablo Martin. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Calori, Andrea Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Cuyo. Facultad de Ingeniería; Argentin

Large-amplitude gravity waves above the southern Andes, the Drake Passage, and the Antarctic Peninsula

Above the southern Andes range and its prolongation in the Antarctic Peninsula, large-amplitude mountain and shear gravity waves observed with Weather Research and Forecasting (WRF) mesoscale model simulations during winter 2009 are analyzed. Two specific reasons motivated this study: (1) a decade of satellite observations of temperature fluctuations in the stratosphere, allowing us to infer that this region may be launching the largest-amplitude gravity waves into the upper atmosphere, and (2) the recent design of a research program to investigate these features in detail, the Southern Andes Antarctic Gravity wave Initiative (SAANGRIA). The simulations are forced with ERA-Interim data from the European Centre for Medium-Range Weather Forecasts. The approach selected for the regional downscaling is based on consecutive integrations with weekly reinitialization with 24 h of spin-up, and the outputs during this period are excluded from the analysis. From 1 June to 31 August 2009, five case studies were selected on the basis of their outstanding characteristics and large wave amplitudes. In general, one or two prevailing modes of oscillation are identified after applying continuous wavelet transforms at constant pressure levels and perpendicularly to the nominal orientation of the dominant wave crests. In all cases, the dominant modes are characterized by horizontal wavelengths around 50 km. Their vertical wavelengths, depending on a usually strong background wind shear, are estimated to be between 2 and 11 km. The corresponding intrinsic periods range between 10 and 140 min. In general, the estimated vertical wavelength (intrinsic period) maximizes (minimizes) around 250–300 hPa. The synoptic circulation for each case is described. Zonal and meridional components of the vertical flux of horizontal momentum are shown in detail for each case, including possible horizontal wavelengths between 12 and 400 km. Large values of this flux are observed at higher pressure levels, decreasing with increasing height after a progressive deposition of momentum by different mechanisms. As expected, in the wintertime upper troposphere and lower stratosphere in this region, a prevailing zonal component is negative almost everywhere, with the exception of one case above the northern tip of the Antarctic Peninsula. A comparison with previous experimental results reported in the region from in situ and remote sensing measurements suggests a good agreement with the momentum flux profiles computed from the simulations. Partial wave reflection near the tropopause was found, as considerable departures from equipartition between potential and kinetic wave energy are obtained in all cases and at all pressure levels. This ratio was always less than 1 below the lower stratosphere.Fil: de la Torre, Alejandro. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alexander, Pedro Manfredo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Hierro, Rodrigo Federico. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Llamedo Soria, Pablo Martin. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rolla, Alfredo Luis. Universidad Austral. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Schmidt, T.. Helmholtz Centre Potsdam; AlemaniaFil: Wickert, J.. Helmholtz Centre Potsdam; Alemani