High gravity‐wave activity observed in Patagonia, Southern America: generation by a cyclone passage over the Andes mountain range

Pulido, Manuel; Rodas, Claudio José Francisco; Dechat, Diego; Lucini, María Magdalena

doi:10.1002/qj.1983

Cited by 11 publications

(9 citation statements)

References 37 publications

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“…In addition to a discussion of the available sources, regarding GW propagation it must be kept in mind that in the region considered, upward and downward GWs are expected to be strongly deviated by vertical and horizontal (poleward) refraction in the presence of the jet (Jiang et al, 2013;Pulido et al, 2012).…”

Section: Satellite Data Analysismentioning

confidence: 99%

11 Years of Rayleigh Lidar Observations of Gravity Wave Activity Above the Southern Tip of South America

et al. 2019

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Gravity wave (GW) activity is analyzed using temperature (T) data retrieved from a Rayleigh light detection and ranging (lidar) at Río Gallegos, Argentina (51.6°S, 69.3°W). GW characteristics are derived from 302 nights of observations providing more than 1,018 hr of high‐resolution lidar data between 20‐ and 56‐km height from August 2005 to December 2015. T measurements are performed by a Differential Absorption Lidar instrument. This lidar was the southernmost outside Antarctica until the end of 2017. Río Gallegos is an exceptional place to observe large amplitude GW. Every lidar measurement is classified according to its relative position to the polar vortex. The lidar measurements are compared with collocated Sounding of the Atmosphere using Broadband Emission Radiometry and Global Positioning System‐Radio Occultation data. The different instruments show different windows of the GW spectrum, providing complementary observations. In general, the geometric mean of the specific GW potential energy (PE) is larger during winter and spring than during summer and autumn. The largest geometric mean of PE is found inside the vortex and decreases monotonically at its edge, outside it and when there is no vortex. The same behavior is observed with satellite data. On average, it can be seen that lidar observations provide larger PE values than limb sounding measurements. From a Morlet continuous wavelet transform analysis, three distinct modes are captured from Sounding of the Atmosphere using Broadband Emission Radiometry and from Global Positioning System‐Radio Occultation data at the upper and lower stratosphere, respectively. In particular, a systematic 3.5‐ to 4‐year oscillation, possibly related to El Niño–Southern Oscillation is observed.

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Section: Satellite Data Analysismentioning

confidence: 99%

11 Years of Rayleigh Lidar Observations of Gravity Wave Activity Above the Southern Tip of South America

et al. 2019

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“…One particularly striking feature is the presence of a global maximum in gravity-wave momentum flux, extending eastwards for several thousand kilometres at ∼ 60 • S from the Drake Passage during the Southern Hemisphere winter (e.g. Spiga et al, 2008;Ern et al, 2011;de la Torre et al, 2012;Pulido et al, 2013). Recent studies (Sato et al, 2012;Jiang et al, 2013Jiang et al, , 2014 suggest that horizontal propagation of mountain waves generated by remote mountain sources such as the southern Andes and Antarctic Peninsula may contribute significantly to this maximum.…”

Section: Introductionmentioning

confidence: 99%

Mountain waves and wakes generated by South Georgia: implications for drag parametrization

Vosper

2015

Quart J Royal Meteoro Soc

113

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This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland.High-resolution simulations of flows over South Georgia (South Atlantic) are used to increase understanding of the likely influence of small isolated mountainous islands on the large-scale flow and to ascertain the extent to which parametrization schemes can account for the missing drag in models where such islands are only partially resolved. Long-duration (1 month) austral winter forecasts with a horizontal grid spacing of 1.5 km are used to quantify the mountain-wave momentum fluxes generated by the island and the low-level drag associated with flow-blocking dynamics. The characteristics of the drag, such as the occurrence of high and low drag states, its dependence on wind direction and the spectral contributions to the mountain-wave momentum flux, are considered. Flow splitting and low-level wave breaking are shown to be responsible for wake regions that extend for hundreds of kilometres from the island. Regions of deceleration are also evident in the stratosphere, due to mountain-wave dissipation. The extent to which an orographic drag parametrization scheme can reproduce the drag is investigated by comparison with coarse-resolution (15 km grid spacing) simulations in which the orography is poorly resolved and a large proportion of the drag is parametrized. It is demonstrated that the total of the resolved plus parametrized drag in these simulations closely resembles that at high resolution, although it is underpredicted during instances of high drag. Simple modifications to the scheme, which enhance the drag when the low-level flow is approximately normal to the major axis of the subgrid orography, are shown to rectify this. The study demonstrates that, at least for relatively simple isolated mountain ranges, the drag and mountain-wave momentum fluxes can be predicted in a deterministic sense by a well-tuned parametrization scheme of suitable complexity, although inclusion of stochastic effects might lead to yet further improvements.

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“…Alexander et al 2008Alexander et al , 2010. Further observational evidence in Patagonia also showed the presence of high-amplitude gravity waves generated from the Andes mountain range with 240 km of zonal wavelength and an intrinsic frequency of f /Ω ≈ 0.3 (Pulido et al 2013) so that the waves found in the Patagonia region and the Antarctic peninsula propagate very long distances and are affected significantly by rotation effects. Apart from orographic forcing, other significant sources of inertio-gravity waves are fronts and jets in middle latitudes (O 'Sullivan & Dunkerton 1995;Zhang 2004) and deep convection in the tropics (Lane, Reeder & Clark 2001).…”

mentioning

confidence: 94%

“…In this work, we have achieved a generalization to the full frequency range of gravity waves with respect to a previous work (Pulido & Rodas 2008), a necessary step towards our main aim, which is the development of a gravity wave parametrization for atmospheric models based on the Gaussian beam approximation. This approximation applied to inertio-gravity waves may account for the long horizontal propagation found for inertio-gravity waves observed in high latitudes and in particular in South America (Dunkerton 1984;Sato et al 2012;Pulido et al 2013). An important further step in the development of such a gravity wave parametrization based on the Gaussian beam formulation is the consideration of time-dependent and horizontally varying background winds, effects that can give more realistic momentum depositions (Dunkerton & Butchart 1984;Senf & Achatz 2011).…”

mentioning

confidence: 99%

The breaking of transient inertio-gravity waves in a shear flow using the Gaussian beam approximation

Rodas

Pulido

2014

J. Fluid Mech.

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The propagation of transient inertio-gravity waves in a shear flow is examined using the Gaussian beam formulation. This formulation assumes Gaussian wavepackets in the spectral space and uses a second-order Taylor expansion of the phase of the wave field. In this sense, the Gaussian beam formulation is also an asymptotic approximation like spatial ray tracing; however, the first one is free of the singularities found in spatial ray tracing at caustics. Therefore, the Gaussian beam formulation permits the examination of the evolution of transient inertio-gravity wavepackets from the initial time up to the destabilization of the flow close to the critical levels. We show that the transience favours the development of the dynamical instability relative to the convective instability. In particular, there is a well-defined threshold for which small initial amplitude transient inertio-gravity waves never reach the convective instability criterion. This threshold does not exist for steady-state inertio-gravity waves for which the wave amplitude increases indefinitely towards the critical level. The Gaussian beam formulation is shown to be a powerful tool to treat analytically several aspects of inertio-gravity waves in simple shear flows. In more realistic shear flows, its numerical implementation is readily available and the required numerical calculations have a low computational cost.

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High gravity‐wave activity observed in Patagonia, Southern America: generation by a cyclone passage over the Andes mountain range

Cited by 11 publications

References 37 publications

11 Years of Rayleigh Lidar Observations of Gravity Wave Activity Above the Southern Tip of South America

11 Years of Rayleigh Lidar Observations of Gravity Wave Activity Above the Southern Tip of South America

Mountain waves and wakes generated by South Georgia: implications for drag parametrization

The breaking of transient inertio-gravity waves in a shear flow using the Gaussian beam approximation

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