Energy Flux and Wavelet Diagnostics of Secondary Mountain Waves

Woods, Bryan; Smith, Ronald B.

doi:10.1175/2009jas3285.1

Cited by 34 publications

(41 citation statements)

References 37 publications

(30 reference statements)

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“…11. The variance wavelet for w 0 and covariance wavelets for p 0 w 0 are computed using the method of Woods and Smith (2010). Figures 10 and 11 show that the w variance is dominated by short waves with l ' 8 km with smaller peaks at intermediate (40 km) and long (80 km) wavelengths.…”

Section: Scale Analysismentioning

confidence: 99%

Stratospheric Gravity Wave Fluxes and Scales during DEEPWAVE

Smith

Nugent

Kruse

et al. 2016

Journal of the Atmospheric Sciences

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101

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During the Deep Propagating Gravity Wave Experiment (DEEPWAVE) project in June and July 2014, the Gulfstream V research aircraft flew 97 legs over the Southern Alps of New Zealand and 150 legs over the Tasman Sea and Southern Ocean, mostly in the low stratosphere at 12.1-km altitude. Improved instrument calibration, redundant sensors, longer flight legs, energy flux estimation, and scale analysis revealed several new gravity wave properties. Over the sea, flight-level wave fluxes mostly fell below the detection threshold. Over terrain, disturbances had characteristic mountain wave attributes of positive vertical energy flux (EF z ), negative zonal momentum flux, and upwind horizontal energy flux. In some cases, the fluxes changed rapidly within an 8-h flight, even though environmental conditions were nearly unchanged. The largest observed zonal momentum and vertical energy fluxes were MF x 5 2550 mPa and EF z 5 22 W m 22 , respectively. A wide variety of disturbance scales were found at flight level over New Zealand. The vertical wind variance at flight level was dominated by short ''fluxless'' waves with wavelengths in the 6-15-km range. Even shorter scales, down to 500 m, were found in wave breaking regions. The wavelength of the flux-carrying mountain waves was much longer-mostly between 60 and 150 km. In the strong cases, however, with EF z . 4 W m 22, the dominant flux wavelength decreased (i.e., ''downshifted'') to an intermediate wavelength between 20 and 60 km. A potential explanation for the rapid flux changes and the scale ''downshifting'' is that low-level flow can shift between ''terrain following'' and ''envelope following'' associated with trapped air in steep New Zealand valleys.

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Section: Scale Analysismentioning

confidence: 99%

Stratospheric Gravity Wave Fluxes and Scales during DEEPWAVE

Smith

Nugent

Kruse

et al. 2016

Journal of the Atmospheric Sciences

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101

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“…The scatter is quite large for both the northern and southern legs, and above 12 km the momentum flux becomes positive. A further discussion of the momentum and energy flux can be found in Smith et al (2008) and Woods and Smith (2010).…”

Section: Vertical Flux Of Horizontal Momentummentioning

confidence: 99%

“…The G-V data were only displayed in this narrow portion of the flight leg so that the characteristics of the long-wavelength primary wave can be distinguished from the short-wavelength waves apparent downstream of the primary wave. The shorter secondary waves may be trapped or downward propagating (e.g., Smith et al 2008;Woods and Smith 2010) and the characteristics of these waves may not be intimately related to the terrain below. In general, the maximum horizontal and vertical velocity magnitude lies close to the diagonal, especially for the weaker cases.…”

Section: E Wave Characteristicsmentioning

confidence: 99%

“…They found up-and downgoing waves and short wavelength trapped waves in one of the T-REX G-V flights. In a followup study, Woods and Smith (2010) discovered collocated long upgoing and short downgoing waves in the stratosphere in at least four cases and in two other cases noted trapped waves along the tropopause inversion layer. We build on these previous studies through exploration of the three-dimensional characteristics of gravity waves generated by the Sierra using analysis of the G-V and UWKA observations along with nonhydrostatic numerical model simulations.…”

Section: Introductionmentioning

confidence: 97%

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Three-Dimensional Characteristics of Stratospheric Mountain Waves during T-REX

Doyle

Jiang

Smith

et al. 2011

Monthly Weather Review

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Measurements from the National Science Foundation/National Center for Atmospheric Research (NSF/ NCAR) Gulfstream V (G-V) obtained during the recent Terrain-Induced Rotor Experiment (T-REX) indicate marked differences in the character of the wave response between repeated flight tracks across the Sierra Nevada, which were separated by a distance of approximately 50 km. Observations from several of the G-V research flights indicate that the vertical velocities in the primary wave exhibited variations up to a factor of 2 between the southern and northern portions of the racetrack flight segments in the lower stratosphere, with the largest amplitude waves most often occurring over the southern flight leg, which has a terrain maximum that is 800 m lower than the northern leg. Multiple racetracks at 11.7-and 13.1-km altitudes indicate that these differences were repeatable, which is suggestive that the deviations were likely due to vertically propagating mountain waves that varied systematically in amplitude rather than associated with transients. The cross-mountain horizontal velocity perturbations are also a maximum above the southern portion of the Sierra Nevada ridge.Real data and idealized nonhydrostatic numerical model simulations are used to test the hypothesis that the observed variability in the wave amplitude and characteristics in the along-barrier direction is a consequence of blocking by the three-dimensional Sierra Nevada and the Coriolis effect. The numerical simulation results suggest that wave launching is sensitive to the overall three-dimensional characteristics of the Sierra Nevada barrier, which has an important impact on the wave amplitude and characteristics in the lower stratosphere. Real-time high-resolution Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS) forecasts successfully capture the along-barrier variations in the wave amplitude (using vertical velocity as a proxy) as well as skillfully distinguishing between large-and small-amplitude stratospheric wave events during T-REX.

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“…The solution is formed by three modes; two are inertio-gravity waves governed by the wave operator in (11). These are secondary waves and have been found in observations (Scavuzzo et al 1998;Woods and Smith 2010). There is a third mode that is a steady geostrophic growing mode (e.g., Pulido and Thuburn 2005).…”

Section: Conceptual Frameworkmentioning

confidence: 65%

A Simple Technique to Infer the Missing Gravity Wave Drag in the Middle Atmosphere Using a General Circulation Model: Potential Vorticity Budget

Pulido

2014

Journal of the Atmospheric Sciences

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A simple technique to infer the missing momentum forcing in a general circulation model is developed and evaluated. The response of the large-scale dynamic equations to an external momentum forcing presents a nonlocal response in the zonal and meridional wind. On the other hand, the response to the external momentum forcing in the potential vorticity (PV) is a local growing geostrophic mode, so that there is a direct relationship between the external momentum forcing and the response in PV. In this work, this fact is exploited to diagnose the missing momentum forcing in the extratropics using a general circulation model. The capability of the simple technique to estimate a concentrated gravity wave forcing is evaluated. A dynamical model is evolved with prescribed sources and sinks of PV and then the technique is used to estimate these known momentum sources and sinks. PV is found to give a much better diagnostic of gravity wave drag compared to the more traditional zonal wind differences. The technique is also used in a realistic environment, in which the sources and sinks of PV in Met Office analyses are determined. The estimation of this missing forcing with this simple technique is compared with the estimation given by a more complex data assimilation technique developed by Pulido and Thuburn and, in general, a good agreement is found. The simple gravity wave drag estimation technique can be used in an online data assimilation cycle, using the increments of the analysis, and also offline, using a general circulation model and observations.

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Energy Flux and Wavelet Diagnostics of Secondary Mountain Waves

Cited by 34 publications

References 37 publications

Stratospheric Gravity Wave Fluxes and Scales during DEEPWAVE

Stratospheric Gravity Wave Fluxes and Scales during DEEPWAVE

Three-Dimensional Characteristics of Stratospheric Mountain Waves during T-REX

A Simple Technique to Infer the Missing Gravity Wave Drag in the Middle Atmosphere Using a General Circulation Model: Potential Vorticity Budget

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