Small‐scale orographic gravity wave drag in stable boundary layers and its impact on synoptic systems and near‐surface meteorology

Tsiringakis, Aristofanis; Steeneveld, G.J.; Holtslag, A.A.M.

doi:10.1002/qj.3021

Cited by 30 publications

(31 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the SBL, IGW may transport momentum between small-scale terrain and the lowermost critical level [195]. The related wave drag can be of the same amplitude of, or even larger than, the turbulent drag [196][197][198]; it has a significant impact on the SBL dynamics, but it can also affect larger scales of motion [199].…”

Section: The Role Of Gravity Wavesmentioning

confidence: 99%

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

et al. 2018

View full text Add to dashboard Cite

Abstract:The exchange of heat, momentum, and mass in the atmosphere over mountainous terrain is controlled by synoptic-scale dynamics, thermally driven mesoscale circulations, and turbulence. This article reviews the key challenges relevant to the understanding of exchange processes in the mountain boundary layer and outlines possible research priorities for the future. The review describes the limitations of the experimental study of turbulent exchange over complex terrain, the impact of slope and valley breezes on the structure of the convective boundary layer, and the role of intermittent mixing and wave-turbulence interaction in the stable boundary layer. The interplay between exchange processes at different spatial scales is discussed in depth, emphasizing the role of elevated and ground-based stable layers in controlling multi-scale interactions in the atmosphere over and near mountains. Implications of the current understanding of exchange processes over mountains towards the improvement of numerical weather prediction and climate models are discussed, considering in particular the representation of surface boundary conditions, the parameterization of sub-grid-scale exchange, and the development of stochastic perturbation schemes.

show abstract

Section: The Role Of Gravity Wavesmentioning

confidence: 99%

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

et al. 2018

View full text Add to dashboard Cite

show abstract

“…For this reason, there is some debate on which source of low‐level mountain drag should be better represented, the results in Tsiringakis et al . () suggesting that trapped lee waves could contribute as much as blocked‐flow mountain drag (Lott and Miller, ) or turbulent subgrid‐scale orographic drag (Beljaars et al . ).…”

Section: Introductionmentioning

confidence: 99%

Trapped mountain waves with a critical level just below the surface

Soufflet

Lott

Damiens

2019

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

The trapped mountain waves produced when the incident wind near the surface is small compared with its value aloft are analyzed with a theory adapted from Long (1953) and compared with fully nonlinear simulations performed with the Weather Research and Forecasting model (WRF). Although small near‐surface incident winds occur naturally in fronts via a combination of the thermal wind balance and the boundary layer, they pose at least two problems in mountain meteorology: zero surface incident winds produce no wave in the fully linear case; they also correspond to places where mountain waves have a critical level. Despite these problems, theory and WRF show that, for small mountains, trapped lee waves (a) can occur and (b) are favored when the surface Richardson number J = N 2/(∂u/∂z)2 is small. This last result is related to the theoretical fact that the surface absorption of stationary gravity waves increases when J increases. The relation with flow stability is corroborated further by the fact that the trapped lee waves resemble the Kelvin–Helmholtz (KH) modes of instability that exist when J < 0.25. For medium mountains, some aspects of the theory still hold but need to be adapted, the more intense winds and foehn that occur along the lee side of the mountain having a tendency to increase the surface flow stability. For “initially” small J, this can limit the onset of trapped lee waves, again consistent with the fact that mountain‐wave surface absorption increases with surface flow stability. For large J, the dynamics produces wave breaking on the lee side, destabilizing the flow in the wake of the mountain. In the region where the Richardson number is small, trapped waves develop despite the fact that the surface Richardson number can be quite large, suggesting that the trapped lee waves now result from an absolute instability of the wake.

show abstract

“…Tsiringakis et al . () showed that this additional drag can be provided by accounting for the gravity‐wave drag generated in stable conditions by small‐scale orography. This indicates that an accurate representation of small‐scale drag generation is important for simulations of the large‐scale circulation and thus for the conservation of AAM in models.…”

Section: Discussionmentioning

confidence: 96%

“…Studying the contributions of the different torques to the residuals in more detail in further research may provide directions for further model improvement (Madden and Speth, 1995;Huang et al, 1999). Inaccuracies in the torques can be related to uncertainty in the representation of surface drag in stable conditions (Sandu et al, 2013;Tsiringakis et al, 2017). Sandu et al (2013) demonstrated that, in numerical weather prediction models, increasing the turbulent diffusion in stable boundary layers artificially is necessary to simulate the large-scale atmospheric circulation accurately.…”

Section: Aam Balancementioning

confidence: 99%

“…Sandu et al (2013) demonstrated that, in numerical weather prediction models, increasing the turbulent diffusion in stable boundary layers artificially is necessary to simulate the large-scale atmospheric circulation accurately. Tsiringakis et al (2017) showed that this additional drag can be provided by accounting for the gravity-wave drag generated in stable conditions by small-scale orography. This indicates that an accurate representation of small-scale drag generation is important for simulations of the large-scale circulation and thus for the conservation of AAM in models.…”

Section: Aam Balancementioning

confidence: 99%

See 1 more Smart Citation

Trends in and closure of the atmospheric angular momentum budget in the 20th century in ERA‐20C

Veerman

Heerwaarden

2019

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

It is well known that global warming in the 20th century has influenced the global circulation of the atmosphere. Atmospheric angular momentum (AAM), a measure of the rotation of the atmosphere around the Earth's axis, is a useful quantity to investigate changes in the global atmospheric circulation. In this study, 20th century trends in the AAM budget are determined using the ERA‐20C reanalysis data of the European Centre for Medium‐Range Weather Forecasts (ECMWF). In addition, the closure of the AAM budget is determined to assess the ability of ERA‐20C to conserve angular momentum. The total AAM has increased in the 20th century, associated mainly with an increasing relative (zonal wind) AAM in most of the stratosphere and the tropical upper troposphere, and a poleward redistribution in the midlatitudes. These trends can be related to the warming in the troposphere and cooling in the lower stratosphere found in this study, likely caused by increasing atmospheric CO2 concentrations. The Ω‐AAM, representing the rotation of the atmosphere along with the Earth, shows no clear trend, but a spurious peak around 1920. This peak is caused by a global increase in surface pressure and is considered an artefact of changes in the amount of assimilated observations. It is also found that the AAM budget is not well closed in ERA‐20C, which is mainly the result of the assimilation of observations during production of the reanalysis. The trends in the AAM budget in ERA‐20C are likely affected by changes in the number of assimilated observations and should be validated with other reanalyses in further research.

show abstract

Small‐scale orographic gravity wave drag in stable boundary layers and its impact on synoptic systems and near‐surface meteorology

Cited by 30 publications

References 57 publications

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

Exchange Processes in the Atmospheric Boundary Layer Over Mountainous Terrain

Trapped mountain waves with a critical level just below the surface

Trends in and closure of the atmospheric angular momentum budget in the 20th century in ERA‐20C

Contact Info

Product

Resources

About