scholarly journals The Dynamics of Observed Lee Waves over the Snæfellsnes Peninsula in Iceland

2021 ◽  
Author(s):  
Ioana Colfescu ◽  
Joseph B. Klemp ◽  
Massimo A. Bollasina ◽  
Stephen D. Mobbs ◽  
Ralph R. Burton
Keyword(s):  
Wave Train ◽  
Wrf Model ◽  
Weather Research And Forecasting ◽  
Mountain Waves ◽  
Resonant Modes ◽  
Strong Inversion ◽  
Propagating Waves ◽  
Lee Waves ◽  
Vertically Propagating ◽  
Capping Inversion

AbstractOn 20 October 2016, aircraft observations documented a significant train of lee waves above and downstream of the Snæfellsnes Peninsula on the west coast of Iceland. Simulations of this event with the Weather Research and Forecasting (WRF) Model provide an excellent representation of the observed structure of these mountain waves. The orographic features producing these waves are characterized by the isolated Snæfellsjökull volcano near the tip of the peninsula and a fairly uniform ridge along its spine. Sensitivity simulations with the WRF Model document that the observed wave train consists of a superposition of the waves produced individually by these two dominant orographic features. This behavior is consistent with idealized simulations of a flow over an isolated 3-D mountain and over a 2-D ridge, which reproduce the essential behavior of the observed waves and those captured in the WRF simulations. Linear analytic analysis confirms the importance of a strong inversion at the top on the boundary layer in promoting significant wave activity extending far downstream on the terrain. However, analysis of the forced and resonant modes for a two layer atmosphere with a capping inversion suggest that this wave train may not be produced by resonant modes whose energy is trapped beneath the inversion. Rather, these appear to be vertically propagating modes with very small vertical group velocity that can persist far downstream of the mountain. These vertically propagating waves potentially provide a mechanism for producing near-resonant waves further aloft due to interactions with a stable layer in the mid-troposphere.

scholarly journals Roles of the Synoptic-Scale Wave Train, the Intraseasonal Oscillation, and High-Frequency Eddies in the Genesis of Typhoon Manyi (2001)*

2014 ◽  
Vol 71 (10) ◽  
pp. 3706-3722 ◽  
Author(s):  
Yamei Xu ◽  
Tim Li ◽  
Melinda Peng
Keyword(s):  
High Frequency ◽  
Development Process ◽  
Wave Train ◽  
Wrf Model ◽  
Intraseasonal Oscillation ◽  
Wave Activity ◽  
Weather Research And Forecasting ◽  
Synoptic Scale ◽  
Energy Dispersion ◽  
Multiple Episodes

Abstract Experiments using the Weather Research and Forecasting (WRF) Model were conducted to investigate the effects of multiscale motions on the genesis of Typhoon Manyi (2001) in the western North Pacific. The precursor signal associated with this typhoon genesis was identified as a northwest–southeast-oriented synoptic-scale wave train (SWT). The model successfully simulated the genesis of the typhoon in the wake of the SWT. Further experiments were conducted to isolate the effects of the SWT, the intraseasonal oscillation (ISO), and high-frequency (shorter than 3 days) eddies in the typhoon formation. Removing the SWT in the initial and boundary conditions eliminates the typhoon genesis. This points out the importance of the SWT in the typhoon genesis. It was noted that the SWT strengthened the wake cyclone through southeastward energy dispersion. The strengthening wake cyclone triggered multiple episodes of strong sustained convective updrafts, leading to aggregation of vertical vorticity and formation of a self-amplified mesoscale core vortex through a “bottom up” development process. Removing the ISO flow eliminates the typhoon genesis, as the ISO significantly modulated the strength of the SWT through accumulation of wave activity. In the absence of SWT–ISO-scale interaction, the southeastward energy dispersion was weakened significantly, and thus the strengthening of the wake cyclone did not occur. As a result, the successive strong sustained convective updrafts disappeared. Removing the high-frequency eddies did not eliminate the typhoon genesis but postponed the genesis for about 36 h.

scholarly journals Mountain Waves Analysis in the Vicinity of the Madrid-Barajas Airport Using the WRF Model

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Javier Díaz-Fernández ◽  
Lara Quitián-Hernández ◽  
Pedro Bolgiani ◽  
Daniel Santos-Muñoz ◽  
Ángel García Gago ◽  
...  
Keyword(s):  
Wrf Model ◽  
Weather Research And Forecasting ◽  
Mountain Range ◽  
Aircraft Icing ◽  
Microphysics Scheme ◽  
Mountain Waves ◽  
Skill Scores ◽  
Stable Conditions ◽  
Pbl Scheme ◽  
Wind Velocities

Turbulence and aircraft icing associated with mountain waves are weather phenomena potentially affecting aviation safety. In this paper, these weather phenomena are analysed in the vicinity of the Adolfo Suárez Madrid-Barajas Airport (Spain). Mountain waves are formed in this area due to the proximity of the Guadarrama mountain range. Twenty different weather research and forecasting (WRF) model configurations are evaluated in an initial analysis. This shows the incompetence of some experiments to capture the phenomenon. The two experiments showing the best results are used to simulate thirteen episodes with observed mountain waves. Simulated pseudosatellite images are validated using satellite observations, and an analysis is performed through several skill scores applied to brightness temperature. Few differences are found among the different skill scores. Nevertheless, the Thompson microphysics scheme combined with the Yonsei university PBL scheme shows the best results. The simulations produced by this scheme are used to evaluate the characteristic variables of the mountain wave episodes at windward and leeward and over the mountain. The results show that north-northwest wind directions, moderate wind velocities, and neutral or slightly stable conditions are the main features for the episodes evaluated. In addition, a case study is analysed to evidence the WRF ability to properly detect turbulence and icing associated with mountain waves, even when there is no visual evidence available.

scholarly journals ST radar observations of atmospheric waves over mountainous areas: a review

2000 ◽  
Vol 18 (7) ◽  
pp. 750-765 ◽  
Author(s):  
J. Röttger
Keyword(s):  
Middle Atmosphere ◽  
Lower Atmosphere ◽  
Mountainous Areas ◽  
Wave Processes ◽  
Mountain Areas ◽  
Mountain Waves ◽  
Propagating Waves ◽  
Lee Waves ◽  
Tropopause Region ◽  
Energy And Momentum

Abstract. Lee and mountain waves are dominant dynamic processes in the atmosphere above mountain areas. ST VHF radars had been intensively used to investigate these wave processes. These studies are summarized in this work. After discussing features of long-period quasi-stationary lee waves, attention is drawn to the frequent occurrence of freely propagating waves of shorter periods, which seem to be more common and characteristic for wave processes generated over mountainous areas. Characteristics of these waves such as their relation to the topography and background winds, the possibility of trapping by and breaking in the tropopause region and their propagation into the stratosphere is investigated. These orographically produced waves transport energy and momentum into the troposphere and stratosphere, which is considered an important contribution to the kinetic energy of the lower atmosphere. The occurrence of inertia-gravity waves in the stratosphere had been confused with lee waves, which is discussed in conclusion. Finally further questions on mountain and lee waves are drawn up, which remain to be solved and where investigations with ST radars could play a fundamental role.Key words: Meteorology and atmospheric dynamics (Middle atmosphere dynamics; Waves and tides; Instruments and techniques)

scholarly journals Mesoscale Horizontal Kinetic Energy Spectra of a Tropical Cyclone

2018 ◽  
Vol 75 (10) ◽  
pp. 3579-3596 ◽  
Author(s):  
Yuan Wang ◽  
Lifeng Zhang ◽  
Jun Peng ◽  
Saisai Liu
Keyword(s):  
Tropical Cyclone ◽  
Kinetic Energy ◽  
Gravity Waves ◽  
Lower Stratosphere ◽  
Wrf Model ◽  
Weather Research And Forecasting ◽  
Physical Processes ◽  
Upper Troposphere ◽  
Mature Period ◽  
Vertically Propagating

A high-resolution cloud-permitting simulation with the Weather Research and Forecasting (WRF) Model is performed to investigate the mesoscale horizontal kinetic energy (HKE) spectra of a tropical cyclone (TC). The spectrum displays an arc-like shape in the troposphere and a quasi-linear shape in the lower stratosphere for wavelengths below 500 km during the mature period of the TC, while they both develop a quasi −5/3 slope. The total HKE spectrum is dominated by its rotational component in the troposphere but by its divergent component in the lower stratosphere. Further spectral HKE budget diagnosis reveals a generally downscale cascade of HKE, although a local upscale cascade gradually forms in the lower stratosphere. However, the mesoscale energy spectrum is not only governed by the energy cascade, but is evidently influenced also by other physical processes, among which the buoyancy effect converts available potential energy (APE) to HKE in the mid- and upper troposphere and converts HKE to APE in the lower stratosphere, the vertically propagating inertia–gravity waves transport the HKE from the upper troposphere to lower and higher layers, and the vertical transportation of convection always transports HKE upward.

Sensitivity analysis to WRF parameterizations for mountain waves near Madrid airport (Spain)

2021 ◽  
Author(s):  
Javier Díaz Fernández ◽  
Lara Quitián Hernández ◽  
Pedro Bolgiani ◽  
Daniel Santos Muñoz ◽  
Mariano Sastre ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Brightness Temperature ◽  
Traffic Management ◽  
Satellite Images ◽  
Wrf Model ◽  
Weather Research And Forecasting ◽  
Leeward Side ◽  
Aircraft Icing ◽  
Mountain Waves ◽  
Skill Scores

<p>Aircraft icing and turbulence associated with mountain waves events are adverse meteorological phenomena potentially affecting aviation safety and air traffic management. This study analyzes 13 mountain wave events in the vicinity of the Adolfo Suárez Madrid-Barajas airport (Spain) for two years (from 2017 to 2019). Mountain waves are formed in the leeward side of the Guadarrama mountains when the wind flows perpendicular to this orographic barrier (north-northwest winds). The thirteen events are simulated using several parameterizations from the Weather Research and Forecasting (WRF) model. Simulated pseudo-satellite images are validated using the observed brightness temperature from satellite images. Then, a sensitivity analysis is developed through several skill scores applied to brightness temperature in order to select the schemes best performing to forecast mountain waves. Finally, the best parametrization is used to assess several atmospheric variables involved in mountain waves formation. </p><p> </p>

scholarly journals Observed versus simulated mountain waves over Scandinavia – improvement by enhanced model resolution?

2016 ◽  
Author(s):  
Johannes Wagner ◽  
Andreas Dörnbrack ◽  
Markus Rapp ◽  
Sonja Gisinger ◽  
Benedikt Ehard ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Lower Troposphere ◽  
Static Stability ◽  
High Energy ◽  
Horizontal Resolution ◽  
Trapped Waves ◽  
Mountain Waves ◽  
Propagating Waves ◽  
Lee Waves ◽  
Energy And Momentum

Abstract. Two mountain wave events, which occured over northern Scandinavia in December 2013 are analysed by means of airborne observations and global and mesoscale numerical simulations with horizontal mesh sizes of 16 km, 7.2 km, 2.4 km and 0.8 km. During both events westerly cross-mountain flow induced upward propagating waves in the troposphere and stratosphere and trapped waves in the lee of the mountains. Despite similar forcing conditions gravity wave breaking occured during the first event at altitudes between 25 km to 30 km due to weak stratospheric background winds, while waves propagated to altitudes above 30 km during the second event. In the lower troposphere trapped lee waves with horizontal wavelengths of 15 km to 40 km, which propagated horizontally up to 300 km in the lee of the mountains were observed. Global and mesoscale simulations with 16 km and 7.2 km grid sizes were not able to simulate the mountain and trapped lee waves properly due to unresolved mountain peaks. In simulations with 2.4 km and 0.8 km horizontal resolution mountain waves were captured, but exhibited too small amplitudes, too strong decay of trapped waves in the lee of the mountains and too high energy and momentum fluxes at flight level. Increased fluxes in simulations are caused by reduced downward propagating waves due to weaker jumps in static stability at the tropopause and reduced gravity wave reflection.

scholarly journals Numerical Simulations of Two Trapped Mountain Lee Waves Downstream of Oahu

2017 ◽  
Vol 56 (5) ◽  
pp. 1305-1324 ◽  
Author(s):  
Liye Li ◽  
Yi-Leng Chen
Keyword(s):  
Large Scale ◽  
Convective Available Potential Energy ◽  
Inversion Layer ◽  
Wrf Model ◽  
Transverse Mode ◽  
Trade Wind ◽  
Mountain Waves ◽  
Sensitivity Tests ◽  
Lee Waves ◽  
Lee Wave

AbstractTwo trapped lee-wave events dominated by the transverse mode downstream of the island of Oahu in Hawaii—27 January 2010 and 24 January 2003—are simulated using the Weather Research Forecasting (WRF) Model with a horizontal grid size of 1 km in conjunction with the analyses of soundings, weather maps, and satellite images. The common factors for the occurrences of these transverse trapped mountain-wave events are 1) Froude number [Fr = U/(Nh)] > 1, where U is the upstream speed of the cross-barrier flow, N is stability, and h is the mountain height; 2) insufficient convective available potential energy for the air parcel to become positively buoyant after being lifted to the top of the stable trade wind inversion layer; and 3) increasing cross-barrier wind speed with respect to height through the stable inversion layer, satisfying Scorer’s criteria between the inversion layer and the layer aloft. Within the inversion layer, where the Scorer parameter has a maximum, the wave amplitudes are the greatest. The two trapped mountain waves in winter occurred under strong prefrontal stably stratified southwesterly flow. On the other islands in Hawaii, where the mountaintops are below the base of the inversion, transverse trapped lee waves can occur under similar large-scale settings if the mountain height is lower than U/N. The high-spatial-and-temporal-resolution WRF Model successfully simulates the onset, development, and dissipation of these two events. Sensitivity tests for the 27 January 2010 case are performed with reduced relative humidity (RH). With a lower RH and less-significant latent heating, trapped lee waves have smaller amplitudes and shorter wavelengths.

scholarly journals Energy Flux and Wavelet Diagnostics of Secondary Mountain Waves

2010 ◽  
Vol 67 (11) ◽  
pp. 3721-3738 ◽  
Author(s):  
Bryan K. Woods ◽  
Ronald B. Smith
Keyword(s):  
Energy Flux ◽  
Inversion Layer ◽  
Secondary Wave ◽  
Trapped Waves ◽  
Mountain Waves ◽  
Propagating Waves ◽  
Rotor Experiment ◽  
Flux Estimation ◽  
Vertically Propagating ◽  
Perturbation Pressure

Abstract In recent years, aircraft data from mountain waves have been primarily analyzed using velocity and temperature power spectrum and momentum flux estimation. Herein it is argued that energy flux wavelets (i.e., pressure–velocity wavelet cross-spectra) provide a more powerful tool for locating and classifying different types of mountain waves. In the first part of the paper, pressure–velocity cross-spectra using various linear mountain-wave solutions are shown to be capable of disentangling collocated waves with different propagation directions and wavelength. A field of group velocity vectors can also be determined. In the second part, the energy flux wavelet technique is applied to five cases of mountain waves entering the stratosphere from the Terrain-Induced Rotor Experiment (T-REX) in 2006. Perturbation pressure along the flight track is determined using aircraft static pressure corrected hydrostatically with GPS altitude. In four of the cases, collocated long up-propagating and short down-propagating waves are seen in the stratosphere. These waves have strong, but opposite, p′w′ cospectra. In one of these cases, a patch of turbulence is collocated with the up and down waves. In two other cases, trapped waves riding on the tropopause inversion layer (TIL) are seen. These trapped waves have p′w′ quadrature spectra that reverse sign across the tropopause. These newly discovered wave types may arise from secondary wave generation (i.e., a nonlinear transfer of energy from the long vertically propagating waves to shorter modes).

scholarly journals Laboratory investigations on the resonant feature of ‘dead water’ phenomenon

2019 ◽  
Vol 61 (1) ◽  
Author(s):  
Karim Medjdoub ◽  
Imre M. Jánosi ◽  
Miklós Vincze
Keyword(s):  
Internal Wave ◽  
Internal Waves ◽  
Wave Train ◽  
Interfacial Wave ◽  
Maritime Literature ◽  
Propagating Waves ◽  
Lee Waves ◽  
Vertical Density ◽  
Resonant Feature ◽  
Dead Water

Abstract Interfacial internal wave excitation in the wake of towed ships is studied experimentally in a quasi-two-layer fluid. At a critical ‘resonant’ towing velocity, whose value depends on the structure of the vertical density profile, the amplitude of the internal wave train following the ship reaches a maximum, in unison with the development of a drag force acting on the vessel, known in the maritime literature as ‘dead water’. The amplitudes and wavelengths of the emerging internal waves are evaluated for various ship speeds, ship lengths and stratification profiles. The results are compared to linear two- and three-layer theories of freely propagating waves and lee waves. We find that despite the fact that the observed internal waves can have considerable amplitudes, linear theories can still provide a surprisingly adequate description of subcritical-to-supercritical transition and the associated amplification of internal waves. We argue that the latter can be interpreted as a coalescence of frequencies of two fundamental stable wave motions, namely lee waves and propagating interfacial wave modes. Graphic abstract

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