scholarly journals Small-scale gravity waves in ER-2 MMS/MTP wind and temperature measurements during CRYSTAL-FACE

2005 ◽  
Vol 5 (6) ◽  
pp. 11377-11412
Author(s):  
L. Wang ◽  
M. J. Alexander ◽  
T. P. Bui ◽  
M. J. Mahoney
Keyword(s):  
Gravity Waves ◽  
Temperature Measurements ◽  
Small Scale ◽  
Maximum Magnitude ◽  
Horizontal Scale ◽  
Crystal Face ◽  
Cloud Models ◽  
S Transform ◽  
Momentum Fluxes ◽  
The Cross

Abstract. ER-2 MMS and MTP wind and temperature measurements during the CRYSTAL-FACE campaign in July 2002 were analyzed to retrieve information on small scale gravity waves (GWs) at aircraft's flight level. For a given flight segment, the S-transform was used to search for and identify small horizontal scale GW events, and to estimate the apparent horizontal wavelengths of the events. The horizontal propagation directions of the events were determined using the Stokes parameters method combined with the cross S-transform analysis. The MTP temperature gradient method was used to determine the vertical wavelengths of the events. GW momentum fluxes were calculated from the cross S-transform. Other wave parameters such as intrinsic frequencies were calculated using the GW dispersion relation. More than 100 GW events were identified. They were generally short horizontal scale and high frequency waves with λz of ~5 km and λh generally shorter than 20 km. Their intrinsic propagation directions were predominantly toward the east, whereas their ground-based propagation directions were primarily toward the west. Among the events, ~20% of them had very short horizontal wavelength (<10 km), very high intrinsic frequency (ω/N≥0.8), and relatively small momentum fluxes, and thus they were likely trapped in the lower stratosphere. The averaged magnitude of vertical flux of horizontal momentum was ~0.026 kg m−1 s−2, and the maximum magnitude was ~0.13 kg m−1 s−2. Using the estimated GW parameters and the background winds and stabilities from the NCAR/NCEP reanalysis data, we were able to trace the sources of the events using a simple reverse ray-tracing. More than 70% of the events were traced back to convective sources in the troposphere, and the sources were generally located upstream to the events. Finally, a probability density function of GW cooling rates was obtained in this study, which may be used in cirrus cloud models.

scholarly journals Small-scale gravity waves in ER-2 MMS/MTP wind and temperature measurements during CRYSTAL-FACE

2006 ◽  
Vol 6 (4) ◽  
pp. 1091-1104 ◽  
Author(s):  
L. Wang ◽  
M. J. Alexander ◽  
T. B. Bui ◽  
M. J. Mahoney
Keyword(s):  
Gravity Waves ◽  
Temperature Measurements ◽  
Small Scale ◽  
Parameter Method ◽  
Crystal Face ◽  
Cloud Models ◽  
S Transform ◽  
Momentum Fluxes ◽  
The Cross ◽  
Horizontal Wavelength

Abstract. Lower stratospheric wind and temperature measurements made from NASA's high-altitude ER-2 research aircraft during the CRYSTAL-FACE campaign in July 2002 were analyzed to retrieve information on small scale gravity waves (GWs) at the aircraft's flight level (typically ~20 km altitude). For a given flight segment, the S-transform (a Gaussian wavelet transform) was used to search for and identify small horizontal scale GW events, and to estimate their apparent horizontal wavelengths. The horizontal propagation directions of the events were determined using the Stokes parameter method combined with the cross S-transform analysis. The vertical temperature gradient was used to determine the vertical wavelengths of the events. GW momentum fluxes were calculated from the cross S-transform. Other wave parameters such as intrinsic frequencies were calculated using the GW dispersion relation. More than 100GW events were identified. They were generally high frequency waves with vertical wavelength of ~5 km and horizontal wavelength generally shorter than 20 km. Their intrinsic propagation directions were predominantly toward the east, whereas their ground-based propagation directions were primarily toward the west. Among the events, ~20% of them had very short horizontal wavelength, very high intrinsic frequency, and relatively small momentum fluxes, and thus they were likely trapped in the lower stratosphere. Using the estimated GW parameters and the background winds and stabilities from the NCAR/NCEP reanalysis data, we were able to trace the sources of the events using a simple reverse ray-tracing. More than 70% of the events were traced back to convective sources in the troposphere, and the sources were generally located upstream of the locations of the events observed at the aircraft level. Finally, a probability density function of the reversible cooling rate due to GWs was obtained in this study, which may be useful for cirrus cloud models.

scholarly journals Mesospheric gravity wave activity estimated via airglow imagery, multistatic meteor radar, and SABER data taken during the SIMONe–2018 campaign

2020 ◽  
Author(s):  
Fabio Vargas ◽  
Jorge L. Chau ◽  
Harikrishnan Charuvil Asokan ◽  
Michael Gerding
Keyword(s):  
Gravity Waves ◽  
Momentum Flux ◽  
Large Scale ◽  
Lower Thermosphere ◽  
Small Scale ◽  
Meteor Radar ◽  
Mean Flow ◽  
Horizontal Scale ◽  
Momentum Fluxes ◽  
Mesosphere And Lower Thermosphere

Abstract. We describe in this study the analysis of small and large horizontal scale gravity waves from datasets composed of images from multiple mesospheric nightglow emissions as well as multistatic specular meteor radar (MSMR) winds collected in early November 2018, during the SIMONe–2018 campaign. These ground-based measurements are supported by temperature and neutral density profiles from TIMED/SABER satellite in orbits near Kühlungsborn, northern Germany (54.1° N, 11.8° E). The scientific goals here include the characterization of gravity waves and their interaction with the mean flow in the mesosphere and lower thermosphere and their relationship to dynamical conditions in the lower and upper atmosphere. We obtain intrinsic parameters of small and large horizontal scale gravity waves and characterize their impact in the mesosphere region via momentum flux and flux divergence estimations. We have verified that a small percent of the detected wave events are responsible for most of the momentum flux measured during the campaign from oscillations seen in the airglow brightness and MSMR winds. From the analysis of small-scale gravity waves in airglow images, we have found wave momentum fluxes ranging from 0.38 to 24.74 m2/s2 (0.88 ± 0.73 m2/s2 on average), with a total of 586.96 m2/s2 (sum over all 362 detected waves). However, small horizontal scale waves with flux > 3 m2/s2 (11 % of the events) transport 50 % of the total measured flux. Likewise, wave events having flux > 10 m2/s2 (2 % of the events) transport 20 % of the total flux. The examination of two large-scale waves seen simultaneously in airglow keograms and MSMR winds revealed relative amplitudes > 35 %, which translates into momentum fluxes of 21.2–29.6 m/s. In terms of gravity wave–mean flow interactions, these high momentum flux waves could cause decelerations of 22–41 m/s/day (small-scale waves) and 38–43 m/s/day (large-scale waves) if breaking or dissipating within short distances in the mesosphere and lower thermosphere region. The dominant large-scale waves might be the result of secondary gravity excited from imbalanced flow in the stratosphere caused by primary wave breaking.

scholarly journals Gravity wave amplitudes and momentum fluxes inferred from OH airglow intensities and meteor radar winds during SpreadFEx

2009 ◽  
Vol 27 (6) ◽  
pp. 2361-2369 ◽  
Author(s):  
F. Vargas ◽  
D. Gobbi ◽  
H. Takahashi ◽  
L. M. Lima
Keyword(s):  
Gravity Waves ◽  
Horizontal Wind ◽  
Small Scale ◽  
Meteor Radar ◽  
Plasma Bubble ◽  
Spatial And Temporal Scales ◽  
Analysis Technique ◽  
Momentum Fluxes ◽  
Different Types ◽  
Wave Directionality

Abstract. We show in this report the momentum flux content input in the mesosphere due to relatively fast and small scale gravity waves (GWs) observed through OH airglow images. The acquisition of OH NIR images was carried out in Brazil at Brasilia (14.8° S, 47.6° W) and Cariri (7.4° S, 36.5° W) from September 2005 to November 2005 during the SpreadFEx Campaign. Horizontal wind information from meteor radar was available in Cariri only. Our findings showed strong wave activity in both sites, mainly in Cariri. High wave directionality was also observed in both sites during SpreadFEx, which have been observed by other investigators using different analysis' techniques and different types of data during the campaign. We discuss also the possibility of plasma bubble seeding by gravity waves presenting spatial and temporal scales estimated with our novel analysis technique during the SpreadFEx campaign.

scholarly journals Diurnal Characteristics of Gravity Waves over the Tibetan Plateau in 2015 Summer Using 10-km Downscaled Simulations from WRF-EnKF Regional Reanalysis

Atmosphere ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 631
Author(s):  
Tingting Qian ◽  
Fuqing Zhang ◽  
Junhong Wei ◽  
Jie He ◽  
Yinghui Lu
Keyword(s):  
Tibetan Plateau ◽  
Gravity Waves ◽  
Power Spectra ◽  
Reanalysis Data ◽  
Small Scale ◽  
The Tibetan Plateau ◽  
Wave Source ◽  
Momentum Fluxes ◽  
Regional Reanalysis ◽  
Meso Scale

Diurnal variations of gravity waves over the Tibetan Plateau (TP) in summer 2015 were investigated based on high-resolution downscaled simulations from WRF-EnKF (Weather Research and Forecasting model and an ensemble Kalman filter) regional reanalysis data with particular emphasis on wave source, wave momentum fluxes and wave energies. Strong diurnal precipitations, which mainly happen along the south slope of the TP, tend to excite upward-propagating gravity waves. The spatial and temporal distributions of the momentum fluxes of small-scale (10–200 km) and meso-scale (200–500 km) gravity waves agree well with the diurnal precipitation distributions. The power spectra of momentum fluxes also show that the small- and meso-scale atmospheric processes become important during the period of the strongest rainfall. Eastward momentum fluxes and northward momentum fluxes are dominant. Wave energies are described in terms of kinetic energy (KE), potential energy (PE) and vertical fluctuation energy (VE). The diurnal variation and spatial distribution of VE in the lower stratosphere correspond to the diurnal rainfall in the troposphere.

scholarly journals Can gravity waves significantly impact PSC occurrence in the Antarctic?

2009 ◽  
Vol 9 (22) ◽  
pp. 8825-8840 ◽  
Author(s):  
A. J. McDonald ◽  
S. E. George ◽  
R. M. Woollands
Keyword(s):  
Antarctic Peninsula ◽  
Gravity Waves ◽  
Clustering Algorithm ◽  
Small Scale ◽  
Temperature Threshold ◽  
Aerosol Extinction ◽  
Polar Stratospheric Clouds ◽  
Mountain Wave ◽  
Stratospheric Clouds ◽  
The Antarctic

Abstract. A combination of POAM III aerosol extinction and CHAMP RO temperature measurements are used to examine the role of atmospheric gravity waves in the formation of Antarctic Polar Stratospheric Clouds (PSCs). POAM III aerosol extinction observations and quality flag information are used to identify Polar Stratospheric Clouds using an unsupervised clustering algorithm. A PSC proxy, derived by thresholding Met Office temperature analyses with the PSC Type Ia formation temperature (TNAT), shows general agreement with the results of the POAM III analysis. However, in June the POAM III observations of PSC are more abundant than expected from temperature threshold crossings in five out of the eight years examined. In addition, September and October PSC identified using temperature thresholding is often significantly higher than that derived from POAM III; this observation probably being due to dehydration and denitrification. Comparison of the Met Office temperature analyses with corresponding CHAMP observations also suggests a small warm bias in the Met Office data in June. However, this bias cannot fully explain the differences observed. Analysis of CHAMP data indicates that temperature perturbations associated with gravity waves may partially explain the enhanced PSC incidence observed in June (relative to the Met Office analyses). For this month, approximately 40% of the temperature threshold crossings observed using CHAMP RO data are associated with small-scale perturbations. Examination of the distribution of temperatures relative to TNAT shows a large proportion of June data to be close to this threshold, potentially enhancing the importance of gravity wave induced temperature perturbations. Inspection of the longitudinal structure of PSC occurrence in June 2005 also shows that regions of enhancement are geographically associated with the Antarctic Peninsula; a known mountain wave "hotspot". The latitudinal variation of POAM III observations means that we only observe this region in June–July, and thus the true pattern of enhanced PSC production may continue operating into later months. The analysis has shown that early in the Antarctic winter stratospheric background temperatures are close to the TNAT threshold (and PSC formation), and are thus sensitive to temperature perturbations associated with mountain wave activity near the Antarctic peninsula (40% of PSC formation). Later in the season, and at latitudes away from the peninsula, temperature perturbations associated with gravity waves contribute to about 15% of the observed PSC (a value which corresponds well to several previous studies). This lower value is likely to be due to colder background temperatures already achieving the TNAT threshold unaided. Additionally, there is a reduction in the magnitude of gravity waves perturbations observed as POAM III samples poleward of the peninsula.

Atmospheric general circulation and waves simulated by a Venus AORI GCM with topographical and radiative forcings

2021 ◽  
Author(s):  
Masaru Yamamoto ◽  
Takumi Hirose ◽  
Kohei Ikeda ◽  
Masaaki Takahashi
Keyword(s):  
Gravity Waves ◽  
General Circulation ◽  
Circulation Model ◽  
Stationary Wave ◽  
Static Stability ◽  
Small Scale ◽  
Mean Flow ◽  
Short Period ◽  
Low Latitudes ◽  
Thermal Tides

&lt;p&gt;General circulation and waves are investigated using a T63 Venus general circulation model (GCM) with solar and thermal radiative transfer in the presence of high-resolution surface topography. This model has been developed by Ikeda (2011) at the Atmosphere and Ocean Research Institute (AORI), the University of Tokyo, and was used in Yamamoto et al. (2019, 2021). In the wind and static stability structures similar to the observed ones, the waves are investigated. Around the cloud-heating maximum (~65 km), the simulated thermal tides accelerate an equatorial superrotational flow with a speed of ~90 m/s&lt;sup&gt;&lt;/sup&gt;with rates of 0.2&amp;#8211;0.5 m/s/(Earth day) via both horizontal and vertical momentum fluxes at low latitudes. Over the high mountains at low latitudes, the vertical wind variance at the cloud top is produced by topographically-fixed, short-period eddies, indicating penetrative plumes and gravity waves. In the solar-fixed coordinate system, the variances (i.e., the activity of waves other than thermal tides) of flow are relatively higher on the night-side than on the dayside at the cloud top. The local-time variation of the vertical eddy momentum flux is produced by both thermal tides and solar-related, small-scale gravity waves. Around the cloud bottom, the 9-day super-rotation of the zonal mean flow has a weak equatorial maximum and the 7.5-day Kelvin-like wave has an equatorial jet-like wind of 60-70 m/s. Because we discussed the thermal tide and topographically stationary wave in Yamamoto et al. (2021), we focus on the short-period eddies in the presentation.&lt;/p&gt;

scholarly journals Application of a fast and efficient algorithm to assess landslide-prone areas in sensitive clays in Sweden

2015 ◽  
Vol 15 (12) ◽  
pp. 2703-2713 ◽  
Author(s):  
C. Melchiorre ◽  
A. Tryggvason
Keyword(s):  
Optimal Algorithm ◽  
Model Performance ◽  
Small Scale ◽  
Depth Information ◽  
Computationally Efficient ◽  
Cross Sectional ◽  
Bedrock Depth ◽  
The Cross ◽  
Intelligent Filtering ◽  
Filtering Procedure

Abstract. We refine and test an algorithm for landslide susceptibility assessment in areas with sensitive clays. The algorithm uses soil data and digital elevation models to identify areas which may be prone to landslides and has been applied in Sweden for several years. The algorithm is very computationally efficient and includes an intelligent filtering procedure for identifying and removing small-scale artifacts in the hazard maps produced. Where information on bedrock depth is available, this can be included in the analysis, as can information on several soil-type-based cross-sectional angle thresholds for slip. We evaluate how processing choices such as of filtering parameters, local cross-sectional angle thresholds, and inclusion of bedrock depth information affect model performance. The specific cross-sectional angle thresholds used were derived by analyzing the relationship between landslide scarps and the quick-clay susceptibility index (QCSI). We tested the algorithm in the Göta River valley. Several different verification measures were used to compare results with observed landslides and thereby identify the optimal algorithm parameters. Our results show that even though a relationship between the cross-sectional angle threshold and the QCSI could be established, no significant improvement of the overall modeling performance could be achieved by using these geographically specific, soil-based thresholds. Our results indicate that lowering the cross-sectional angle threshold from 1 : 10 (the general value used in Sweden) to 1 : 13 improves results slightly. We also show that an application of the automatic filtering procedure that removes areas initially classified as prone to landslides not only removes artifacts and makes the maps visually more appealing, but it also improves the model performance.

scholarly journals The South Georgia Wave Experiment: A Means for Improved Analysis of Gravity Waves and Low-Level Wind Impacts Generated from Mountainous Islands

2018 ◽  
Vol 99 (5) ◽  
pp. 1027-1040 ◽  
Author(s):  
D. R. Jackson ◽  
A. Gadian ◽  
N. P. Hindley ◽  
L. Hoffmann ◽  
J. Hughes ◽  
...  
Keyword(s):  
High Resolution ◽  
Gravity Waves ◽  
Numerical Models ◽  
Small Island ◽  
Small Scale ◽  
The South ◽  
South Georgia ◽  
Low Level ◽  
Wave Experiment ◽  
Realistic Representation

AbstractGravity waves (GWs) play an important role in many atmospheric processes. However, the observation-based understanding of GWs is limited, and representing them in numerical models is difficult. Recent studies show that small islands can be intense sources of GWs, with climatologically significant effects on the atmospheric circulation. South Georgia, in the South Atlantic, is a notable source of such “small island” waves. GWs are usually too small scale to be resolved by current models, so their effects are represented approximately using resolved model fields (parameterization). However, the small-island waves are not well represented by such parameterizations, and the explicit representation of GWs in very-high-resolution models is still in its infancy. Steep islands such as South Georgia are also known to generate low-level wakes, affecting the flow hundreds of kilometers downwind. These wakes are also poorly represented in models.We present results from the South Georgia Wave Experiment (SG-WEX) for 5 July 2015. Analysis of GWs from satellite observations is augmented by radiosonde observations made from South Georgia. Simulations were also made using high-resolution configurations of the Met Office Unified Model (UM). Comparison with observations indicates that the UM performs well for this case, with realistic representation of GW patterns and low-level wakes. Examination of a longer simulation period suggests that the wakes generally are well represented by the model. The realism of these simulations suggests they can be used to develop parameterizations for use at coarser model resolutions.

scholarly journals Spatial and seasonal variability of medium- and high-frequency gravity waves in the lower atmosphere revealed by US radiosonde data

2014 ◽  
Vol 32 (9) ◽  
pp. 1129-1143 ◽  
Author(s):  
S. D. Zhang ◽  
C. M. Huang ◽  
K. M. Huang ◽  
F. Yi ◽  
Y. H. Zhang ◽  
...  
Keyword(s):  
Energy Density ◽  
Gravity Waves ◽  
Seasonal Variability ◽  
High Frequency ◽  
Lower Atmosphere ◽  
Radiosonde Data ◽  
High Latitudes ◽  
Middle Latitudes ◽  
Momentum Fluxes ◽  
Horizontal Momentum

Abstract. We extended the broad spectral method proposed by Zhang et al. (2013) for the extraction of medium- and high-frequency gravity waves (MHGWs). This method was applied to 11 years (1998–2008) of radiosonde data from 92 stations in the Northern Hemisphere to investigate latitudinal, continuous vertical and seasonal variability of MHGW parameters in the lower atmosphere (2–25 km). The latitudinal and vertical distributions of the wave energy density and horizontal momentum fluxes as well as their seasonal variations exhibit considerable consistency with those of inertial gravity waves. Despite the consistency, the MHGWs have much larger energy density, horizontal momentum fluxes and wave force, indicating the more important role of MHGWs in energy and momentum transportation and acceleration of the background. For the observed MHGWs, the vertical wavelengths are usually larger than 8 km; the horizontal wavelengths peak in the middle troposphere at middle–high latitudes. These characteristics are obviously different from inertial gravity waves. The energy density and horizontal momentum fluxes have similar latitude-dependent seasonality: both of them are dominated by a semiannual variation at low latitudes and an annual variation at middle latitudes; however at high latitudes, they often exhibit more than two peaks per year in the troposphere. Compared with the inertial GWs, the derived intrinsic frequencies are more sensitive to the spatiotemporal variation of the buoyancy frequency, and at all latitudinal regions they are higher in summer. The wavelengths have a weaker seasonal variation; an evident annual cycle can be observed only at middle latitudes.

Sign in / Sign up

Export Citation Format

Share Document