scholarly journals Measuring Gravity Wave Parameters from a Nighttime Satellite Low-Light Image Based on Two-Dimensional Stockwell Transform

2019 ◽  
Vol 36 (1) ◽  
pp. 41-51 ◽  
Author(s):  
Shensen Hu ◽  
Shuo Ma ◽  
Wei Yan ◽  
Neil P. Hindley ◽  
Kai Xu ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Two Dimensional ◽  
General Shape ◽  
Low Light ◽  
Wave Parameters ◽  
Moonless Night ◽  
Wave Patterns ◽  
Stockwell Transform ◽  
Atmospheric Gravity

AbstractAtmospheric gravity waves are a kind of mesoscale disturbance, commonly found in the atmospheric system, that plays a key role in a series of mesospheric dynamic processes. When propagating to the upper atmosphere, the gravity waves will disturb the local temperature and density, and then modulate the intensity of the surrounding airglow radiation. As a result, the presence of gravity waves on a moonless night can usually cause the airglow to reveal ripple features in low-light images. In this paper we have applied a two-dimensional Stockwell transform technique (2DST) to airglow measurements from nighttime low-light images of the day–night band on the Suomi National Polar-Orbiting Partnership. To our knowledge this study is the first to measure localized mesospheric gravity wave brightness amplitudes, horizontal wavelengths, and propagation directions using such a method and data. We find that the method can characterize the general shape and amplitude of concentric gravity wave patterns, capturing the dominant features and directions with a good degree of accuracy. The key strength of our 2DST application is that our approach could be tuned and then automated in the future to process tens of thousands of low-light images, globally characterizing gravity wave parameters in this historically poorly studied layer of the atmosphere.

Response of GPS occultation signals to atmospheric gravity waves and retrieval of gravity wave parameters

GPS Solutions ◽  
2004 ◽  
Vol 8 (2) ◽  
Author(s):  
Y.A. Liou ◽  
A.G. Pavelyev ◽  
J. Wickert ◽  
C.Y. Huang ◽  
S.K. Yan ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Atmospheric Gravity Waves ◽  
Wave Parameters ◽  
Atmospheric Gravity ◽  
Gps Occultation

scholarly journals A two-dimensional Stockwell Transform for gravity wave analysis of AIRS measurements

2016 ◽  
Author(s):  
N. P. Hindley ◽  
N. D. Smith ◽  
C. J. Wright ◽  
N. J. Mitchell
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Momentum Flux ◽  
General Circulation ◽  
Middle Atmosphere ◽  
Critical Role ◽  
General Circulation Models ◽  
Two Dimensional ◽  
Wave Analysis ◽  
Stockwell Transform

Abstract. Gravity waves play a critical role in the dynamics of the middle atmosphere due to their ability to transport energy and momentum from their sources to great heights. The accurate parametrization of gravity wave momentum flux is of key importance to general circulation models. For the last decade, the nadir-viewing Atmospheric Infrared Sounder (AIRS) aboard NASA’s Aqua satellite has made global, two-dimensional (2-D) measurements of stratospheric radiances in which gravity waves can be detected. Current methods for gravity wave analysis of these data can introduce unwanted biases. Here, we present a new analysis method. Our method uses a 2-D Stockwell transform (2DST) to determine gravity wave horizontal wavelengths and directions in both directions simultaneously. We demonstrate that our method can accurately recover horizontal wavelengths and directions from a specified wave field. We show that the use of an elliptical spectral windowing function in the 2DST, in place of a Gaussian, can dramatically improve the recovery of wave amplitude. We measure momentum flux in two granules of AIRS measurements in two regions known to be intense hot spots of gravity wave activity: (i) the Drake Pas- sage/Antarctic Peninsula and (ii) the isolated mountainous island of South Georgia. We show that our 2DST method provides improved spatial localisation of key gravity wave properties over current methods. The added flexibility offered by alternative spectral windowing functions and scaling parameters presented here extend the usefulness of our 2DST method to other areas of geophysical data analysis.

Calculating Atmospheric Gravity Wave Parameters from Infrasound Measurements

2018 ◽  
pp. 701-719 ◽  
Author(s):  
Graeme Marlton ◽  
Andrew Charlton-Perez ◽  
Giles Harrison ◽  
Christopher Lee
Keyword(s):  
Gravity Wave ◽  
Atmospheric Gravity Wave ◽  
Wave Parameters ◽  
Atmospheric Gravity

scholarly journals A statistical study of gravity waves from radiosonde observations at Wuhan (30° N, 114° E) China

2005 ◽  
Vol 23 (3) ◽  
pp. 665-673 ◽  
Author(s):  
S. D. Zhang ◽  
F. Yi
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Extreme Values ◽  
Dynamical Instability ◽  
Strong Wind ◽  
Data Set ◽  
Height Range ◽  
Wave Parameters ◽  
Thermal Structures ◽  
Radiosonde Observation

Abstract. Several works concerning the dynamical and thermal structures and inertial gravity wave activities in the troposphere and lower stratosphere (TLS) from the radiosonde observation have been reported before, but these works were concentrated on either equatorial or polar regions. In this paper, background atmosphere and gravity wave activities in the TLS over Wuhan (30° N, 114° E) (a medium latitudinal region) were statistically studied by using the data from radiosonde observations on a twice daily basis at 08:00 and 20:00 LT in the period between 2000 and 2002. The monthly-averaged temperature and horizontal winds exhibit the essential dynamic and thermal structures of the background atmosphere. For avoiding the extreme values of background winds and temperature in the height range of 11-18km, we studied gravity waves, respectively, in two separate height regions, one is from ground surface to 10km (lower part), and the other is within 18-25km (upper part). In total, 791 and 1165 quasi-monochromatic inertial gravity waves were extracted from our data set for the lower and upper parts, respectively. The gravity wave parameters (intrinsic frequencies, amplitudes, wavelengths, intrinsic phase velocities and wave energies) are calculated and statistically studied. The statistical results revealed that in the lower part, there were 49.4% of gravity waves propagating upward, and the percentage was 76.4% in the upper part. Moreover, the average wave amplitudes and energies are less than those at the lower latitudinal regions, which indicates that the gravity wave parameters have a latitudinal dependence. The correlated temporal evolution of the monthly-averaged wave energies in the lower and upper parts and a subsequent quantitative analysis strongly suggested that at the observation site, dynamical instability (strong wind shear) induced by the tropospheric jet is the main excitation source of inertial gravity waves in the TLS.

scholarly journals Simultaneous lidar observations of temperatures and waves in the polar middle atmosphere on both sides of the Scandinavian mountains: a case study on 19/20 January 2003

2004 ◽  
Vol 4 (1) ◽  
pp. 969-989 ◽  
Author(s):  
U. Blum ◽  
K. H. Fricke ◽  
G. Baumgarten ◽  
A. Schöch
Keyword(s):  
Gravity Waves ◽  
Middle Atmosphere ◽  
Temperature Structure ◽  
Vertical Wavelength ◽  
Mountain Ridge ◽  
Induced Gravity ◽  
Simultaneous Measurements ◽  
Wave Patterns ◽  
Atmospheric Gravity

Abstract. Atmospheric gravity waves have been the subject of intense research for several decades because of their extensive effects on the atmospheric circulation and the temperature structure. The U. Bonn lidar at the Esrange and the ALOMAR RMR lidar at the Andøya Rocket Range are located in northern Scandinavia 250 km apart on either side of the Scandinavian mountain ridge. During January and February 2003 both lidar systems conducted measurements and retrieved atmospheric temperatures. On 19/20 January 2003 simultaneous measurements for more than 7 h were possible. Although during most of the campaign time the atmosphere was not transparent for the propagation of orographically induced gravity waves, they could propagate and were observed at both lidar stations during these simultaneous measurements. The wave patterns at ALOMAR show a random distribution with time whereas at the Esrange a persistency in the wave patterns is observable. This persistency can also be found in the distribution of the most powerful vertical wavelengths. The mode values are both at about 5 km vertical wavelength, however the distributions are quite different, narrow at the Esrange containing values from λz=2–6 km and broad at ALOMAR, covering λz=1–12 km vertical wavelength. At both stations the waves deposit energy in the atmosphere with increasing altitude, which leads to a decrease of the observed gravity wave potential energy density with altitude. These measurements show unambigiously orographically induced gravity waves on both sides of the mountains as well as a clear difference of the characteristics of these waves, which might be caused by different excitation and propagation conditions on either side of the Scandinavian mountain ridge.

scholarly journals Automatic Extraction of Gravity Waves from All-Sky Airglow Image Based on Machine Learning

2019 ◽  
Vol 11 (13) ◽  
pp. 1516 ◽  
Author(s):  
Chang Lai ◽  
Jiyao Xu ◽  
Jia Yue ◽  
Wei Yuan ◽  
Xiao Liu ◽  
...  
Keyword(s):  
Neural Network ◽  
Object Detection ◽  
Convolutional Neural Network ◽  
Gravity Waves ◽  
Classification Model ◽  
Atmospheric Gravity Waves ◽  
Detection Model ◽  
Wave Patterns ◽  
Airglow Image ◽  
Atmospheric Gravity

With the development of ground-based all-sky airglow imager (ASAI) technology, a large amount of airglow image data needs to be processed for studying atmospheric gravity waves. We developed a program to automatically extract gravity wave patterns in the ASAI images. The auto-extraction program includes a classification model based on convolutional neural network (CNN) and an object detection model based on faster region-based convolutional neural network (Faster R-CNN). The classification model selects the images of clear nights from all ASAI raw images. The object detection model locates the region of wave patterns. Then, the wave parameters (horizontal wavelength, period, direction, etc.) can be calculated within the region of the wave patterns. Besides auto-extraction, we applied a wavelength check to remove the interference of wavelike mist near the imager. To validate the auto-extraction program, a case study was conducted on the images captured in 2014 at Linqu (36.2°N, 118.7°E), China. Compared to the result of the manual check, the auto-extraction recognized less (28.9% of manual result) wave-containing images due to the strict threshold, but the result shows the same seasonal variation as the references. The auto-extraction program applies a uniform criterion to avoid the accidental error in manual distinction of gravity waves and offers a reliable method to process large ASAI images for efficiently studying the climatology of atmospheric gravity waves.

scholarly journals Studies on atmospheric gravity wave activity in the troposphere and lower stratosphere over a tropical station at Gadanki

2005 ◽  
Vol 23 (10) ◽  
pp. 3237-3260 ◽  
Author(s):  
I. V. Subba Reddy ◽  
D. Narayana Rao ◽  
A. Narendra Babu ◽  
M. Venkat Ratnam ◽  
P. Kishore ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Lower Stratosphere ◽  
Wave Length ◽  
Wave Activity ◽  
Lower Atmosphere ◽  
Wind Fields ◽  
Atmospheric Gravity Wave ◽  
Short Period ◽  
Atmospheric Gravity

Abstract. MST radars are powerful tools to study the mesosphere, stratosphere and troposphere and have made considerable contributions to the studies of the dynamics of the upper, middle and lower atmosphere. Atmospheric gravity waves play a significant role in controlling middle and upper atmospheric dynamics. To date, frontal systems, convection, wind shear and topography have been thought to be the sources of gravity waves in the troposphere. All these studies pointed out that it is very essential to understand the generation, propagation and climatology of gravity waves. In this regard, several campaigns using Indian MST Radar observations have been carried out to explore the gravity wave activity over Gadanki in the troposphere and the lower stratosphere. The signatures of the gravity waves in the wind fields have been studied in four seasons viz., summer, monsoon, post-monsoon and winter. The large wind fluctuations were more prominent above 10 km during the summer and monsoon seasons. The wave periods are ranging from 10 min-175 min. The power spectral densities of gravity waves are found to be maximum in the stratospheric region. The vertical wavelength and the propagation direction of gravity waves were determined using hodograph analysis. The results show both down ward and upward propagating waves with a maximum vertical wave length of 3.3 km. The gravity wave associated momentum fluxes show that long period gravity waves carry more momentum flux than the short period waves and this is presented.

scholarly journals Meteorological Source Variability in Atmospheric Gravity Wave Parameters Derived From a Tropical Infrasound Station

2019 ◽  
Vol 124 (8) ◽  
pp. 4352-4364
Author(s):  
G. J. Marlton ◽  
A. J. Charlton‐Perez ◽  
R. G. Harrison ◽  
E. Blanc ◽  
L. Evers ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Atmospheric Gravity Wave ◽  
Wave Parameters ◽  
Atmospheric Gravity

scholarly journals Beyond the Rigid Lid: Baroclinic Modes in a Structured Atmosphere

2017 ◽  
Vol 74 (11) ◽  
pp. 3551-3566 ◽  
Author(s):  
Jacob P. Edman ◽  
David M. Romps
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Green's Functions ◽  
Green’S Functions ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Mode Decomposition ◽  
Wide Range ◽  
Tropospheric Heating ◽  
Baroclinic Modes

Abstract The baroclinic-mode decomposition is a fixture of the tropical-dynamics literature because of its simplicity and apparent usefulness in understanding a wide range of atmospheric phenomena. However, its derivation relies on the assumption that the tropopause is a rigid lid that artificially restricts the vertical propagation of wave energy. This causes tropospheric buoyancy anomalies of a single vertical mode to remain coherent for all time in the absence of dissipation. Here, the authors derive the Green’s functions for these baroclinic modes in a two-dimensional troposphere (or, equivalently, a three-dimensional troposphere with one translational symmetry) that is overlain by a stratosphere. These Green’s functions quantify the propagation and spreading of gravity waves generated by a horizontally localized heating, and they can be used to reconstruct the evolution of any tropospheric heating. For a first-baroclinic two-dimensional right-moving or left-moving gravity wave with a characteristic width of 100 km, its initial horizontal shape becomes unrecognizable after 4 h, at which point its initial amplitude has also been reduced by a factor of 1/π. After this time, the gravity wave assumes a universal shape that widens linearly in time. For gravity waves on a periodic domain the length of Earth’s circumference, it takes only 10 days for the gravity waves to spread their buoyancy throughout the entire domain.

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