Latitudinal Variations of the Convective Source and Propagation Condition of Inertio-Gravity Waves in the Tropics

2007 ◽  
Vol 64 (5) ◽  
pp. 1603-1618 ◽  
Author(s):  
Hye-Yeong Chun ◽  
Jung-Suk Goh ◽  
In-Sun Song ◽  
Lucrezia Ricciardulli
Keyword(s):  
Wave Propagation ◽  
Gravity Waves ◽  
Low Frequency ◽  
Phase Speed ◽  
Simple Relationship ◽  
Propagation Condition ◽  
Zonal Wavenumber ◽  
Vertical Propagation ◽  
Latitudinal Variations ◽  
The Tropics

Abstract Latitudinal variations of the convective source and vertical propagation condition of inertio-gravity waves (IGWs) in the tropical region (30°S–30°N) are examined using high-resolution Global Cloud Imagery (GCI) and 6-hourly NCEP–NCAR reanalysis data, respectively, for 1 yr (March 1985–February 1986). The convective source is estimated by calculating the deep convective heating (DCH) rate using the brightness temperature of the GCI data. The latitudinal variation of DCH is found to be significant throughout the year. The ratio of the maximum to minimum values of DCH in the annual mean is 3.2 and it is much larger in the June–August (JJA) and December–February (DJF) means. Spectral analyses show that DCH has a dominant period of 1 day, a zonal wavelength of about 1600 km, and a Gaussian-type phase-speed spectrum with a peak at the zero phase speed. The vertical propagation condition of IGWs is determined, in the zonal wavenumber and frequency domain, by two factors: (i) latitude, which determines the Coriolis parameter, and (ii) the basic-state wind structure in the target height range of wave propagation. It was found that the basic-state wind significantly influences the wave propagation condition in the lower stratosphere between 150 and 30 hPa, and accordingly a large portion of the source spectrum is filtered out. This is prominent not only in the latitudes higher than 15° where strong negative shear exists, but also near the equator where strong positive shear associated with the westerly phase of the quasi-biennial oscillation (QBO) filters out large portions of the low-frequency components of the convective source. There is no simple relationship between the ground-based frequency and latitude; lower latitudes are not always favorable for low-frequency IGWs to be observed in the stratosphere. The basic-state wind in the Tropics, which has seasonal, annual, and interannual variations, plays a major role not only in determining the wave propagation condition in the stratosphere but also in producing convective sources in the troposphere.

scholarly journals Gravity Wave Propagation from the Stratosphere into the Mesosphere Studied with Lidar, Meteor Radar, and TIMED/SABER

Atmosphere ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 81 ◽  
Author(s):  
Shaohua Gong ◽  
Guotao Yang ◽  
Jiyao Xu ◽  
Xiao Liu ◽  
Qinzeng Li
Keyword(s):  
Wave Propagation ◽  
Gravity Wave ◽  
Low Frequency ◽  
Phase Speed ◽  
Static Stability ◽  
Temperature Structure ◽  
Meteor Radar ◽  
Atmospheric Gravity Wave ◽  
Vertical Wavelength ◽  
Hodograph Method

A low-frequency inertial atmospheric gravity wave (AGW) event was studied with lidar (40.5° N, 116° E), meteor radar (40.3° N, 116.2° E), and TIMED/SABER at Beijing on 30 May 2012. Lidar measurements showed that the atmospheric temperature structure was persistently perturbed by AGWs propagating upward from the stratosphere into the mesosphere (35–86 km). The dominant contribution was from the waves with vertical wavelengths λ z = 8 − 10   km and wave periods T ob = 6.6 ± 0.7   h . Simultaneous observations from a meteor radar illustrated that MLT horizontal winds were perturbed by waves propagating upward with an azimuth angle of θ = 247 ° , and the vertical wavelength ( λ z = 10   km ) and intrinsic period ( T in = 7.4   h ) of the dominant waves were inferred with the hodograph method. TIMED/SABER measurements illustrated that the vertical temperature profiles were also perturbed by waves with dominant vertical wavelength λ z = 6 − 9   km . Observations from three different instruments were compared, and it was found that signatures in the temperature perturbations and horizontal winds were induced by identical AGWs. According to these coordinated observation results, the horizontal wavelength and intrinsic phase speed were inferred to be ~560 km and ~21 m/s, respectively. Analyses of the Brunt-Väisälä frequency and potential energy illustrated that this persistent wave propagation had good static stability.

Planetary (Rossby) waves and inertia–gravity (Poincaré) waves in a barotropic ocean over a sphere

2013 ◽  
Vol 726 ◽  
pp. 123-136 ◽  
Author(s):  
Nathan Paldor ◽  
Yair De-Leon ◽  
Ofer Shamir
Keyword(s):  
Gravity Waves ◽  
Rossby Waves ◽  
Phase Speed ◽  
Mode Number ◽  
Rotating Sphere ◽  
Zonal Wavenumber ◽  
Speed Of Gravity ◽  
Meridional Mode ◽  
Poincare Waves ◽  
The Waves

AbstractThe construction of approximate Schrödinger eigenvalue equations for planetary (Rossby) waves and for inertia–gravity (Poincaré) waves on an ocean-covered rotating sphere yields highly accurate estimates of the phase speeds and meridional variation of these waves. The results are applicable to fast rotating spheres such as Earth where the speed of barotropic gravity waves is smaller than twice the tangential speed on the equator of the rotating sphere. The implication of these new results is that the phase speed of Rossby waves in a barotropic ocean that covers an Earth-like planet is independent of the speed of gravity waves for sufficiently large zonal wavenumber and (meridional) mode number. For Poincaré waves our results demonstrate that the dispersion relation is linear, (so the waves are non-dispersive and the phase speed is independent of the wavenumber), except when the zonal wavenumber and the (meridional) mode number are both near 1.

scholarly journals Propagating characteristics of mesospheric gravity waves observed by an OI 557.7 nm airglow all-sky camera at Mt. Bohyun (36.2°N, 128.9°E)

2021 ◽  
Author(s):  
Jun-Young Hwang ◽  
Young-Sook Lee ◽  
Yong Ha Kim ◽  
Hosik Kam ◽  
Young-Sil Kwak ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Narrow Band ◽  
Phase Speed ◽  
Image Data ◽  
Lower Atmosphere ◽  
Band Filter ◽  
Vertical Propagation ◽  
Narrow Band Filter ◽  
Filtering Effect ◽  
The Waves

Abstract. We analyzed all-sky camera images observed at Mt. Bohyun observatory (36.2°N, 128.9°E) for the period of 2017–2019. The image data were acquired with a narrow band filter centered at 557.7 nm for the OI airglow emission at ~96 km altitude. The total of 150 wave events were identified in the images of 144 clear nights. The interquartile ranges of wavelength, phase speed, and periods of the identified waves are 20.5–35.5 km, 27.4–45.0 m/s and 10.8–13.7 min with the median values of 27.8 km, 36.3 m/s and 11.7 min, respectively. The summer and spring bias of propagation directions of northeast- and northward, respectively, can be interpreted as the effect of filtering by the prevailing winds in the lower atmosphere. In winter the subdominant northwestward waves may be observed due to nullified filtering effect by small northward background wind or secondary waves generated in the upper atmosphere. Intrinsic phase speeds and periods of the waves were also derived by using the wind data simultaneously observed by a nearly co-located meteor radar. The nature of vertical propagation was evaluated in each season. The majority of observed waves are found to be freely propagating, and thus can be attributed to wave sources in the lower atmosphere.

scholarly journals Influence of the cloud-level neutral layer on the vertical propagation of topographically generated gravity waves on Venus

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Takeru Yamada ◽  
Takeshi Imamura ◽  
Tetsuya Fukuhara ◽  
Makoto Taguchi
Keyword(s):  
Layer Thickness ◽  
Gravity Wave ◽  
Local Time ◽  
Gravity Waves ◽  
Analytical Approach ◽  
Wave Activity ◽  
Neutral Layer ◽  
Low Latitudes ◽  
Vertical Propagation ◽  
The Waves

AbstractThe reason for stationary gravity waves at Venus’ cloud top to appear mostly at low latitudes in the afternoon is not understood. Since a neutral layer exists in the lower part of the cloud layer, the waves should be affected by the neutral layer before reaching the cloud top. To what extent gravity waves can propagate vertically through the neutral layer has been unclear. To examine the possibility that the variation of the neutral layer thickness is responsible for the dependence of the gravity wave activity on the latitude and the local time, we investigated the sensitivity of the vertical propagation of gravity waves on the neutral layer thickness using a numerical model. The results showed that stationary gravity waves with zonal wavelengths longer than 1000 km can propagate to the cloud-top level without notable attenuation in the neutral layer with realistic thicknesses of 5–15 km. This suggests that the observed latitudinal and local time variation of the gravity wave activity should be attributed to processes below the cloud. An analytical approach also showed that gravity waves with horizontal wavelengths shorter than tens of kilometers would be strongly attenuated in the neutral layer; such waves should originate in the altitude region above the neutral layer.

scholarly journals A study of the low-frequency inertio-gravity waves observed during the Pyrénées Experiment

1998 ◽  
Vol 103 (D2) ◽  
pp. 1747-1758 ◽  
Author(s):  
C. M. Scavuzzo ◽  
M. A. Lamfri ◽  
H. Teitelbaum ◽  
F. Lott
Keyword(s):  
Gravity Waves ◽  
Low Frequency
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