scholarly journals Seasonal transition in gravity wave activity during the springtime stratospheric vortex breakdown

2000 ◽  
Vol 27 (21) ◽  
pp. 3477-3480 ◽  
Author(s):  
Thomas J. Duck ◽  
James A. Whiteway
Keyword(s):  
Gravity Wave ◽  
Vortex Breakdown ◽  
Wave Activity ◽  
Seasonal Transition

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 11 Years of Rayleigh Lidar Observations of Gravity Wave Activity Above the Southern Tip of South America

2019 ◽  
Vol 124 (2) ◽  
pp. 451-467 ◽  
Author(s):  
P. Llamedo ◽  
J. Salvador ◽  
A. Torre ◽  
J. Quiroga ◽  
P. Alexander ◽  
...  
Keyword(s):  
South America ◽  
Gravity Wave ◽  
Wave Activity ◽  
Rayleigh Lidar ◽  
Lidar Observations

scholarly journals Rayleigh/Raman lidar observations of gravity wave activity from 15 to 70 km altitude over Syowa (69°S, 40°E), the Antarctic

2017 ◽  
Vol 122 (15) ◽  
pp. 7869-7880 ◽  
Author(s):  
Masaru Kogure ◽  
Takuji Nakamura ◽  
Mitsumu K. Ejiri ◽  
Takanori Nishiyama ◽  
Yoshihiro Tomikawa ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Wave Activity ◽  
Raman Lidar ◽  
The Antarctic ◽  
Lidar Observations

scholarly journals Enhanced gravity-wave activity and interhemispheric coupling during the MaCWAVE/MIDAS northern summer program 2002

2006 ◽  
Vol 24 (4) ◽  
pp. 1175-1188 ◽  
Author(s):  
E. Becker ◽  
D. C. Fritts
Keyword(s):  
Gravity Wave ◽  
Rossby Wave ◽  
Lower Thermosphere ◽  
Wave Activity ◽  
Lower Atmosphere ◽  
Summer Program ◽  
Latent Heating ◽  
Austral Winter ◽  
Northern Summer ◽  
Mesosphere And Lower Thermosphere

Abstract. We present new sensitivity experiments that link observed anomalies of the mesosphere and lower thermosphere at high latitudes during the MaCWAVE/MIDAS summer program 2002 to enhanced planetary Rossby-wave activity in the austral winter troposphere. We employ the same general concept of a GCM having simplified representations of radiative and latent heating as in a previous study by Becker et al. (2004). In the present version, however, the model includes no gravity wave (GW) parameterization. Instead we employ a high vertical and a moderate horizontal resolution in order to describe GW effects explicitly. This is supported by advanced, nonlinear momentum diffusion schemes that allow for a self-consistent generation of inertia and mid-frequency GWs in the lower atmosphere, their vertical propagation into the mesosphere and lower thermosphere, and their subsequent dissipation which is induced by prescribed horizontal and vertical mixing lengths as functions of height. The main anomalies in northern summer 2002 consist of higher temperatures than usual above 82 km, an anomalous eastward mean zonal wind between 70 and 90 km, an altered meridional flow, enhanced turbulent dissipation below 80 km, and enhanced temperature variations associated with GWs. These signals are all reasonably described by differences between two long-integration perpetual model runs, one with normal July conditions, and another run with modified latent heating in the tropics and Southern Hemisphere to mimic conditions that correspond to the unusual austral winter 2002. The model response to the enhanced winter hemisphere Rossby-wave activity has resulted in both an interhemispheric coupling through a downward shift of the GW-driven branch of the residual circulation and an increased GW activity at high summer latitudes. Thus a quantitative explanation of the dynamical state of the northern mesosphere and lower thermosphere during June-August 2002 requires an enhanced Lorenz energy cycle and correspondingly enhanced GW sources in the troposphere, which in the model show up in both hemispheres.

Gravity wave activity associated with tropical convection detected in TOGA COARE Sounding data

1996 ◽  
Vol 23 (3) ◽  
pp. 261-264 ◽  
Author(s):  
D. J. Karoly ◽  
G. L. Roff ◽  
M. J. Reeder
Keyword(s):  
Gravity Wave ◽  
Wave Activity ◽  
Tropical Convection ◽  
Toga Coare

scholarly journals Validation of a new signal processing scheme for the MST radar at Aberystwyth

2008 ◽  
Vol 26 (11) ◽  
pp. 3253-3268 ◽  
Author(s):  
D. A. Hooper ◽  
J. Nash ◽  
T. Oakley ◽  
M. Turp
Keyword(s):  
Signal Processing ◽  
Measurement Error ◽  
Gravity Wave ◽  
Wave Activity ◽  
Horizontal Wind ◽  
Time Averaging ◽  
Random Measurement Error ◽  
Processing Scheme ◽  
Random Measurement ◽  
Short Period

Abstract. This paper describes a new signal processing scheme for the 46.5 MHz Doppler Beam Swinging wind-profiling radar at Aberystwyth, in the UK. Although the techniques used are similar to those already described in literature – i.e. the identification of multiple signal components within each spectrum and the use of radial- and time-continuity algorithms for quality-control purposes – it is shown that they must be adapted for the specific meteorological environment above Aberystwyth. In particular they need to take into account the three primary causes of unwanted signals: ground clutter, interference, and Rayleigh scatter from hydrometeors under stratiform precipitation conditions. Attention is also paid to the fact that short-period gravity-wave activity can lead to an invalidation of the fundamental assumption of the wind field remaining stationary over the temporal and spatial scales encompassed by a cycle of observation. Methods of identifying and accounting for such conditions are described. The random measurement error associated with horizontal wind components is estimated to be 3.0–4.0 m s−1 for single cycle data. This reduces to 2.0–3.0 m s−1 for data averaged over 30 min. The random measurement error associated with vertical wind components is estimated to be 0.2–0.3 m s−1. This cannot be reduced by time-averaging as significant natural variability is expected over intervals of just a few minutes under conditions of short-period gravity-wave activity.

scholarly journals Seasonal changes in gravity wave activity measured by lidars at mid-latitudes

2008 ◽  
Vol 8 (22) ◽  
pp. 6775-6787 ◽  
Author(s):  
M. Rauthe ◽  
M. Gerding ◽  
F.-J. Lübken
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Low Frequency ◽  
Weather Conditions ◽  
Wave Activity ◽  
Data Set ◽  
Atmospheric Physics ◽  
Adverse Weather Conditions ◽  
Comprehensive Information ◽  
Adverse Weather

Abstract. More than 230 nights of temperature measurements between 1 and 105 km have been performed at the Leibniz-Institute of Atmospheric Physics in Kühlungsborn with a combination of two different lidars, i.e. a Rayleigh-Mie-Raman lidar and a potassium lidar. About 1700 h of measurements have been collected between 2002 and 2006. Apart from some gaps due to the adverse weather conditions the measurements are well distributed throughout the year. Comprehensive information about the activity of medium- and low-frequency gravity waves was extracted from this data set. The dominating vertical wavelengths found are between 10 and 20 km and do not show any seasonal variation. In contrast the temperature fluctuations due to gravity waves experience a clear annual cycle with a maximum in winter. The most significant differences exist around 60 km where the fluctuations in winter are more than two times larger than they are in summer. Only small seasonal differences are observed above 90 km and below 35 km. Generally, the fluctuations grow from about 0.5 K up to 8 K between 20 and 100 km. Damping of waves is observed at nearly all altitudes and in all seasons. The planetary wave activity shows a similar structure in altitude and season as the gravity wave activity which indicates that similar mechanisms influencing different scales. Combining the monthly mean temperatures and the fluctuations we show that the transition between winter and summer season and vice versa seems to start in the mesopause region and to penetrate downward.

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