scholarly journals Rayleigh lidar observations of enhanced stratopause temperature over Gadanki (13.5° N, 79.2° E) during major stratospheric warming in 2006

2009 ◽  
Vol 27 (1) ◽  
pp. 373-379 ◽  
Author(s):  
S. Sridharan ◽  
S. Sathishkumar ◽  
K. Raghunath
Keyword(s):  
Gravity Wave ◽  
High Latitude ◽  
Planetary Wave ◽  
Planetary Waves ◽  
Stratospheric Warming ◽  
Linear Interaction ◽  
Zonal Wavenumber ◽  
Low Latitudes ◽  
Rayleigh Lidar ◽  
Lidar Observations

Abstract. Rayleigh lidar observations of temperature structure and gravity wave activity were carried out at Gadanki (13.5° N, 79.2° E) during January–February 2006. A major stratospheric warming event occurred at high latitude during the end of January and early February. There was a sudden enhancement in the stratopause temperature over Gadanki coinciding with the date of onset of the major stratospheric warming event which occurred at high latitudes. The temperature enhancement persisted even after the end of the high latitude major warming event. During the same time, the UKMO (United Kingdom Meteorological Office) zonal mean temperature showed a similar warming episode at 10° N and cooling episode at 60° N around the region of stratopause. This could be due to ascending (descending) motions at high (low) latitudes above the critical level of planetary waves, where there was no planetary wave flux. The time variation of the gravity wave potential energy computed from the temperature perturbations over Gadanki shows variabilities at planetary wave periods, suggesting a non-linear interaction between gravity waves and planetary waves. The space-time analysis of UKMO temperature data at high and low latitudes shows the presence of similar periodicities of planetary wave of zonal wavenumber 1.

scholarly journals Rayleigh lidar observations of double stratopause structure over three different northern hemisphere stations

2006 ◽  
Vol 6 (4) ◽  
pp. 6933-6956 ◽  
Author(s):  
V. Sivakumar ◽  
H. Bencherif ◽  
A. Hauchecorne ◽  
P. Keckhut ◽  
D. N. Rao ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Northern Hemisphere ◽  
Planetary Wave ◽  
Middle Level ◽  
Lidar Data ◽  
Upper Level ◽  
Rayleigh Lidar ◽  
First Time ◽  
Lidar Observations

Abstract. Using four years of Rayleigh lidar data collected from three different northern hemisphere stations (Gadanki 13.5° N, 79.2° E ; Mt. Abu 24.5° N, 72.7° E and Observatoire de Haute Provence: OHP; 44° N, 6° E), the characteristics of double (separated) stratopause occurrence are presented here, for the first time. The characteristics are illustrated by a seasonal change during summer and winter and the variation in percentage of occurrence from place to place. It is found that the over-all mean normal stratopause (NS) positioned at the middle level of double stratopause (upper and lower level) with its location nearer to the lower level of double stratopause (LDS) than to the upper level of double stratopause (UDS). The frequency distribution of NS, LDS and UDS demonstrated variability with location, indicating role of dynamical activity. By making use of a quasi-continuous 40 days of lidar observations over Gadanki and OHP, the responsibility of Gravity Wave (GW) and Planetary Wave (PW) activity for the LDS and UDS occurrence are examined and presented.

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 A Short-Term Negative Eddy Feedback on Midlatitude Jet Variability due to Planetary Wave Reflection

2016 ◽  
Vol 73 (11) ◽  
pp. 4311-4328 ◽  
Author(s):  
Gwendal Rivière ◽  
Loïc Robert ◽  
Francis Codron
Keyword(s):  
Planetary Wave ◽  
Physical Nature ◽  
Planetary Waves ◽  
Critical Layer ◽  
Zonal Wavenumber ◽  
Acceleration And Deceleration ◽  
Poleward Shift ◽  
Jet Variability ◽  
Quasigeostrophic Model

Abstract A three-level quasigeostrophic model on the sphere is used to identify the physical nature of the negative planetary wave feedback on midlatitude jet variability. A first approach consists of studying the nonlinear evolution of normal-mode disturbances in a baroclinic westerly zonal jet. For a low-zonal-wavenumber disturbance, successive acceleration and deceleration of the jet occur as a result of reflection of the wave on either side of the jet. The planetary wave deposits momentum in opposite ways during its poleward or equatorward propagation. In contrast, a high-zonal-wavenumber disturbance is not reflected but absorbed within the subtropical critical layer. It thus only induces poleward momentum fluxes, which accelerate the jet and shift it slightly poleward. A long-term simulation forced by a relaxation toward a zonally symmetric temperature profile is then analyzed. Planetary waves are shown to be baroclinically excited. When they propagate equatorward, they induce an acceleration of the jet together with a slight poleward shift. About two-thirds of the planetary waves are absorbed by the subtropical critical layer, which allows the accelerated poleward-shifted jet to persist for a while. For the remaining third, the potential vorticity equatorward of the jet is so well homogenized that a reflection occurs. It is followed by an abrupt jet deceleration during the subsequent poleward propagation. The reflection of planetary waves on the poleward side of the jet is more systematic because of the quasi-permanent presence of a turning latitude there. This negative planetary wave feedback is shown to act more on pulses of the jet than on its latitudinal shifts.

scholarly journals Dynamical evolution of a minor sudden stratospheric warming in the Southern Hemisphere in 2019

2021 ◽  
Author(s):  
Guangyu Liu ◽  
Toshihiko Hirooka ◽  
Nawo Eguchi ◽  
Kirstin Krüger
Keyword(s):  
Southern Hemisphere ◽  
Vertical Component ◽  
Polar Vortex ◽  
Planetary Waves ◽  
High Latitudes ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Zonal Wavenumber ◽  
Westerly Winds ◽  
A Minor

Abstract. This study analyzes the Japanese 55-year Reanalysis (JRA-55) dataset from 2002 to 2019 to examine the sudden stratospheric warming event that occurred in the Southern Hemisphere (SH) in 2019 (hereafter referred to as SSW2019). Strong warming at the polar cap and decelerated westerly winds were observed, but since there was no reversal of westerly winds to easterly winds at 60° S in the middle to lower stratosphere, the SSW2019 is classified as a minor warming event. The results show that quasi-stationary planetary waves of zonal wavenumber 1 developed during the SSW2019. The strong vertical component of the Eliassen–Palm flux with zonal wavenumber 1 is indicative of pronounced propagation of planetary waves to the stratosphere. The wave driving in September 2019 shows that the values are larger than those of the major SSW event in 2002 (hereafter referred to as SSW2002). Since there was no pronounced preconditioning (as in SSW2002) and the polar vortex was already strong before the SSW2019 occurred, a major disturbance of the polar vortex was unlikely to have taken place. The strong wave driving in SSW2019 occurred in high latitudes. Waveguides (i.e., positive values of the refractive index) are found at high latitudes in the upper stratosphere during the warming period, which provided favorable conditions for quasi-stationary planetary waves to propagate upward and poleward.

scholarly journals Planetary wave activity in the Arctic and Antarctic lower stratospheres during 2007 and 2008

2009 ◽  
Vol 9 (4) ◽  
pp. 14601-14643
Author(s):  
S. P. Alexander ◽  
M. G. Shepherd
Keyword(s):  
Northern Hemisphere ◽  
Planetary Wave ◽  
Travelling Waves ◽  
Maximum Amplitude ◽  
Wave Activity ◽  
Planetary Waves ◽  
The Arctic ◽  
Stationary Waves ◽  
Wave Amplification ◽  
Zonal Wavenumber

Abstract. Temperature data from the COSMIC GPS-RO satellite constellation are used to study planetary wave activity in both polar stratospheres from September 2006 until November 2008. One major and several minor sudden stratospheric warmings (SSWs) were recorded during the boreal winters of 2006/2007 and 2007/2008. Planetary wave morphology is studied using space-time spectral analysis while individual waves are extracted using a linear least squares fitting technique. Results show the planetary wave frequency and zonal wavenumber distribution varying between hemisphere and altitude. Most of the large Northern Hemisphere wave activity is associated with the winter SSWs, while the largest amplitude waves in the Southern Hemisphere occur during spring. Planetary wave activity during the 2006/2007 and 2007/2008 Arctic SSWs is due largely to travelling waves with zonal wavenumbers |s|=1 and |s|=2 having periods of 12, 16 and 23 days and stationary waves with |s|=1 and |s|=2. The latitudinal variation of wave amplification during the two Northern Hemisphere winters is studied. Most planetary waves show different structure and behaviour during each winter. Abrupt changes in the latitude of maximum amplitude of some planetary waves is observed co-incident in time with some of the SSWs.

Rayleigh lidar observations of gravity wave characteristics in the middle atmosphere at Gadanki, India (13.5 degrees N, 79.2 degreesE.)

2002 ◽  
Author(s):  
K. Parameswaran ◽  
K. Rajeev ◽  
M. N. Sasi ◽  
Geetha Ramkumar ◽  
B. V. Krishna Murthy ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Middle Atmosphere ◽  
Wave Characteristics ◽  
Rayleigh Lidar ◽  
Lidar Observations

Importance of gravity wave forcing for springtime southern polar vortex breakdown as revealed by ERA5

2021 ◽  
Author(s):  
Aman Gupta ◽  
Thomas Birner ◽  
Andreas Doernbrack ◽  
Inna Polichtchouk
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Zonal Wind ◽  
Planetary Wave ◽  
Climate Models ◽  
Vortex Breakdown ◽  
Polar Vortex ◽  
Wave Drag ◽  
Planetary Waves ◽  
The Mean

<p>Planetary waves and gravity waves are the key drivers of middle atmospheric circulation and variability. While planetary waves are well resolved in climate models, inaccuracies in representation of gravity waves in climate models persist. Inaccuracies in representation of gravity waves limit our understanding of the planetary wave-gravity wave interactions that can be crucial during the Antarctic polar vortex breakdown. Moreover, "missing" gravity wave drag around 60<sup>o</sup>S in the upper stratosphere is considered to be responsible for the "cold-pole" bias in comprehensive climate models that employ parameterizations to appproximately represent the gravity wave drag.</p><p>We illustrate the strength of the high-resolution ERA-5 reanalysis in resolving a broad spectrum of gravity waves in southern hemisphere midlatitudes and to estimate their contribution to the momentum budget around 60<sup>o</sup>S. We find that most of the resolved mountain waves excited over the Andes and Antarctic peninsula propagate away from their source and deposit momentum around 60<sup>o</sup>S over the Southern Ocean. Further, a composite analysis around 60<sup>o</sup>S during the vortex breakdown period using ERA-5 reveals considerably large fractional contribution of resolved + parameterized GWD towards the vortex deceleration. Upto 30 days prior to the breakdown, a balance between the Coriolis acceleration and the planetary wave deceleration provides a weak net deceleration of the mean winds, following which, they provide a net acceleration of the mean winds. The gravity waves, however, provide a steady deceleration of the mean winds throughout the breakdown period. The resolved drag in ERA-5 accounts for as much as one-fourth of the zonal wind deceleration at 60<sup>o</sup>S and 10 hPa, while the parameterized drag in ERA-5 accounts for more than one-half of the zonal wind deceleration.  The findings establish the crucial role of gravity waves in wintertime stratospheric circulation and opens avenues for further stratospheric gravity wave analysis using ERA-5.</p>

Burst of Unusual Quasi-10 day Wave During the 2019 Southern Sudden Stratospheric Warming

2021 ◽  
Author(s):  
Jack Wang ◽  
Scott Palo ◽  
Jeffrey Forbes ◽  
John Marino ◽  
Tracy Moffat-Griffin
Keyword(s):  
Southern Hemisphere ◽  
Planetary Wave ◽  
Wave Activity ◽  
Stratospheric Warming ◽  
Atmospheric Conditions ◽  
Meteor Radar ◽  
Sudden Stratospheric Warming ◽  
Zonal Wavenumber ◽  
Wind Measurements ◽  
Mlt Region

<div> <p>An unusual sudden stratospheric warming (SSW) occurred in the Southern hemisphere in September 2019. Ground-based and satellite observations show the presence of a transient westward-propagating quasi-10 day planetary wave with zonal wavenumber one during the SSW. The planetary wave activity maximizes in the MLT region approximately 10 days after the SSW onset. Analysis indicates the quasi-10 day planetary wave is symmetric about the equator which is contrary to theory for such planetary waves. </p> </div><div> <p>Observations from MLS and SABER provide a unique opportunity to study the global structure and evolution of the symmetric quasi-10 day wave with observations of both geopotential height and temperature during these unusual atmospheric conditions. The space-based measurements are combined with meteor radar wind measurements from Antarctica, providing a comprehensive view of the quasi-10 day wave activity in the southern hemisphere during this SSW. We will also present the results of our mesospheric and lower thermospheric analysis along with a preliminary analysis of the ionospheric response to these wave perturbations.</p> </div>

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