scholarly journals Variability of MLT winds and waves over mid-latitude during the 2000/2001 and 2009/2010 winter stratospheric sudden warming

2012 ◽  
Vol 30 (6) ◽  
pp. 991-1001 ◽  
Author(s):  
X. Chen ◽  
X. Hu ◽  
C. Xiao
Keyword(s):  
Gravity Waves ◽  
Zonal Wind ◽  
Lower Thermosphere ◽  
Temporal Variations ◽  
Low Latitude ◽  
Stratospheric Sudden Warming ◽  
Stratospheric Temperature ◽  
Wind Structure ◽  
Polar Stratosphere ◽  
Mlt Region

Abstract. The mesosphere and lower thermosphere (MLT) wind structure over Wuhan (30° N, 114° E) in 2000/2001 winter and over Langfang (39.4° N, 116.6° E) in 2009/2010 winter are examined to reveal the effects of stratospheric sudden warming (SSW) in mid-low-latitude MLT region. The result shows that the MLT daily zonal wind over these two sites reversed from eastward wind to westward wind for several days during the SSW events. The reversals were almost coincident with the polar stratospheric temperature reaching its maximum at 10 hPa, 90° N and were about ten days prior to the reversal of high latitude stratospheric zonal wind at 10 hPa, 60° N. The temporal variations of tides, gravity waves and 2-day planetary waves in the mid-latitude MLT showed different behavior during the two SSW events. During the 2001 SSW event, MLT diurnal tide reached its maximum when the MLT zonal wind decreased rapidly and SSW event began in polar stratosphere; the activity of 2-day waves decreased after the onset of the 2001 SSW, while the gravity wave increased when the 2001 SSW developed into a major warming. However, in the 2009/2010 winter, the semidiurnal tide and 2-day wave in MLT over Langfang reached a peak about two days earlier than zonal wind reversal at 10 hPa, 60° N; no significant features were found in diurnal tides, terdiurnal tides and gravity waves related to the 2010 SSW event.

scholarly journals Equatorial counter electrojets and polar stratospheric sudden warmings – a classical example of high latitude-low latitude coupling?

2009 ◽  
Vol 27 (8) ◽  
pp. 3147-3153 ◽  
Author(s):  
C. Vineeth ◽  
T. Kumar Pant ◽  
R. Sridharan
Keyword(s):  
Zonal Wind ◽  
High Latitude ◽  
Planetary Wave ◽  
Maximum Intensity ◽  
Low Latitude ◽  
Stratospheric Sudden Warming ◽  
Stratospheric Temperature ◽  
Stratospheric Sudden Warmings ◽  
Subsequent Modification ◽  
Circulation Changes

Abstract. Favored occurrences of Equatorial Counter Electrojets (CEJs) with a quasi 16-day periodicity over Trivandrum (8.5° N, 76.5° E, 0.5° N diplat.) in association with the polar Stratospheric Sudden Warming (SSW) events are presented. It is observed that, the stratospheric temperature at ~30 km over Trivandrum shows a sudden cooling prior to the SSWs and the CEJs of maximum intensity which occurs around this time. In general stronger CEJs are associated with more intense SSW events. The stratospheric zonal mean zonal wind over Trivandrum also exhibits a distinctly different pattern during the SSW period. These circulation changes are proposed to be conducive for the upward propagation of the lower atmospheric waves over the equatorial latitudes. The interaction of such waves with the tidal components at the upper mesosphere and its subsequent modification are suggested to be responsible for the occurrence of CEJs having planetary wave periods.

The Momentum Budget in the Stratosphere, Mesosphere, and Lower Thermosphere. Part II: The In Situ Generation of Gravity Waves

2018 ◽  
Vol 75 (10) ◽  
pp. 3635-3651 ◽  
Author(s):  
Ryosuke Yasui ◽  
Kaoru Sato ◽  
Yasunobu Miyoshi
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Lower Thermosphere ◽  
Shear Instability ◽  
Wave Forcing ◽  
Momentum Budget ◽  
Mesosphere And Lower Thermosphere ◽  
In Situ Generation ◽  
Mlt Region

The contributions of gravity waves to the momentum budget in the mesosphere and lower thermosphere (MLT) is examined using simulation data from the Ground-to-Topside Model of Atmosphere and Ionosphere for Aeronomy (GAIA) whole-atmosphere model. Regardless of the relatively coarse model resolution, gravity waves appear in the MLT region. The resolved gravity waves largely contribute to the MLT momentum budget. A pair of positive and negative Eliassen–Palm flux divergences of the resolved gravity waves are observed in the summer MLT region, suggesting that the resolved gravity waves are likely in situ generated in the MLT region. In the summer MLT region, the mean zonal winds have a strong vertical shear that is likely formed by parameterized gravity wave forcing. The Richardson number sometimes becomes less than a quarter in the strong-shear region, suggesting that the resolved gravity waves are generated by shear instability. In addition, shear instability occurs in the low (middle) latitudes of the summer (winter) MLT region and is associated with diurnal (semidiurnal) migrating tides. Resolved gravity waves are also radiated from these regions. In Part I of this paper, it was shown that Rossby waves in the MLT region are also radiated by the barotropic and/or baroclinic instability formed by parameterized gravity wave forcing. These results strongly suggest that the forcing by gravity waves originating from the lower atmosphere causes the barotropic/baroclinic and shear instabilities in the mesosphere that, respectively, generate Rossby and gravity waves and suggest that the in situ generation and dissipation of these waves play important roles in the momentum budget of the MLT region.

scholarly journals Tropical connection to the polar stratospheric sudden warming through quasi 16-day planetary wave

2010 ◽  
Vol 28 (11) ◽  
pp. 2007-2013 ◽  
Author(s):  
C. Vineeth ◽  
T. K. Pant ◽  
K. K. Kumar ◽  
S. G. Sumod
Keyword(s):  
Numerical Simulations ◽  
Zonal Wind ◽  
Planetary Wave ◽  
Stratospheric Sudden Warming ◽  
The Past ◽  
Numerical Studies ◽  
Stratospheric Wind ◽  
Polar Stratosphere ◽  
The Tropics ◽  
First Time

Abstract. The Planetary Waves (PWs) are believed to have significant role in generating the wintertime warming over the polar stratosphere, known as Stratospheric Sudden Warming (SSW). However, the origin, characteristics and evolution of these waves are still speculative. The possibility that the PWs over the polar stratosphere, which play an important role in the generation of SSW, could also have contribution from the tropics has been indicated through many numerical simulations in the past, but due to the paucity of global measurements it could not be established unequivocally. The earlier numerical studies also indicated the presence of a zero-wind line (more general the critical layer, where the zonal wind amplitude becomes zero) whose real counterparts were not observed in the atmosphere. The present study based on the NCEP/NCAR reanalysis of stratospheric wind and temperatures of recent years clearly shows that (i) the zero-wind line appears over the tropics ~60 days prior to the major SSWs and progresses towards the Pole and (ii) an enhanced PW activity of quasi periodicity 16-days, which is also seen almost simultaneously with the zero-wind line, shows a propagation from equator to the Pole. This result is significant as it presents for the first time the connection between the tropics during the SSW events and the pole, through the quasi 16-day wave.

scholarly journals Stratospheric influence on the mesosphere–lower thermosphere over mid latitudes in winter observed by a Fabry–Perot interferometer

2021 ◽  
Vol 39 (1) ◽  
pp. 267-276
Author(s):  
Olga S. Zorkaltseva ◽  
Roman V. Vasilyev
Keyword(s):  
Zonal Wind ◽  
Emission Intensity ◽  
Lower Thermosphere ◽  
Optical Emission ◽  
Temporal Variations ◽  
Upper Atmosphere ◽  
Eastern Siberia ◽  
Siberian Branch ◽  
Fabry Perot ◽  
Academy Of Sciences

Abstract. In this paper, we study the response of the mesosphere–lower thermosphere (MLT) to sudden stratospheric warmings (SSWs) and the activity of planetary waves (PWs). We observe the 557.7 nm optical emission to retrieve the MLT wind and temperature with the only Fabry–Perot interferometer (FPI) in Russia. The FPI is located at the mid latitudes of eastern Siberia within the Tory Observatory (TOR) at the Institute of Solar-Terrestrial Physics of the Siberian Branch of the Russian Academy of Sciences (ISTP SB RAS, 51.8∘ N, 103.1∘ E). Regular interferometer monitoring started in December 2016. Here, we address the temporal variations in the 557.7 nm emission intensity as well as the variations in wind and temperature measured during the 2016–2020 winters. Both SSWs and PWs appear to have equally strong effects in the upper atmosphere. When the 557.7 nm emission decreases due to some influences from below (SSWs or PWs), the temperature increases significantly, as does its variability. The dispersion of zonal wind does not show significant PW- and SSW-correlated variations, but the dominant MLT zonal wind reverses during major SSW events simultaneously with the averaged zonal wind at 60∘ N in the stratosphere.

scholarly journals First results from the CAWSES-India Tidal Campaign

2008 ◽  
Vol 26 (8) ◽  
pp. 2323-2331 ◽  
Author(s):  
S. Gurubaran ◽  
D. Narayana Rao ◽  
G. Ramkumar ◽  
T. K. Ramkumar ◽  
G. Dutta ◽  
...  
Keyword(s):  
Lower Thermosphere ◽  
Weather Data ◽  
Atmospheric Tides ◽  
Data Sets ◽  
Low Latitude ◽  
First Results ◽  
Mesosphere And Lower Thermosphere ◽  
Nonmigrating Tides ◽  
The Western Pacific ◽  
Mlt Region

Abstract. The first CAWSES-India Tidal Campaign was conducted by the Indian scientific community during March–April 2006. The objectives of this campaign were: (1) To determine the characteristics of tides in the troposphere and lower stratosphere (0–20 km) and mesosphere and lower thermosphere (MLT) region (80–100 km), (2) to explore and identify what lower atmospheric processes drive middle atmospheric tides in the Indian continental region and (3) to provide information on those short-term variabilities of MLT tides that are likely to have an impact on the ionospheric variabilities and contribute to the upper atmospheric weather. Data sets from experiments conducted at the three low latitude radar sites, namely, Trivandrum (8.5° N, 76.9° E), Tirunelveli (8.7° N, 77.8° E) and Gadanki (13.5° N, 79.2° E) and fortnightly rocket launches from Thumba were made use of in this study. An important observational finding reported in this work is that the radar observations at Tirunelveli/Trivandrum indicate the presence of 15–20 day modulation of diurnal tide activity at MLT heights during the February–March period. A similar variation in the OLR fields in the western Pacific (120–160° longitude region) suggests a possible link between the observed tidal variabilities and the variations in the deep tropical convection through the nonmigrating tides it generates.

scholarly journals Stratospheric influence on MLT over mid-latitudes in winter by Fabry-Perot interferometer data

2020 ◽  
Author(s):  
Olga S. Zorkaltseva ◽  
Roman V. Vasilyev
Keyword(s):  
Zonal Wind ◽  
Lower Thermosphere ◽  
Optical Emission ◽  
Temporal Variations ◽  
Eastern Siberia ◽  
Wind Dispersion ◽  
Fabry Perot ◽  
Mesosphere And Lower Thermosphere ◽  
Academy Of Sciences ◽  
Parameters Measurement

Abstract. In this paper, we study the response of the mesosphere and lower thermosphere (MLT) to sudden stratospheric warmings (SSWs) and the activity of stationary planetary waves (SPWs). We observe the 557.7-nm optical emission for retrieve the MLT wind, temperature with the Fabry-Perot interferometer (FPI) that has no analogues in Russia. The FPI is located at the mid-latitudes of Eastern Siberia within the Tory Observatory (TOR) at the Institute of Solar-Terrestrial Physics of the Siberian Branch of the Russian Academy of Sciences (ISTP SB RAS, 51.8N, 103.1E). Regular interferometer monitoring started in Dec 2016. Here, we address the temporal variations in the 557.7-nm emission intensity, as well as the variations in wind, temperature, and their variability obtained by using the line parameters measurement during the 2016–2020 winters. Both SSWs and SPWs appear to have equally strong effects in the upper atmosphere. When the 557.7-nm emission decreases due to some influences from below (SSWs or SPWs), the temperature variation observed by using this line and the temperature itself increase significantly. The zonal wind dispersion does not show significant SPW- and SSW-correlated variations, but the dominant zonal wind reverses during major SSW events the same as the averaged zonal wind at 60N in the stratosphere does without significant delays.

scholarly journals Observations of thermosphere and ionosphere changes due to the dissipative 6.5-day wave in the lower thermosphere

2015 ◽  
Vol 33 (7) ◽  
pp. 913-922 ◽  
Author(s):  
Q. Gan ◽  
J. Yue ◽  
L. C. Chang ◽  
W. B. Wang ◽  
S. D. Zhang ◽  
...  
Keyword(s):  
Zonal Wind ◽  
Lower Thermosphere ◽  
Temporal Correlation ◽  
Satellite System ◽  
Electron Content ◽  
Total Electron ◽  
Ionospheric Total Electron Content ◽  
Mesosphere And Lower Thermosphere ◽  
Global Navigation Satellite ◽  
Mlt Region

Abstract. In the current work, temperature and wind data from the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite during the years 2002–2007 were used to describe the seasonal variations of the westward propagating 6.5-day planetary wave in the mesosphere and lower thermosphere (MLT). Thermospheric composition data from the TIMED satellite and ionospheric total electron content (TEC) from the International Global Navigation Satellite System (GNSS) Service were then employed to carry out two case studies on the effect of this dissipating wave on the thermosphere/ionosphere. In both cases, there were westward anomalies of ~ 30–40 m s−1 in zonal wind in the MLT region that were caused by momentum deposition of the 6.5-day wave, which had peak activity during equinoxes. The westward zonal wind anomalies led to extra poleward meridional flows in both hemispheres. Meanwhile, there were evident overall reductions of thermospheric column density O / N2 ratio and ionospheric TEC with magnitudes of up to 16–24 % during these two strong 6.5-day wave events. Based on the temporal correlation between O / N2 and TEC reductions, as well as the extra poleward meridional circulations associated with the 6.5-day waves, we conclude that the dissipative 6.5-day wave in the lower thermosphere can cause changes in the thermosphere/ionosphere via the mixing effect, similar to the quasi-two-day wave (QTDW) as predicted by Yue and Wang (2014).

scholarly journals Global balanced wind derived from SABER temperature and pressure observations and its validations

2021 ◽  
Vol 13 (12) ◽  
pp. 5643-5661
Author(s):  
Xiao Liu ◽  
Jiyao Xu ◽  
Jia Yue ◽  
You Yu ◽  
Paulo P. Batista ◽  
...  
Keyword(s):  
Zonal Wind ◽  
Lower Thermosphere ◽  
Temporal Variations ◽  
Meteor Radar ◽  
Quasi Biennial Oscillation ◽  
Height Range ◽  
Zonal Winds ◽  
Wind Theory ◽  
Temperature And Pressure ◽  
Identical Zero

Abstract. Zonal winds in the stratosphere and mesosphere play important roles in atmospheric dynamics and aeronomy. However, the direct measurement of winds in this height range is difficult. We present a dataset of the monthly mean zonal wind in the height range of 18–100 km and at latitudes of 50∘ S–50∘ N from 2002 to 2019, derived by the gradient balance wind theory and the temperature and pressure observed by the SABER instrument. The tide alias above 80 km at the Equator is replaced by the monthly mean zonal wind measured by a meteor radar at 0.2∘ S. The dataset (named BU) is validated by comparing with the zonal wind from MERRA2 (MerU), UARP (UraU), the HWM14 empirical model (HwmU), meteor radar (MetU), and lidar (LidU) at seven stations from around 50∘ N to 29.7∘ S. At 18–70 km, BU and MerU have (i) nearly identical zero wind lines and (ii) year-to-year variations of the eastward and westward wind jets at middle and high latitudes, and (iii) the quasi-biennial oscillation (QBO) and semi-annual oscillation (SAO) especially the disrupted QBO in early 2016. The comparisons among BU, UraU, and HwmU show good agreement in general below 80 km. Above 80 km, the agreements among BU, UraU, HwmU, MetU, and LidU are good in general, except some discrepancies at limited heights and months. The BU data are archived as netCDF files and are available at https://doi.org/10.12176/01.99.00574 (Liu et al., 2021). The advantages of the global BU dataset are its large vertical extent (from the stratosphere to the lower thermosphere) and 18-year internally consistent time series (2002–2019). The BU data is useful to study the temporal variations with periods ranging from seasons to decades at 50∘ S–50∘ N. It can also be used as the background wind for atmospheric wave propagation.

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