scholarly journals Semidiurnal solar tide differences between fall and spring transition times in the Northern Hemisphere

2018 ◽  
Vol 36 (4) ◽  
pp. 999-1008 ◽  
Author(s):  
J. Federico Conte ◽  
Jorge L. Chau ◽  
Fazlul I. Laskar ◽  
Gunter Stober ◽  
Hauke Schmidt ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Gravity Waves ◽  
Wave Activity ◽  
Wave Number ◽  
Meteor Radar ◽  
Strong Shift ◽  
Spring Transition ◽  
Solar Tide ◽  
Wind Measurements ◽  
Transition Times

Abstract. We present a study of the semidiurnal solar tide (S2) during the fall and spring transition times in the Northern Hemisphere. The tides have been obtained from wind measurements provided by three meteor radars located at Andenes (69∘ N, 16∘ E), Juliusruh (54∘ N, 13∘ E) and Tavistock (42∘ N, 81∘ W). During the fall, S2 is characterized by a sudden and pronounced decrease occurring every year and at all height levels. The spring transition also shows a decrease in S2, but not sudden and that ascends from lower to higher altitudes during an interval of ∼ 15 to 40 days. To assess contributions of different semidiurnal tidal components, we have examined a 20-year free-run simulation by the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA). We found that the differences exhibited by the S2 tide between equinox times are mainly due to distinct behaviors of the migrating semidiurnal and the non-migrating westward-propagating wave number 1 tidal components (SW2 and SW1, respectively). Specifically, during the fall both SW2 and SW1 decrease, while during the springtime SW2 decreases but SW1 remains approximately constant or decreases only slightly. The decrease shown by SW1 during the fall occurs later than that of SW2 and S2, which indicates that the behavior of S2 is mainly driven by the migrating component. Nonetheless, the influence of SW1 is necessary to explain the behavior of S2 during the spring. In addition, a strong shift in the phase of S2 (of SW2 in the simulations) is also observed during the fall. Our meteor radar wind measurements show more gravity wave activity in the fall than during the spring, which might be indicating that the fall decrease is partly due to interactions between SW2 and gravity waves.

scholarly journals Semidiurnal solar tide differences between fall and spring transition times in the Northern Hemisphere

2018 ◽  
Author(s):  
J. Federico Conte ◽  
Jorge L. Chau ◽  
Fazlul I. Laskar ◽  
Gunter Stober ◽  
Hauke Schmidt ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Gravity Waves ◽  
Wave Activity ◽  
Wave Number ◽  
Meteor Radar ◽  
Strong Shift ◽  
Spring Transition ◽  
Solar Tide ◽  
Wind Measurements ◽  
Transition Times

Abstract. We present a study of the semidiurnal solar tide (S2) during the fall and spring transition times in the Northern Hemisphere. The tides have been obtained from wind measurements provided by three meteor radars located at: Andenes (69° N, 16° E), Juliusruh (54° N, 13° E) and Tavistock (42° N, 81° W). During the autumn, S2 is characterized by a sudden and pronounced decrease occurring every year and at all height levels. The spring transition also shows a decrease of S2, but not sudden and that ascends from lower to higher altitudes during an interval of ~ 15 to 40 days. To assess contributions of different semidiurnal tidal components, we have examined a 20-year free run simulation by the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA). We found that the differences exhibited by the S2 tide between equinox times are mainly due to distinct behaviors of the migrating semidiurnal and the non-migrating westward propagating wave number 1 tidal components (SW2 and SW1, respectively). Specifically, during the fall both, SW2 and SW1 decrease, while during the spring time SW2 decreases but SW1 remains approximately constant or decreases only slightly. The decrease shown by SW1 during the fall occurs later than that of SW2 and S2, which indicates that the behavior of S2 is mainly driven by the migrating component. Nonetheless, the influence of SW1 is necessary to explain the behavior of S2 during the spring. In addition, a strong shift in the phase of S2 (of SW2 in the simulations) is also observed during the fall. Our meteor radar wind measurements show more gravity wave activity in the autumn than during the spring, which might be indicating that the fall decrease is partly due to interactions between SW2 and gravity waves.

scholarly journals The quasi-two-day wave studied using the Northern Hemisphere SuperDARN HF radars

2007 ◽  
Vol 25 (8) ◽  
pp. 1767-1778 ◽  
Author(s):  
S. B. Malinga ◽  
J. M. Ruohoniemi
Keyword(s):  
Northern Hemisphere ◽  
Spectral Power ◽  
Auroral Zone ◽  
Meridional Flow ◽  
Wave Activity ◽  
Wave Number ◽  
Strongly Correlated ◽  
Mean Flow ◽  
Abstract Data ◽  
Zonal Wave Number

Abstract. Data from the Super Dual Radar Network (SuperDARN) radars for 2002 were used to study the behaviour of the quasi-two-day wave (QTDW) in the Northern Hemisphere auroral zone. The period of the QTDW is observed to vary in the range of ~42–56 h, with the most dominant period being ~48 h and secondary peaks at ~42- and ~52-h. The spectral power shows a seasonal variation with a peak power (max~70) in summer. The power shows variations of several days and there is also evidence of changes in wave strength with longitude. The 42-h and the 48-h components tend to be strongly correlated in summer. The onset of enhanced wave activity tends to coincide with the westward acceleration of the zonal mean flow and occurs at a time of strong southward meridional flow. The most frequent instantaneous hourly period is in the 40 to 50 h period band, in line with the simultaneous dominance of the 42-h and the 48-h components. The wave numbers are less variable and are around −2 to −4 during times of strong wave activity. For a period of ~48 h, the zonal wave number is about −3 to −4, using a negative value to indicate westward propagating waves. The 42-h and the 52-h components cover a wider band in the −4 to 1 range. The wide zonal wave number spectrum in our results may account for the observed longitudinal variation in the spectral power of the wave.

scholarly journals Parameters of internal gravity waves in the mesosphere-lower thermosphere region derived from meteor radar wind measurements

2005 ◽  
Vol 23 (11) ◽  
pp. 3431-3437 ◽  
Author(s):  
A. N. Oleynikov ◽  
Ch. Jacobi ◽  
D. M. Sosnovchik
Keyword(s):  
Gravity Waves ◽  
High Frequency ◽  
Lower Thermosphere ◽  
Radar Data ◽  
Internal Gravity Waves ◽  
Meteor Radar ◽  
Energy Propagation ◽  
Data Set ◽  
Wind Measurements ◽  
Phase Progression

Abstract. A procedure of revealing parameters of internal gravity waves from meteor radar wind measurements is presented. The method is based on dividing the measuring volume into different parts and, using wavelet analysis, calculating the phase progression of frequency peaks in the vertical and horizontal direction. Thus, the distribution of vertical and horizontal wavelengths and directions of IGW energy propagation, using meteor radar data, has been obtained. The method was applied to a 4-month data set obtained in July and August, 1998 and 1999. As expected, the majority of waves have been found to propagate upwards, although a considerable number seem to propagate downwards as well. High-frequency (intrinsic periods T* of less than 2 h) waves are dominating. The distribution of waves over the course of an average day is only weakly structured, with weak maxima in the morning and evening.

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>

scholarly journals Simultaneous observations of the 2-day wave at London (43°N, 81°W) and Saskatoon (52°N, 107°W) near 91 km altitude during the two years of 1993 and 1994

1997 ◽  
Vol 15 (10) ◽  
pp. 1324-1339 ◽  
Author(s):  
T. Thayaparan ◽  
W. K. Hocking ◽  
J. MacDougall ◽  
A. H. Manson ◽  
C. E. Meek
Keyword(s):  
Northern Hemisphere ◽  
Wave Activity ◽  
Wave Number ◽  
Time Intervals ◽  
Geographical Data ◽  
Significant Wave ◽  
Annual Variability ◽  
Propagating Waves ◽  
Zonal Wave Number

Abstract. Simultaneous observations are valuable in providing further insights into the character of the quasi 2-day wave. In this study we investigate the period and amplitude for the quasi 2-day wave near 91 km using MF radars at London and Saskatoon, Canada, and in addition look at possible values of the zonal wave number. The results of the present study bring out certain new aspects of the quasi 2-day wave at mid-latitudes in the Northern Hemisphere. In particular we show that the period of the quasi 2-day wave determined from our study (specially at large amplitudes) is smaller (46–47 h) than the 51–52 h period often suggested by other Northern Hemisphere results, and that the periods also showed variability as a function of time. We also draw attention to the annual variability, and especially highlight the occurrence of the wave in non-summer months. Our observations show significant wave correlation between the London and Saskatoon sites during time intervals of strong 2-day wave activity. These results suggest that the 2-day waves of 1993/4 are westward propagating waves of zonal wave number 3, although sometimes the zonal wave number 5 is also indicated (specially at large amplitudes). Our study also contributes additional mid-latitude geographical data which should aid in developing a better picture of the quasi 2-day wave.

The Response of the Polar Vortex to Tropospheric Temperature Eddies in an Idealized General Circulation Model

2022 ◽  
Keyword(s):  
General Circulation Model ◽  
Northern Hemisphere ◽  
General Circulation ◽  
Polar Vortex ◽  
Circulation Model ◽  
Wave Activity ◽  
Wave Number ◽  
Tropospheric Temperature ◽  
Stratospheric Polar Vortex ◽  
Geometric Moments

Abstract A dry-core idealized general circulation model with a stratospheric polar vortex in the northern hemisphere is run with a combination of simplified topography and imposed tropospheric temperature perturbations, each located in the northern hemisphere with a zonal wave number of one. The phase difference between the imposed temperature wave and the topography is varied to understand what effect this has on the occurrence of polar vortex displacements. Geometric moments are used to identify the centroid of the polar vortex for the purposes of classifying whether or not the polar vortex is displaced. Displacements of the polar vortex are a response to increased tropospheric wave activity. Compared to a model run with only topography, the likelihood of the polar vortex being displaced increases when the warm region is located west of the topography peak, and decreases when the cold region is west of the topography peak. This response from the polar vortex is due to the modulation of vertically propogating wave activity by the temperature forcing. When the southerly winds on the western side of the topographically forced anticyclone are collocated with warm or cold temperature forcing, the vertical wave activity flux in the troposphere becomes more positive or negative, respectively. This is in line with recent reanalysis studies which showed that anomalous warming west of the surface pressure high, in the climatological standing wave, precedes polar vortex disturbances.

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.

Diurnal and seasonal variability of short-period gravity waves at ∼40° N using meteor radar wind observations

2021 ◽  
Author(s):  
Caixia Tian ◽  
Xiong Hu ◽  
Alan Z. Liu ◽  
Zhaoai Yan ◽  
Qingchen Xu ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Seasonal Variability ◽  
Meteor Radar ◽  
Short Period

Comparison of Key Characteristics of Remarkable SSW Events in the Southern and Northern Hemisphere

2021 ◽  
Author(s):  
Michal Kozubek ◽  
Peter Krizan
Keyword(s):  
Northern Hemisphere ◽  
Planetary Wave ◽  
Polar Vortex ◽  
Wave Number ◽  
Strong Activity ◽  
Key Characteristics ◽  
Zonal Wave Number ◽  
Show Difference ◽  
Temperature Enhancement ◽  
Stationary Planetary Wave

<p>An exceptionally strong sudden stratospheric warming (SSW) in the Southern Hemisphere (SH) during September 2019 was observed. Because SSW in the SH is very rare, comparison with the only recorded major SH SSW is done. According to World Meteorological Organization (WMO) definition, the SSW in 2019 has to be classified as minor. The cause of SSW in 2002 was very strong activity of stationary planetary wave with zonal wave-number (ZW) 2, which reached its maximum when the polar vortex split into two circulations with polar temperature enhancement by 30 K/week and it penetrated deeply to the lower stratosphere and upper troposphere. On the other hand, the minor SSW in 2019 involved an exceptionally strong wave-1 planetary wave and a large polar temperature enhancement by 50.8 K/week, but it affected mainly the middle and upper stratosphere. The strongest SSW in the Northern Hemisphere was observed in 2009. This study provides comparison of two strongest SSW in the SH and the strongest SSW in the NH to show difference between two hemispheres and possible impact to the lower or higher layers.</p>

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