On the seasonal dependence of medium-scale atmospheric gravity waves in the upper atmosphere at high latitudes

1996 ◽  
Vol 101 (A7) ◽  
pp. 15685-15699 ◽  
Author(s):  
W. A. Bristow ◽  
R. A. Greenwald ◽  
J. P. Villain
Keyword(s):  
Gravity Waves ◽  
Upper Atmosphere ◽  
High Latitudes ◽  
Atmospheric Gravity Waves ◽  
Medium Scale ◽  
Atmospheric Gravity ◽  
Seasonal Dependence

scholarly journals Climatology of Medium-Scale Traveling Ionospheric Disturbances (MSTIDs) Observed with GPS Networks in the North African Region

2020 ◽  
Author(s):  
Temitope Seun Oluwadare ◽  
Norbert Jakowski ◽  
Cesar E. Valladares ◽  
Andrew Oke-Ovie Akala ◽  
Oladipo E. Abe ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Occurrence Rate ◽  
Ionospheric Disturbances ◽  
North African ◽  
African Region ◽  
Atmospheric Gravity Waves ◽  
Medium Scale ◽  
Traveling Ionospheric Disturbances ◽  
The North ◽  
Atmospheric Gravity

Abstract We present for the first time the climatology of medium-scale traveling ionospheric disturbances (MSTIDs) by using Global Positioning System (GPS) receiver networks on geomagnetically quiet days (Kp ≤ 3) over the North African region during 2008-2016. The MSTIDs appear frequently as oscillating waves or wave-like structures in electron density induced by the passage of Atmospheric Gravity Waves (AGW) propagating through the neutral atmosphere and consequently, causing fluctuation in the ionospheric Total Electron Content (TEC). The TEC perturbations (dTEC) data are derived from dual frequency GPS-measurements. We have statistically analyzed the MSTIDs characteristics, occurrence rate, seasonal behavior as well as the interannual dependence. The results show a local and seasonal dependence of nighttime and daytime MSTIDs. The propagation direction is predominantly towards the South (equatorward), MSTIDs event period is (12 ≤ period ≤ 53 mins), and dominant amplitude (0.08 ≤ amp ≤ ~1.5 TECU), with a propagation velocity higher at daytime than nighttime. The amplitudes of the MSTIDs increase with solar activity. The local MSTIDs Spatio-temporal heat reveals variability in disturbance occurrence time, but seems to be dominant within the hours of (Northwest: 1200–1600 LT) and (Northeast: 1000–1400 LT) in December solstice during daytime, and around (NW: 2100–0200 LT) and (NE: 1900–0200 LT) in June solstice, but get extended to March equinox during solar maximum (2014) during the nighttime. The time series of MSTIDs regional distribution map is also generated. Atmospheric gravity waves (AGW) seems to be responsible for the daytime MSTIDs occurrence.

Propagation factors influencing observations of resonances of atmospheric gravity waves

2020 ◽  
Author(s):  
Nikolay Zabotin ◽  
Oleg Godin
Keyword(s):  
Wave Packet ◽  
Gravity Waves ◽  
Numerical Solutions ◽  
Broad Band ◽  
Ground Level ◽  
Hf Radar ◽  
Upper Atmosphere ◽  
Atmospheric Gravity Waves ◽  
Atmospheric Wave ◽  
Atmospheric Gravity

<p>Observations of the ionosphere with the airglow, GPS-TEC, and HF radar techniques reveal a resonance-kind response of the middle and upper atmosphere to broad-band excitation by earthquakes, volcano eruptions, and convective storms. The resonances occur at such frequencies that an atmospheric wave, which is radiated at the ground level and is reflected from a turning point in the middle or upper atmosphere, upon return to the ground level satisfies boundary conditions on the ground. The "buoyancy" resonances (resonances of atmospheric gravity waves) with periods from several minutes and up to several hours arise in addition to well-known "acoustic" resonances with periods of about 3–4 minutes. The buoyancy resonances occur on the gravity branch of the dispersion relation for the acoustic-gravity waves. Infragravity waves in the ocean covering the same frequency band may serve as an efficient source of excitation of the buoyancy resonances. We have obtained dispersion relations for buoyancy resonances earlier. In this paper we investigate the influence of specific propagation characteristics of the gravity waves (their oblique propagation and dissipative attenuation) on conditions of their observation. We use  asymptotic (WKB and ray tracing) methods to investigate relationship between the gravity wave skip distance and the dimensions of typical infragravity wave packets in the oceans and find that conditions can be met for interaction of the same atmospheric wave packet with the same ocean wave packet. The dissipative attenuation eliminates some of the resonance modes, but still many of them remain intact. We use numerical solutions of the full wave equation to confirm results obtained by asymptotic methods. Calculations of this kind demonstrate a possibility of resonance-like behavior of the gravity waves in situations when partial reflections (caused by extrema of the refractive index) appear in addition to the total reflection. Unlike acoustic resonances, buoyancy resonances exhibit high sensitivity to the wind velocity profile and its variations. Non-stationarity of the atmosphere is an important factor limiting possibilities to observe the buoyancy resonances. Nevertheless, relatively low threshold for meeting all other conditions for their appearance and temporal/geographical diversity of the atmosphere makes it still quite probable to see their manifestations. The resonances correspond to most efficient coupling between the atmosphere and its lower boundary and are promising for detection of such coupling.</p>

scholarly journals The influence of solar wind on extratropical cyclones – Part 2: A link mediated by auroral atmospheric gravity waves?

2009 ◽  
Vol 27 (1) ◽  
pp. 31-57 ◽  
Author(s):  
P. Prikryl ◽  
D. B. Muldrew ◽  
G. J. Sofko
Keyword(s):  
Solar Wind ◽  
Gravity Waves ◽  
Significant Response ◽  
Extratropical Cyclones ◽  
High Latitudes ◽  
Atmospheric Gravity Waves ◽  
Low Latitudes ◽  
Slantwise Convection ◽  
High Level ◽  
Atmospheric Gravity

Abstract. Cases of mesoscale cloud bands in extratropical cyclones are observed a few hours after atmospheric gravity waves (AGWs) are launched from the auroral ionosphere. It is suggested that the solar-wind-generated auroral AGWs contribute to processes that release instabilities and initiate slantwise convection thus leading to cloud bands and growth of extratropical cyclones. Also, if the AGWs are ducted to low latitudes, they could influence the development of tropical cyclones. The gravity-wave-induced vertical lift may modulate the slantwise convection by releasing the moist symmetric instability at near-threshold conditions in the warm frontal zone of extratropical cyclones. Latent heat release associated with the mesoscale slantwise convection has been linked to explosive cyclogenesis and severe weather. The circumstantial and statistical evidence of the solar wind influence on extratropical cyclones is further supported by a statistical analysis of high-level clouds (<440 mb) extracted from the International Satellite Cloud Climatology Project (ISCCP) D1 dataset. A statistically significant response of the high-level cloud area index (HCAI) to fast solar wind from coronal holes is found in mid-to-high latitudes during autumn-winter and in low latitudes during spring-summer. In the extratropics, this response of the HCAI to solar wind forcing is consistent with the effect on tropospheric vorticity found by Wilcox et al. (1974) and verified by Prikryl et al. (2009). In the tropics, the observed HCAI response, namely a decrease in HCAI at the arrival of solar wind stream followed by an increase a few days later, is similar to that in the northern and southern mid-to-high latitudes. The amplitude of the response nearly doubles for stream interfaces associated with the interplanetary magnetic field BZ component shifting southward. When the IMF BZ after the stream interface shifts northward, the autumn-winter effect weakens or shifts to lower (mid) latitudes and no statistically significant response is found at low latitudes in spring-summer. The observed effect persists through years of low and high volcanic aerosol loading. The similarity of the response in mid-to-high and low latitudes, the lack of dependence upon aerosol loading, and the enhanced amplitude of the effect when IMF BZ component shifts southward, favor the proposed AGW link over the atmospheric electric circuit (AEC) mechanism (Tinsley et al., 1994). The latter requires the presence of stratospheric aerosols for a significant effect and should produce negative and positive cloud anomalies in mid-to-high and low latitudes, respectively. However, if the requirement of aerosols for the AEC mechanism can be relaxed, the AGW and AEC mechanisms should work in synergy at least in mid-to-high latitudes.

THE VISCOUS DAMPING OF ATMOSPHERIC GRAVITY WAVES

1963 ◽  
Vol 41 (12) ◽  
pp. 1935-1948 ◽  
Author(s):  
M. L. V. Pitteway ◽  
C. O. Hines
Keyword(s):  
Gravity Waves ◽  
Thermal Conduction ◽  
Upper Atmosphere ◽  
Viscous Damping ◽  
Atmospheric Gravity Waves ◽  
Atmospheric Gravity

Dissipation produced by viscous damping and thermal conduction is important in the study of atmospheric gravity waves, which are themselves important in a study of "irregular" motions in the upper atmosphere. The mathematics of this damping is considered in some detail here, and charts are given to assess the effects of viscous damping and thermal conduction at meteor heights in the upper atmosphere. The results of this paper are consistent with the conclusions of an earlier analysis, insofar as the two overlap, and extend the range of conditions considered.

scholarly journals Preliminary Dual-Satellite Observations of Atmospheric Gravity Waves in Airglow

Atmosphere ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 650
Author(s):  
Jia Yue ◽  
Septi Perwitasari ◽  
Shuang Xu ◽  
Yuta Hozumi ◽  
Takuji Nakamura ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Numerical Models ◽  
Space Station ◽  
Upper Atmosphere ◽  
Lower Atmosphere ◽  
Atmospheric Gravity Waves ◽  
Spectral Imager ◽  
Atmospheric Gravity

Atmospheric gravity waves (AGWs) are among the important energy and momentum transfer mechanisms from the troposphere to the middle and upper atmosphere. Despite their understood importance in governing the structure and dynamics of these regions, mesospheric AGWs remain poorly measured globally, and largely unconstrained in numerical models. Since late 2011, the Suomi National Polar-orbiting Partnership (NPP) Visible/Infrared Imaging Radiometer Suite (VIIRS) day–night band (DNB) has observed global AGWs near the mesopause by virtue of its sensitivity to weak emissions of the OH* Meinel bands. The wave features, detectable at 0.75 km spatial resolution across its 3000 km imagery swath, are often confused by the upwelling emission of city lights and clouds reflecting downwelling nightglow. The Ionosphere, Mesosphere, upper Atmosphere and Plasmasphere (IMAP)/ Visible and near-Infrared Spectral Imager (VISI) O2 band, an independent measure of the AGW structures in nightglow based on the International Space Station (ISS) during 2012–2015, contains much less noise from the lower atmosphere. However, VISI offers much coarser resolution of 14–16 km and a narrower swath width of 600 km. Here, we present preliminary results of comparisons between VIIRS/DNB and VISI observations of AGWs, focusing on several concentric AGW events excited by the thunderstorms over Eastern Asia in August 2013. The comparisons point toward suggested improvements for future spaceborne airglow sensor designs targeting AGWs.

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