Internal gravitational waves (IGW) or inertial gravitational waves (IGW) is one of the forms of oscillatory movements that exist in the atmosphere as an elastic medium. The term “gravitational” in the name of this type of wave indicates that gravity is one of the factors determining the existence of HBV [1] .
Content
Education Mechanism
The occurrence of HBV occurs orographically , for example, when wind flows around mountain massifs, in jet streams, etc. [2] . Similar processes generate a wide range of waves. As they propagate upward, the wave amplitudes increase exponentially due to a decrease in the molecular density of air . Growth continues until the temperature variations dT / dh caused by the HBV become larger than the adiabatic temperature gradient. From this moment, the HBV intensifies turbulent diffusion , which prevents a further increase in amplitude. In this case, the HBV are destroyed, giving an excess of energy to the “average” air flow movement [3] .
Features
The determination of HBV parameters, usually from lidar sensing data, is carried out both visually and using methods of statistical (usually Wavelet -) analysis. According to studies [4] [5] [6] , the phase velocity of the HBV lies in the range 0.02–0.71 m, with the most common values being 0.1–0.3 m, the vertical wavelength is in the range of 3–20 km; and the oscillation period is 5-27 hours
Scope
To assess the intensity of wave disturbances, a height profile of the density of potential energy of the IGW is used, which, as a rule, is calculated using temperature according to lidar sensing data. Some high-resolution global climate models use this data to determine the source of waves, study the propagation and dissipation of waves, and also to take into account energy transfer to the upper stratosphere and lower mesosphere . According to [7] , the altitude density profile of the potential energy of the HBV is determined by the formula:
where h is the height above sea level; g (h) is the acceleration of gravity; N (h) is the Brent-Väisälä frequency; - rms value of temperature fluctuations; T 0 (h) is the average temperature profile. The frequency of Brent-Väisälä is determined by the formula:
where c p is the heat capacity of air at constant pressure; the derivative dT 0 / dh is found from lidar measurements by differentiating the spline describing the smooth part of the spectrum .
Sources
- ↑ Stratosphere lidar control - Books published with the support of the RFBR - Library - RFBR Portal . www.rfbr.ru. Date of treatment April 20, 2016.
- ↑ Gossard E.E., Hook W.H. Waves in the atmosphere: Infrasound and gravitational waves in the atmosphere — their origin and propagation (Russian) // M: World: book. - 1978. - T. 1-2 .
- ↑ RS Lindzen. Turbulence and stress owing to gravity wave and tidal breakdown (English) // Journal of Geophysical Research: Oceans. - 1981-10-20. - Vol. 86 , iss. C10 . - P. 9707–9714 . - ISSN 2156-2202 . - DOI : 10.1029 / JC086iC10p09707 .
- ↑ AKP Marsh, NJ Mitchell, L. Thomas. Lidar studies of stratospheric gravity-wave spectra // Planetary and Space Science. - 1991-11-01. - T. 39 , no. 11 . - S. 1541-1548 . - DOI : 10.1016 / 0032-0633 (91) 90081-K .
- ↑ R. Wilson, ML Chanin, A. Hauchecorne. Gravity waves in the middle atmosphere observed by Rayleigh lidar: 2. Climatology (Eng.) // Journal of Geophysical Research: Atmospheres. - 1991-03-20. - Vol. 96 , iss. D3 . - P. 5169-5183 . - ISSN 2156-2202 . - DOI : 10.1029 / 90JD02610 .
- ↑ "Rayleigh Lidar Measurements of the Temporal Frequency and Vertical Wav" by X Gao, J W. Meriwether et al. . digitalcommons.usu.edu. Date of treatment April 20, 2016.
- ↑ James A. Whiteway, Allan I. Carswell. Lidar observations of gravity wave activity in the upper stratosphere over Toronto (Eng.) // Journal of Geophysical Research: Atmospheres. - 1995-07-20. - Vol. 100 , iss. D7 - P. 14113-14124 . - ISSN 2156-2202 . - DOI : 10.1029 / 95JD00511 .