At 12:15 on January 15,2022(Beijing time),a massive eruption of the Hunga Tonga-Hunga Ha'apai volcano produced violent atmospheric fluctuations,which in turn generated a global tsunami through an abrupt air pressu...At 12:15 on January 15,2022(Beijing time),a massive eruption of the Hunga Tonga-Hunga Ha'apai volcano produced violent atmospheric fluctuations,which in turn generated a global tsunami through an abrupt air pressure shock upon the sea surface.Two main components of tsunami waves,phase-locked waves and free gravity waves,were identified by significant differences in propagating speeds across the deep ocean.The phase-locked wave propagated through the ocean basin synchronously with the atmospheric Lamb wave at an average speed of approximately 306 m/s,followed by the free gravity wave at a slower speed.The locked wave reached the coast of eastern Taiwan Island at about 20:00 on January 15,in coincidence with the Lamb wave arrival.However,on the coast of Chinese mainland,tidal gauges did not record tsunami signals until at least 2 h after the Lamb wave arrivals.Theoretical analyses and numerical experiments both suggested that as a result of the incoming wave shoaling above the vast continental shelf of Chinese mainland,the locked wave was no longer trapped by the air pressure shock and gradually transformed into freely-propagating shallow water waves by slowing down its propagation.Due to the longlasting planetary atmospheric fluctuations circling the earth many times,the sea level oscillations continuously propagated onto the Chinese shelf,which resulted in the tsunami waves excited along the Chinese coasts for at least 36 h.The maximum wave amplitude recorded on the coast of eastern Taiwan Island was 44 cm at Wushi,while on the coasts of eastern and southern Chinese mainland,the maximum amplitudes were 22 cm at Shipu and 13 cm at Zhuhai.Fourier and wavelet analyses were performed to identify the major components of the tsunami waves on the Chinese coasts.The results indicated that eastern Taiwan Island was impacted mainly by the waves with periods of approximately 10-40 min.Chinese mainland was hit by the evolved shallow water waves and subsequent free waves,with periods of approximately 40-100 and 16-20 min,resp展开更多
Study of seismo-ionospheric coupling mechanism demands the quiet geomagnetic condition to eliminate any kind of contamination in the lower atmospheric and ionospheric parameters. In this manuscript, we present the eff...Study of seismo-ionospheric coupling mechanism demands the quiet geomagnetic condition to eliminate any kind of contamination in the lower atmospheric and ionospheric parameters. In this manuscript, we present the effect of back to back two geomagnetic storms before a strong earthquake happened in Imphal, India on January 4, 2016 (M</span><span style="font-family:""> </span><span style="font-family:Verdana;">=</span><span style="font-family:""> </span><span style="font-family:Verdana;">6.7). We studied the lower ionospheric irregularities for </span><span style="font-family:Verdana;">the</span><span style="font-family:Verdana;"> duration of 31 days by computing the nighttime fluctuations in Very Low Frequency (VLF) radio signal received transmitter JJI (22.2 kHz) in Japan at Ionospheric and Earthquake Research Centre & Optical Observatory (IERCOO), Sitapur, India. We also studied the presence of Atmospheric Gravity Wave (AGW) in nighttime VLF signal in lower ionospheric heights and the same computed that from SABER/TIMED satellite. Two geomagnetic storms occurred on December 21, and 31, 2015. By the conventional analysis, we found that there is a significant decrease in nighttime trend and an increase in nighttime fluctuations around 15 days before the earthquake and just on the first storm and thus the pre-seismic effects on VLF signal gets contaminated due to the presence of storms. The wave-like structure in VLF fluctuations shows significant increase in intensity by using Fourier and Wavelet analysis before the earthquake. By analysis of SABER data, we found significant enhancement in AGW around 10 days before the earthquake. As the wavelike structures are coming from neutral acoustics reasons from pressure or temperature variations, this paper exhibits a significant example of contamination in ionospheric parameters due to geomagnetic storm where the acoustics parameters remain un-contaminated.展开更多
In this paper the influences of nonuniform stratification on the propagating paths of internal inertial-gravity and pure gravity wave energy are discussed by using the WKB approximation method.The conditions for conse...In this paper the influences of nonuniform stratification on the propagating paths of internal inertial-gravity and pure gravity wave energy are discussed by using the WKB approximation method.The conditions for conservation of wave energy,generalized wave action and wave enstrophy are obtained.The necessary condition of instability for inter- nal gravity waves and the equation governing the refraction of wave rays are derived.Two types of critical levels are giv- en.Finally,the wave rays for different distributions of stratification are calculated by using the fourth-order Runge-Kutta method.展开更多
The effects of constant wind shear on atmospheric gravity wave spectrum are examined.At first a three- dimensional equilibrium spectral model of gravity waves is established in which wind shear rate β is implicit. Ba...The effects of constant wind shear on atmospheric gravity wave spectrum are examined.At first a three- dimensional equilibrium spectral model of gravity waves is established in which wind shear rate β is implicit. Based on this model,the expressions for one-dimensional frequency spectrum of atmospheric gravity waves are derived in which β is explicit.Numerical results show that (1) if we assume that mean wind U(z)=βz (z represents the altitude) and the internal gravity wave spectrum at the altitude of U=0 (that is,z=0) is VanZandt one,then the effect of Doppler shifting due to mean wind may be ignored;(2) when Richardson number J(J=N^2/β~2,N is Brunt-V(?)is(?)l(?) frequency,and is equal to 10^(-2)s^(-1) in this paper) satisfies J≥10.0,the effects ofwind shear arealso ignored;(3)for f^2(?)ω~2(?)N^2 (f is the inertia frequency,and f=10^(-4)s^(-1) in this paper,and co is the observed frequency),the wind shear only affects the spectral amplitude,and does not alter the spectral shape;and (4) as wind shear becomes strong,a part of wave potential energy turns into wave kinetic one,and a part of the vertical kinetic energy further turns into the horizontal one.展开更多
A novel amplitude factorization method is applied to solve a discrete buoyancy wave equation with arbitrary wind and temperature height distribution.The solution is given in the form of a cumulative product of complex...A novel amplitude factorization method is applied to solve a discrete buoyancy wave equation with arbitrary wind and temperature height distribution.The solution is given in the form of a cumulative product of complex factors,which are computed by a nonlinear,inhomogeneous,two-member recurrence formula,initiated from a radiative condition on top.Singularities of the wave equation due to evanescent winds are eliminated by turbulent friction.The method provides an estimation of the minimal vertical resolution,required to attain a stable accurate solution.The areas of application of the developed numerical scheme are high resolution modelling of orographic waves for arbitrary orography in general atmospheric stratification conditions,and testing of adiabatic kernels of numerical weather prediction models.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2022YFC3003800)the Asian Cooperation Fund Project(Grand No.99950410)。
文摘At 12:15 on January 15,2022(Beijing time),a massive eruption of the Hunga Tonga-Hunga Ha'apai volcano produced violent atmospheric fluctuations,which in turn generated a global tsunami through an abrupt air pressure shock upon the sea surface.Two main components of tsunami waves,phase-locked waves and free gravity waves,were identified by significant differences in propagating speeds across the deep ocean.The phase-locked wave propagated through the ocean basin synchronously with the atmospheric Lamb wave at an average speed of approximately 306 m/s,followed by the free gravity wave at a slower speed.The locked wave reached the coast of eastern Taiwan Island at about 20:00 on January 15,in coincidence with the Lamb wave arrival.However,on the coast of Chinese mainland,tidal gauges did not record tsunami signals until at least 2 h after the Lamb wave arrivals.Theoretical analyses and numerical experiments both suggested that as a result of the incoming wave shoaling above the vast continental shelf of Chinese mainland,the locked wave was no longer trapped by the air pressure shock and gradually transformed into freely-propagating shallow water waves by slowing down its propagation.Due to the longlasting planetary atmospheric fluctuations circling the earth many times,the sea level oscillations continuously propagated onto the Chinese shelf,which resulted in the tsunami waves excited along the Chinese coasts for at least 36 h.The maximum wave amplitude recorded on the coast of eastern Taiwan Island was 44 cm at Wushi,while on the coasts of eastern and southern Chinese mainland,the maximum amplitudes were 22 cm at Shipu and 13 cm at Zhuhai.Fourier and wavelet analyses were performed to identify the major components of the tsunami waves on the Chinese coasts.The results indicated that eastern Taiwan Island was impacted mainly by the waves with periods of approximately 10-40 min.Chinese mainland was hit by the evolved shallow water waves and subsequent free waves,with periods of approximately 40-100 and 16-20 min,resp
文摘Study of seismo-ionospheric coupling mechanism demands the quiet geomagnetic condition to eliminate any kind of contamination in the lower atmospheric and ionospheric parameters. In this manuscript, we present the effect of back to back two geomagnetic storms before a strong earthquake happened in Imphal, India on January 4, 2016 (M</span><span style="font-family:""> </span><span style="font-family:Verdana;">=</span><span style="font-family:""> </span><span style="font-family:Verdana;">6.7). We studied the lower ionospheric irregularities for </span><span style="font-family:Verdana;">the</span><span style="font-family:Verdana;"> duration of 31 days by computing the nighttime fluctuations in Very Low Frequency (VLF) radio signal received transmitter JJI (22.2 kHz) in Japan at Ionospheric and Earthquake Research Centre & Optical Observatory (IERCOO), Sitapur, India. We also studied the presence of Atmospheric Gravity Wave (AGW) in nighttime VLF signal in lower ionospheric heights and the same computed that from SABER/TIMED satellite. Two geomagnetic storms occurred on December 21, and 31, 2015. By the conventional analysis, we found that there is a significant decrease in nighttime trend and an increase in nighttime fluctuations around 15 days before the earthquake and just on the first storm and thus the pre-seismic effects on VLF signal gets contaminated due to the presence of storms. The wave-like structure in VLF fluctuations shows significant increase in intensity by using Fourier and Wavelet analysis before the earthquake. By analysis of SABER data, we found significant enhancement in AGW around 10 days before the earthquake. As the wavelike structures are coming from neutral acoustics reasons from pressure or temperature variations, this paper exhibits a significant example of contamination in ionospheric parameters due to geomagnetic storm where the acoustics parameters remain un-contaminated.
基金This research is supported by the National Natural Science Foundation of China.
文摘In this paper the influences of nonuniform stratification on the propagating paths of internal inertial-gravity and pure gravity wave energy are discussed by using the WKB approximation method.The conditions for conservation of wave energy,generalized wave action and wave enstrophy are obtained.The necessary condition of instability for inter- nal gravity waves and the equation governing the refraction of wave rays are derived.Two types of critical levels are giv- en.Finally,the wave rays for different distributions of stratification are calculated by using the fourth-order Runge-Kutta method.
文摘The effects of constant wind shear on atmospheric gravity wave spectrum are examined.At first a three- dimensional equilibrium spectral model of gravity waves is established in which wind shear rate β is implicit. Based on this model,the expressions for one-dimensional frequency spectrum of atmospheric gravity waves are derived in which β is explicit.Numerical results show that (1) if we assume that mean wind U(z)=βz (z represents the altitude) and the internal gravity wave spectrum at the altitude of U=0 (that is,z=0) is VanZandt one,then the effect of Doppler shifting due to mean wind may be ignored;(2) when Richardson number J(J=N^2/β~2,N is Brunt-V(?)is(?)l(?) frequency,and is equal to 10^(-2)s^(-1) in this paper) satisfies J≥10.0,the effects ofwind shear arealso ignored;(3)for f^2(?)ω~2(?)N^2 (f is the inertia frequency,and f=10^(-4)s^(-1) in this paper,and co is the observed frequency),the wind shear only affects the spectral amplitude,and does not alter the spectral shape;and (4) as wind shear becomes strong,a part of wave potential energy turns into wave kinetic one,and a part of the vertical kinetic energy further turns into the horizontal one.
基金supported by Estonian Science Foundation under Research Grant 5711.
文摘A novel amplitude factorization method is applied to solve a discrete buoyancy wave equation with arbitrary wind and temperature height distribution.The solution is given in the form of a cumulative product of complex factors,which are computed by a nonlinear,inhomogeneous,two-member recurrence formula,initiated from a radiative condition on top.Singularities of the wave equation due to evanescent winds are eliminated by turbulent friction.The method provides an estimation of the minimal vertical resolution,required to attain a stable accurate solution.The areas of application of the developed numerical scheme are high resolution modelling of orographic waves for arbitrary orography in general atmospheric stratification conditions,and testing of adiabatic kernels of numerical weather prediction models.
