The vertical and horizontal propagation of internal gravity waves forced by a local thermal source at the lowerboundary is examined using the irrotational two-dimensional model developed by Zhang et al. (1995).The sou...The vertical and horizontal propagation of internal gravity waves forced by a local thermal source at the lowerboundary is examined using the irrotational two-dimensional model developed by Zhang et al. (1995).The sourcegenerates waves with the same absolute frequency 1/15 d-1 but different wavenumber.Internal gravity waves withwide spreading frequencies and wavenumbers appear due to wave-wave interactions. The foreced waves iW (westward-propagating with wavenumber 1)and iE (eastward-propagating with wavenumber 1),whose absolute phasespeeds are 31 m s-1,are predominant. Other forced waves with smaller phase speeds are relatively weaker.Thesewaves interact with the zonal mean flow,causing the flow to alternate with easterly and westerly with a 32-month period. The absolute maximum wind speeds of easterly and westerly are 35 m s-l which is larger than the largest phasespeed of forced waves. The forced waves iE and iW may accelerate easterly and westerly up to i 31 m s',respectively.The excessive accelerations are due to the self--acceleration of waves iE and iW or newly generated highfrequency waves iE and IW.The horizontal propagation of the waves are mainly affected by the forcing and wave--flow interactions whichlead to fast-slow variations of wave phase speed and amplitude.展开更多
文摘The vertical and horizontal propagation of internal gravity waves forced by a local thermal source at the lowerboundary is examined using the irrotational two-dimensional model developed by Zhang et al. (1995).The sourcegenerates waves with the same absolute frequency 1/15 d-1 but different wavenumber.Internal gravity waves withwide spreading frequencies and wavenumbers appear due to wave-wave interactions. The foreced waves iW (westward-propagating with wavenumber 1)and iE (eastward-propagating with wavenumber 1),whose absolute phasespeeds are 31 m s-1,are predominant. Other forced waves with smaller phase speeds are relatively weaker.Thesewaves interact with the zonal mean flow,causing the flow to alternate with easterly and westerly with a 32-month period. The absolute maximum wind speeds of easterly and westerly are 35 m s-l which is larger than the largest phasespeed of forced waves. The forced waves iE and iW may accelerate easterly and westerly up to i 31 m s',respectively.The excessive accelerations are due to the self--acceleration of waves iE and iW or newly generated highfrequency waves iE and IW.The horizontal propagation of the waves are mainly affected by the forcing and wave--flow interactions whichlead to fast-slow variations of wave phase speed and amplitude.
