In order to determine nonlinear energy exchanges into individual triad interactions in the frequency domain,spectral formulas are derived by use of the cross-spectral technique. First time attempt has been made to und...In order to determine nonlinear energy exchanges into individual triad interactions in the frequency domain,spectral formulas are derived by use of the cross-spectral technique. First time attempt has been made to understandthe problem of maintenance of low frequency waves for tropical weather system by using this technique.The TOGAbasic level ill daily wind analyses on a 2.5 degree square grid around the global zone from 20°S-30°N at 200 hpa for92-day periods covering June, July and August of 1988 are used. Kinetic energy is gained at high frequencies and lostat low frequencies.In the planetary scale dynamics over tropics, barotropic nonlinear energy transfer plays a negativerole.Low frequency wave of period 45 day loses maximum amount of energy when it interacted with frequencies ofperiods 92 day and 30 day.45 day cycle is also the main source of energy for other frequencies. Distrubances of periodl 5 day gain maximum amount of energy.The major contribution comes from the triad interaction of the frequencies<7,l,6>.North of 20'N low frequency waves of period 30 to 92--day gain energy through nonlinear triadinteraction with the maximum gain at 22.5'N. The study may help to investigate the rapid loss of predictability of lowfrequency modes over tropics.展开更多
文摘In order to determine nonlinear energy exchanges into individual triad interactions in the frequency domain,spectral formulas are derived by use of the cross-spectral technique. First time attempt has been made to understandthe problem of maintenance of low frequency waves for tropical weather system by using this technique.The TOGAbasic level ill daily wind analyses on a 2.5 degree square grid around the global zone from 20°S-30°N at 200 hpa for92-day periods covering June, July and August of 1988 are used. Kinetic energy is gained at high frequencies and lostat low frequencies.In the planetary scale dynamics over tropics, barotropic nonlinear energy transfer plays a negativerole.Low frequency wave of period 45 day loses maximum amount of energy when it interacted with frequencies ofperiods 92 day and 30 day.45 day cycle is also the main source of energy for other frequencies. Distrubances of periodl 5 day gain maximum amount of energy.The major contribution comes from the triad interaction of the frequencies<7,l,6>.North of 20'N low frequency waves of period 30 to 92--day gain energy through nonlinear triadinteraction with the maximum gain at 22.5'N. The study may help to investigate the rapid loss of predictability of lowfrequency modes over tropics.
