里查森数对α中尺度涡旋波不稳定的影响

Influences of Richardson Number on the Instability of Meso-α Scale Vortex Wave

作者讨论了里查森数对α中尺度涡旋波不稳定的影响。结果表明:α中尺度涡旋波的失稳与里查森数有很大关系;当里查森数不太大时,才存在α中尺度涡旋波的不稳定;里查森数越小,越容易出现斜交型不稳定,且斜交型不稳定扰动的波长越短。此时在α中尺度波段以斜交型不稳定占优;在弱稳定层结下,更有利于出现α中尺度涡旋波的不稳定,而大的风切变仅有利于该不稳定增长率的增大。

The influences of Richardson number Ri on the instability of meso-α scale vortex wave is discussed. The results are as follows. There is close relationship between Ri and the destabilization of meso-a scale vortex wave. The instability of meso-α scale vortex wave appears only when Ri is not large. The smaller Ri is, the easier the appearance of heterotropic instability is and the shorter it's wavelength is, temporality the heterotropic instability is ascendent in meso-a scale waveband. The condition of weak stable stratification is advantageous to instability of meso-a scale vortex wave, but the augment of wind shear is only advantageous to the increase of the unstable growth rate.