辐射冷却与低频振荡中的宽频带现象

RADIATIVE COOL ING AND BROADBAND PHENOMENA IN LOW-FREQUENCY WAVES

利用赤道Ｂ平面近似和长波近似分析了辐射冷却效应对热带地区纯斜压低频波的作用，发现辐射冷却并不仅是对波动的发展起阻尼作用。在辐射对流的微妙平衡条件下，辐射冷却通过调整对流加热垂直廓线而影响低频波相速度和波动周期，使之呈现出宽频带的现象。而非绝热加热强度也并非越大越好。只有在强度适中的情况下，低频波才会被激发和维持下去，并出现宽频带现象。要得到适中的加热强度，辐射冷却的的影响不容忽视。

We analyze the effects of radiative cooling on the pure baroclinic low-frequency waves under the approximation of equatorial B-plane and semi -geostrophic condition. The resul is show that rediative cooling doesn't providethe mere damping effects on the development of low--frequency waves. Under thedelicate rediative-convective equilibrium, radiative effects will alter thephase speed and wave period, and bring about the broadband of phase velocityand wave period by adjusting the vertical profiles of diabatic heat lug. Whenthe intensity of diabatic heat lug is moderate and appropriate, it is conductiveto the development and sustaining of the low--frequency waves and their broadbandphenomena, not the larger, the better. The radiative cool lug can not be neglectedin order to reach the moderate and appropriate intensity of diabatic heating.