INSTABILITY PROPERTIES OF ATMOSPHERIC DISTURBANCES

There are some basic problems in previous theoretical studies of baroclinic instability.The derived criticalbaroclinity was considerably lower than the time averaged mean meridional temperature gradient,especially in the lowertroposphere.Also,the linear mechanism of baroclinic disturbance development which is noted restricted by the criticalbaroclinity was not studied sufficiently.The realistic critical baroclinity and disturbance development are discussed inthis study.It will be shown that the critical condition of instability and typical time and space scales of disturbances de-pend on three-dimensional structures of atmosphere and sphericity of the earth,other than the horizontal temperaturegradient alone.The variant behaviour of atmospheric disturbances depends highly on their specific scales that may bedescribed by the same theoretical model.Thus,there would be no substantial differences in the basic instability mecha-nism of many disturbances including the polar lows and explosive cyclones.