Analytical Study of the Evolution of an Amplifying Baroclinic Wave: Part II. Vertical Motions and Transport Properties

Abstract

From the analytical model described in the previous article (Part I) we show how second-order non-geostrophic effects modify the initially sinusoidal pattern of vertical motion accompanying an unstable baroclinic wave, and also show how the zonal mean forced Ferrel circulation local to the wave system is altered. The most general modification of the complete ? field is the introduction of strong north-south variations of which the most significant synoptic feature is a region of strong descending motion south of the surface low center. Similar distributions of ? have been noted in observational and numerical studies. For this two-layer system the vertical transport of heat associated with the second-order ? field is directed downward at the middle level thereby tending to ?brake? the overall wave growth. The second-order ? field also leads to a significant downward flux of westerly momentum especially in middle and lower levels, but if this field were weakened, as might be the case, for example, if the static stability increased strongly, the system could exhibit a strong upward flux of momentum as revealed in some recent observational and numerical studies.