Topographic Effect on Geostrophic Adjustment and Frontogenesis  

地形对地转适应和锋生的影响(英文)

作　　者：方娟 伍荣生 

出　　处：《Advances in Atmospheric Sciences》2001年第4期524-538,共15页大气科学进展（英文版）

基　　金：the National Natural Science Foundation of China under Grant49735180;the State Key Basic Program: CHERES.

摘　　要：Three conservative principles: potential vorticity, absolute momentum and potential temperature are used to study the influence of topography on the local frontogenesis and geostrophic adjustment, which are induced by the inhomogeneous thermal fields. It is found that the horizontal distribution of the initial potential temperature and its position relative to the mountain play important roles during the geostrophic adjustment and local frontogenesis. The frontogenesis is weakened by the mountain when the initial thermal perturbation is located at the base of the upwind slope. The frontal discontinuity cannot occur unless the horizontal contrast of the initial potential temperature is great enough. Whereas, the situation is opposite when the initial thermal disturbance is main-ly situated near the peak of the mountain. Complementary to the aforementioned cases, the effect of topog-raphy on the frontogenesis depends on the stratification of the flow when the initial thermal disturbance lies at the foot of lee slope. For weak stratification, topography is favorable to the formation of frontal discontinuity, vice versa. This discrepancy is attributed to the difference of subsidence warming, caused by the mountain, when the stratification is either strong or weak. Furthermore, the energy conversion ratio between the kinetic and potential energy during the geostrophic adjustment process is also affected by the topography. In contrast to the flat bottom case, the ratio is reduced (increased) when the initial thermal perturbation lies in the up-wind slope (lee slope). The reason is that the gravity force does negative work in the former case while does positive work in the latter case. Key words Topography - Geostrophic adjustment - Frontogenesis This work was supported by the National Natural Science Foundation of China under Grant 49735180, and by the State Key Basic Program: CHERES.Three conservative principles: potential vorticity, absolute momentum and potential temperature are used to study the influence of topography on the local frontogenesis and geostrophic adjustment, which are induced by the inhomogeneous thermal fields. It is found that the horizontal distribution of the initial potential temperature and its position relative to the mountain play important roles during the geostrophic adjustment and local frontogenesis. The frontogenesis is weakened by the mountain when the initial thermal perturbation is located at the base of the upwind slope. The frontal discontinuity cannot occur unless the horizontal contrast of the initial potential temperature is great enough. Whereas, the situation is opposite when the initial thermal disturbance is main-ly situated near the peak of the mountain. Complementary to the aforementioned cases, the effect of topog-raphy on the frontogenesis depends on the stratification of the flow when the initial thermal disturbance lies at the foot of lee slope. For weak stratification, topography is favorable to the formation of frontal discontinuity, vice versa. This discrepancy is attributed to the difference of subsidence warming, caused by the mountain, when the stratification is either strong or weak. Furthermore, the energy conversion ratio between the kinetic and potential energy during the geostrophic adjustment process is also affected by the topography. In contrast to the flat bottom case, the ratio is reduced (increased) when the initial thermal perturbation lies in the up-wind slope (lee slope). The reason is that the gravity force does negative work in the former case while does positive work in the latter case. Key words Topography - Geostrophic adjustment - Frontogenesis This work was supported by the National Natural Science Foundation of China under Grant 49735180, and by the State Key Basic Program: CHERES.

关 键 词：TOPOGRAPHY Geostrophic adjustment FRONTOGENESIS 

分 类 号：P461[天文地球—大气科学及气象学]