热力适应、过流、频散和副高 I.热力适应和过流

Thermal Adaptation, Overshooting, Dispersion, and Subtropical Anticyclone Part I: Thermal Adaptation and Overshooting

利用位涡性质 ,讨论了因非绝热加热导致的大气动力特征的变化 ,阐明了大气动力过程向外加热强迫适应的原理。证明在热力适应过程中 ,沿着加热区的侧边界斜压位涡为负 ,且大于正压位涡 ,那里的大气出现对称不稳定。在加热区的上空尽管非绝热加热为零 ,仍然存在上升、辐散、反气旋环流及冷中心 ,证明这是由于“过流”引起的。通过总位涡的收支分析证明 ,由于边界层的摩擦作用 ,加热区上空多余的负位涡向外排放而成为大气中负涡度的源地。

Based upon potential vorticity theory, this paper investigates the feature of atmospheric motion as a result of diabetic heating, and stresses the principle of atmospheric thermal adaptation to external thermal forcing. It is proved that, during thermal adaptation the baroclinic component of potential vorticity along the boundary of the heating region becomes negative and larger than the barotropic component, where the atmosphere becomes symmetrically unstable. It is shown that over the top layer of a heating region, although there is no diabatic heating, but still exist ascent, divergence, anticyclonic circulation, and cold center. This is proved to be a result of the so-called “over shooting” accompanied with the thermal adaptation. Budget analysis of total potential vorticity reveals that, through thermal adaptation, the vorticity generation due to surface friction forms an upper-layer source of negative vorticity, and affects atmospheric motions. These are further verified by a series of numerical experiment.