Wave-Flow Interaction and Wave-Propagation Modes

Wave and basic flow are the two primary forms of atmospheric motions,and their interaction may lead to various weather phenomena. As a basic subject of atmospheric dynamics,studies of wave-flow interaction are of significance in academic and scientific senses.The wave-flow interaction theory includes two aspects:(1) the "wave-activity"(conservation) equation which describes the effect of basic flow on wave;(2) the E-P flux and wave transformation and propagation theories that represent the feedback of wave to basic flow.Not only many important advancements had been made in the theoretical researches,such as the proposal of E-P flux,introduction of residual circulation,appearance of extended E-P flux,construction of three-dimension EP flux,and progresses of "wave-activity" conservation equation,abrupt change of wave,wave-flow steady structure,wave transforming and its great circle route and remote correlation of low-frequency waves,etc.,but also a lot of achievements had been accomplished in the applications of these theories,including the scientific explanations to the quasi-biennial oscillation(QBO) of stratospheric zonal wind in the equator,the stratospheric sudden warming over the polar region,the maintaining effect of transient wave on blocking high,the acceleration of upper level jet stream and the remote correlation of low-frequency waves.Especially,these researches of wave-flow interaction provide the theoretical foundations and scientific methods for the forecast of planetary wave propagation,the investigations of storm track and the diagnosis of convergence and divergence of wave energy in real atmosphere.From small-amplitude and finite-amplitude aspects,the research progresses of wave-flow interaction and wave propagation theories in China and overseas countries are reviewed in this paper.Focusing on the investigations of wave-flow interaction and wave-propagation modes in large-scale circulation,the authors bring forward the mechanism and theoretical mode for multi-scale wave-flow interaction under various dynamic and thermal backgrounds,and reveal the nonlinear atmospheric dynamic abrupt change and its steady structure theories.Compared with the above investigations,the stability study of complicated wave-flow interaction caused by heating source and topography forcings is unsubstantial.Especially,the effects of atmospheric water cycle and topography of the Tibetan Plateau on wave-flow interaction of synoptic systems with various scales are not clearly known.It would become an important branch for wave-flow interaction research in the future.