夏季东亚阻塞高压形成维持的波数域动能分析

KINETIC ENERGY ANALYSES OF THE FORMATION AND MAINTENANCE PROCESSES OF EAST ASIAN BLOKING HIGH IN SUMMER

用波数域动能方程分析了１９８６年夏季东亚阻塞高压的形成、维持和衰退过程．发现该夏季代表阻塞高压的波动是５波（长波），而不是２波（超长波）．在阻高形成和维持阶段，波与波非线性相互作用向５波输送动能，使５波动能增大；而波与平均流的相互作用则使５波动能减小．在阻高维持阶段，有效位能向５波转换动能，维持阻高．波与平均流的相互作用却使５波维持．在阻高衰退阶段则完全相反，波与波相互作用项以及有效位能与动能转换项均为负值，使５波动能变小，阻高衰退．而波与平均流相互作用，却使高纬西风减小，有利阻高维持．

he formation, maintenance and decay processes of blocking high over East Asia in summer of 1986 are analysed by kinetic energy equations with various wavenumber domains. It is found that the representative wave number of blocking high is wavenumber 5 in the case, which is in the long wave domain, not wavenumber 2. During the formation and maintenance stages of blocking episodes, the kinetic energy at wavenumber 5 increases through the wavewave nonlinear interaction and decreases through the wavemean flow interaction. During the maintenance stage, the available poteneial energy at wavenumber 5 is transformed into kinetic energy as to maintain the blocking. These physical processes are reversed in the decay stage, but the wavemean flow interaction leads to the decreasing of westerlies in the high latitude, and maintaining the bloking high.