1979年500百帕各波拟能非线性转换的季节变化

SEASONAL VARIATION OF THE NONLINEAR CASCADE OF ENSTROPHY AT THE 500 hPa IN 1979

本文用1979年500百帕候平均高度场,计算了各个季节,不同纬度带地区,各波拟能的平衡和非线性转换特征。结果表明,在中、高纬度冬、春季节,超长波1—3波和长波5—7波是其它波和纬向运动拟能的提供者。夏季长波波段不再是拟能的“源”,这个“源”移向较短的短波波段。4波也由冬春季节的拟能“汇”变成“源”。秋季是由夏季型向冬季型的过渡型。4波和5波以及短波波段均是拟能“源”。在各个季节里,超长波1—3波,基本都是拟能的提供者;但是,超长波作为“源”、“汇”,随纬度带的分布是不均匀的。作为“源”区,仅限于约20个纬距宽的某一纬带内,冬季约位于37.5—57.5°N纬度带,夏季这个源区向北移10—15纬距。而35°N以南的副热带地区,各个季节平均都表现为超长波拟能的“汇”区。

Diagnostic analyses are done for the equilibrium of enstrophy and its nonlinear cascade in the wavenumber domain for each season and different latitude zones by using the 500 hpa pentad average data for 1979. Results indicate that in winter and spring super-long waves (wavenumber 1-3) and Rossby long waves(wavenumber 5-6) are suppliers of enstrophy for the other waves and the zonal flows in middle and higher latitudes. In summer, Rossby waves are no longer the enstrophy 'source', which shifts to shorter waves. Meanwhile, the wavenumber 4 component, which is the enstrophy 'sink' in winter and spring, now becomes the 'source' In autumn, the wavenumber 4-5 components are the 'source', a transitional pattern from summer to winter superlong waves are the 'source' in all seasons but their distribution differs with latitudes The width is only 20 latitudes, in about 37.5-57.5°N in winter and shifting northward about 10-15 latitudes in summer. In the subtropics south of 35°N, super-long waves are the enstrophy 'sink' in almost all seasons.