Kinetic Energy of Tropical Circulations and Gravity Waves in a Global Spectral Model

[摘要] To gain some information for the initialization process in maintaining the proper tropical circulations, the kinetic energy of tropical gravity waves among vertical modes, meridional indices, and zonal wave numbers is investigated for the NCAR Community Climate Model. Kinetic energy is decomposed into divergent and nondivergent parts. In particular, the divergent kinetic energy is split into zonal and meridional components which measure the strengths of the Walker and Hadley circulations, respectively. The gravity waves associated with the third internal mode corresponding to wave number 3 and meridional index 1 play the most important role in the Walker circulation. However, the gravity waves related to the third internal mode, the longest zonal wave, and the first meridional index contribute the most to the Hadley circulation. To retain proper tropical circulations in the forecast, we suggest that the gravity waves associated with the internal modes 2-6, meridional indices 1-6, and zonal wave numbers 1-11 not be adjusted. Adjustment of gravity waves in the initialization using only a cutoff frequency or period is not recommended. The results based only on the normalized tropical data are qualitatively similar to those for the global region but normalized by the global gravitational energy in Ko et al., 1989b. This implies that the normalized values are more appropriate than the absolute values in the energetics analysis.

[学科分类] 大气科学