On the Role of Transient Eddies in the Tropical Troposphere

[摘要] We studied the contributions of eddies with various time scale to the covariances of the zonal wind component, temperature and geopotential height with the meridional wind component in the tropical troposphere by the spectral analysis of time series data of Pacific stations for April-July 1962. In the equatorial region disturbances with periods near 4 days play an important role in the covariances. On the other hand, disturbances with period near 6 days and those with periods longer than 10 days mostly contribute to the covariances in sub-tropical latitudes (near 20°N).Average horizontal transports of zonal momentum, sensible heat and potential energy due to transient eddies and partial contributions of disturbances with periods near 4 days to the transports are examined as functions of latitude and altitude. Strong energy fluxes due to disturbances with periods longer than 6 days enter into the tropics from higher latitudes. This results agrees with that obtained theoretically by Mak (1969). Equatorward heat fluxes exist in the lower and the middle troposphere. Large poleward heat fluxes are observed in the upper troposphere. In higher latitudes, contributions of disturbances with periods near 4 days to the horizontal transports are small, but in the equatorial region these become large.A partial estimate of the energy transformation process of eddies contained between the equator and 15°N. Large energy fluxes (pressure work) from higher latitudes converge in the equatorial region. The eddy kinetic energy is transformed to the zonal kinetic energy and the eddy available potential energy is transformed to the zonal potential energy. The convergence of energy flux from higher latitudes is one order of magnitude larger than both energy conversions from eddy to zonal energy and from eddy to zonal available potential energy.

[学科分类] 大气科学