The large-scale meridional transport of sensible heat in wavenumber frequency space

The longitude-time co-spectra of the meridional transport of sensible theat across 20°, 40°, 60°, and 80° N at 100, 200, 500, and 850 mb for the summer and winter seasons of 1964 have been computed and analyzed. It is found that there exists a preferred spectral band in the wave-number frequency spectra at various latitudes, which indicates the wave-number frequency domain of interaction between the meridional velocity and temperature. In the middle latitudes, the spectral band is oriented in a domain extending from the region of low wave-numbers and frequencies to that of high wave-numbers and negative frequencies. In the high latitudes, the heat transport is confined to a domain of low wave-numbers and frequencies. In the lower latitudes, however, the transport is confined to a very narrow band centered near the zero frequency.

The total meridional transport of sensible heat at all four levels is mostly directed toward the North Pole, except at 20° N there is a weak equatorward transport of sensible heat at the 100, 200, and 850 mb levels. In the troposphere, the maximum heat transport is found to occur near 40° N, whereas in the stratosphere it occurs near 60° N.

It is also found that most of the poleward transport of sensible heat in both the troposphere and stratosphere is accomplished by the stationary and eastward moving, long and medium waves, and that the equatorward transport is mostly accomplished by the westward moving, low frequency waves. Most of the convergence and divergence of the meridional transport in the troposphere is the contribution of the transient waves, whereas in the stratosphere it is mainly the result of the stationary waves.