The transfer of physical quantities in QDPO and its relation to the interaction between the NH and SH Circulations

Based on the 1979 FGGE Level III b data, calculation is made of the transfer of sensible and latent heat and momentum due to a quasi-40-day periodic oscillation (QDPO) on a cross-equatorial meridional vertical cross-section, and analysis is done of the characteristics of the transfer at all phases of QDPO, with the following results obtained:

1. During the monsoon's QDPO activation and break phases, a strong transfer of sensible heat to the SH is felt in the upper troposphere over the Asian monsoon region; the conversion of perturbation effective potential into its kinetic energy attains its maximum at 500-300 hPa (15°N), serving as the source of kinetic energy for the quasi-40-day periodic perturbation; an intense transfer of potential energy is found above 200 hPa from the monsoon area to the SH to maintain the QDPO at the tropical latitudes
2. During the QDPO activation-break (and reverse) transitional phase the conversion of perturbation effective potential into kinetic energy reaches its maximum in the middle and lower troposphere over the SH middle latitudes and an appreciable lower transfer of potential energy occurs towards the SH tropical latitudes and the NH.
3. The upper-tropospheric powerful transfer of westerly momentum caused by QDPO is discovered from the SH tropical latitudes to the NH, and the resulting momentum divergence and convergence are unfavorable for the maintenance of the seasonal mean fields of the NH tropical easterly and SH subtropical westerly winds.

Finally, possible synoptical processes responsible for QDPO are discussed together with its relation to the interaction between the circulations of both the hemispheres. It is found that QDPO is both the result of and medium for the interaction.