A simulation study of the winter monsoon circulation

The objective of this study is to delineate the time mean monsoonal response to a global observation-based self-regulating thermal forcing field in the absence of orography. The analysis is done in the context of a two-layer primitive equation semi-spectral model. For limitation of space, we only present and discuss the results for the winter simulation. The broad aspects of the observed winter mean circulation are successfully simulated, including the distribution of surface pressure, lower- and upper-level flows, temperature, net diabatic heating rate and vertical velocity. Even the structure of the model winter storm tracks is compatible with observation. The strong radiative cooling over Asia and N America, the strong heating over the tropical continental regions (including the maritime continent, S America and Africa) and the diabatic heating associated with the storm tracks over the extratropical oceanic regions are shown to be important to the maintenance of the winter monsoon circulation. The interaction between the zonally symmetrical and asymmetrical parts in the tropical circulation as well. as the interaction between the tropical and extratropical parts of the circulation are both crucially important to the monsoon circulation One implication is that it would be very useful for forecasting purposes if we could anticipate the intensity and global distribution of the seasonal net diabatic heating field.