Study on future change of vertical circulation over East Asia by analyzing terms of the omega equation

In this study, future change of vertical circulation in the East Asian monsoon system is investigated by using dynamically downscaled results from global future scenarios. The omega equation consists of the vorticity advection, temperature advection and diabatic heating terms, which describes contribution of each factor on vertical motion. It is analyzed that updrafts are generally enhanced over the East Asia region with the global warming trend, which induces increased precipitation in summer season. In historical period, it is investigated that the diabatic heating and the vorticity advection has large contribution to upward motions. The diabatic heating and the vorticity advection are induced by surface heat fluxes and the baroclinic instability in mid-troposphere, respectively. In the downscaled future scenarios, it is shown that enhanced upward motions are mainly caused by strengthened diabatic heating from increased land surface temperature. It is also shown that the decreased latitudinal temperature gradient in mid-troposphere supports to deepen the trough structure, which enhances vorticity advection over the East Asia region. Presented results describe detailed processes how the global warming changes the future precipitation of the East Asian monsoon system by enhanced vertical circulation.