Relative Importance of Land and Ocean Processes for Asian Monsoon Variability and the Role of Hydrological Cycle
Tetsuzo Yasunari
Frontier Research System for Global Change (FRSGC)
Tokyo, Japan
The seasonal cycle of solar insolation is a basic forcing factor for the climate system, but actual heating/cooling process of the atmosphere is greatly modified by the complex geographical distribution of the continents and oceans due to their large difference of effective heat capacities. These differential heating/cooling between the continents and the oceans form the monsoon systems which actually produce diverse climatic zones and seasonal cycles on the earth. Inter-annual variability of the monsoon systems largely depends upon anomalous heating/cooling processes associated with anomalous conditions on the continents and oceans. The oceans posses large heat content which produces long climatic memory effect, while the continents can change the thermal condition of the atmosphere quickly due to the small heat content. The monsoon variability, including seasonal cycle and inter-annual variability; may be produced by the combination of these two long-lasting and quickly-changing thermal forcing. The abrupt changes and step-like stages of seasonal march in the monsoon system, and the ENSO-monsoon coupling are resulted from these two forcings. The hydrological processes in the atmosphere and at the surface play important roles to modify these forcings. In this presentation, I will discuss some key issues to be adressed, particularly from the viewpoints of modeling. Particular emphasis will be put on the following problems;
1) Role of heterogeneous seasonal heating over the Eurasian continent, including the relative importance of the Tibetan Plateau
2) Role of changing land/ocean heating contrast in large-scale convection
3) Role of atmosphere/ocean interaction in the warm pool regions of the western Pacific and the Indian Ocean
