The Impact of Orbital Insolation Changes on East Asian Climate

Thursday, 18 December 2014
Shih-Yu Lee, Academia Sinica, Taipei, Taiwan, Chuan-Chou Shen, NTU National Taiwan University, Taipei, Taiwan and Chi-Hua Wu, Research Center for Environmental Changes Academia Sinica, Taipei, Taiwan
Recent paleoclimate proxy records, particularly cave and lake records, have reconstructed the precipitation changes in past. It was generally believed that such records from East to Southeast Asia reflected local precipitation, which is closely associated to summer monsoon strength. In present day meteorology, the mid-to-late July summer monsoon onset is associated with the northward shift of the Western North Pacific high pressure controlled by the thermal gradient between Asian continent and Pacific Ocean that closely linked to seasonal insolation heating. The concept of insolation control over monsoonal circulation was well accepted in the paleoclimate community. However, the dynamical adjustment of insolation driven large-scale circulation changes have yet to be discussed in further detail for the Western North Pacific region.

In this study we explore the impact of insolation on large-scale atmospheric circulation changes using idealized numerical model simulations and data from the Paleoclimate Modelling Intercomparison Project Phase III (PMIP3). We findthat the orbital forcing had a significant influence on the Western North Pacific summer monsoon. The Western North Pacific monsoon trough was weaker in the early-to-mid-Holocene when at precession maximum; the strength of South Asia and East Asia monsoon undergoes anti-phasing changes. The insolation driven monsoonal precipitation change, however, is not spatially uniform. For example, precession maximum was found to be associated with enhanced precipitation over the Himalayas and East Asia but not Southwestern Asia. Our results may provide information for interpreting regional paleoclimate records.