Impacts of the dynamic and thermodynamic forcing of Tibetan-Plateau on Asian summer monsoon onset and climate formation

Abstract:

This study developed the “Tibetan- Plateau sensible- heat driven air- pump” theory, the thermal adaptation theory, and constructed a heating- induced vertical motion model; Proved that the surface sensible heating and cooling on the slopes of large-scale plateau play significant roles in driving the Asian monsoon and regulating climate in Asia; Discovered that in winter half year the dynamic resistance of the plateau on the atmospheric westerly can inspire an atmospheric stationary wave pattern of asymmetric dipole- type, affecting the circulation and climate in Asia.

Based on the theories developed, this study brought forward firstly that the onset of the Asian tropical summer monsoon consists of three dynamically consequential stages: Due to the anchoring effects of the Tibetan Plateau forcing on the circulation the onset first occurs over the area from the eastern Bay of Bengal (BOB) to the western coast of Indochina Peninsula in early May. With the westerly advection the TP heating generates cold temperature trough upstream and warm temperature ridge downstream of the TP, contributing to the following monsoon onset over the South China Sea (SCS) in mid-May. Consequently the strong latent heat release of the BOB and SCS monsoon stimulates the westward development of the South Asian High (SAH), and the pumping on the southwest of the SAH finally leads to the Indian Summer Monsoon (ISM) onset in early June.

It was demonstrated that each stage of the onset is accompanied by an abrupt warming over the TP corresponding to the two- to three- week oscillations (TTO) of the warm phase of the southeastward propagating upper-layer temperature in middle latitudes, the rising phase of the westward propagating TTO from the northwestern Pacific in the subtropics, and the upper- layer divergence phase of the northward propagating Madden–Julian oscillation (MJO) from the southern tropics. It was concluded that the timing of the Asian monsoon onset is determined when the favorable phases of different low-frequency oscillations are locked over the Asian monsoon area.

Prof. Guoxiong Wu was born in Guangdong, China in 1943. Since 1985 he has become the full Professor at the Institute of Atmospheric Physics (IAP). He was elected Academician of CAS and Life Tenure Professor in 1997; Honorary Fellow of the Royal Meteorological Society (UK) in 2012. He graduated from Nanjing Institute of Meteorology in 1966, received his Ph.D. in atmospheric science from Imperial College of Science and Technology, London University in 1983. He worked as a visiting scientist at the European Centre for Medium Range Weather Forecasts (ECMWF) from 1983 to 1984, and Senior visiting Research Professor at Geophysical Fluid Dynamics Laboratory (GFDL) of Princeton University, USA from 1989 to 1991. He served as Director of the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG, IAP), CAS from 1993 to 2000, and Director of the LASG Academic Committee from 2001 to 2010.

Prof. Wu’s research involves weather and climate dynamics, including numerical modeling and data diagnosis. He has published more than 200 peer-reviewed papers, and been conferred the Grade I and Grade II of the Science and Technology Progress Award of the Chinese Academy of Sciences (CAS), the Grade II of National Natural Science Award, and the HLHL Science and Technology Progress Award. He has been editor or chief editor of several international science journals. Prof. Wu has been actively involved in the international climate community, including President of International Association of Meteorology and Atmospheric Sciences (IAMAS) from 2007-2011, Officer of WMO/ICO/ICSU Joint Science Committee (JSC), World Climate Research Program (WCRP) from 2005-2010, member of the Executive Board of ICSU, Chairman of the Chinese National Committee for ICSU and Chairman of the Chinese National Committee for IUGG. He has been PI of many major climate related projects in China, and is currently the Chairman of the Science Steering Group of the National Key Science Research Program on Global Change funded by the Ministry of Science and Technology of China, and of the Science Steering Group of the National Key Research Program “Variability of the land-air coupling system over the Tibetan Plateau and its impact on global climate”.