| Session Details | |
| Section | AS - Atmospheric Sciences |
| Session Title | Past and Future Changes in the Hadley and Walker Circulations |
| Main Convener | Dr. Hanh Nguyen (Bureau of Meteorology, Australia) |
| Co-convener(s) | Dr. Scott Power (Bureau of Meteorology, Australia) Dr. Tim Li (University of Hawaii, United States) Prof. Soon Il An (Yonsei University, Korea, South) |
| Session Description | The Hadley and Walker Cells are thermally driven, large scale features of atmospheric circulation with distinct seasonality and interannual variability. While these circulation features explain a large percentage of global tropical climate, long term changes in large scale circulation have been the focus of numerous studies. Evidence from a large number of data sources and methods of detection are indicative of an anthropogenic widening of the Hadley circulation, corroborated by climate model simulations of the 20th and 21st centuries. In contrast, it remains unclear as to whether the Hadley and Walker circulation have weakened or intensified. Some research has shown a weakening in the Walker circulation throughout the 20th century, with a further decrease projected into the 21st century, whereas other studies provide evidence of intensification over the past two decades. Trends in Hadley circulation intensity also show discrepancies. Most observations hint at a strengthening whereas model simulations indicate a weakening under anthropogenic global warming, arguably in direct relationship with an expansion. The aim of this session is to provide insight and assess the role of large scale atmospheric circulation and associated changes in the tropical monsoon system. Emphasis is given to the tropical Indo-Pacific sector and the teleconnections to the climate of the sub-tropics and extra-tropics. We invite contributions addressing changes in large-scale circulation under global warming within context of multi-timescale variability and how such changes impact regional tropical climate. |