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Relationships among the monsoon-like southwest Australian circulation,the Southern Annular Mode,and winter rainfall over southwest Western Australia |
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| Authors: | Juan Feng Jianping Li Yun Li Jianlei Zhu Fei Xie |
| Institution: | 1. College of Global Change and Earth System Science, Beijing Normal University, Beijing, 100875, China 2. State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China 3. Joint Center for Global Change Studies, Beijing, 1000875, China 4. Data Analytics, CSIRO Digital Productivity FlagshipFloreat, 6083, Western Australia, Australia |
| Abstract: | This study examines the relationships among the monsoon-like southwest Australian circulation (SWAC), the Southern Annular Mode (SAM), and southwest Western Australia winter rainfall (SWR), based on observed rainfall, reanalysis datasets, and the results of numerical modeling. By decomposing the SWAC into two components using a linear model, i.e. the component related to SAM (RSAM) and the component unrelated to SAM (SWACI*), we find it is the SWACI* that shows a significant influence on SWR. Similarly, it is the component of SAM associated with SWAC that exhibits an impact on SWR, whereas the component unrelated to SAM. A similar result is obtained in terms of the circulation associated with SWAC and the SAM. These facts suggest the SAM plays an indirect role in influencing SWR, and raise the possibility that SWAC acts as a bridge between the SAM and SWR, by which the SAM passes its influences onto SWR. This is due to the fact that the variations of SWAC are closely linked to the thermal contrast between land and sea across the southern Indian Ocean and southwest Australia. By contrast, the SAM does not significantly relate to this thermal structure, particularly for the component unrelated to SWAC. The variations of surface sea temperature over the southern Indian Ocean contribute to the favored rainfall circulation patterns. This finding is supported by the numerical modeling results. The strong coupling between SWAC and SWR may be instrumental for understanding the interactions between SWR and the southern Indian Ocean, and provides another perspective in examining the variations in SWR. |
| Keywords: | monsoon-like Southwest Australian Circulation Southern Annular Mode southwest Western Australian winter rainfall |
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