The South Asian summer monsoon （SASM） during the mid-Piacenzian is analyzed through climate modelling with CAM4. The model results reveal a non-uniform spatial difference in the SASM during the mid-Piacenzian compar...The South Asian summer monsoon （SASM） during the mid-Piacenzian is analyzed through climate modelling with CAM4. The model results reveal a non-uniform spatial difference in the SASM during the mid-Piacenzian compared to the pre-industrial era, with the SASM being more intense north of -20°N but weaker south of -20°N. In particular, summer precipitation is higher in South Asia north of -20°N, accompanied by anomalous low-level southwesterlies from the Arabian Sea, whereas the precipitation is lower in South Asia south of-20°N, with anomalous low-level easterlies. These differences in the SASM are related to changes in sea level pressure （SLP） due to the different boundary conditions between the two periods. Further analysis isolates the climate effects of the different boundary conditions and indicates the combined difference in atmospheric carbon dioxide concentration and SST to be the most important factor in this difference in the SASM through the changes in SLR By comparison, the differences in vegetation and topography have limited effects. The availability of geological evidence is relative greater in northern India than in southern India, and comparison with this geological evidence shows the simulated monsoon climate to be qualitatively consistent with it, particularly for the wetter climate in northern India.展开更多
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences[grant number XDB03020602]the National Natural Science Foundation of China[grant number 41305073]
文摘The South Asian summer monsoon （SASM） during the mid-Piacenzian is analyzed through climate modelling with CAM4. The model results reveal a non-uniform spatial difference in the SASM during the mid-Piacenzian compared to the pre-industrial era, with the SASM being more intense north of -20°N but weaker south of -20°N. In particular, summer precipitation is higher in South Asia north of -20°N, accompanied by anomalous low-level southwesterlies from the Arabian Sea, whereas the precipitation is lower in South Asia south of-20°N, with anomalous low-level easterlies. These differences in the SASM are related to changes in sea level pressure （SLP） due to the different boundary conditions between the two periods. Further analysis isolates the climate effects of the different boundary conditions and indicates the combined difference in atmospheric carbon dioxide concentration and SST to be the most important factor in this difference in the SASM through the changes in SLR By comparison, the differences in vegetation and topography have limited effects. The availability of geological evidence is relative greater in northern India than in southern India, and comparison with this geological evidence shows the simulated monsoon climate to be qualitatively consistent with it, particularly for the wetter climate in northern India.
