Non-uniform spatial difference in the South Asian summer monsoon during the mid-Piacenzian
AbstractThe 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 SLP. By comparison, the differences...