Numerical Simulation of the Asian Monsoon for the Mid-Holocene Using a Numerical Model

Abstract

The change in global climate and Asian monsoon patterns during the mid-Holocene, 6000 years before present (6ka), is simulated by a climate model at spectral truncations of T170 with 18 vertical layers, corresponding to grid-cell sizes of roughly 75 km. The present simulation is forced with the observed monthly data of sea surface temperatures, and the specified concentration of atmospheric carbon dioxide, while in the mid-Holocene experiment, orbital parameters such as obliquity, precession, and eccentricity are changed to the 6ka conditions. Under such conditions, the precipitation associated with the summer monsoon is enhanced over a wider zonal band from the Middle East to Southeast Asia, while no significant alteration takes place in winter. The monsoonal wind also increases over the Arabian Sea, showing the enhanced southwesterly wind during summer and northeasterly wind during winter. Overall, the strength of the Asian monsoon is enhanced during the mid-Holocene, especially in summer, which is consistent with the proxy estimates and other previous model simulations.