Simulation of the Climate Change in Asia for the mid-Holocene and the Last Glacial Maximum

Abstract

The simulations were performed with the Community Climate Model version 3 (CCM3) atmospheric general circulation model at about 75 km with 18 vertical levels. In the mid-Holocene summer, surface temperature increases in Asian continent by 3-5°C. Associated with the increase in surface temperature, surface pressure becomes deeper inside the continent and this intensifies the landward winds. An increase in landward winds is also shown in the northeast Pacific. In the LGM, on the other hand, the surface temperature decreases and consequently sea level pressure increases in the Tibetan Plateau, which leads to a marked decrease in southwest winds and thus the summer monsoon circulation. The change in spatial wind pattern is closely linked to the distribution of precipitation. In the mid-Holocene summer, precipitation is larger than MOD over most of Asia, especially over Saudi Arabia, India, South Asia, and north East Asia. This increase seems to be associated with the increase in landward winds. In the LGM, precipitation decreases in most regions. The precipitation decrease is especially large in western India and western South Asia presumably due to the weakening of the southwest wind in the Indian Ocean. The Asian summer monsoon becomes stronger in the mid-Holocene and weaker in the LGM. These model results agree with observational proxy evidence and other previous model simulations.