Mid-Holocene and last glacial maximum changes in monsoon area and precipitation over China

Abstract

Sixty-one climate models participating in the Paleoclimate Modeling Intercomparison Project phases one (PMIP1) to three (PMIP3) were first evaluated in terms of their ability to reproduce the present annual, summer (May-September), and winter (November-March) precipitation climatology of China. Changes in monsoon area (CMA), monsoon precipitation (CMP), and monsoon precipitation intensity (CMPI) over China were then investigated using the results of 26 and 16 reliable climate models for mid-Holocene (MH) and last glacial maximum (LGM), respectively. Results show that relative to the reference period, the MH CMA, CMP, and CMPI consistently increased in 26, 26, and 22 models, respectively, with averages of 10.7% for CMA, 18.7% for CMP, and 7.3% for CMPI. Those changes were collectively attributable to an orbitally induced decrease in summer meridional temperature gradient and increases in summer land-sea thermal contrast between the East Asian continent and adjacent oceans. The role of the dynamic ocean was limited. Model results are generally consistent with geologic records over the monsoon regions in China. At the LGM, the CMA and CMP decreased in 15 models and the CMPI weakened in all 16 models, with averages of -7.7%, -25.1%, and -14.3%, respectively. In response to LGM forcing, the increase in summer meridional temperature gradient and decreases in zonal and meridional land-sea thermal contrast were the underlying mechanisms, and interactive ocean had a suppression effect. The simulated changes agree qualitatively with most of the limited proxy data across the CMA.