Natural variability of summer rainfall over China in HadCM3

Abstract

Summer rainfall over China has shown decadal variability in the past half century, which has resulted in major north-south shifts in rainfall with important implications for flooding and water resource management. This study has demonstrated how multi-century climate model simulations can be used to explore interdecadal natural variability in the climate system in order to address important questions around recent changes in Chinese summer rainfall, and whether or not anthropogenic climate change is playing a role. Using a 1,000-year simulation of HadCM3 with constant pre-industrial external forcing, the dominant modes of total and interdecadal natural variability in Chinese summer rainfall have been analysed. It has been shown that these modes are comparable in magnitude and in temporal and spatial characteristics to those observed in the latter part of the twentieth century. However, despite 1,000 years of model simulation it has not been possible to demonstrate that these modes are related to similar variations in the global circulation and surface temperature forcing occurring during the latter half of the twentieth century. This may be in part due to model biases. Consequently, recent changes in the spatial distribution of Chinese summer rainfall cannot be attributed solely to natural variability, nor has it been possible to eliminate the likelihood that anthropogenic climate change has been the driving factor. It is more likely that both play a role.

Responses of East Asian summer monsoon to natural and anthropogenic forcings in the 17 latest CMIP5 models

“…However, the decreasing trends of EASM under external forcing is weaker than the observation, as evidenced in the circulation trend pattern (Figure b), SAT trend magnitude (Figure b). This discrepancy indicates that the internal variability mode of PDO may play a dominant role in the monsoon weakening as previously suggested [ Li et al ., ; Lei et al ., ; Zhou et al ., ], while the aerosol forcing plays a secondary or complementary role. Considering the model uncertainty and nonlinearity, how to determine the relative contributions of internal variability and external forcing deserves further study.…”

“…Recently, Lei et al . [] suggested that both internal variability and anthropogenic forcing play roles in the observed weakening of EASM. Up to now, there is no consensus on the mechanisms of EASM weakening [ Zhou et al ., ].…”

Aerosol and monsoon climate interactions over Asia

“…P . Li et al ., 2010; Zhou et al ., ; Lei et al ., ], while ADRF plays a secondary or complimentary role.…”

The impact of the direct effects of sulfate and black carbon aerosols on the subseasonal march of the East Asian subtropical summer monsoon

“…The EASM exerts a dominant effect on the summer climate in East Asia, providing about 40–50% of the annual mean precipitation over southern China and about 60–70% over northern China [ Lei et al ., , ; Song et al ., ]. Some studies found a weakening trend and southward migration of the precipitation zone of EASM beginning in the late 1970s [ Wang , ; Yu et al ., ; Xu et al ., ; Ding et al ., , ; Zhou et al ., ].…”

“…The possible mechanisms for the interdecadal change in the EASM is an active research topic [ Zhou et al ., ; Song et al ., ]. Various factors, such as sea surface temperature (SST) variability [ Xue , ; Wang , ; Yang and Lau , ; Li et al ., ; Zhou and Zou , ], sensible heat flux over the Tibetan Plateau [ Ding et al ., ; Wu et al ., ; Liu et al ., ], anthropogenic forcing (aerosols and greenhouse gases) [ Xu , ; Menon et al ., ; Ueda et al ., ; Liu et al ., ; Li et al ., ; He et al ., ; Wang et al ., ; Song et al ., ; Zhu et al ., ], and natural decadal variability [ Jiang and Wang , ; Lei et al ., , ] have been linked to the interdecadal change in the EASM. Song et al .…”