Early Summer Response of the East Asian Summer Monsoon to Atmospheric CO_2 Forcing and Subsequent Sea Surface Warming
The early summer regional climate change of the East Asian summer monsoon (EASM) is investigated in the phase 5 of the Coupled Model Intercomparison Project (CMIP5) archive. In the greenhouse gas–forced scenario, reduction of radiative cooling and increase in continental surface temperature occur much more rapidly than changes in sea surface temperatures (SSTs). Without changes in SSTs, the early summer rainfall in the monsoon region decreases (increases) over ocean (land) in most models. On longer time scales, as SSTs increase, rainfall changes are opposite. The total response to atmospheric CO_2 forcing and subsequent SST warming is a large (modest) increase in rainfall over ocean (land) in the EASM region. Dynamic changes, in spite of significant contributions from the thermodynamic component, play an important role in setting up the spatial pattern of precipitation changes. Early summer rainfall anomalies over east China are a direct consequence of local land–sea contrast, while changes in the large-scale oceanic rainfall band are closely associated with the displacement of the larger-scale North Pacific subtropical high (NPSH). Ad hoc numerical simulations with the AM2.1 general circulation model show that topography and SST patterns play an important role in early summer rainfall changes in the EASM region.
Additional Information© 2016 American Meteorological Society. Manuscript received 11 September 2015, in final form 29 April 2016, Published online: 11 July 2016. We thank the editor Aiguo Dai and three anonymous reviewers for their insightful comments that helped improve the manuscript. We use the NCAR Command Language (version 6.1.2; http://dx.doi.org/10.5065/D6WD3XH5) to create the plots and analyze the data. The data analyses and simulations were conducted on the Caltech's Division of Geological and Planetary Sciences high-performance computing cluster.
Published - jcli-d-15-0649.1.pdf
Submitted - CB_future.pdf