第二届未来大气科学论坛

During the pre-summer rainy season in southern China, heavy rainfall frequently occurs in the warm sector hundreds of kilometers to the south of a front or without any front, which is one of the major contributors for coastal flooding events during this period. The intensity and frequency of strong convective storms are expected to rise with warming climate, posing a greater threat of extreme rainfall in the future. This study aims at revealing the future changes of coastal warm-sector heavy rainfall and essential mesoscale process in southern China based on quasi-idealized WRF simulations and pseudo global warming (PGW) approach.

Typical warm-sector heavy rainfall events are selected to produce composite environments that force the quasi-idealized simulation in current climate (CTRL). After that, the climate sensitivity experiment (PGW) is conducted with the same configurations except that it is forced by reanalysis data plus the climate dynamic and thermodynamic perturbations derived from a 15-model CMIP5 ensemble mean climate change signal for SSP2-4.5 scenario by the end of 2100. Similarly, the climate change signals from each of the 15 CMIP members were also used to produce 15 individual PGW ensemble runs. Counterintuitively, the ensemble mean PGW and 10/15 ensemble PGW runs showed significantly decrease in accumulated precipitation over coastal region, though with overall larger CAPE. Further analyses showed that this decrease was largely relevant to the future changes in LLJs. In the PGW ensemble runs where the coastal precipitation severely decreased, the marine boundary layer jet over the northern South China Sea was significantly weaker and slightly more to the west than CTRL. Therefore, our results suggest that favorable thermodynamics changes in a warming climate might be overwhelmed by the dynamic changes associated with the low-level wind fields, suggesting the uncertainty of the future coastal heavy rainfall.
 

Coastal Heavy Rainfall,PGW