Institute of Atmospheric Physics, Chinese Academy of Sciences
This study projects the change in the environmental fields and genesis potential index of typhoon (GPI) over the western North Pacific (0°–40°N and 100°–180°E) at the end of the 21st century (2080–2099) using outputs from the Coupled Model Intercomparison Project Phase 5 (CMIP5) RCP4.5 and RCP8.5 experiments undertaken by 19 climate models. These models are capable of reproducing modern background fields of typhoon reasonably and are selected out for the analysis. Compared to the reference period of 1986–2005, there appears increased sea surface temperature (SST) over the western North Pacific, weakened vertical wind shear (VWS) and decreased outgoing longwave radiation (OLR) over the key regions where there are significantly negative correlations between these factors and the typhoon frequency, beneficial to the formation and development of typhoon; in contrast, the low pressure system extending from the mainland to the South China Sea is weakened, suppressing typhoon activities. Overall, the changes of environmental fields of typhoon under the RCP8.5 scenario are larger than under RCP4.5 scenario. Further, the signal to noise ratio is examined for measuring consistency across individual models. It is shown that such a ratio is higher than 3.0 for the change of SST and larger than 1.0 for sea level pressure over regions under the domination of low pressure system; for changes of VWS and OLR, the ratio of less than 0.6 denotes a degree of disagreement across models; nevertheless, models agree well on the sign of the change of OLR in regions associated with typhoon activities. The aforementioned changes of environmental fields of typhoon are in line with increased GPI in the future.