The role of global warming in tropical cyclone behaviours : case study of the western North Pacific region

Abstract

Since the 19th century, anthropogenic warming has played an important part to climate change globally and resulted in various impacts including changing activities of tropical cyclones (TCs). This study described TC behaviours over the western North Pacific (WNP) region from 1978 to 2015, a period of accelerated warming, and evaluated the relative importance of global warming in affecting the patterns as described. Data obtained from the International Best Track Archive for Climate Stewardship (IBTrACS) dataset and the NCEP reanalysis dataset was presented graphically and analyzed. It was identified that TC frequency over the WNP has fallen (-1.123 decade-1) while the intensity has increased (1.257 decade-1) and there has been a poleward shift (0.487oN decade-1) of where TC reaches its lifetime-maximum intensity (LMI). In addition, inter-annual and -decadal variabilities were found to be obvious among the time series of TC frequency. It was concluded that the general trends are consequences of global warming, which has made the conditions for tropical cyclogenesis more favourable thermodynamically but less favourable dynamically. The former dominates changes of TC in terms of intensity and location where LMI is reached while the latter factors exert larger influence on frequency. As for the inter-annual and -decadal patterns, they can be attributed to El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO). The results enhance knowledge about the relative importance of global warming to TC development, which can improve future TC projection under changing climate.