Quantitative and climatological analysis on the tracks of typhoons in the North West Pacific

Abstract:

Increased strength of typhoons in the North West Pacific (NWP) especially in the recent years is linked with the increasing sea surface temperature in various oceans due to climate change. This research aims to quantitatively and climatologically analyze the tracks and cyclogenesis locations of all typhoons that occurred after 1976 in the NWP during typhoon season. The International Best Track Archive for Climate Stewardship (IBTrACS) and Optimum Interpolation (OI) Sea Surface Temperature (SST) V2 data directly accessed by National Oceanic and Atmospheric Administration (NOAA), and COBE SST2 data of Japan Meteorological Agency (JMA) indirectly accessed by NOAA are used. A well-established track sinuosity index (SI) is used as a measure of the level of curviness in the track of a typhoon as curvier track of a typhoon makes forecasting more challenging for the atmospheric models, resulting in likely more prospective damages. A statistical analysis is carried out, on fundamental typhoon parameters, including the ocean of cyclogenesis, and phase of El Niño Southern Oscillation (ENSO) at cyclogenesis. Further statistical analysis on the relationships among all typhoon parameters through Fisher’s Exact and Chi-square (χ2) tests supports the above crucial finding and reveals that the sinuous nature of tracks of typhoons is more responsible for the longer survival of typhoons along with its strength. More than double cyclogenesis is detected during the warm phase of ENSO than the cold phase, which is also gradually rising in the last 4 decades. A significant rise in the SST by more than 0.4 °C is measured in typhoon originating oceans for the whole typhoon season during the last 40 years. The role of El-Niño epochs is found very crucial for the major SST anomaly (SSTA) changes during the typhoon season. Climatological analysis is fully consistent with statistical findings and lead to global warming as the major cause of the rising strength of typhoons in the NWP during the recent years.