A Possible Reduction in the Severity of Typhoon Wind in the Northern Part of Japan under Global Warming: A Case Study

Abstract

Typhoon Songda (2004), while undergoing an extratropical transition and reintensification over the Sea of Japan, spawned serious damages over forest areas in the northern part of Japan. To clarify influences of anticipated global warming on the typhoon hazard in high-latitude regions, we carried out numerical experiments on Typhoon Songda in a current climate and a pseudo global warming climate and examined the impacts of climate change on the typhoon intensify and windstorms for the region. The typhoon intensity at its maturity becomes stronger in a warming climate, and the typhoon while passing over the Sea of Japan weakens more rapidly in the warming climate. Thus the strong wind over the northern part of Japan in the warming climate also becomes weaker. We examined atmospheric environmental factors in the higher-latitude region: sea surface temperature, vertical shear, and meridional gradient of temperature. It was found that the environmental meridional gradient of temperature at the 500 hPa level is smaller in the warming climate than in the current climate, which indicates that the baroclinicity becomes weak under global warming. The weak baroclinicity makes the typhoon environment unfavorable for the extratropical transition, and therefore, possibly reduces the severity of typhoon wind in northern Japan.

Effects of global warming on the impacts of Typhoon Mireille (1991) in the Kyushu and Tohoku regions

“…All the domains had 57 vertical levels, and the model top was set to be 20 hPa. The parameterizations for physical processes were chosen in the same way as used in Ito et al (2016).…”

“…In addition, the TC bogus scheme was used to initialize the TC vortex, based on the best-track data of the Regional Specialized Meteorological Center (RSMC) in Tokyo. The options for spectral nudging and the TC bogus scheme are the same as those used in Ito et al (2016). The initial time for time integration was 1200 UTC 25 September 1991.…”

“…We also conducted three other experiments with fully added increments (except relative humidity and wind) from the AGCM runs with three SST clusters (referred to as PGWC1 for SST Cluster 1, PGWC2 for SST Cluster 2, and PGWC3 for SST Cluster 3). The incremental data used here are exactly the same as in Ito et al (2016). The spatial distributions of the increments can be found in Ito et al (2016).…”

“…Ito et al (2016) indicated, by conducting PGW experiments, that the severity of Typhoon Songda (2004) in the northern part of Japan, i.e., Hokkaido, was reduced under warmed climate conditions, although the maximum intensity of the typhoon was strengthened. Thus, it is possible that an extreme typhoon, similar to Typhoon Songda, may have contrasting impacts in the southern and the northern part of Japan under global warming.…”

“…The impact assessment for forested areas is important because forests play a critical role in hydrological processes and the water cycle. For this purpose, PGW experiments and a simulation for reproducing the past event, similar to those in Ito et al (2016), are conducted for Typhoon Mireille. Because the tracks of Mireille and Songda are similar, the robustness of the finding in Ito et al (2016) is expected to be increased.…”