[A-CG45] Promotion of climate and earth system sciences using manned/unmanned aircrafts

[ACG45-04] The 30-year variation of strong typhoons found in the Japan Meteorological Agency's Dvorak Reanalysis Data

*Yasuhiro Kawabata¹, Udai Shimada¹, Munehiko Yamaguchi¹ (1.Meteorological Research Institute)

Keywords:tropical cyclone, strong typhoon, Dvorak analysis, trend analysis, typhoon climatology

It is important for disaster prevention and social activities to understand long-term trends in the number of strong typhoons above Hurricane Scale Category 4 in the western North Pacific. Mei and Xie (2016) investigated long-term changes in the number of strong typhoons from 1977 to 2014, using best track data of the Japan Meteorological Agency (JMA) and the Joint Typhoon Warning Center, USA (JTWC). JMA maximum sustained wind speed (Vmax) is 10-minute average, while JTWC Vmax is 1-minute average. Therefore, Mei and Xie (2016) adjusted best track Vmax values estimated by JMA. The result showed an increase in the number of strong typhoons in both data. However, the dataset used in Mei and Xie (2016) is temporarily inhomogeneous because it was constructed using mostly aircraft observations from 1977 to 1986, and mostly Dvorak estimates from 1987 to 2014. Moreover, the number of satellite observation data used to create best track data has increased over the years, affecting the quality of the best track (Shimada et al. 2020). Thus, the homogeneity of data used in research also requires careful attention to accumulate new insight on the long-term changes of strong typhoons. Thus, JMA produced the Dvorak reanalysis data with a consistent method for a period of 1987 to 2016 (Nishimura et al. 2023). In this study, we analyzed the long-term changes of strong typhoons using the Dvorak reanalysis data. Results showed no statistically significant increasing trend in the number of strong typhoons with large inter-annual and multi-year scale variations. It was also found that the genesis location of strong typhoons shifted to the west, and the location of strong typhoons reaching their lifetime maximum intensities shifted to the northwest. In climatological studies of typhoons, homogeneous data over long periods are needed to assess long-term changes in typhoons and effects of global warming more accurately and confidently. Aircraft observations are important for this purpose.

Reference:
Kawabata, Y., U. Shimada, and M. Yamaguchi, 2023: The 30-year (1987-2016) trend of strong typhoons and genesis locations found in the Japan Meteorological Agency’s Dvorak reanalysis data. Journal of the Meteorological Society of Japan, 101, 435-443.