Editorial for the special edition on Typhoons in 2018 – 2019
2022 Volume 100 Issue 6 Pages 851-853
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2022 Volume 100 Issue 6 Pages 851-853
The 2018–2019 typhoon season was of interest to many people because of the specified cases that caused natural disasters and had their impacts on Japanese society, economy, and human life. The number of typhoons that made landfall in Japan was five in each of 2018 and 2019 typhoon season. In particular, typhoons Jebi (2018), Faxai (2019), and Hagibis (2019) caused serious natural disasters in various areas of Japan and resulted in the record-breaking amount of insurance claims paid due to strong winds, torrential rainfalls, high waves, and storm surge. This special edition was organized jointly with the Scientific Online Letters on the Atmosphere (SOLA). The eight papers published in the Journal of the Meteorological Society of Japan (JMSJ) as well as eight papers published in SOLA are briefly summarized below.
Typhoon Jebi (2018) that made landfall in Japan in early September in 2018 caused severe damage due to extremely high winds and storm surge. Ohtaki et al. (2022) investigated the possible storm surge caused by Jebi by using a storm surge model with surface winds obtained from track ensemble simulations based on a meteorological model and with those calculated by a parametric tropical cyclone (TC) model.
Regarding the prediction of typhoon intensity in 2018–2019, rapid intensification and weakening of typhoons remain challenging scientific topics. The interactions between a TC and the ocean differed between typhoons Trami (2018) and Kong-Rey (2018) (Wada 2021). Wada et al. (2022) noted that variations in atmospheric initial conditions yield variations in the effect of the uppertropospheric cold-core low on the track simulation of Typhoon Jongdari (2018). There studies are interesting in understanding the effect of the ocean on TC track predictions and the associated TC intensity predictions.
The following published papers mainly covered Faxai and Hagibis. As for Faxai, there were only 4 days for notification prior to landfall after the genesis at 18 UTC on 4 September in 2019. The condition of enhanced lower-troposphere easterly wave was favorable for vortex formation, whereas the enhancement and upper tropospheric westerly wind increased the vertical wind shear, which suppress the development of the vortex into a TC (Fudeyasu et al. 2022). While Faxai made landfall in Japan, results simulated by a nohydrostatic atmosphere model relatively showed that simulated Faxai underwent superintensity having an axisymmetric flow with the presence of supergradient flow in the boundary layer under the atmospheric and oceanic environments such as slow translation, weak vertical shear, and high air-sea latent heat flux (Miyamoto et al. 2022). Sakurai et al. (2022) investigated lightning over a large area of Faxai in the decaying phase using observations obtained from the 3-D Tokyo Lightning Mapping Array, a Japan Meteorological Agency C-band Doppler radar, and the Japanese Lightning Detection Network. Faxai was highly unusual in that it produced a high percentage of positive cloud-to-ground flashes.
In October 2019, torrential rain in Typhoon Hagibis caused more than 100 fatalities mainly in the eastern part of Honshu, Japan's largest island. It was one of the nation's most devastating typhoon disasters in recent decades. In addition, Hagibis was a large TC and became intense during the intensification phase, The operational forecasts failed to capture rapid intensification (RI) of Hagibis. From the sensitivity experiments by the Coupled Ocean/Atmosphere Mesoscale Prediction System-Tropical Cyclone (COAMP-TC), Jin et al (2022) showed that the use of 1.33 km horizontal resolution enabled to facilitate more realistic prediction of the explosive RI and its associated structural change such as a secondary eyewall formation and an eyewall replacement cycle.
From the results of ensemble numerical experiment, Nakashita and Enomoto (2022) showed the significance of tropical disturbance on accurately predict the track of Hagibis. In this special edition, there were several papers that used a numerical model and focused on the sensitivity of atmospheric, oceanic and topographic boundary condition. Kawase et al. (2021) demonstrated that the atmospheric and oceanic warming trends for 40 years enhanced the precipitation. The warm SST feature affect the track of Hagibis (Ito and Ichikawa 2021) and rainfall distribution along the Pacific coast of northeastern Japan (Iizuka et al. 2021). Yanase et al. (2022) demonstrated from the numerical simulation results that the baroclinic zone at middle latitudes north of Hagibis played different roles in precipitation, which depended on the distance from the storm. In the central Japan, topography affected precipitation in Hagibis (Yamada and Kuribayashi 2022).
Numerical simulations were conducted for Trami (2018) (Kanada et al. 2021b) and Hagibis (2019) (Kanada et al. 2021a) under pseudo-global warming climate using a sophisticated atmosphere- ocean coupled model in order to clarify the effect of global warming in the atmosphereocean coupled framework. Sea surface cooling induced by the two typhoons mitigated the amount of heavy rainfall compared to the amount simulated with the fixed sea surface temperature. The western North Pacific had a region that had linearly increased the upper ocean heat content measured by a TC heat potential although the inherent internal oceanic variation was related to TC activity (Wada and Chan 2021).
Most papers in this special issue addressed understanding the unusual characteristics of individual typhoons during the typhoon season in 2018–2019, while at the same time the papers presented challenging issues for the advancement of current science and technology. We hope that this special issue will contribute to the development of TC and TC-related research in the future.
