Assessment of the Environmental and Societal Impacts of the Category-3 Typhoon Hato

Abstract

The destructiveness and potential hazards brought to the Pearl River Delta (PRD) by the category-3 typhoon Hato in 2017 have been studied. The results show that wind flow is one of the key parameters influenced by tropical cyclones. The observed wind at Shenzhen station changed from median southwesterly and calm northerly to strong easterly during the evolution of Hato as it approached the PRD and during landfall, respectively. The peak wind intensity at the surface level and a height of 300 m reached over 17 m s−1 and 30 m s−1, respectively. In Zhuhai, the area closest to the landfall location, the situ observation shows that the maximum wind and the maximum gust on 23 August 2017 reached 29.9 m s−1 and over 50 m s−1, respectively, which is a record-breaking intensity compared with the highest recorded intensity during tropical cyclone (TC) activity in Vicente in 2012. The maximum sea level during 23 August 2017, with an added influence from the storm surge and the astronomical tide, was found to be over 3.9 m to the west of Hong Kong. Extreme high temperature was also recorded on 22 August 2017 before the landfall, with 38.4, 38, and 36.9 °C of daily maximum temperature in Shenzhen, Macao, and Hong Kong, respectively. Based on the heat index calculated with the temperature record at Shenzhen’s station, the hot temperature hazard reached “danger” levels. On the other hand, a prominent air quality deterioration was observed on 21 August 2017. The concentrations rapidly increased to 1 time greater than those on the previous day in Hong Kong. The TC-induced sinking motion, continental advection, and less amount of cloud cover were observed before the landfall, and would be the possible factors causing the extreme high temperature and the poor air quality. This case study illustrates that the influences of Hato to the PRD were not only limited to their destructiveness during landfall, but also brought the extreme high temperature and poor air quality.