日本地球惑星科学連合2019年大会

講演情報

[E] ポスター発表

セッション記号 M (領域外・複数領域) » M-TT 計測技術・研究手法

[M-TT46] 統合地球観測システムとしてのGPS/GNSSの新展開

2019年5月27日(月) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:小司 禎教(気象研究所気象衛星・観測システム研究部第2研究室)、市川 香(九州大学応用力学研究所)、太田 雄策(東北大学大学院理学研究科附属地震・噴火予知研究観測センター)、津川 卓也(情報通信研究機構)

[MTT46-P04] Estimation of typhoon wind speed using CYGNSS observations: A case study of Typhoon Lan in 2017

*加古 真一郎1富田 裕之2市川 香3 (1.鹿児島大学大学院理工学研究科、2.名古屋大学 宇宙地球環境研究所、3.九州大学応用力学研究所 )

キーワード:CYGNSS、AMSR2、台風

We conducted a case study of Typhoon Lan, which occurred in 2017, to investigate the impact of the Cyclone Global Navigation Satellite System (CYGNSS) on the estimation of extremely high wind speeds, such as those occurring during typhoons. We studied CYGNSS because it is expected to be capable of observing wind speeds in regions with extremely high wind speeds and heavy rains (i.e., typhoons) where it is difficult to perform measurements using the current microwave instrument. Firstly, we compared CYGNSS-derived wind speeds produced by NASA with those derived from AMSR2 produced by the Japan Aerospace Exploration Agency. CYGNSS was found to underestimate the wind speeds around Typhoon Lan compared with AMSR2. We then attempted to estimate the wind speeds using the leading edge slope (LES) and mean square slope (MSS) derived from the CYGNSS observations. Although the relationship between the MSS and wind speed differs depending on the wave age (Zhao and Tobe, 2003), it is difficult to estimate the wave age because this estimation is required the wind and wave speeds. We used the wave period as a substitute for the wave age since the wave period is expected to be similar to the wave age. We therefore first computed the fourth power of the wave period (T4) in line with Wang and Ichikawa (2016). Next, we classified the ocean into three regions based on T4 to investigate the relationship between the MSS and the wind speed observed by AMSR2 in each region. Finally, we approximated the curves relating the MSS to the wind speed using exponential functions in the three regions and estimated the wind speed using these curves. The comparison between the wind speeds produced by NASA and those estimated in this study demonstrated that our method can estimate high wind speeds more accurate than the CYGNSS wind speeds produced by NASA.