日本地球惑星科学連合2023年大会

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[E] 口頭発表

セッション記号 A (大気水圏科学) » A-AS 大気科学・気象学・大気環境

[A-AS02] 気象の予測可能性から制御可能性へ

2023年5月22日(月) 15:30 〜 16:45 104 (幕張メッセ国際会議場)

コンビーナ:三好 建正(理化学研究所)、中澤 哲夫(東京大学大気海洋研究所)、Shu-Chih Yang(National Central University)、高玉 孝平(科学技術振興機構)、座長:三好 建正(理化学研究所)、Tetsuo Nakazawa(Meteorological Research Institute, Japan Meteorological Agency)

16:30 〜 16:45

[AAS02-10] How much the vertical mixing effect is enhanced by the intervention such as the released deep sea water using the cooling parameter

*筆保 弘徳1、宮本 佳明2,1、伊藤 耕介3,1 (1.横浜国立大学、2.慶応義塾大学、3.琉球大学)

キーワード:台風、クーリングパラメータ、鉛直混合

A project of Moonshot Goal 8 supported by Japan Science and Technology Agency is to study the possibility to reduce typhoon intensity by artificial interventions. Ocean thermal energy conversion (OTEC) is considered to be one of the artificial interventions. The OTEC technology mixes cold deep sea water at a depth of 800 m with warm sea water at a depth of 20 m and discharges the mixed water to a depth of 20 m, resulting in not only a decrease in the sea surface temperature (SST), but also an enhanced vertical mixing. There is few studies that quantitively estimate effects of vertical mixing. Miyamoto et al. (2017) developed an index “cooling parameter (Co)” that is theoretically formulated by considering the effects of vertical mixing, and Iida et al. (2022) showed that the amounts of SST decrease after the passage of Typhoon FAXAI and HAGIBIS in 2019 can be captured by Co. The purpose of this study is to investigate how much the vertical mixing effect is enhanced by the intervention such as OTEC using sensitivity experiments with Co.
Co is a dimensionless number, indicating the degree of vertical mixing from the characteristics of typhoons and oceans. This study used the long-term ocean reanalysis (FORA-WNP30) and the Best Track data created by the Regional Specialized Meteorological Center Tokyo-Typhoon Center to obtain the vertical profile of sea water temperature directly below the typhoon center position. Maximum winds and radius of strong winds, and moving speed of typhoons were used to estimate Co. For 865 typhoons that occurred in the Northwest Pacific from 1982 to 2015, Co was calculated at a total of 30,300 points every 6 hours. The ”TC-Co” was calculated by averaging Co over time during the development period of each typhoon, from the genesis time to the time of maximum intensity.
A single OTEC peaks at a depth of about 30 m and decreases the temperature by about 0.25°C. Assuming that the water temperature can drop further if the number of OTEC is increased to several tens, an OTEC sensitivity experiment was conducted to estimate Co from a temperature profile that peaks at a depth of about 30m and decease to 0.1-1.0°C. As a result, from the median value of TC-Co in 0.0°C experiment (CTL), the increase rate of the mixed layer after the passage of typhoons was theoretically about 4.4 times, but in the 0.25°C decrease experiment, it was about 4.5 times. In the 1.0°C drop experiment, it is 4.8 times. The amount of SST decrees after the mixing that effectively affects the typhoon’s intensity will be investigated. This research was supported by JST Moonshot R&D Grant Number JPMJMS2282.