[A-AS02] From weather predictability to controllability

[AAS02-P06] Impacts of decrease in sea surface temperature through the released deep sea water on Typhoon’s intensity

*Takafumi Hosogi¹, Hironori Fudeyasu^2,1, Yasutomo Kiyohara², Hiroaki Yoshioka², Kosuke Ito^3,2, Koji Inoue⁴, Katsumi Takayama⁵, Kazuhiro Takeuchi⁵ (1.Yokohama National University, College of Education, 2.Yokohama National University, Typhoon Science and Technology Research Center, 3.Ryukyu University, 4.NPO The Society of Ocean Romantics, 5.IDEA Consultants, Inc)

Keywords:Typhoon

A project ” Moonshot Goal 8” supported by Japan Science and Technology Agency is to study the possibility of a typhoon intensity decline due to artificial interventions. An ocean thermal energy conversion (OTEC) which is planned to be established in the ocean near Okinawa islands is considered one of artificial interventions. An OTEC collects cold deep sea water at a depth of 800m and warm sea water at a depth of 20m, and discharges this mixed water to a depth of 20m. Namely an OTEC decreases the sea surface temperature (SST). When a typhoon passes over the ocean where the SSTs are decreased by OTEC, it is considered that the typhoon intensity is lower than the one without an OTEC. The purpose of this study is to conduct a numerical simulation of real typhoons using an atmospheric model with a SST distribution simulated by ocean model including the effects of OTECs (OTEC experiment), and to evaluate the impact of a SST forcing on a typhoon intensity (sensitivity experiment).
This time, WRFver4.4.1 is used for the numerical simulation. The WRF calculation conditions were as follows: horizontal resolution: 3 km, number of grids: 300 x 300 x 50, initial and boundary data: NCEP GDAS Final Analysis (0.25 degree) and DREAMS-SST (every 1 h), scheme: physics_suite (tropical). The duration of the experiment is from 12UTC 5 to 6 September 2020.
In the case of 2020, Typhoon Haishen passed through the OTEC influence zone, and the central pressures of Haishen were 930hPa by the Best Track data created by the Regional Specialized Meteorological Center Tokyo-Typhoon Center, 924.4hPa by our experiment without OTECs effect, and 924.6hPa by the OTEC experiment with the cooled SST (-0.05~ -0.02℃) spread from each point of OTECs to the north by 50-70 km (OTEC influence zone). The OTEC experiment with the cooled SST (-0.05~-0.02℃) showed little change in typhoon intensity compared to the experiment without OTECs effect. In the sensitivity experiment, the central pressure of Haishen increased by 0.57hPa and the maximum wind speed decreased by 0.82m/s at SST forcing with -0.5℃ in the OTEC influence zone. At SST forcing with -1.0℃, the central pressure increased by 1.00hPa and the maximum wind speed decreased by 0.97m/s. At SST forcing with -2.0℃, the central pressure increased by 1.34hPa and the maximum wind speed decreased by 1.05m/s.
The sensitivity experiment of the OTEC or SST forcing that effectively affects the other cases of typhoons will be investigated. This research was supported by JST Moonshot R&D Grant Number JPMJMS2282.