[A-AS02] Evolution of Global Environmental Research based on Atmospheric Vertical Motions

[AAS02-P05] Validation of a Vertical Model of Ocean Wind using “Synchronous Ocean Observation” Data from UAV (multicopter) and Wave Glider

*Yusuke Umemiya¹, Naoko Kosaka¹, Tatsuya Iizuka¹, Go Itami¹, Toru Nakamura¹, Tsuneko Kura¹, Akinori Murata², Satoshi Mitarai² (1.NTT Space Environment and Energy Laboratories, 2.Okinawa Institute of Science and Technology Graduate University)

Keywords:ocean observation, unmanned aerial vehicle (UAV, multicopter, drone), Wave Glider, ocean wind, vertical profile, Sea Surface Wind speed (SSW)

When using ocean observation data in research, wind speed is generally converted into a value at an altitude of 10 m (U₁₀) to ignore the effect of drag due to the sea surface. In this conversion, we usually use an approximate formula that assumes a logarithmic distribution in the height direction, considering the drag force (Large and Pond, 1981). This drag force is expressed as a C_d depending on the wind speed and set depending on the model and the place of the observation (e.g., Hara and Belcher, 2004, Zedlar et al., 2002). Although there have been some studies to estimate and validate this conversion equation using buoys and other offshore observation data, direct observations in the region above 10 m altitude at sea (ocean atmosphere) are difficult to do, so satellite data is mostly used for those regions in these attempts (e.g., Suzuki et al., 2018).

To improve this situation, we conducted the observation experiment in the sea near Okinawa in November 2021 and obtained data on the vertical profile of the ocean atmosphere by direct observation. In this experiment, we simultaneously used a wave glider (Liquid Robotics) as an instrument to measure the ocean surface and an unmanned aerial vehicle (UAV) (ACSL) as an instrument to measure the ocean atmosphere. In this study, we compared the vertical distribution equation described by Large and Pond (1981) with our observation data to evaluate the effectiveness of the “synchronous observation” and to verify the formula with local observation data. If the accurate vertical distribution equation of the sea wind in various wind speed ranges can be estimated by the continuous “synchronous observation” in the future, observation data of ocean winds and associated water vapor transport that can be useful for extreme weather forecasting may be obtained by water floats with a track record of observations under extreme weather conditions such as wave gliders (Mitarai and McWilliams, 2016).