17:15 〜 19:15
[AOS18-P04] In situ sea surface wind measurement and calibration beneath the typhoon using unmanned surface vehicles
キーワード：台風、海上風、ウェーブグライダー
Recent global warming has intensified typhoons, leading to more severe damage to social infrastructure. To proactively respond to typhoons, improving the accuracy of typhoon forecasting is essential. Additionally, elucidating their mechanisms is crucial for refining forecasting models. For these objectives, in situ observations of the atmosphere and ocean are critically important, in addition to remote sensing from satellites.
We have repeatedly conducted meteorological and oceanographic observations directly beneath typhoons using unmanned surface vehicles called wave gliders (WGs) [Kosaka et al., 2023, SOLA]. High-resolution ocean wind data improve the accuracy of typhoon intensity predictions in numerical forecast models. Ocean wind information is essential for predicting typhoon central pressure and wind velocity distributions. In this study, we focused on sea surface winds (SSWs), which are particularly important for predicting typhoon intensity. SSW is measured by meteorological instruments installed on the mast of WG. Therefore, especially during typhoon approach, the WG’s ability to measure SSWs accurately was affected by tilt due to significant turbulence caused by high waves. Specifically, the following errors can be considered: 1) the apparent wind velocity is reduced by the angle due to the inclination of the instruments, 2) the wind velocity is reduced by the lower sea surface height due to the inclination of the mast, 3) the instrument motion speed is contaminated as wind velocity, and 4) the effect of the wind being blocked by high waves where the wind should be observed. This study aimed to calibrate for the effects of WG tilt (1-3).
A direct comparison of the observed wind velocity with model values (e.g., Satellite data (GCOM-W1), LFM-GPV (Local Forecast Model GPV of JMA)) reveals a discrepancy, with the data from the WG falling below the model estimates. An examination of the tilt data indicates that both roll and pitch values are particularly large during the typhoon approach. For the roll value, there are many times (several times for 5 minutes) when the motion reaches +/-180 degrees, indicating that the WG has made one rotation. A combined analysis of the wind velocity and attitude data reveals a substantial discrepancy between the observed values and the model predictions during periods of significant agitation of the WG. This suggests the possibility that the WG's tilt may have a notable influence on the apparent values of instantaneous wind velocity observed. Except for tilt that significantly affect the measurement, an error of about several m/s may occur in terms of apparent wind velocity.
Henceforth, we intend to undertake quantitative corrections with the objective of measuring precise wind velocity, even in the presence of substantial turbulence. Furthermore, the impact of wave shielding will be examined, and its extent will be verified in actual sea conditions.
We have repeatedly conducted meteorological and oceanographic observations directly beneath typhoons using unmanned surface vehicles called wave gliders (WGs) [Kosaka et al., 2023, SOLA]. High-resolution ocean wind data improve the accuracy of typhoon intensity predictions in numerical forecast models. Ocean wind information is essential for predicting typhoon central pressure and wind velocity distributions. In this study, we focused on sea surface winds (SSWs), which are particularly important for predicting typhoon intensity. SSW is measured by meteorological instruments installed on the mast of WG. Therefore, especially during typhoon approach, the WG’s ability to measure SSWs accurately was affected by tilt due to significant turbulence caused by high waves. Specifically, the following errors can be considered: 1) the apparent wind velocity is reduced by the angle due to the inclination of the instruments, 2) the wind velocity is reduced by the lower sea surface height due to the inclination of the mast, 3) the instrument motion speed is contaminated as wind velocity, and 4) the effect of the wind being blocked by high waves where the wind should be observed. This study aimed to calibrate for the effects of WG tilt (1-3).
A direct comparison of the observed wind velocity with model values (e.g., Satellite data (GCOM-W1), LFM-GPV (Local Forecast Model GPV of JMA)) reveals a discrepancy, with the data from the WG falling below the model estimates. An examination of the tilt data indicates that both roll and pitch values are particularly large during the typhoon approach. For the roll value, there are many times (several times for 5 minutes) when the motion reaches +/-180 degrees, indicating that the WG has made one rotation. A combined analysis of the wind velocity and attitude data reveals a substantial discrepancy between the observed values and the model predictions during periods of significant agitation of the WG. This suggests the possibility that the WG's tilt may have a notable influence on the apparent values of instantaneous wind velocity observed. Except for tilt that significantly affect the measurement, an error of about several m/s may occur in terms of apparent wind velocity.
Henceforth, we intend to undertake quantitative corrections with the objective of measuring precise wind velocity, even in the presence of substantial turbulence. Furthermore, the impact of wave shielding will be examined, and its extent will be verified in actual sea conditions.