Extended Data Fig. 1: Buoy current and wind observations under TC conditions.

a, Relationship of observed wind speed and ageostrophic current speed considering latitudes under TC conditions (blue dots). Linear regression (red line) is also plotted between the binned averages of the observed wind speeds and current speeds (red dots), with \({V}_{0}\) in the regression equation being coupling between the ageostrophic current speed \(V\) and latitude \(\phi \) as \({V}_{0}=V\times \sqrt{{\rm{\sin }}\left|\phi \right|}\), and the slope of the fitted line (along with the 95% margin of error and the p-value of the t-test) is reported in the bottom right corner. The binned averages of the current speeds are calculated from the ageostrophic current speeds in every 0.1 m s⁻¹ bin, and the corresponding observed wind speeds are taken to calculate the binned averages of the observed wind speeds. b, Comparison of the binned averages of the theoretical wind speeds estimated from the ageostrophic currents and observed wind speeds (red dots). The binned averages of the observed wind speeds are calculated from the observed wind speeds in every 1 m s⁻¹ bin, and the corresponding theoretical wind speeds are taken to calculate the binned averages of the theoretical wind speeds. c, Distribution of buoys with current and wind observations in the TC-coordinate system (dots), with the purple dots indicating that the maximum wind speeds of the corresponding TCs are larger than 35 kt. The results are based on observations from the TAO/TRITON, RAMA, and PIRATA buoy arrays.