Observed near‐surface currents under high wind speeds

Abstract

[1] From the Surface Velocity Program (SVP) drifter current and QuikSCAT wind data, the relationship between the observed near-surface current vectors and surface wind vectors for the northwestern Pacific Ocean under high winds (20-50 m s À1 ) are obtained with quantitative estimations of near-surface drift ratio (current speed versus wind speed) r ($2%) and near-surface drift angle a ($0 -10 to the right of the winds). These estimations keep unchanged after removing the surface geostrophic component. From the SVP drifter current and daily WindSat wind data, the estimated r is still approximately 2%. Three linear regression equations are obtained between the observed near-surface current speeds and the surface wind stress for the high wind range.

Observed near-surface currents under four super typhoons

“…9 as the color blue. The mean velocity and error bars of one standard deviation in the study under S = 0, 1, 2 (red color) are consistent with the results of Chang et al (2012).…”

“…The SVP drifter-measured ocean current velocities have errors of 0.3, 0.4, and 0.5 m s −1 for 20, 35, and 47 m s −1 winds, respectively. The results of Chang et al (2012) were also plotted in Fig. 9 as the color blue.…”

“…9). Chang et al (2012) used 11 years of wind and drifter data to show the relationship between the mean SVP drifter-measured ocean current speeds and the observed wind speeds of QuikSCAT with the error bars of one standard deviation for high wind speed of 20-50 m s −1 . The SVP drifter-measured ocean current velocities have errors of 0.3, 0.4, and 0.5 m s −1 for 20, 35, and 47 m s −1 winds, respectively.…”

Tropical cyclone footprint in the ocean mixed layer observed by Argo in the Northwest Pacific

“…The cooling and deepening are generally more evident on the right side of TC's tracks in the Northern Hemisphere [Price, 1981;Shay et al, 1992;Chu et al, 1999Chu et al, , 2000aJacob et al, 2000;Zheng et al, 2008;Nam et al, 2011]. Under storms, energy transferred from atmosphere to ocean generates upwelling, near-inertial waves, and currents [Price et al, 1994;Wang and Huang, 2004;Liu et al, 2008;Jaimes and Shay, 2010;Chang et al, 2012Chang et al, , 2013. As TC's translation speed is less than phase speed of the first baroclinic mode, oceanic response tends to be barotropic, geostrophic, and cyclonic gyre with upwelling in the storm's center [Chang and Anthes, 1978;Chang, 1985;Ginis and Sutyrin, 1995], which weakens the IL deepening near the storm's centers [Wu and Chen, 2012].…”

Wind induced variability in the Northern Current (North-Western Mediterranean Sea) as depicted by a multi-platform observing system

“…• ) and also considering the magnitude of the ageostrophic component compared to wind speed (about 2% as previously observed by Chang et al (2012) and Poulain et al (2009)). Surface 5 currents appear to respond to the wind quite homogeneously in space over the whole HF radar field.…”