Wind Stress Curl

Wind-stress curl is the vertical curl of the surface wind-stress vector. Through the Sverdrup balance it sets the meridional transport of the interior wind-driven ocean, and through Ekman pumping it forces upwelling under positive (cyclonic) curl and downwelling under negative curl. The zero-curl line between the trade winds and the westerlies marks the gyre boundary and the bands of subtropical convergence and subpolar divergence.