Using the results of the vertical mode expansion described on other pages, we quantified the effect of wind stress (the force of wind dragging seawater) on the water masses in each mode, respectively.

　The figure below shows the conceptual diagram with yellow arrows representing the force of wind stress dragging seawater at the sea surface and green arrows representing the force pushing water masses in the mixed layer, and the eigenvalue vectors of modes 1 to 3 obtained by creating a vertical profile of density from OFES temperature and salinity data in the tropical Pacific Ocean, rewriting it into a profile of buoyancy frequency, and performing vertical mode expansion. These are the eigenvalue vectors of modes 1 to 3. The depth of the mixed layer in the tropical Pacific Ocean is about 45 meters. From the eigenvalue vectors obtained by the mode expansion, the wind stress was distributed to each mode.

　The following equation shows the actual distribution of wind stress.

 The distribution coefficient of wind stress to each mode in the Pacific Ocean is 0.34 for mode 1, 0.38 for mode 2, and 0.29 for mode 3. It can be said that the wind stress contributes the most to mode 2.