Fig. 8

Zonal sections of vertical velocity w (\({\text {m\,s}}^{-1}\), color shades) and potential density \({\sigma }_{\theta }\) (\({\text {kg\,m}}^{-3}\), contours) at the latitude of \(12.6^{\circ }\)N averaged in a all months, b January–March, c April–June, d July–September, and e October–December during 1993–2016. Positive values show upward velocity. Contour intervals of \({\sigma }_{\theta }\) are 0.25 \({\text {kg\,m}}^{-3}\)