The North Equatorial Countercurrent and the Zonality of the Intertropical Convergence Zone

Abstract

AbstractThe zonality of the Intertropical Convergence Zone (ITCZ) denotes the appearance of the ITCZ precipitation as a continuous band across a vast zonal span, say, the whole Pacific. Here, we emphasize the essential role of the North Equatorial Countercurrent (NECC) in maintaining the zonality of the ITCZ. By transporting warm water eastward and hence reducing the zonal contrast of sea surface temperature (SST), the NECC induces a narrow but continuous band of SST maxima, over which the ITCZ is formed. It is found in observation that the stronger the eastward NECC is, the more uniform the zonal distribution of the ITCZ precipitation between 150°E and 135°W is. Modeling simulation suggests that the zonality of the ITCZ may well be broken when contribution of the NECC to the SST maxima is largely removed. The importance of two‐way interaction between the NECC and the ITCZ is highlighted.