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- Title
The North Equatorial Countercurrent and the Zonality of the Intertropical Convergence Zone.
- Authors
Sun, Zhikuo; Lu, Jianhua
- Abstract
The 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. Plain Language Summary: The Intertropical Convergence Zone (ITCZ) over tropical Pacific appears as a continuous precipitation band across a vast zonal span, say, the whole Pacific. This feature is denoted as the zonality of the ITCZ. The mechanism for the ITCZ zonality is not obvious for the real Earth with separated ocean basins and zonal asymmetry in land–sea distribution. Based on both observational data and model simulations, we emphasize that the North Equatorial Countercurrent (NECC), a narrow and strong eastward ocean current in the tropical Pacific, plays an essential role in maintaining the zonality of the ITCZ. The NECC transports warm water eastward and hence reduces the zonal contrast of sea surface temperature (SST) between the warmer western Pacific and the colder eastern Pacific, inducing a narrow but continuous band of SST maxima, over which the ITCZ is formed. Both observations and modeling simulations confirm that the stronger the eastward NECC is, the more uniform the zonal distribution of the ITCZ precipitation is. Considering together with the well‐known roles of the ITCZ in seeding tropical cyclones and in maintaining the NECC, we highlight the importance of interactive NECC–ITCZ pair in tropical and global circulation and climate. Key Points: The North Equatorial Countercurrent maintains the zonality of the Intertropical Convergence ZoneThe stronger the eastward NECC is, the more uniform the zonal distribution of the ITCZ precipitation isThe two‐way interaction between the NECC and the ITCZ may be important to tropical and global climate
- Subjects
INTERTROPICAL convergence zone; PACIFIC Ocean currents; OCEAN temperature; TROPICAL cyclones; DISTRIBUTION (Probability theory); TROPICAL climate
- Publication
Geophysical Research Letters, 2021, Vol 48, Issue 24, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2021GL095657