South Pacific convergence zone

The South Pacific Convergence Zone (SPCZ), a reverse-oriented monsoon trough, is a band of low-level convergence, cloudiness and precipitation extending from the west Pacific warm pool south-eastwards towards French Polynesia. It is a portion of the Intertropical Convergence Zone (ITCZ) which lies just south of the Equator, but can be more extratropical in nature, especially east of the Dateline. It is considered the largest and most important piece of the ITCZ, and has the least dependence upon heating from a nearby landmass during the summer than any other portion of the monsoon trough. [E. Linacre and B. Geerts. [http://www-das.uwyo.edu/~geerts/cwx/notes/chap12/spcz.html Movement of the South Pacific Convergence Zone.] Retrieved on 2006-11-26.]

Position

This zone occurs where the southeast trades from transitory anticyclones to the south meet with the semipermanent easterly flow from the eastern South Pacific anticyclone. The SPCZ exists in summer and winter, with approximately the same orientation and location. It is often distinct from the ITCZ over Australia, but at times they become one continuous zone of convergence. The location of the SPCZ is affected by ENSO and Interdecadal Pacific Oscillation conditions. It generally stretches from the Solomon Islands through Fiji, Samoa, and Tonga. Low level convergence along this band forms cloudiness as well as showers and thunderstorms. [Glossary of Meteorology. [http://amsglossary.allenpress.com/glossary/search?id=south-pacific-convergence-zone1 South Pacific convergence zone.] Retrieved on 2006-11-26.] Thunderstorm activity, or convection, within the band is dependent upon the season, as the more equatorward portion is most active in the Southern Hemisphere summer, and the more poleward portion is most active during transition seasons of fall and spring. [Stephen B. Cocks. [https://txspace.tamu.edu/bitstream/1969.1/374/1/etd-tamu-2003C-ATMO-Cocks-1.pdf An Observational Study of the South Pacific Convergence Zone Using Satellite and Model Re-Analysis Data.] Retrieved on 2006-11-26.] The convergence zone shifts east or west depending on the existence of El Niño, or the phase of ENSO.

Related Oceanography

At its southeast edge, the circulation around the feature forces a salinity gradient in the ocean, with fresher and warmer waters of the western Pacific lying to its west. Cooler and saltier waters lie to its east. [Braddock K. Linsley, Alexey Kaplan, Yves Gouriou, Jim Salinger, Peter B. deMenocal, Gerard M. Wellington, and Stephen S. Howe. [http://www.agu.org/pubs/crossref/2006/2005GC001115.shtml Tracking the extent of the South Pacific Convergence Zone since the early 1600s.] Retrieved on 2006-11-26.]

Progression

The South Pacific Convergence Zone moves northeast during El Niño and southwest during La Niña events. The same movement takes place during positive IPO and negative IPO phases respectively. West of about 140 W, both the SOI and IPO strongly influence the SPCZ latitude, but farther east only the SOI is a significant factor. Only near 170 W is there any indication of an interaction between the two factors. (Folland et al, 2002)

ee also

*ENSO
*Monsoon trough
*Tropical cyclogenesis
*Tropical cyclone

References

World Wide Web

Print Media

* [http://www.niwa.cri.nz/ncc/icu/2002-10/article]