South Pacific Convergence Zone (SPCZ)
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Revision as of 09:11, 8 July 2019 by Integration.Manager
The South Pacific Convergence Zone (SPCZ) is a persistent band of cloudiness and storms, that originates in Southeast Asia and stretches southeast to French Polynesia and the Cook Islands.
The South Pacific Convergence Zone (SPCZ), a reverse-oriented monsoon trough, is a band of low-level convergence, cloudiness and precipitation extending from the Western Pacific Warm Pool at the maritime continent south-eastwards towards French Polynesia and as far as the Cook Islands (160W, 20S). The SPCZ is a portion of the Intertropical Convergence Zone (ITCZ) which lies in a band extending east-west near the Equator but can be more extratropical in nature, especially east of the International Date Line. 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. The SPCZ can affect the precipitation on Polynesian islands in the southwest Pacific Ocean, so it is important to understand how the SPCZ behaves with large-scale, global climate phenomenon, such as the ITCZ, El Niño–Southern Oscillation, and the Interdecadal Pacific oscillation (IPO), a portion of the Pacific decadal oscillation.
The SPCZ 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 but can change its 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 Vanuatu, Fiji, Samoa, and Tonga. Low-level convergence along this band forms cloudiness as well as showers and thunderstorms. 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. The convergence zone shifts east or west depending on the existence of El Niño, or the phase of ENSO.
It is fueled by moisture from the warm western Pacific basin, and is most active from October to April (during the Southern Hemisphere summer) due to propagated monsoon activity from India (Vincent 1994). Rainfall varies greatly by season in the Central South Pacific sub-region: approximately 75% of annual rainfall occurs from November to April, when the SPCZ is located about halfway between Western Samoa and Fiji. During the dry season, the SPCZ moves out of the area, and often becomes weak or inactive
- Inter Tropical Convergence Zone (ITCZ)
- Trade Winds
- Tropical Revolving Storm
- Weather Radar: Storm Avoidance
- Regional Climate Trends and Scenarios for the U.S. National Climate Assessment: Part 8. Climate of the Pacific Islands, NOAA Technical Report NESDIS 142-8, January 2013.