South Pacific convergence zone
The South Pacific Convergence Zone (SPCZ), a reverse-oriented
Position
The SPCZ occurs where the southeast trades from transitory
Measuring SPCZ position
The climatological position can be estimated by computing its mean position over 30 or more years.[4] There are several metrics to measure the position of the SPCZ. The location of maximum rainfall, maximum of low level convergence, maxima of the 500 hPa vertical motion, and the minimum in outgoing longwave radiation (OLR) are four indicators of the SPCZ axis.[4] Figure 1 shows qualitative agreement between all of these SPCZ indicators.
Changes in SPCZ position
The position of the SPCZ can change on seasonal, interannual, and possibly longer timescales.
Observations
Research into SPCZ movements of the 20th century are linked to changes in the IPO and ENSO.
Determining the position of the SPCZ over longer timescales in the past (pre-20th century) has been studied using coral records of the southwest Pacific.[5] Linsley et al. (2006) reconstructed sea-surface temperature and sea surface salinity in the southwest Pacific starting circa 1600CE by measuring the oxygen isotopic composition of four Porites coral records from Rarotonga and two from Fiji. Coral isotope measurements provide information on both sea surface temperature and sea surface salinity, so they can indicate times of increased or decreased temperature and/or precipitation associated with changes in the position of the SPCZ. Their coral oxygen isotope index indicated an eastward shift of the decadal mean position of the SPCZ since the mid 1800s. A shift of the SPCZ in this direction suggests there were more La Niña-like or cold-phase conditions in the Pacific, during this period, often called the Little Ice Age.[5] Additional paleoclimate studies are still needed in order to test the reliability of these coral results.
The IPO and ENSO can interact together to produce changes in the position of the SPCZ. West of about 140 W, both ENSO (measured with
Climate modelling
Besides observations of the SPCZ and movement in its position, there have been modelling studies as well.
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.[5]
See also
References
World Wide Web
- ^ E. Linacre and B. Geerts. Movement of the South Pacific Convergence Zone. Retrieved on 2006-11-26.
- ^ Glossary of Meteorology. South Pacific convergence zone. Archived 2007-09-30 at the Wayback Machine Retrieved on 2006-11-26.
- hdl:1969.1/374.
- ^ doi:10.1029/2001GL014201.)
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: CS1 maint: multiple names: authors list (link - ^ a b c Braddock K. Linsley, Alexey Kaplan, Yves Gouriou, Jim Salinger, Peter B. deMenocal, Gerard M. Wellington, and Stephen S. Howe. Tracking the extent of the South Pacific Convergence Zone since the early 1600s. Archived 2011-06-06 at the Wayback Machine Retrieved on 2006-11-26.
- ^ a b Matthew J. Widlansky, Axel Timmermann, Karl Stein, Shayne McGregor, Niklas Schneider, Matthew H. England, Matthieu Lengaigne, and Wenju Cai. Changes in South Pacific rainfall bands in a warming climate
- (in French)
Tropical textbook : from trade winds to cyclone (2 vol) Archived 2012-12-16 at
- C. K. Folland, J. A. Renwick, doi:10.1029/2001GL014201.)
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: CS1 maint: multiple names: authors list (link