scholarly journals The South Pacific Convergence Zone as Depicted in Reanalysis and Satellite Products

2021 ◽  
Author(s):  
◽  
Harvey Thomas Luke
Keyword(s):  
Twentieth Century ◽  
Southern Oscillation ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Past Century ◽  
Enso Cycle ◽  
Convergence Zone ◽  
The South ◽  
Southwest Pacific ◽  
Extended Analysis

<p>The South Pacific Convergence Zone (SPCZ) is the largest rainfall feature in the Southern Hemisphere, and is a critical component of the climate of Southwest Pacific Island nations. The small size and isolated nature of these islands leaves them vulnerable to short and long term changes in the position of the SPCZ. Its location and strength is strongly modulated by the El Niño-Southern Oscillation (ENSO) cycle and the Inter-decadal Pacific Oscillation (IPO), leading to large inter-annual and decadal variability in rainfall across the Southwest Pacific. Much of the analysis on the SPCZ has been restricted to the modern period, more specifically the “satellite era”, starting in 1979. Here, the representation of the SPCZ in the Twentieth Century Reanalysis (20CR) product, which reconstructs the three-dimensional state of the atmosphere based only on surface observations is discussed. The performance of two versions of the 20CR (versions 2 and 2c) in the satellite era is tested via inter-comparison with other reanalysis and observational satellite products, before using 20CR version 2c (20CRv2c) to perform extended analysis back to the early twentieth century. This study demonstrates that 20CR performs well in the satellite era, and is considered suitable for extended analysis. It is established that extra data added in the SPCZ region between 20CR versions 2 and 2c has improved the representation of the SPCZ during 1908-1958. Well-established relationships between ENSO and the IPO with the SPCZ are shown to be present through the entire 1908-2011 period, although it is suggested that the physical link between the IPO and the SPCZ has changed between the first and second half of the twentieth century. Finally, evidence of a southward trend of the SPCZ over the past century is presented, potentially due to an expansion of the tropics as a result of climate change.</p>

scholarly journals The South Pacific Convergence Zone as Depicted in Reanalysis and Satellite Products

2021 ◽  
Author(s):  
◽  
Harvey Thomas Luke
Keyword(s):  
Twentieth Century ◽  
Southern Oscillation ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Past Century ◽  
Enso Cycle ◽  
Convergence Zone ◽  
The South ◽  
Southwest Pacific ◽  
Extended Analysis

<p>The South Pacific Convergence Zone (SPCZ) is the largest rainfall feature in the Southern Hemisphere, and is a critical component of the climate of Southwest Pacific Island nations. The small size and isolated nature of these islands leaves them vulnerable to short and long term changes in the position of the SPCZ. Its location and strength is strongly modulated by the El Niño-Southern Oscillation (ENSO) cycle and the Inter-decadal Pacific Oscillation (IPO), leading to large inter-annual and decadal variability in rainfall across the Southwest Pacific. Much of the analysis on the SPCZ has been restricted to the modern period, more specifically the “satellite era”, starting in 1979. Here, the representation of the SPCZ in the Twentieth Century Reanalysis (20CR) product, which reconstructs the three-dimensional state of the atmosphere based only on surface observations is discussed. The performance of two versions of the 20CR (versions 2 and 2c) in the satellite era is tested via inter-comparison with other reanalysis and observational satellite products, before using 20CR version 2c (20CRv2c) to perform extended analysis back to the early twentieth century. This study demonstrates that 20CR performs well in the satellite era, and is considered suitable for extended analysis. It is established that extra data added in the SPCZ region between 20CR versions 2 and 2c has improved the representation of the SPCZ during 1908-1958. Well-established relationships between ENSO and the IPO with the SPCZ are shown to be present through the entire 1908-2011 period, although it is suggested that the physical link between the IPO and the SPCZ has changed between the first and second half of the twentieth century. Finally, evidence of a southward trend of the SPCZ over the past century is presented, potentially due to an expansion of the tropics as a result of climate change.</p>

scholarly journals The Representation of the South Pacific Convergence Zone in the Twentieth Century Reanalysis

2019 ◽  
Vol 147 (3) ◽  
pp. 841-851 ◽  
Author(s):  
Thomas Harvey ◽  
James A. Renwick ◽  
Andrew M. Lorrey ◽  
Arona Ngari
Keyword(s):  
Twentieth Century ◽  
Southern Oscillation ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Past Century ◽  
Convergence Zone ◽  
The South ◽  
Southwest Pacific ◽  
Surface Observations ◽  
Twentieth Century Reanalysis

Abstract The South Pacific convergence zone (SPCZ) is the largest rainfall feature in the Southern Hemisphere, and is a critical component of the climate for South Pacific island nations and territories. The small size and isolated nature of these islands leaves them vulnerable to short- and long-term changes in the position of the SPCZ. Its position and strength is strongly modulated by El Niño–Southern Oscillation (ENSO), leading to large interannual variability in rainfall across the southwest Pacific including seasonal droughts and pluvials. Currently much of the analysis about SPCZ activity has been restricted to the satellite observation period starting in 1979. Here, the representation of the SPCZ in the Twentieth Century Reanalysis (20CR), which is a three-dimensional atmospheric reconstruction based only on surface observations, is discussed for the period since 1908. The performance of two versions of the 20CR (version 2 and version 2c) in the satellite era is compared with other reanalyses and climate observation products. The 20CR performs well in the satellite era. Extra surface observations spanning the SPCZ region from the longitude of the Cook Islands has improved the representation of the SPCZ during 1908–57 between 20CRv2 and 20CRv2c. The well-established relationship with ENSO is observed in both the representation of mean SPCZ position and intensity, and this relationship remains consistent through the entire 1908–2011 period. This suggests that the ENSO–SPCZ relationship has remained similar over the course of the past century, and gives further evidence that 20CRv2c performs well back to 1908 over the southwest Pacific region.

A 1300-year reconstruction of the South Pacific Convergence Zone using a Pacific-wide tree-ring network

2020 ◽  
Author(s):  
Philippa Higgins ◽  
Jonathan Palmer ◽  
Christian Turney ◽  
Martin Andersen ◽  
Edward Cook
Keyword(s):  
Tree Ring ◽  
General Circulation ◽  
Southern Oscillation ◽  
South Pacific ◽  
Ice Age ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
Pacific Island ◽  
The South ◽  
Island Communities

&lt;p&gt;The South Pacific Convergence Zone (SPCZ) is the largest driver of precipitation variability over South Pacific island communities during the austral warm season influencing the severity and duration of drought and the frequency of tropical cyclones. The SPCZ is known to exhibit variability on a range of timescales, from intra-seasonal to multidecadal variations, modulated by the Interdecadal Pacific Oscillation (IPO). Despite its climatic and societal importance, determining the causes of low frequency variability in the SPCZ has been hampered by the short instrumental data record, with most comprehensive analyses since the satellite era. Here we report the first paleoclimate reconstruction of the SPCZ, allowing climate variability in the South Pacific region to be explored back to 700 CE. Our 1300-year reconstruction of the SPCZI (South Pacific Convergence Zone Index; the difference between mean sea level pressure between Apia, Samoa and Suva, Fiji) is based on a trans-Pacific network of precisely dated tree-ring proxies. Capturing SPCZ teleconnections from both sides of the Pacific has produced a robust, unbiased reconstruction with excellent reconstruction skill over the entire period. El Ni&amp;#241;o-Southern Oscillation periodicities (&amp;#8764;3-7 years) are pervasive throughout the SPCZI reconstruction. Multidecadal periodicities wax and wane, apparently coinciding with the timing of the Medieval Climate Anomaly (c. 1000-1200 CE) and Little Ice Age (1300-1700 CE). We discuss some of the drivers of SPCZI variability including global dimming events. Our reconstruction helps improve our understanding of past hydroclimatic behaviour in the southwest Pacific and can be used to validate general circulation model projections for Pacific Island communities in the twenty-first century.&lt;/p&gt;

scholarly journals Evaluation of the South Pacific Convergence Zone in IPCC AR4 Climate Model Simulations of the Twentieth Century

2011 ◽  
Vol 24 (6) ◽  
pp. 1565-1582 ◽  
Author(s):  
Josephine R. Brown ◽  
Scott B. Power ◽  
Francois P. Delage ◽  
Robert A. Colman ◽  
Aurel F. Moise ◽  
...  
Keyword(s):  
Twentieth Century ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Interannual Variability ◽  
South Pacific ◽  
Sea Surface ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
The South ◽  
Model Simulations

Abstract Understanding how the South Pacific convergence zone (SPCZ) may change in the future requires the use of global coupled atmosphere–ocean models. It is therefore important to evaluate the ability of such models to realistically simulate the SPCZ. The simulation of the SPCZ in 24 coupled model simulations of the twentieth century is examined. The models and simulations are those used for the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC). The seasonal climatology and interannual variability of the SPCZ is evaluated using observed and model precipitation. Twenty models simulate a distinct SPCZ, while four models merge intertropical convergence zone and SPCZ precipitation. The majority of models simulate an SPCZ with an overly zonal orientation, rather than extending in a diagonal band into the southeast Pacific as observed. Two-thirds of models capture the observed meridional displacement of the SPCZ during El Niño and La Niña events. The four models that use ocean heat flux adjustments simulate a better tropical SPCZ pattern because of a better representation of the Pacific sea surface temperature pattern and absence of cold sea surface temperature biases on the equator. However, the flux-adjusted models do not show greater skill in simulating the interannual variability of the SPCZ. While a small subset of models does not adequately reproduce the climatology or variability of the SPCZ, the majority of models are able to capture the main features of SPCZ climatology and variability, and they can therefore be used with some confidence for future climate projections.

Impacts of Detoured Madden-Julian Oscillations on the South Pacific Convergence Zone

2021 ◽  
pp. 1-41
Author(s):  
Lei Zhou ◽  
Ruomei Ruan ◽  
Raghu Murtugudde
Keyword(s):  
Southern Hemisphere ◽  
Rossby Waves ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Boreal Winter ◽  
Convergence Zone ◽  
The South ◽  
Maritime Continent ◽  
Meridional Winds ◽  
Southern Pacific Ocean

AbstractMadden-Julian Oscillations (MJOs) are a major component of tropical intraseasonal variabilities. There are two paths for MJOs across the Maritime Continent; one is a detoured route into the Southern Hemisphere and the other one is around the equator across the Maritime Continent. Here, it is shown that the detoured and non-detoured MJOs have significantly different impacts on the South Pacific convergence zone (SPCZ). The detoured MJOs trigger strong cross-equatorial meridional winds from the Northern Hemisphere into the Southern Hemisphere. The associated meridional moisture and energy transports due to the background states carried by the intraseasonal meridional winds are favorable for reinforcing the SPCZ. In contrast, the influences of non-detoured MJOs on either hemisphere or the meridional transports across the equator are much weaker. The detoured MJOs can extend their impacts to the surrounding regions by shedding Rossby waves. Due to different background vorticity during detoured MJOs in boreal winter, more ray paths of Rossby waves traverse the Maritime Continent connecting the southern Pacific Ocean and the eastern Indian Ocean, but far fewer Rossby wave paths traverse Australia. Further studies on such processes are expected to contribute to a better understanding of extreme climate and natural disasters on the rim of the southern Pacific and Indian Oceans.

Origin of the South Pacific Convergence Zone

1989 ◽  
Vol 2 (10) ◽  
pp. 1185-1195 ◽  
Author(s):  
George N. Kiladis ◽  
Hans von Storch ◽  
Harryvan Loon
Keyword(s):  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
The South
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