The role of air-sea coupling on the simulation of intraseasonal rainfall variability over the South Pacific in ECHAM5-SIT

2021 ◽  
Author(s):  
Sunil Kumar Pariyar ◽  
Noel Keenlyside ◽  
Wan-Ling Tseng
Keyword(s):  
General Circulation ◽  
Rainfall Variability ◽  
Intraseasonal Variability ◽  
Phase Relationship ◽  
Coupled Model ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
The South ◽  
The Impact

<p><span>We investigate the impact of air-sea coupling on the simulation of the intraseasonal variability of rainfall over the South Pacific using the ECHAM5 atmospheric general circulation model coupled with Snow-Ice-Thermocline (SIT) ocean model. We compare the fully coupled simulation with two uncoupled simulations forced with sea surface temperature (SST) climatology and daily SST from the coupled model. The intraseasonal rainfall variability over the South Pacific Convergence Zone (SPCZ) is reduced by 17% in the uncoupled model forced with SST climatology and increased by 8% in the uncoupled simulation forced with daily SST. The coupled model best simulates the key characteristics of the two intraseasonal rainfall modes of variability in the South Pacific, as identified by an Empirical Orthogonal Function (EOF) analysis. The spatial structure of the two EOF modes in all three simulations is very similar, suggesting these modes are independent of air-sea coupling and primarily generated by the dynamics of the atmosphere. The southeastward propagation of rainfall anomalies associated with two leading rainfall modes in the South Pacific depends upon the eastward propagating </span><span>Madden-Julian Oscillation (</span><span>MJO</span><span>)</span><span> signals over the Indian Ocean and western Pacific. Air-sea interaction seems crucial for such propagation as both eastward and southeastward propagations substantially reduced in the uncoupled model forced with SST climatology. Prescribing daily SST from the coupled model improves the simulation of both eastward and southeastward propagations in the uncoupled model forced with daily SST, showing the role of SST variability on the propagation of the intraseasonal variability, but the periodicity differs from the coupled model. The change in the periodicity is attributed to a weaker SST-rainfall relationship that shifts from SST leading rainfall to a nearly in-phase relationship in the uncoupled model forced with daily SST.</span></p>

scholarly journals The Role of Air-Sea Coupling on November-April Intraseasonal Rainfall Variability Over the South Pacific

2021 ◽  
Author(s):  
Sunil Kumar Pariyar ◽  
Noel Keenlyside ◽  
Wan-Ling Tseng ◽  
Huang Hsiung Hsu ◽  
Ben-jei Tsuang
Keyword(s):  
General Circulation ◽  
Rainfall Variability ◽  
Phase Relationship ◽  
Coupled Model ◽  
Circulation Model ◽  
South Pacific ◽  
Ocean Model ◽  
The South ◽  
The Impact

Abstract We investigate the impact of resolving air-sea interaction on the simulation of the intraseasonal rainfall variability over the South Pacific using the ECHAM5 atmospheric general circulation model coupled with the Snow-Ice-Thermocline (SIT) ocean model. We compare the fully coupled simulation with two uncoupled ECHAM5 simulations, one forced with sea surface temperature (SST) climatology and one forced with daily SST from the coupled model. The intraseasonal rainfall variability over the South Pacific is reduced by 17% in the uncoupled model forced with SST climatology and increased by 8% in the uncoupled simulation forced with daily SST, suggesting the role of air-sea coupling and SST variability. The coupled model best simulates the key characteristics of two intraseasonal rainfall modes over the South Pacific with reasonable propagation and correct periodicity. The spatial structure of the two rainfall modes in all three simulations is very similar, suggesting these modes are primarily generated by the dynamics of the atmosphere. The southeastward propagation of rainfall anomalies associated with two leading rainfall modes in the South Pacific depends upon the eastward propagating MJO signals over the Indian Ocean and western Pacific. Air-sea interaction seems crucial for such propagation as both eastward and southeastward propagations are substantially reduced in the uncoupled model forced with SST climatology. The simulation of both eastward and southeastward propagations improved considerably in the uncoupled model forced with daily SST; however, the periodicity differs from the coupled model. Such discrepancy in the periodicity is attributed to the changes in the SST-rainfall relationship with weaker correlations and the nearly in-phase relationship.

Decadal Sea Level Variability in the South Pacific in a Global Eddy-Resolving Ocean Model Hindcast

2008 ◽  
Vol 38 (8) ◽  
pp. 1731-1747 ◽  
Author(s):  
Yoshi N. Sasaki ◽  
Shoshiro Minobe ◽  
Niklas Schneider ◽  
Takashi Kagimoto ◽  
Masami Nonaka ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
General Circulation ◽  
Decadal Variability ◽  
Southern Oscillation ◽  
Circulation Model ◽  
South Pacific ◽  
The South ◽  
Sea Level Variability ◽  
The Impact

Abstract Sea level variability and related oceanic changes in the South Pacific from 1970 to 2003 are investigated using a hindcast simulation of an eddy-resolving ocean general circulation model (OGCM) for the Earth Simulator (OFES), along with sea level data from tide gauges since 1970 and a satellite altimeter since 1992. The first empirical orthogonal function mode of sea level anomalies (SLAs) of OFES exhibits broad positive SLAs over the central and western South Pacific. The corresponding principal component indicates roughly stable high, low, and high SLAs, separated by a rapid sea level fall in the late 1970s and sea level rise in the late 1990s, consistent with tide gauge and satellite observations. These decadal changes are accompanied by circulation changes of the subtropical gyre at 1000-m depth, and changes of upper-ocean zonal current and eddy activity around the Tasman Front. In general agreement with previous related studies, it is found that sea level variations in the Tasman Sea can be explained by propagation of long baroclinic Rossby waves forced by wind stress curl anomalies, if the impact of New Zealand is taken into account. The corresponding atmospheric variations are associated with decadal variability of El Niño–Southern Oscillation (ENSO). Thus, decadal sea level variability in the western and central South Pacific in the past three and half decades and decadal ENSO variability are likely to be connected. The sea level rise in the 1990s, which attracted much attention in relation to the global warming, is likely associated with the decadal cooling in the tropical Pacific.

Role of the South Pacific Convergence Zone in West Antarctic Decadal Climate Variability

2019 ◽  
Vol 46 (12) ◽  
pp. 6900-6909 ◽  
Author(s):  
Kyle R. Clem ◽  
Benjamin R. Lintner ◽  
Anthony J. Broccoli ◽  
James R. Miller
Keyword(s):  
Climate Variability ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Convergence Zone ◽  
Decadal Climate Variability ◽  
The South ◽  
West Antarctic ◽  
Decadal Climate

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

<p>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 Niño-Southern Oscillation periodicities (∼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.</p>

scholarly journals Application of Clustering Algorithms to TRMM Precipitation over the Tropical and South Pacific Ocean

2020 ◽  
Vol 33 (13) ◽  
pp. 5767-5785 ◽  
Author(s):  
Maxwell Pike ◽  
Benjamin R. Lintner
Keyword(s):  
Southern Oscillation ◽  
Rainfall Variability ◽  
Deep Convection ◽  
South Pacific ◽  
Empirical Orthogonal Functions ◽  
South Pacific Convergence Zone ◽  
Specific Humidity ◽  
The South ◽  
Cluster Assignment ◽  
Trmm Precipitation

AbstractUnderstanding multiscale rainfall variability in the South Pacific convergence zone (SPCZ), a southeastward-oriented band of precipitating deep convection in the South Pacific, is critical for both the human and natural systems dependent on its rainfall, and for interpreting similar off-equatorial diagonal convection zones around the globe. A k-means clustering method is applied to daily austral summer (December–February) Tropical Rainfall Measuring Mission (TRMM) satellite rainfall to extract representative spatial patterns of rainfall over the SPCZ region for the period 1998–2013. For a k = 4 clustering, pairs of clusters differ predominantly via spatial translation of the SPCZ diagonal, reflecting either warm or cool phases of El Niño–Southern Oscillation (ENSO). Within each of these ENSO phase pairs, one cluster exhibits intense precipitation along the SPCZ while the other features weakened rainfall. Cluster temporal behavior is analyzed to investigate higher-frequency forcings (e.g., the Madden–Julian oscillation and synoptic-scale disturbances) that trigger deep convection where SSTs are sufficiently warm. Pressure-level winds and specific humidity from the Climate Forecast System Reanalysis are composited with respect to daily cluster assignment to investigate differences between active and quiescent SPCZ conditions to reveal the conditions supporting enhanced or suppressed SPCZ precipitation, such as low-level poleward moisture transport from the equator. Empirical orthogonal functions (EOFs) of TRMM precipitation are computed to relate the “modal view” of SPCZ variability associated with the EOFs to the “state view” associated with the clusters. Finally, the cluster number is increased to illustrate the change in TRMM rainfall patterns as additional degrees of freedom are permitted.

scholarly journals Scope for predicting seasonal variation of the SPCZ with ACCESS-S1

2021 ◽  
Author(s):  
Thomas A. Beischer ◽  
Paul Gregory ◽  
Kavina Dayal ◽  
Josephine R. Brown ◽  
Andrew N. Charles ◽  
...  
Keyword(s):  
Pacific Islands ◽  
Southern Oscillation ◽  
Rainfall Variability ◽  
South Pacific ◽  
Seasonal Rainfall ◽  
South Pacific Convergence Zone ◽  
The South ◽  
Local Conditions ◽  
Local Climate ◽  
Seasonal Rainfall Forecasts

AbstractRegional seasonal forecasting requires accurate simulation of the variability of local climate drivers. The South Pacific Convergence Zone (SPCZ) is a large region of low-level convergence, clouds and precipitation in the South Pacific, whose effects extend as far as northeast Australia (NEA). The location of the SPCZ is modulated by the El Niño-Southern Oscillation (ENSO) which causes rainfall variability in the region. Correctly simulating the ENSO-SPCZ teleconnection and its interplay with local conditions is essential for improving seasonal rainfall forecasts. Here we analyse the ability of the ACCESS-S1 seasonal forecast system to predict the SPCZ’s relationship with ENSO including its latitudinal shifts, zonal slope and rainfall magnitude between 1990 and 2012 for the December–January–February (DJF) season. We found improvements in ACCESS-S1’s SPCZ prediction capability compared to its predecessor (POAMA), although prediction of the slope is still limited. The inability of ACCESS-S1 to replicate seasons with a strong anti-zonal SPCZ slope is attributed to its atmospheric model. This has implications for accurate seasonal rainfall forecasts for NEA and South Pacific Islands. Future challenges in seasonal prediction facing regional communities and developers of coupled ocean–atmosphere forecast models are discussed.

Receiving Leniency After Hurting a Female Norm-Violator: The Mediating Role of Victim and Harm-Doer Empathy

2019 ◽  
Vol 26 (10) ◽  
pp. 1164-1187
Author(s):  
James D. Johnson ◽  
Nishael Raj ◽  
Shonell Smith-Enoe ◽  
Len Lecci
Keyword(s):  
Domestic Violence ◽  
South Pacific ◽  
Victim Blame ◽  
Moral Outrage ◽  
The South ◽  
Mediating Role ◽  
Blame Attributions ◽  
The Impact

Data from 140 participants from the South Pacific, where domestic violence rates are high, demonstrated less punitive responding toward the male harm-doer of a female sexual norm-violator (SNV) relative to a control victim. The impact of victim type on punitive responding was mediated by empathy toward the victim and harm-doer. In Study 2, data from 240 individuals from the South Pacific demonstrated less punitive responding toward the harm-doer of an SNV victim relative to a control and a career-focused mother victim. The victim type-punitive responding relationship was also mediated by victim blame attributions and victim moral outrage.

scholarly journals The Role of Tropical–Extratropical Interaction and Synoptic Variability in Maintaining the South Pacific Convergence Zone in CMIP5 Models

2015 ◽  
Vol 28 (8) ◽  
pp. 3353-3374 ◽  
Author(s):  
Matthew J. Niznik ◽  
Benjamin R. Lintner ◽  
Adrian J. Matthews ◽  
Matthew J. Widlansky
Keyword(s):  
Climate Models ◽  
Coupled Model ◽  
South Pacific ◽  
South Pacific Convergence Zone ◽  
Cmip5 Models ◽  
Convective Heating ◽  
Convergence Zone ◽  
The South ◽  
Synoptic Variability ◽  
Background State

Abstract The South Pacific convergence zone (SPCZ) is simulated as too zonal a feature in the current generation of climate models, including those in phase 5 of the Coupled Model Intercomparison Project (CMIP5). This zonal bias induces errors in tropical convective heating, with subsequent effects on global circulation. The SPCZ structure, particularly in the subtropics, is governed by the tropical–extratropical interaction between transient synoptic systems and the mean background state. In this study, analysis of synoptic variability in the simulated subtropical SPCZ reveals that the basic mechanism of tropical–extratropical interaction is generally well simulated, with storms approaching the SPCZ along comparable trajectories to observations. However, there is a broad spread in mean precipitation and its variability across the CMIP5 ensemble. Intermodel spread appears to relate to a biased background state in which the synoptic waves propagate. In particular, the region of mean negative zonal stretching deformation or “storm graveyard” in the upper troposphere is displaced in CMIP5 models to the northeast of its position in reanalysis data, albeit with pronounced (≈25°) intermodel longitudinal spread. Precipitation along the eastern edge of the SPCZ shifts in accordance with a storm graveyard shift, and in general models with stronger storm graveyards show higher precipitation variability. Building on prior SPCZ research, it is suggested that SPCZs simulated by CMIP5 models are not simply too zonal; rather, in models the subtropical SPCZ manifests a diagonal tilt similar to observations while SST biases force an overly zonal tropical SPCZ, resulting in a more discontinuous SPCZ than observed.

Tourism Development in the South Pacific: The Cases of Nauru and Tuvalu

2019 ◽  
Vol 39 (1) ◽  
Author(s):  
Nick Towner ◽  
Semisi Taumoepeau
Keyword(s):  
Swot Analysis ◽  
Tourism Development ◽  
Geographic Location ◽  
South Pacific ◽  
The South ◽  
South Pacific Ocean ◽  
Economic Survival ◽  
Processing Centre ◽  
Remote Island ◽  
The Impact

Abstract Tuvalu and Nauru are isolated developing island nations located in the South Pacific Ocean. In contrast to the established larger Pacific destinations such as Fiji and Tahiti, the tourism industries on both Tuvalu and Nauru are in their infancy. Tourism development in these remote island nations faces a myriad of challenges which include a lack of infrastructure, environmental susceptibility, economic vulnerability, difficulties with access and considerable distances from major tourist markets. This paper reviews tourism on Tuvalu and Nauru and evaluates their current situation regarding potential tourism development through workshops with relevant stakeholders, surveys and subsequent SWOT analysis. The results of the paper outlined a large number of challenges faced by Tuvalu and Nauru due to their geographic location but also highlighted that both Islands possess fascinating and unique features that have the potential to attract niche tourism markets. A key finding of this paper is that the tourism stimulus or potential attraction can also be the chief threat to the islands’ economic survival hence the two edges of the sword. Further research is required to assess the effect of the withdrawal of the Refugee Processing Centre on Nauru’s economy and to evaluate the impact of climate change on Tuvalu’s society and potential adaption strategies.

Sign in / Sign up

Export Citation Format

Share Document