scholarly journals Analysis of variability of tropical Pacific sea surface temperatures

2016 ◽  
Vol 2 (2) ◽  
pp. 155-169
Author(s):  
Georgina Davies ◽  
Noel Cressie
Keyword(s):  
Standard Deviation ◽  
Pacific Ocean ◽  
Climate Models ◽  
Robust Regression ◽  
Southern Oscillation ◽  
Tropical Pacific ◽  
Global Climate Models ◽  
Sea Surface ◽  
The Pacific ◽  
Sst Anomalies

Abstract. Sea surface temperature (SST) in the Pacific Ocean is a key component of many global climate models and the El Niño–Southern Oscillation (ENSO) phenomenon. We shall analyse SST for the period November 1981–December 2014. To study the temporal variability of the ENSO phenomenon, we have selected a subregion of the tropical Pacific Ocean, namely the Niño 3.4 region, as it is thought to be the area where SST anomalies indicate most clearly ENSO's influence on the global atmosphere. SST anomalies, obtained by subtracting the appropriate monthly averages from the data, are the focus of the majority of previous analyses of the Pacific and other oceans' SSTs. Preliminary data analysis showed that not only Niño 3.4 spatial means but also Niño 3.4 spatial variances varied with month of the year. In this article, we conduct an analysis of the raw SST data and introduce diagnostic plots (here, plots of variability vs. central tendency). These plots show strong negative dependence between the spatial standard deviation and the spatial mean. Outliers are present, so we consider robust regression to obtain intercept and slope estimates for the 12 individual months and for all-months-combined. Based on this mean–standard deviation relationship, we define a variance-stabilizing transformation. On the transformed scale, we describe the Niño 3.4 SST time series with a statistical model that is linear, heteroskedastic, and dynamical.

scholarly journals El Niño in a changing climate: a multi-model study

Ocean Science ◽  
2005 ◽  
Vol 1 (2) ◽  
pp. 81-95 ◽  
Author(s):  
G. J. van Oldenborgh ◽  
S. Y. Philip ◽  
M Collins
Keyword(s):  
Standard Deviation ◽  
Pacific Ocean ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Tropical Pacific ◽  
Enso Cycle ◽  
Tropical Pacific Ocean ◽  
Enso Variability ◽  
The Tropical Pacific

Abstract. In many parts of the world, climate projections for the next century depend on potential changes in the properties of the El Niño - Southern Oscillation (ENSO). The current staus of these projections is assessed by examining a large set of climate model experiments prepared for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Firstly, the patterns and time series of present-day ENSO-like model variability in the tropical Pacific Ocean are compared with that observed. Next, the strength of the coupled atmosphere-ocean feedback loops responsible for generating the ENSO cycle in the models are evaluated. Finally, we consider the projections of the models with, what we consider to be, the most realistic ENSO variability. Two of the models considered do not have interannual variability in the tropical Pacific Ocean. Three models show a very regular ENSO cycle due to a strong local wind feedback in the central Pacific and weak sea surface temperature (SST) damping. Six other models have a higher frequency ENSO cycle than observed due to a weak east Pacific upwelling feedback loop. One model has much stronger upwelling feedback than observed, and another one cannot be described simply by the analysis technique. The remaining six models have a reasonable balance of feedback mechanisms and in four of these the interannual mode also resembles the observed ENSO both spatially and temporally. Over the period 2051-2100 (under various scenarios) the most realistic six models show either no change in the mean state or a slight shift towards El Niño-like conditions with an amplitude at most a quarter of the present day interannual standard deviation. We see no statistically significant changes in amplitude of ENSO variability in the future, with changes in the standard deviation of a Southern Oscillation Index that are no larger than observed decadal variations. Uncertainties in the skewness of the variability are too large to make any statements about the future relative strength of El Niño and La Niña events. Based on this analysis of the multi-model ensemble, we expect very little influence of global warming on ENSO.

scholarly journals Role of Sea Surface Temperatures in Forcing Circulation Anomalies Driving U.S. Great Plains Pluvial Years

2019 ◽  
Vol 32 (20) ◽  
pp. 7081-7100 ◽  
Author(s):  
Paul X. Flanagan ◽  
Jeffrey B. Basara ◽  
Jason C. Furtado ◽  
Elinor R. Martin ◽  
Xiangming Xiao
Keyword(s):  
Great Plains ◽  
Reanalysis Data ◽  
Tropical Pacific ◽  
Specific Pattern ◽  
Sea Surface ◽  
Northern Great Plains ◽  
The Pacific ◽  
Precipitation Anomalies ◽  
Circulation Anomalies ◽  
Sst Anomalies

Abstract In the U.S. Great Plains (GP), diagnosing precipitation variability is key in developing an understanding of the present and future availability of water in the region. Building on previous work investigating U.S. GP pluvial years, this study uses ERA twentieth century (ERA-20C) reanalysis data to investigate key circulation anomalies driving GP precipitation anomalies during a subset of GP pluvial years (called in this paper Pattern pluvial years). With previous research showing links between tropical Pacific sea surface temperature (SST) anomalies and GP climate variability, this study diagnoses the key circulation anomalies through an analysis of SSTs and their influence on the atmosphere. Results show that during Pattern southern Great Plains (SGP) pluvial years, central tropical Pacific SST anomalies are coincident with key atmospheric anomalies across the Pacific basin and North America. During northern Great Plains (NGP) Pattern pluvial years, no specific pattern of oceanic anomalies emerges that forces the circulation anomaly feature inherent in specific NGP pluvial years. Utilizing the results for SGP pluvial years, a conceptual model is developed detailing the identified pathway for the occurrence of circulation patterns that are favorable for pluvial years over the SGP. Overall, results from this study show the importance of the identified SGP atmospheric anomaly signal and the potential for predictability of such events.

scholarly journals Frequency- or amplitude-dependent effects of the Atlantic meridional overturning on the tropical Pacific Ocean

Ocean Science ◽  
2009 ◽  
Vol 5 (3) ◽  
pp. 293-301 ◽  
Author(s):  
G. J. van Oldenborgh ◽  
L. A. te Raa ◽  
H. A. Dijkstra ◽  
S. Y. Philip
Keyword(s):  
Pacific Ocean ◽  
Southern Oscillation ◽  
Atlantic Multidecadal Oscillation ◽  
Meridional Overturning Circulation ◽  
Sea Surface ◽  
Tropical Pacific Ocean ◽  
The Pacific ◽  
Meridional Overturning ◽  
The Pacific Ocean ◽  
The Tropical Pacific

Abstract. Using the ECHAM5/MPI-OM model, we study the relation between the variations in the Atlantic meridional overturning circulation (AMOC) and both the Pacific sea surface temperature (SST) and the El Niño-Southern Oscillation (ENSO) amplitude. In a 17-member 20C3M/SRES-A1b ensemble for 1950–2100 the Pacific response to AMOC variations on different time scales and amplitudes is considered. The Pacific response to AMOC variations associated with the Atlantic Multidecadal Oscillation (AMO) is very small. In a 5-member hosing ensemble where the AMOC collapses due to a large freshwater anomaly, the Pacific SST response is large and in agreement with previous work. Our results show that the modelled connection between AMOC and ENSO depends very strongly on the frequency and/or the modelled amplitude of the AMOC variations. Interannual AMOC variations, decadal AMOC variations and an AMOC collapse lead to entirely different responses in the Pacific Ocean.

scholarly journals The Pacific–Indian Ocean associated mode in CMIP5 models

Ocean Science ◽  
2020 ◽  
Vol 16 (2) ◽  
pp. 469-482 ◽  
Author(s):  
Minghao Yang ◽  
Xin Li ◽  
Weilai Shi ◽  
Chao Zhang ◽  
Jianqi Zhang
Keyword(s):  
Indian Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Climate Models ◽  
Southern Oscillation ◽  
Sea Surface ◽  
Cmip5 Models ◽  
Future Climate Change ◽  
The Pacific ◽  
Basin Scale

Abstract. The Pacific–Indian Ocean associated mode (PIOAM), defined as the first dominant mode (empirical orthogonal function, EOF1) of sea surface temperature anomalies (SSTAs) in the Pacific–Indian Ocean between 20∘ S and 20∘ N, is the product of the tropical air–sea interaction at the cross-basin scale and the main mode of ocean variation in the tropics. Evaluating the capability of current climate models to simulate the PIOAM and finding the possible factors that affect the simulation results are beneficial in the pursuit of more accurate future climate change prediction. Based on the 55-year Hadley Centre Global Sea Ice and Sea Surface Temperature (HadISST) dataset and the output data from 21 Coupled Model Intercomparison Project (CMIP) phase 5 (CMIP5) models, the PIOAM in these CMIP5 models is assessed. Instead of using the time coefficient (PC1) of the PIOAM as its index, we chose to utilize the alternative PIOAM index (PIOAMI), defined with SSTA differences in the boxes, to describe the PIOAM. It is found that the explained variance of the PIOAM in almost all 21 CMIP5 models is underestimated. Although all models reproduce the spatial pattern of the positive sea surface temperature anomaly in the eastern equatorial Pacific well, only one-third of these models successfully simulate the El Niño–Southern Oscillation (ENSO) mode with the east–west inverse phase in the Pacific Ocean. In general, CCSM4, GFDL-ESM2M and CMCC-CMS have a stronger capability to capture the PIOAM than the other models. The strengths of the PIOAM in the positive phase in less than one-fifth of the models are slightly greater, and very close to the HadISST dataset, especially CCSM4. The interannual variation of the PIOAM can be measured by CCSM4, GISS-E2-R and FGOALS-s2.

Tropical-ocean-atmosphere interactions in a coupled model

1989 ◽  
Vol 329 (1604) ◽  
pp. 207-223 ◽  
Keyword(s):  
Pacific Ocean ◽  
General Circulation ◽  
Southern Oscillation ◽  
Heat Budget ◽  
Circulation Model ◽  
Ocean Model ◽  
Tropical Pacific ◽  
Sea Surface ◽  
Tropical Pacific Ocean ◽  
Tropical Ocean

A high-resolution tropical Pacific Ocean model coupled to a medium-resolution atmospheric general circulation model has been integrated for 2 years. A seasonal cycle was included. The atmospheric model when forced with climatological seasonally varying sea surface temperatures simulates the surface stress and net surface heating over the tropical Pacific Ocean to within the uncertainty in the climatological estimates in these quantities. When coupled, however, the models drift into an annually recurring anomalous state, similar in many respects to the El Nino Southern Oscillation observed in the ocean and atmosphere. The model results emphasize the role of off-equatorial anomalies in temperature, atmospheric heating and wind response. Air—sea heat exchange is found to be dominant in determining sea surface temperature changes in these off-equatorial regions. Both cloud and evaporative feedbacks are important in the anomalous surface heat budget.

scholarly journals El Niño in a changing climate: a multi-model study

2005 ◽  
Vol 2 (3) ◽  
pp. 267-298 ◽  
Author(s):  
G. J. van Oldenborgh ◽  
S. Philip ◽  
M. Collins
Keyword(s):  
Standard Deviation ◽  
Pacific Ocean ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Tropical Pacific ◽  
Enso Cycle ◽  
Tropical Pacific Ocean ◽  
Enso Variability ◽  
The Tropical Pacific

Abstract. In many parts of the world, climate projections for the next century depend on potential changes in the properties of the El Niño - Southern Oscillation (ENSO). The current staus of these projections is assessed by examining a large set of climate model experiments prepared for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Firstly, the patterns and time series of present-day ENSO-like model variability in the tropical Pacific Ocean are compared with that observed. Next, the strength of the coupled atmosphere-ocean feedback loops responsible for generating the ENSO cycle in the models are evaluated. Finally, we consider the projections of the models with, what we consider to be, the most realistic ENSO variability. Two of the models considered do not have interannual variability in the tropical Pacific Ocean. Three models show a very regular ENSO cycle due to a strong local wind feedback in the central Pacific and weak sea surface temperature (SST) damping. Six other models have a higher frequency ENSO cycle than observed due to a weak east Pacific upwelling feedback loop. One model has much stronger upwelling feedback than observed, and another one cannot be described simply by the analysis technique. The remaining six models have a reasonable balance of feedback mechanisms and in four of these the interannual mode also resembles the observed ENSO both spatially and temporally. Over the period 2051-2100 (under various scenarios) the most realistic six models show either no change in the mean state or a slight shift towards El Niño-like conditions with an amplitude at most a quarter of the present day interannual standard deviation. We see no statistically significant changes in amplitude of ENSO variability in the future, with changes in the standard deviation of a Southern Oscillation Index that are no larger than observed decadal variations. Uncertainties in the skewness of the variability are too large to make any statements about the future relative strength of El Niño and La Niña events. Based in this analysis of the multi-model ensemble, we expect very little influence of global warming on ENSO.

scholarly journals The covariability of sea surface temperature and MAM rainfall on East Africa using singular value decomposition analysis

2020 ◽  
Vol 24 (4) ◽  
pp. 261-270
Author(s):  
Makula Kisesa ◽  
Marie Umutoni ◽  
Lovina Japheth ◽  
Elias Lipiki ◽  
Laban Kebacho ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Indian Ocean ◽  
Singular Value Decomposition ◽  
Atlantic Ocean ◽  
Singular Value ◽  
Sea Surface ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Value Decomposition ◽  
Sst Anomalies

The study assesses the covariability of Sea Surface Temperature (SST) and March to May (MAM) rainfall variability on East Africa (EA) from 1981 to 2018. Singular Value Decomposition (SVD) analysis reveals the significant influence of SST anomalies on MAM rainfall, with covariability of 91%, 88.61%, and 82.9% for Indian, Atlantic, and the Pacific Ocean, respectively. The Indian Ocean explains the variability of rainfall to the large extent followed by the Atlantic Ocean and the Pacific Ocean. The rainfall patterns over the EA correspond to SST variability over the western, central, and Eastern Indian Ocean. Likewise, the variability of SST anomalies was observed over the central, south, and North of the Atlantic Ocean while the Pacific Ocean captured the El Nino Modoki (ENSO) like pattern in the SVD1 (SVD2). The heterogeneous correlation of Indian SST anomalies and rainfall over EA of the first (second) principal component (PC) shows a positive correlation over much of the domain (central region). The SST anomalies over the Pacific Ocean show higher correlation values with the rainfall over much of the study domain except over the southwestern highland and southern region of Tanzania. Over the Atlantic Ocean, the correlation result shows the patterns of positive (negative) values over the northern (southern) part for PC1, while PC2 depicts negative correlation values over much of the Ocean. SST anomalies over the Indian (Atlantic) Ocean are highly correlated with MAM rainfall when SST leads by 1(7) month(s). The Pacific Ocean shows a weak (strong) correlation across all (zero) lead seasons.

scholarly journals Frequency-dependent effects of the Atlantic meridional overturning on the tropical Pacific Ocean

2009 ◽  
Vol 6 (1) ◽  
pp. 477-490 ◽  
Author(s):  
L. A. te Raa ◽  
G. J. van Oldenborgh ◽  
H. A. Dijkstra ◽  
S. Y. Philip
Keyword(s):  
Pacific Ocean ◽  
Southern Oscillation ◽  
Atlantic Multidecadal Oscillation ◽  
Meridional Overturning Circulation ◽  
Sea Surface ◽  
Tropical Pacific Ocean ◽  
The Pacific ◽  
Meridional Overturning ◽  
The Pacific Ocean ◽  
The Tropical Pacific

Abstract. Using the ECHAM5/MPI-OM model, we study the relation between the variations in the Atlantic meridional overturning circulation (AMOC) and both the Pacific sea surface temperature (SST) and the El Niño-Southern Oscillation (ENSO) amplitude. In a 17-member 20C3M/SRES-A1b ensemble for 1950–2100 the Pacific response to AMOC variations on different time scales and amplitudes is considered. The Pacific response to AMOC variations associated with the Atlantic Multidecadal Oscillation (AMO) is very small. In a 5-member hosing ensemble where the AMOC collapses due to a large freshwater anomaly, the Pacific SST response is large and in agreement with previous work. Our results show that the modelled connection between AMOC and ENSO depends very strongly on the frequency and/or the amplitude of the AMOC variations. Interannual AMOC variations, decadal AMOC variations and an AMOC collapse lead to with entirely different responses in the Pacific Ocean.

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