scholarly journals Linking the Pacific Meridional Mode to ENSO: Coupled Model Analysis

2009 ◽  
Vol 22 (12) ◽  
pp. 3488-3505 ◽  
Author(s):  
Li Zhang ◽  
Ping Chang ◽  
Link Ji
Keyword(s):  
Southern Oscillation ◽  
Coupled Model ◽  
Enso Event ◽  
Boreal Spring ◽  
Enso Events ◽  
Maximum Variance ◽  
Surface Circulation ◽  
The Pacific ◽  
Anomalous Surface ◽  
Thermodynamic Coupling

Abstract The occurrence of a boreal spring phenomenon referred to as the Pacific meridional model (MM) is shown to be intimately linked to the development of El Niño–Southern Oscillation (ENSO) in a long simulation of a coupled model. The MM, characterized by an anomalous north–south SST gradient and anomalous surface circulation in the northeasterly trade regime with maximum variance in boreal spring, is shown to be inherent to thermodynamic ocean–atmosphere coupling in the intertropical convergence zone (ITCZ) latitude, and the MM existence is independent of ENSO. The thermodynamic coupling enhances the persistence of the anomalous winds in the deep tropics, forcing energetic equatorially trapped oceanic waves to occur in the central western Pacific, which in turn initiate an ENSO event. The majority of ENSO events in both nature and the coupled model are preceded by MM events.

scholarly journals Modeling the Mechanisms of Linear and Nonlinear ENSO Responses to the Pacific Meridional Mode

2016 ◽  
Vol 29 (24) ◽  
pp. 8745-8761 ◽  
Author(s):  
Erin E. Thomas ◽  
Daniel J. Vimont
Keyword(s):  
Southern Oscillation ◽  
Surface Wind ◽  
Coupled Model ◽  
Enso Event ◽  
Ocean Dynamics ◽  
Large Variability ◽  
Enso Events ◽  
The Pacific ◽  
Meridional Mode ◽  
Pacific Meridional Mode

Abstract Interactions between the Pacific meridional mode (PMM) and El Niño–Southern Oscillation (ENSO) are investigated using the National Center for Atmospheric Research (NCAR) Community Earth System Model (CESM) and an intermediate coupled model (ICM). The two models are configured so that the CESM simulates the PMM but not ENSO, and the ICM simulates ENSO but not the PMM, allowing for a clean separation between the PMM evolution and the subsequent ENSO response. An ensemble of CESM simulations is run with an imposed surface heat flux associated with the North Pacific Oscillation (NPO) generating a sea surface temperature (SST) and wind response representative of the PMM. The PMM wind is then applied as a forcing to the ICM to simulate the ENSO response. The positive (negative) ensemble-mean PMM wind forcing results in a warm (cold) ENSO event although the responses are not symmetric (warm ENSO events are larger in amplitude than cold ENSO events), and large variability between ensemble members suggests that any individual ENSO event is strongly influenced by natural variability contained within the CESM simulations. Sensitivity experiments show that 1) direct forcing of Kelvin waves by PMM winds dominates the ENSO response, 2) seasonality of PMM forcing and ENSO growth rates influences the resulting ENSO amplitude, 3) ocean dynamics within the ICM dominate the ENSO asymmetry, and 4) the nonlinear relationship between PMM wind anomalies and surface wind stress may enhance the La Niña response to negative PMM variations. Implications for ENSO variability are discussed.

Influence of Pacific meridional mode on ENSO evolution and predictability: asymmetric modulation and ocean preconditioning

2020 ◽  
Author(s):  
Hanjie Fan ◽  
Bohua Huang ◽  
Song Yang
Keyword(s):  
Deep Convection ◽  
Low Frequency ◽  
Heat Content ◽  
Coupled Model ◽  
Enso Event ◽  
Ensemble Prediction ◽  
Enso Events ◽  
The Pacific ◽  
Meridional Mode ◽  
Pacific Meridional Mode

<p>This study investigates the mechanisms for the Pacific meridional mode (PMM) to influence the development of an ENSO event and its seasonal predictability. To examine the relative importance of several factors that might modulate the efficiency of the PMM influence, we conduct a series of prediction experiments to selected ENSO events with different intensity from a long simulation of the Community Earth System Model (CESM). Using the same coupled model, each of the ensemble prediction is conducted from slightly different ocean initial states but under a common prescribed PMM surface heat flux forcing. In general, the matched PMM forcing to ENSO, i.e., a positive (negative) PMM prior to an El Niño (a La Niña), plays an enhancing role while a mismatched PMM forcing plays a damping role. For the matched PMM-ENSO events, the positive PMM exerts greater influence than its negative counterpart does, with stronger enhancement of positive PMM events on an El Niño than that of negative PMM events on a La Niña. This asymmetry in ENSO influence largely originates from the intensity asymmetry between the positive and negative PMM events in the tropics, which can be explained by the nonlinearity in the growth and equatorward propagation of the PMM-related SST and surface zonal wind anomalies through both wind-evaporation-SST (WES) feedback and summer deep convection (SDC) response. Furthermore, the response of ENSO to an imposed PMM forcing is modulated by the preconditioning of the upper ocean heat content, which provides the memory for the coupled low-frequency evolution in the tropical Pacific.</p>

scholarly journals LINEARIZATION OF RELATIVE HUMIDITY OVER THE PACIFIC OCEAN ON THE EQUATORIAL LINE

2019 ◽  
Vol 16 (33) ◽  
pp. 630-640
Author(s):  
C. M. DÍEZ ◽  
C. J. SOLANO
Keyword(s):  
Pacific Ocean ◽  
Relative Humidity ◽  
Earth Science ◽  
Southern Oscillation ◽  
Correlation Coefficients ◽  
East Side ◽  
The West ◽  
Enso Events ◽  
The Pacific ◽  
The Pacific Ocean

The atmosphere system is ruled by the interaction of many meteorological parameters, causing a dependency between them, i.e., moisture and temperature, both suitable in front of any anomaly, such as storms, hurricanes, El Niño-Southern Oscillation (ENSO) events. So, understanding perturbations of the variation of moistness along the time may provide an indicator of any oceanographic phenomenon. Annual relative humidity data around the Equatorial line of the Pacific Ocean were processed and analyzed to comprehend the time evolution of each dataset, appreciate anomalies, trends, histograms, and propose a way to predict anomalous episodes such ENSO events, observing abnormality of lag correlation coefficients between every pair of buoys. Datasets were taken from the Tropical Atmosphere Ocean / Triangle Trans-Ocean Network (TAO/TRITON) project, array directed by Pacific Environmental Laboratory (PMEL) of the National Oceanic and Atmospheric Administration (NOAA), and the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). All the datasets were processed, and the code was elaborated by the author or adapted from Mathworks Inc. Even occurrences of relative humidity in the east side of the Pacific Ocean seem to oscillate harmonically, while occurrences in the west side, do not, because of the size of their amplitudes of oscillations. This fact can be seen in the histograms that show Peak shapes in the east side of the ocean, and Gaussians in the west; lag correlation functions show that no one pair of buoys synchronize fluctuations, but western buoys are affected in front of ENSO events, especially between 1997-98. Definitely, lag correlations in western buoys are determined to detect ENSO events.

On the influence of ENSO complexity on Pan-Pacific coastal wave extremes

2021 ◽  
Vol 118 (47) ◽  
pp. e2115599118
Author(s):  
Julien Boucharel ◽  
Rafael Almar ◽  
Elodie Kestenare ◽  
Fei-Fei Jin
Keyword(s):  
Southern Oscillation ◽  
Wave Activity ◽  
Spatial Behavior ◽  
Coastal Hazards ◽  
Climate Control ◽  
Enso Events ◽  
The Pacific ◽  
Coastal Impacts ◽  
Climate Mode

Wind-generated waves are dominant drivers of coastal dynamics and vulnerability, which have considerable impacts on littoral ecosystems and socioeconomic activities. It is therefore paramount to improve coastal hazards predictions through the better understanding of connections between wave activity and climate variability. In the Pacific, the dominant climate mode is El Niño Southern Oscillation (ENSO), which has known a renaissance of scientific interest leading to great theoretical advances in the past decade. Yet studies on ENSO’s coastal impacts still rely on the oversimplified picture of the canonical dipole across the Pacific. Here, we consider the full ENSO variety to delineate its essential teleconnection pathways to tropical and extratropical storminess. These robust seasonally modulated relationships allow us to develop a mathematical model of coastal wave modulation essentially driven by ENSO’s complex temporal and spatial behavior. Accounting for this nonlinear climate control on Pan-Pacific wave activity leads to a much better characterization of waves’ seasonal to interannual variability (+25% in explained variance) and intensity of extremes (+60% for strong ENSO events), therefore paving the way for significantly more accurate forecasts than formerly possible with the previous baseline understanding of ENSO’s influence on coastal hazards.

scholarly journals Coastal upwelling along the southwest coast of India – ENSO modulation

2008 ◽  
Vol 26 (6) ◽  
pp. 1331-1334 ◽  
Author(s):  
K. Muni Krishna
Keyword(s):  
Coastal Upwelling ◽  
Southern Oscillation ◽  
Monsoon Season ◽  
Trade Winds ◽  
Southwest Coast Of India ◽  
Southwest Coast ◽  
Enso Events ◽  
The Pacific ◽  
Basin Scale ◽  
Using Data

Abstract. An index of El Niño Southern Oscillation (ENSO) in the Pacific during pre monsoon season is shown to account for a significant part of the variability of coastal Sea Surface Temperature (SST) anomalies measured a few months later within the wind driven southwest coast of India coastal upwelling region 7° N–14° N. This teleconnection is thought to result from an atmospheric bridge between the Pacific and north Indian Oceans, leading to warm (cold) ENSO events being associated with relaxation (intensification) of the Indian trade winds and of the wind-induced coastal upwelling. This ENSO related modulation of the wind-driven coastal upwelling appears to contribute to the connection observed at the basin-scale between ENSO and SST in the Arabian Sea. The ability to use this teleconnection to give warning of large changes in the southwest coast of India coastal upwelling few months in advance is successfully tested using data from 1998 and 1999 ENSO events.

scholarly journals Coccolithophore response to climate and surface hydrography in Santa Barbara Basin, California, AD 1917–2004

2009 ◽  
Vol 6 (10) ◽  
pp. 2025-2039 ◽  
Author(s):  
M. Grelaud ◽  
A. Schimmelmann ◽  
L. Beaufort
Keyword(s):  
Southern Oscillation ◽  
California Current ◽  
Santa Barbara ◽  
Santa Barbara Basin ◽  
Enso Events ◽  
The Pacific ◽  
Hydrographic Conditions ◽  
Shell Carbonate ◽  
Relative Abundances ◽  
Counter Current

Abstract. The varved sedimentary AD 1917–2004 record from the depositional center of the Santa Barbara Basin (SBB, California) was analyzed with monthly to triannual resolution to yield relative abundances of six coccolithophore species representing at least 96% of the coccolithophore assemblage. Seasonal/annual relative abundances respond to climatic and surface hydrographic conditions in the SBB, whereby (i) the three species G. oceanica, H. carteri and F. profunda are characteristic of the strength of the northward flowing warm California Counter Current, (ii) the two species G. ericsonii and G. muellerae are associated with the cold equatorward flowing California Current, (iii) and E. huxleyi appears to be endemic to the SBB. Spectral analyses on relative abundances of these species show that all are influenced by the El Niño Southern Oscillation (ENSO) and/or by the Pacific Decadal Oscillation (PDO). Increased relative abundances of G. oceanica and H. carteri are associated with warm ENSO events, G. muellerae responds to warm PDO events and the abundance of G. ericsonii increases during cold PDO events. Morphometric parameters measured on E. huxleyi, G. muellerae and G. oceanica indicate increasing coccolithophore shell carbonate mass from ~1917 until 2004 concomitant with rising pCO2 and sea surface temperature in the region of the SBB.

scholarly journals Effects of Tropical Cyclones on ENSO

2019 ◽  
Vol 32 (19) ◽  
pp. 6423-6443 ◽  
Author(s):  
Tao Lian ◽  
Jun Ying ◽  
Hong-Li Ren ◽  
Chan Zhang ◽  
Ting Liu ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Heat Content ◽  
Coupled Model ◽  
Enso Event ◽  
Central Pacific ◽  
Final State ◽  
Enso Dynamics

AbstractNumerous studies have investigated the role of El Niño–Southern Oscillation (ENSO) in modulating the activity of tropical cyclones (TCs) in the western Pacific on interannual time scales, but the effects of TCs on ENSO are less discussed. Some studies have found that TCs sharply increase surface westerly anomalies over the equatorial western–central Pacific and maintain them there for a few days. Given the strong influence of equatorial surface westerly wind bursts on ENSO, as confirmed by much recent literature, the effects of TCs on ENSO may be much greater than previously expected. Using recently released observations and reanalysis datasets, it is found that the majority of near-equatorial TCs (simply TCs hereafter) are associated with strong westerly anomalies at the equator, and the number and longitude of TCs are significantly correlated with ENSO strength. When TC-related wind stresses are added into an intermediate coupled model, the simulated ENSO becomes more irregular, and both ENSO magnitude and skewness approach those of observations, as compared with simulations without TCs. Adding TCs into the model system does not break the linkage between the heat content anomaly and subsequent ENSO event in the model, which manifest the classic recharge–discharge ENSO dynamics. However, the influence of TCs on ENSO is so strong that ENSO magnitude and sometimes its final state—that is, either El Niño or La Niña—largely depend on the number and timing of TCs during the event year. Our findings suggest that TCs play a prominent role in ENSO dynamics, and their effects must be considered in ENSO forecast models.

Impact of the Quasi-Biennial Oscillation on the boreal winter tropospheric circulation in CMIP5/6 models

2020 ◽  
Author(s):  
Jian Rao ◽  
Chaim Garfinkel ◽  
Ian White ◽  
Chen Schwartz
Keyword(s):  
Pacific Ocean ◽  
Southern Oscillation ◽  
Polar Vortex ◽  
Buoyancy Frequency ◽  
Maritime Continent ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Polar Vortex ◽  
Enso Events ◽  
The Pacific ◽  
Biennial Oscillation

<p>Using 17 CMIP5/6 models with a spontaneously-generated quasi-biennial oscillation (QBO)-like phenomenon, this study explores and evaluates three dynamical pathways for impacts of the QBO on the troposphere: (i) the Holtan-Tan (HT) effect on the stratospheric polar vortex and the northern annular mode (NAM), (ii) the subtropical zonal wind downward arching over the Pacific, and (iii) changes in local convection over the Maritime Continent and Indo-Pacific Ocean. More than half of the models can reproduce at least one of the three pathways, but few models can reproduce all of the three routes. Firstly, most models are able to simulate a weakened polar vortex during easterly QBO (EQBO) winters, in agreement with the observed HT effect. However, the weakened polar vortex response during EQBO winters is underestimated or not present at all in other models, and hence the QBO → vortex → tropospheric NAM/AO chain is not simulated. For the second pathway associated with the downward arching of the QBO winds, seven models incorrectly or poorly simulate the extratropical easterly anomaly center over 20–40°N in the Pacific sector during EQBO, and hence the negative relative vorticity anomalies poleward of the easterly center is not resolved in those models, leading to an underestimated or incorrectly modelled height response over North Pacific. However the other ten do capture this effect. The third pathway is only observed in the Indo-Pacific Ocean, where the strong climatological deep convection and the warm pool are situated. Nine models can simulate the convection anomalies associated with the QBO over the Maritime Continent, which is likely caused by the near-tropopause low buoyancy frequency anomalies. No robust relationship between the QBO and El Niño–Southern Oscillation (ENSO) events can be established using the ERA-Interim reanalysis, and nine models consistently confirm little modulation of the ocean basin-wide Walker circulation and ENSO events by the QBO.</p>

scholarly journals Connectivity between Historical Great Basin Precipitation and Pacific Ocean Variability: A CMIP5 Model Evaluation

2015 ◽  
Vol 28 (15) ◽  
pp. 6096-6112 ◽  
Author(s):  
Kimberly Smith ◽  
Courtenay Strong ◽  
Shih-Yu Wang
Keyword(s):  
Pacific Ocean ◽  
Time Scales ◽  
Great Basin ◽  
Southern Oscillation ◽  
Salt Lake ◽  
Coupled Model ◽  
The North ◽  
Sst Variability ◽  
The Pacific ◽  
Cmip5 Model Evaluation

Abstract The eastern Great Basin (GB) in the western United States is strongly affected by droughts that influence water management decisions. Precipitation that falls in the GB, particularly in the Great Salt Lake (GSL) basin encompassed by the GB, provides water for millions of people living along the Wasatch Front Range. Western U.S. precipitation is known to be influenced by El Niño–Southern Oscillation (ENSO) as well as the Pacific decadal oscillation (PDO) in the North Pacific. Historical connectivity between GB precipitation and Pacific Ocean sea surface temperatures (SSTs) on interannual to multidecadal time scales is evaluated for 20 models that participated in phase 5 of the Coupled Model Intercomparison Project (CMIP5). While the majority of the models had realistic ENSO and PDO spatial patterns in the SSTs, the simulated influence of these two modes on GB precipitation tended to be too strong for ENSO and too weak for PDO. Few models captured the connectivity at a quasi-decadal period influenced by the transition phase of the Pacific quasi-decadal oscillation (QDO; a recently identified climate mode that influences GB precipitation). Some of the discrepancies appear to stem from models not capturing the observed tendency for the PDO to modulate the sign of the ENSO–GB precipitation teleconnection. Of all of the models, CCSM4 most consistently captured observed connections between Pacific SST variability and GB precipitation on the examined time scales.

scholarly journals Warm-phase ENSO events modulate the continental freshwater input and the trophic state of sediments in a large South American estuary

2014 ◽  
Vol 65 (1) ◽  
pp. 1 ◽  
Author(s):  
F. García-Rodríguez ◽  
E. Brugnoli ◽  
P. Muniz ◽  
N. Venturini ◽  
L. Burone ◽  
...  
Keyword(s):  
Trophic State ◽  
Surface Sediments ◽  
River Flow ◽  
Southern Oscillation ◽  
Enso Event ◽  
South American ◽  
Freshwater Input ◽  
Enso Events ◽  
Historical Levels ◽  
Geochemical Variables

We studied the changes in geochemical variables in the middle section of Río de la Plata estuary during the 2009–2010 El Niño–Southern Oscillation (ENSO) event. Protein, organic matter, chlorophyll-a and phaeopigment content of surface sediments were significantly correlated with the increased continental freshwater input associated with high total monthly rainfall. During the warm-phase ENSO event, river flow was 5-fold larger than average historical levels, which led to a steady decrease in salinity values and the highest levels of geochemical variables. The evidence presented herein suggests that warm-phase ENSO events increase the trophic state of the sediments because of the increased freshwater input. Thus, our findings may be useful to anticipate potential eutrophication episodes in the study area.

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