Interannual Salinity Variability Associated With the Central Pacific and Eastern Pacific El Niños in the Tropical Pacific

2020 ◽  
Vol 125 (10) ◽  
Author(s):  
Hai Zhi ◽  
Rong‐Hua Zhang ◽  
Pengfei Lin ◽  
Peng Yu ◽  
Guanghui Zhou ◽  
...  
Keyword(s):  
Tropical Pacific ◽  
Eastern Pacific ◽  
Central Pacific ◽  
Salinity Variability ◽  
The Tropical Pacific

scholarly journals Cloud–Radiation Feedback as a Leading Source of Uncertainty in the Tropical Pacific SST Warming Pattern in CMIP5 Models

2016 ◽  
Vol 29 (10) ◽  
pp. 3867-3881 ◽  
Author(s):  
Jun Ying ◽  
Ping Huang
Keyword(s):  
Heat Budget ◽  
Tropical Pacific ◽  
Eastern Pacific ◽  
Shortwave Radiation ◽  
Cmip5 Models ◽  
Central Pacific ◽  
Surface Warming ◽  
Sst Warming ◽  
Radiation Feedback ◽  
The Tropical Pacific

Abstract The role of the intermodel spread of cloud–radiation feedback in the uncertainty in the tropical Pacific SST warming (TPSW) pattern under global warming is investigated based on the historical and RCP8.5 runs from 32 models participating in CMIP5. The large intermodel discrepancies in cloud–radiation feedback contribute 24% of the intermodel uncertainty in the TPSW pattern over the central Pacific. The mechanism by which the cloud–radiation feedback influences the TPSW pattern is revealed based on an analysis of the surface heat budget. A relatively weak negative cloud–radiation feedback over the central Pacific cannot suppress the surface warming as greatly as in the multimodel ensemble and thus induces a warm SST deviation over the central Pacific, producing a low-level convergence that suppresses (enhances) the evaporative cooling and zonal cold advection in the western (eastern) Pacific. With these processes, the original positive SST deviation over the central Pacific will move westward to the western and central Pacific, with a negative SST deviation in the eastern Pacific. Compared with the observed cloud–radiation feedback from six sets of reanalysis and satellite-observed data, the negative cloud–radiation feedback in the models is underestimated in general. It implies that the TPSW pattern should be closer to an El Niño–like pattern based on the concept of observational constraint. However, the observed cloud–radiation feedback from the various datasets also demonstrates large discrepancies in magnitude. Therefore, the authors suggest that more effort should be made to improve the precision of shortwave radiation observations and the description of cloud–radiation feedback in models for a more reliable projection of the TPSW pattern in future.

scholarly journals Response of ENSO and the Mean State of the Tropical Pacific to Extratropical Cooling and Warming: A Study Using the IAP Coupled Model

2009 ◽  
Vol 22 (22) ◽  
pp. 5902-5917 ◽  
Author(s):  
Y. Yu ◽  
D-Z. Sun
Keyword(s):  
Climate Change ◽  
Climate Modeling ◽  
Coupled Model ◽  
Tropical Pacific ◽  
Equatorial Region ◽  
Upper Ocean ◽  
Central Pacific ◽  
Intergovernmental Panel ◽  
Ocean Atmosphere ◽  
The Tropical Pacific

Abstract The coupled model of the Institute of Atmospheric Physics (IAP) is used to investigate the effects of extratropical cooling and warming on the tropical Pacific climate. The IAP coupled model is a fully coupled GCM without any flux correction. The model has been used in many aspects of climate modeling, including the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) climate change and paleoclimate simulations. In this study, the IAP coupled model is subjected to cooling or heating over the extratropical Pacific. As in an earlier study, the cooling and heating is imposed over the extratropical region poleward of 10°N–10°S. Consistent with earlier findings, an elevated (reduced) level of ENSO activity in response to an increase (decrease) in the cooling over the extratropical region is found. The changes in the time-mean structure of the equatorial upper ocean are also found to be very different between the case in which ocean–atmosphere is coupled over the equatorial region and the case in which the ocean–atmosphere over the equatorial region is decoupled. For example, in the uncoupled run, the thermocline water across the entire equatorial Pacific is cooled in response to an increase in the extratropical cooling. In the corresponding coupled run, the changes in the equatorial upper-ocean temperature in the extratropical cooling resemble a La Niña situation—a deeper thermocline in the western and central Pacific accompanied by a shallower thermocline in the eastern Pacific. Conversely, with coupling, the response of the equatorial upper ocean to extratropical cooling resembles an El Niño situation. These results ascertain the role of extratropical ocean in determining the amplitude of ENSO. The results also underscore the importance of ocean–atmosphere coupling in the interaction between the tropical Pacific and the extratropical Pacific.

scholarly journals Reducing Climatology Bias in an Ocean–Atmosphere CGCM with Improved Coupling Physics

2005 ◽  
Vol 18 (13) ◽  
pp. 2344-2360 ◽  
Author(s):  
Jing-Jia Luo ◽  
Sebastien Masson ◽  
Erich Roeckner ◽  
Gurvan Madec ◽  
Toshio Yamagata
Keyword(s):  
Wind Stress ◽  
Surface Current ◽  
Ocean Surface ◽  
Tropical Pacific ◽  
Equatorial Pacific ◽  
Eastern Pacific ◽  
Cold Tongue ◽  
Easterly Wind ◽  
Ocean Atmosphere ◽  
The Tropical Pacific

Abstract The cold tongue in the tropical Pacific extends too far west in most current ocean–atmosphere coupled GCMs (CGCMs). This bias also exists in the relatively high-resolution SINTEX-F CGCM despite its remarkable performance of simulating ENSO variations. In terms of the importance of air–sea interactions to the climatology formation in the tropical Pacific, several sensitivity experiments with improved coupling physics have been performed in order to reduce the cold-tongue bias in CGCMs. By allowing for momentum transfer of the ocean surface current to the atmosphere [full coupled simulation (FCPL)] or merely reducing the wind stress by taking the surface current into account in the bulk formula [semicoupled simulation (semi-CPL)], the warm-pool/cold-tongue structure in the equatorial Pacific is simulated better than that of the control simulation (CTL) in which the movement of the ocean surface is ignored for wind stress calculation. The reduced surface zonal current and vertical entrainment owing to the reduced easterly wind stress tend to produce a warmer sea surface temperature (SST) in the western equatorial Pacific. Consequently, the dry bias there is much reduced. The warming tendency of the SST in the eastern Pacific, however, is largely suppressed by isopycnal diffusion and meridional advection of colder SST from south of the equator due to enhanced coastal upwelling near Peru. The ENSO signal in the western Pacific and its global teleconnection in the North Pacific are simulated more realistically. The approach as adopted in the FCPL run is able to generate a correct zonal SST slope and efficiently reduce the cold-tongue bias in the equatorial Pacific. The surface easterly wind itself in the FCPL run is weakened, reducing the easterly wind stress further. This is related with a weakened zonal Walker cell in the atmospheric boundary layer over the eastern Pacific and a new global angular momentum balance of the atmosphere associated with reduced westerly wind stress over the southern oceans.

scholarly journals Strengthening of the Pacific Equatorial Undercurrent in the SODA Reanalysis: Mechanisms, Ocean Dynamics, and Implications

2014 ◽  
Vol 27 (6) ◽  
pp. 2405-2416 ◽  
Author(s):  
Elizabeth J. Drenkard ◽  
Kristopher B. Karnauskas
Keyword(s):  
Heat Budget ◽  
Tropical Pacific ◽  
Global Climate Models ◽  
Ocean Dynamics ◽  
Eastern Pacific ◽  
Boreal Summer ◽  
Trade Winds ◽  
Equatorial Undercurrent ◽  
The Pacific ◽  
The Tropical Pacific

Abstract Several recent studies utilizing global climate models predict that the Pacific Equatorial Undercurrent (EUC) will strengthen over the twenty-first century. Here, historical changes in the tropical Pacific are investigated using the Simple Ocean Data Assimilation (SODA) reanalysis toward understanding the dynamics and mechanisms that may dictate such a change. Although SODA does not assimilate velocity observations, the seasonal-to-interannual variability of the EUC estimated by SODA corresponds well with moored observations over a ~20-yr common period. Long-term trends in SODA indicate that the EUC core velocity has increased by 16% century−1 and as much as 47% century−1 at fixed locations since the mid-1800s. Diagnosis of the zonal momentum budget in the equatorial Pacific reveals two distinct seasonal mechanisms that explain the EUC strengthening. The first is characterized by strengthening of the western Pacific trade winds and hence oceanic zonal pressure gradient during boreal spring. The second entails weakening of eastern Pacific trade winds during boreal summer, which weakens the surface current and reduces EUC deceleration through vertical friction. EUC strengthening has important ecological implications as upwelling affects the thermal and biogeochemical environment. Furthermore, given the potential large-scale influence of EUC strength and depth on the heat budget in the eastern Pacific, the seasonal strengthening of the EUC may help reconcile paradoxical observations of Walker circulation slowdown and zonal SST gradient strengthening. Such a process would represent a new dynamical “thermostat” on CO2-forced warming of the tropical Pacific Ocean, emphasizing the importance of ocean dynamics and seasonality in understanding climate change projections.

scholarly journals Upper-Ocean Salinity Variability in the Tropical Pacific: Case Study for Quasi-Decadal Shift during the 2000s Using TRITON Buoys and Argo Floats

2013 ◽  
Vol 26 (20) ◽  
pp. 8126-8138 ◽  
Author(s):  
Takuya Hasegawa ◽  
Kentaro Ando ◽  
Iwao Ueki ◽  
Keisuke Mizuno ◽  
Shigeki Hosoda
Keyword(s):  
Tropical Pacific ◽  
Equatorial Pacific ◽  
Sea Surface ◽  
Upper Ocean ◽  
Salinity Variability ◽  
Ocean Salinity ◽  
Central Equatorial Pacific ◽  
Western Equatorial Pacific ◽  
Sea Surface Temperature Anomalies ◽  
The Tropical Pacific

Abstract Upper-ocean salinity variation in the tropical Pacific is investigated during the 2000s, when Triangle Trans-Ocean Buoy Network (TRITON) buoys and Argo floats were deployed and more salinity data were observed than in previous periods. This study focuses on upper-ocean salinity variability during the warming period of El Niño–Southern Oscillation (ENSO)-like quasi-decadal (QD)-scale sea surface temperature anomalies over the central equatorial Pacific (January 2002–December 2005; hereafter “warm QD phase”). It is shown that strong negative salinity anomalies occur in the western tropical Pacific and the off-equatorial Pacific in the upper ocean at depths less than 80 m, showing a horseshoe-like pattern centered at the western tropical Pacific during the warm QD phase. TRITON mooring buoy data in the western equatorial Pacific show that low-salinity and high-temperature water could be transported eastward from the western equatorial Pacific to the central equatorial Pacific during the warm QD phase. Similar patterns, but with the opposite sign of salinity anomalies, appear in the cold QD phase during January 2007–December 2009 with negative sea surface temperature anomalies over the central equatorial Pacific. It is suggested that effects from zonal salinity advection and precipitation could contribute to the generation of the salinity variations in the western equatorial Pacific for QD phases during the 2000s. On the other hand, the contribution of meridional salinity advection is much less than that of zonal salinity advection. In addition, El Niño Modoki and La Niña events could affect salinity changes for warm and cold QD phases via interannual-scale zonal salinity advection variations in the western equatorial Pacific during the 2000s.

scholarly journals Atmospheric Energetics over the Tropical Pacific during the ENSO Cycle

2017 ◽  
Vol 30 (10) ◽  
pp. 3635-3654 ◽  
Author(s):  
Di Dong ◽  
Jianping Li ◽  
Lidou Huyan ◽  
Jiaqing Xue
Keyword(s):  
El Nino ◽  
Tropical Pacific ◽  
La Niña ◽  
Western Pacific ◽  
Eastern Pacific ◽  
Enso Cycle ◽  
Upper Troposphere ◽  
La Nina ◽  
Central Eastern ◽  
The Tropical Pacific

Abstract The atmospheric perturbation potential energy (PPE) over the tropical Pacific is calculated and analyzed in a composite ENSO cycle. The PPE over the tropical Pacific troposphere increases during El Niño and decreases during La Niña, displaying two centers symmetrical about the equator and delaying the central–eastern Pacific SST anomaly by two months. Generated from atmospheric diabatic heating, the smaller part of PPE in the lower troposphere varies synchronously with the central–eastern Pacific SST through sensible heating, while the larger part of PPE lies in the mid- and upper troposphere and lags the central–eastern Pacific SST about one season because of latent heat release. As the tropical Pacific PPE peaks during the boreal late winter in an El Niño event, two anticyclones form in the upper troposphere as a result of the Gill model response. More PPE is converted to atmospheric kinetic energy (KE) above the central–western Pacific, but less over the eastern Pacific, leading to intensified Hadley circulations over the central–western Pacific and weakened Hadley circulations over the eastern Pacific. The strengthened Hadley circulations cause surface easterly wind bursts through KE convergence in the western equatorial Pacific, which may trigger a La Niña event. The reverse situation occurs during La Niña. Thus, the response of the Hadley circulations in the central–western Pacific provides a negative feedback during the ENSO cycle.

scholarly journals Sea surface chlorophyll signature in the tropical Pacific during eastern and central Pacific ENSO events

2012 ◽  
Vol 117 (C4) ◽  
pp. n/a-n/a ◽  
Author(s):  
Marie-Hélène Radenac ◽  
Fabien Léger ◽  
Awnesh Singh ◽  
Thierry Delcroix
Keyword(s):  
Tropical Pacific ◽  
Sea Surface ◽  
Central Pacific ◽  
Enso Events ◽  
Central Pacific Enso ◽  
The Tropical Pacific

scholarly journals Detection of Rainfall Events Using Underwater Passive Aquatic Sensors and Air–Sea Temperature Changes in the Tropical Pacific Ocean

2007 ◽  
Vol 135 (10) ◽  
pp. 3599-3612 ◽  
Author(s):  
Barry B. Ma ◽  
Jeffrey A. Nystuen
Keyword(s):  
Pacific Ocean ◽  
Ambient Noise ◽  
Tropical Pacific ◽  
Eastern Pacific ◽  
Rain Event ◽  
Tropical Pacific Ocean ◽  
Sea Temperature ◽  
Rainfall Events ◽  
Acoustic Discrimination ◽  
The Tropical Pacific

Abstract Several years of long-term high temporal resolution ocean ambient noise data from the tropical Pacific Ocean are analyzed to detect oceanic rainfall. Ocean ambient noise generated by rainfall and wind are identified through an acoustic discrimination process. Once the spectra are classified, wind speed and rainfall rates are quantified using the empirical algorithms. Rainfall-rate time series have temporal resolutions of 1 min. These data provide a unique opportunity to study the rainfall events and patterns in two different climate regions, the intertropical convergence zone (ITCZ) of the tropical eastern Pacific (10° and 12°N, 95°W) and the equatorial western Pacific (0°, 165°E). At both locations the rain events have a mean rainfall of 15 mm h−1, but the events are longer in the eastern Pacific. After the rain event is defined, the probability that a rain event can be detected using the change in air–sea temperature often associated with the rainfall is investigated. The result shows that the rain event accompanied by the decrease of air temperature is a general feature, but that using the temperature difference to detect the rainfall has a very high false alarm rate, which makes it unsuitable for rainfall detection.

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