Impact of Data Assimilation on ECCO2 Equatorial Undercurrent and North Equatorial Countercurrent in the Pacific Ocean

Halpern, David; Menemenlis, Dimitris; Wang, Xiaochun

doi:10.1175/jtech-d-14-00025.1

Cited by 9 publications

(4 citation statements)

References 38 publications

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“…Major improvements from OIv2 to OIv2.1 include (1) large increases in the number of in situ ships, buoys, and Argo floats used and (2) the change of satellite inputs from METOP-A and NOAA-19 to METOP-A and METOP-B to remove degraded satellite data 17 , 18 . The ECCO2 dataset has 50 vertical levels at a maximum model depth of 6150 m with a high global ocean resolution of 0.25° × 0.25° 21 , 22 . ECCO2 is an adjoint method-based state estimation constrained to the available satellite (SST and SSH) and in situ (vertical temperature and salinity profiles) data, is available from 16 Sep. 1992, and is updated with a few months’ delay.…”

Section: Methodsmentioning

confidence: 99%

Validation of satellite-based sea surface temperature products against in situ observations off the western coast of Sumatra

Moteki

2022

Sci Rep

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This study validated the sea surface temperature (SST) datasets from the Group for High-Resolution SST Multi Product Ensemble (GMPE), National Oceanic and Atmospheric Administration (NOAA) Optimal Interpolation (OI) SST version 2 and 2.1 (OIv2 and OIv2.1), and Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) in the area off the western coast of Sumatra against in situ observations. Furthermore, the root mean square differences (RMSDs) of OIv2, OIv2.1, and ECCO2 were investigated with respect to GMPE, whose small RMSD < 0.2 K against in situ observations confirmed its suitability as a reference. Although OIv2 showed a large RMSD (1–1.5 K) with a significant negative bias, OIv2.1 (RMSD < 0.4 K) improved remarkably. In the average SST distributions for December 2017, the differences among the 4 datasets were significant in the areas off the western coast of Sumatra, along the southern coast of Java, and in the Indonesian inland sea. These results were consistent with the ensemble spread distribution obtained with GMPE. The large RMSDs of OIv2 corresponded to high clouds, and it was suggested that the change in the satellites used for SST estimation contributed to the improvement in OIv2.1.

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Section: Methodsmentioning

confidence: 99%

Validation of satellite-based sea surface temperature products against in situ observations off the western coast of Sumatra

Moteki

2022

Sci Rep

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“…The Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) cube92 dataset has 50 vertical levels ranging in thickness from 10 m near the surface to approximately 450 m at a maximum model depth of 6150 m with a high-resolution global ocean 0.25°× 0.25° ( Halpern et al 2015;Menemenlis et al 2008). The ECCO2 is an adjoint method state estimate constrained to the available satellite (sea surface temperature and height) and in situ (vertical temperature and salinity profiles) data.…”

Section: Methods/experimentalmentioning

confidence: 99%

Drastic thickening of the barrier layer off the western coast of Sumatra due to the Madden-Julian oscillation passage during the Pre-Years of the Maritime Continent campaign

Moteki

Katsumata

Yoneyama

et al. 2018

Prog Earth Planet Sci

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The drastic thickening of the barrier layer in the marginal sea off the western coast of Sumatra during the passage of the Madden-Julian oscillation (MJO) observed during December 2015 is investigated. Before the MJO arrival, the halocline above a depth of 20 m was very strong, and the barrier layer thickness was 5-10 m based on R/V Mirai observations. During the MJO forcing of 13-16 December, the isothermal layer drastically deepened from 20 to 100 m. Meanwhile, the mixed layer deepening lagged behind the isothermal layer deepening by 1 day, and the barrier layer underwent dramatic thickening to 60 m within 24 h. An evaluation of the vertical salinity gradient tendency showed that the dramatic thickening of the barrier layer was due to the vertical oceanic mixing by the atmospheric MJO forcing and the vertical stretching by the oceanic downwelling coastal Kelvin wave intruding from the open ocean. In addition, an evaluation of the vertical temperature gradient tendency showed that the temperature inversion in the barrier layer formed by losing heat to the atmosphere due to the MJO forcing and downward advection of the temperature gradient due to the downwelling Kelvin wave resulting in the dramatic isothermal layer deepening. One of the important factors in the drastic barrier layer thickening was the atmospheric external forcing and the oceanic internal wave being in phase. The downwelling oceanic Kelvin wave continuously lowered the thermocline from the middle of November to the end of December, and the salinity stratification in the vicinity of the thermocline was continuously mitigated by the vertical stretching. Under such conditions, the MJO forcing caused vertical mixing of the freshwater with strong salinity stratification and temperature stratification near the surface. The combination of the two distinct processes caused the drastic thickening of the barrier layer, and the barrier layer thickness reached a maximum of 85 m 5 days after the MJO arrival.

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“…This may at first appear at odds with prevailing ENSO theory (e.g., Jin et al, ; Neelin et al, ) and many modeling studies (e.g., Borlace et al, ; Fedorov et al, ; Huang et al, ; Kim et al, ) that emphasize the dominance of the thermocline feedback in the eastern Pacific—although the relative dominance can substantially vary decadally and across different models. GODAS might have stronger bias in its velocity fields than ECCO2, as heat, momentum, and salt are conserved in ECCO2 but not in GODAS (e.g., Halpern et al, ; Huang et al, ). However,

\overset{w}{true} T_{z}^{'}

is even smaller than

u^{'} {\overset{true¯}{T}}_{x}

in ECCO2.…”

Section: Enso Extremesmentioning

confidence: 99%

The Defining Characteristics of ENSO Extremes and the Strong 2015/2016 El Niño

Santoso

McPhaden

Cai

2017

Reviews of Geophysics

403

302

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The year 2015 was special for climate scientists, particularly for the El Niño Southern Oscillation (ENSO) research community, as a major El Niño finally materialized after a long pause since the 1997/1998 extreme El Niño. It was scientifically exciting since, due to the short observational record, our knowledge of an extreme El Niño has been based only on the 1982/1983 and 1997/1998 events. The 2015/2016 El Niño was marked by many environmental disasters that are consistent with what is expected for an extreme El Niño. Considering the dramatic impacts of extreme El Niño, and the risk of a potential increase in frequency of ENSO extremes under greenhouse warming, it is timely to evaluate how the recent event fits into our understanding of ENSO extremes. Here we provide a review of ENSO, its nature and dynamics, and through analysis of various observed key variables, we outline the processes that characterize its extremes. The 2015/2016 El Niño brings a useful perspective into the state of understanding of these events and highlights areas for future research. While the 2015/2016 El Niño is characteristically distinct from the 1982/1983 and 1997/1998 events, it still can be considered as the first extreme El Niño of the 21st century. Its extremity can be attributed in part to unusually warm condition in 2014 and to long‐term background warming. In effect, this study provides a list of physically meaningful indices that are straightforward to compute for identifying and tracking extreme ENSO events in observations and climate models.

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Impact of Data Assimilation on ECCO2 Equatorial Undercurrent and North Equatorial Countercurrent in the Pacific Ocean

Cited by 9 publications

References 38 publications

Validation of satellite-based sea surface temperature products against in situ observations off the western coast of Sumatra

Validation of satellite-based sea surface temperature products against in situ observations off the western coast of Sumatra

Drastic thickening of the barrier layer off the western coast of Sumatra due to the Madden-Julian oscillation passage during the Pre-Years of the Maritime Continent campaign

The Defining Characteristics of ENSO Extremes and the Strong 2015/2016 El Niño

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