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Comparative Analysis of Upper Ocean Heat Content Variability from an Ensemble of Operational Ocean Analyses
Yan Xue (1), Magdalena A. Balmaseda (2), Tim Boyer(6) ,Nicolas Ferry
(3) , Simon Good (4), Ichiro Ishikawa (5) , Arun Kumar(1) Michele
Table 3. Anomaly correlation between HC300 and SST in 1982-2009 averaged in various ocean basins drawn as boxes in Fig. 8. Correlations less than 0.4 are in bold.Anomaly Correlation between HC300 and SST
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HC300 Anomaly Indices for ENSO, IOD and Atlantic Nino
ENSO
IOD
Atlantic Nino
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Linear Trend of HC300 Anomaly in 1993-2009
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1995
2004
1999
HC300 Anomaly Indices for Multi-decadal Variability
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HC300 and HC300 Anomaly Average in 70oS-70oN
El ChichonMt. Pinatubo
2003
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Impacts of HC300 on SST Anomaly
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Role of HC300 for Predictability of ENSO
-Equatorial western Pacific HC300a leads NINO3.4 by 10-12 months.
- The lead/lag relationship between HC300a and NINO3.4 is consistently analyzed by all ORAs.
- NODC is too noisy near the equator.
- The peak correlation between HC300a and NINO3.4 in CFSR is lower than others.
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Role of HC300 for Predictability of Atlantic Nino
-Equatorial eastern Atlantic HC300a leads Atlantic Nino by 4-6 months.
-Equatorial western Atlantic HC300a leads Atlantic Nino by 8-12 months.
-Differences in the lead/lag correlation are quite large.
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Role of HC300 for Predictability of IOD
- Southeastern Indian Ocean HC300a leads IOD by 2 months.
- Southwestern Indian Ocean HC300a leads IOD by 8-12 months.
- Differences in the lead/lag correlation are quite large.
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Summary• Consistency in mean HC300 is generally high south of 30oS except
near the Gulf Stream and Kuroshio-Oyashio Extension (KOE), in the tropical Atlantic, and some regional seas such as Gulf of Mexico and South China Sea.
• Consistency, measured by root-mean-square differences from EN3, tends to increase with time, particularly in the tropical Pacific, the tropical Indian Ocean and extra-tropical southern oceans, which are partly due to constraints from a dense observational network from tropical mooring arrays and Argo floats.
• Consistency in the equatorial Pacific HC300 increased significantly after 1993 when the TAO mooring array was fully implemented.
• Consistency in the equatorial Indian Ocean HC300 increased significantly around 2003 when the two RAMA mooring lines were implemented at 80.5o E and 90o E. All model-based HC300 are too cold relative to EN3 in the eastern tropical Indian Ocean before 1997.
• Consistency in the equatorial Atlantic HC300 is much lower than that in the equatorial Pacific and Indian Ocean, but it improved significantly after 2006.
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Summary• HC300 anomalies (HC300a) associated with ENSO are highly
consistent among ORAs; HC300a associated with IOD are moderately consistent, and model-based analyses are superior to in situ-based analyses in the eastern pole of the IOD; HC300a associated with the Atlantic zonal mode have considerable uncertainties among ORAs, which are comparable to signals.
• Large multi-decadal variability and long-term trends exist in HC300. The consensus among ORAs suggests that the mean HC300 in 70oS-70oN has brief cooling periods during early 1980s and 1992-1993 related to the volcanic eruptions of the El Chichon and Mt. Pinatubo, and a short warming in 1985-1991, and then a continuous warming in 1994-2003, followed by a persistence or weak cooling in 2004-2009.
• Despite of many advances in ORAs in the past decade, uncertainties in HC300 are still large near western boundary currents, in the tropical Atlantic and extra-tropical southern oceans. To improve HC300 analysis in those regions, additional advances, such as improving surface fluxes, model physics, model resolution and data assimilation schemes, will be needed in conjunction with maintaining and enhancing ocean observing systems in those regions.