Impact of TAO observations on Impact of TAO observations on Operational Analysis for Tropical Pacific

Yan Xue

Climate Prediction Center

NCEP

Ocean Climate Observation Annual System Review, October 27-29, 2010, Silver Spring, MD

A Comparative Analysis of Upper Ocean Heat Content Variability from an Ensemble of Operational Ocean Analyses

Yan Xue , M.A. Balmaseda, N. Ferry , S. Good , I. Ishikawa , T. Boyer, M. Rienecker , T. Rosati, Y. Yin, A. Kumar

Workshop on Evaluation of Reanalyses – Developing an Integrated Earth System Analysis (IESA) Capability, Nov 1-3, 2010, Baltimore, MD

• Operational ocean analysis In situ data-based analyses (2)

EN3, NODC Model-based operational analyses (8)

NCEP(GODAS, CFSR), ECMWF, MERCATOR, JMA, BOM, GFDL, GMAO

• Comparison of mean and interannual variability Common period: 1985-2009 Argo period: 2003-2009 Altimetry period: 1993-2002 Pre-altimetry period: 1985-1992 Temporal anomaly correlation Spatial root-mean-square difference (RMSD)

• Climate signals El Nino-Southern Oscillation Indian Ocean Dipole and southern Indian ocean variability Tropical Atlantic Variability North Pacific Decadal Variability North Atlantic Decadal Variability Linear trend

- Differences decrease after 1993 when the TAO array comes in;- However, differences are relatively large during the 1997/98 El Nino. - Differences are larger in the E. Pacific than those in the W. Pacific during the Argo period (2003-2009).

Argo comes in

TAO array comes in

“SUPER” is an average of 7 model-based analyses, including GODAS, ECMWF, JMA, CFSR, GFDL, MERCATOR and BOM

TAO Observing System Simulation Experiments

Climate Prediction Center/NCEP/NOAA

Model: GFDL MOM4, 0.5°x 0.5° (0.25° near Eq), 40 LevelsForcings: NCEP/DOE reanalysisMethod: 3-D VARData: Temperature profiles from TRITON/RAMA/PIRATA

moorings, XBT, Argo and synthetic salinity

ATAOno: All TAO moorings were excluded, but other in situ observations are assimilated;

ETAOno: Eastern (110oW and 95oW) TAO mooring lines, which have undergone some damages in 2009, were excluded, but other in situ observations are assimilated;

TAO: All TAO moorings were included, as well as other in situ observations.

Argo comes in

Differences from TAO Temperature

TAOETAOnoATAOno

170W

140W

110W

95W

Mean Differences from TAO Temperature

1990-2002 (solid line)

2003-2008 (dash line)

- In the pre-Argo period, the central-eastern Pacific (140W, 110W, 95W) is too warm below the surface (red vs. black solid line).

- In the Argo period, the equatorial eastern Pacific is too cold near the surface (red vs. black dash line), indicating the Argo data could not constrain the surface errors.

Mean Differences from TAO Temperature

1990-2002 (solid line)

2003-2008 (dash line)

- Including the TAO moorings west of 110oW constrained the warm bias near the thermocline in the far eastern Pacific where no TAO moorings were available;

- However, the near surface temperature in the far eastern Pacific (110oW, 95oW) is too cold (green vs. black solid line), not constrained well even with the Argo data.

RMSD from TAO Temperature

0-20m 20-200m

RMSD reduction rate in %:Red: the impacts of the TAO moorings west of 110oW (ETAOno vs ATAOno);Green: the impacts of the two eastern TAO moorings (TAO vs. ETAOno).

9

Conclusions• Without the TAO moorings, the model equatorial central-

eastern Pacific (140W, 110W, 95W) temperature is too warm near the thermocline in the pre-Argo period;

• Once the Argo data become available, the warm bias near the thermocline is significantly reduced, but the near surface temperature becomes too cold, likely due to less warming from upwelling;

• Once the TAO moorings west of 110oW become available, the warm bias near the thermocline at 110oW and 95oW is reduced through eastward propagation of Kelvin waves, but the cold bias near the surface remained;

• Once all the TAO moorings are available, both the warm bias below the surface and cold bias near the surface are reduced.

• Therefore, the results indicate that the two eastern TAO moorings are critical in constraining the model biases in the eastern Pacific.

10

Conclusions• However,

• Further analysis against independent data (e.g., CTD, Altimetry etc.) needs to be completed;

• More assimilation runs that exclude other selections of TAO mooring lines, e.g. the western and central Pacific TAO moorings, need to be done;

• Assimilation runs need to be combined with forecast experiments to assess the full impact of the TAO data;

• An approach based on multiple assimilation, and forecast systems is required to gain further confidence.

11

- Differences decrease after 1993 when the TAO array comes in;- However, differences are relatively large during the 1997/98 El Nino. - Differences are larger in the E. Pacific than those in the W. Pacific during the Argo period (2003-2009).

Argo comes in

TAO array comes in

“SUPER” is an average of 7 model-based analyses, including GODAS, ECMWF, JMA, CFSR, GFDL, MERCATOR and BOM

Mean Differences from Weekly OI SST

Pre-Argo period

Argo period

TAOATAOno ETAOno