Case Studies for Particular Applications

As described previously, ocean forecasting systems serve a large number of users. Among the most significant of these are the Navies, who are interested in a number

.08' Global HYCOM (82.4) Median SSH Anomaly Correlation wldocn: number of forecasts 48 (01-Jun-2007 to 22-May-2008)

.08' Global HYCOM (82.4) SSH Median RMS error wldocn: number of forecasts 48 (01-Jun-2007 to 22-May-2008)

.08' Global HYCOM (82.4) Median SSH Anomaly Correlation wldocn: number of forecasts 48 (01-Jun-2007 to 22-May-2008)

— persistence "

forecast length (in days)

.08' Global HYCOM (82.4) SSH Median RMS error wldocn: number of forecasts 48 (01-Jun-2007 to 22-May-2008)

i5 10 1

5 10

forecast length (in days)

.08' Global HYCOM (82.4) Median SSH Anomaly Correlation kurosh: number of forecasts 48 (01-Jun-2007 to 22-May-2008)

i5 10 1

forecast length (in days)

.08' Global HYCOM (82.4) SSH Median RMS eiror kurosh: number of forecasts 48 (01-Jun-2007 to 22-May-2008)

.08' Global HYCOM (82.4) Median SSH Anomaly Correlation kurosh: number of forecasts 48 (01-Jun-2007 to 22-May-2008)

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— persistence "

forecast length (in days)

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— persistence

forecast length (in days)

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5 10

forecast length (in days)

.08' Global HYCOM (82.4) Median SSH Anomaly Correlation nwarab: number of forecasts 48 (01-Jun-2007 to 22-May-2008)

5 10

forecast length (in days)

.08' Global HYCOM (82.4) SSH Median RMS error nwarab: number of forecasts 48 (01-Jun-2007 to 22-May-20 08)

— persistence '

forecast length (in days)

.08' Global HYCOM (82.4) SSH Median RMS error nwarab: number of forecasts 48 (01-Jun-2007 to 22-May-20 08)

5 10

forecast length (in days)

forecast length (in days)

.08' Global HYCOM (82.4) Median SSH Anomaly Correlation yelsea: number of forecasts 48 (01-Jun-2007 to 22-May-2008)

5 10

forecast length (in days)

.08' Global HYCOM (82.4) SSH Median RMS error yelsea: number of forecasts 48 (01-Jun-2007 to 22-May-2008)

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— persistence '

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forecast length (in days)

5 10

forecast length (in days)

— persistence

forecast length (in days)

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forecast length (in days)

Fig. 22.7 Median SSH anomaly correlation (left column) and median SSH RMSD (right column) against the verifying analysis as a function of forecast length for the global ocean (entire domain— top row), the Kuroshio (120-179°E, 21-55°N—second row), the northwest Arabian Sea (51-65°E, 15-26°N—third row) and the Yellow Sea (118-127°E, 30-42°N—bottom row). The red curves are HYCOM/NCODA forecasts, the cyan curves are for persistence of the nowcast and the black curves of RMSE are for the hindcast annual mean

of different outputs including information about sound speed in the ocean in order to model the acoustics (Metzger et al. 2008, 2009). In order to produce accurate sound speed estimates, the temperature and salinity fields must be accurately determined, with the mixed-layer depth (MLD) and sonic-layer depth (SLD, Millero and Li 1994) of particular interest (amongst other parameters).

Metzger et al. (2008, 2009) investigate the accuracy of the MLD and SLD forecasts in the HYCOM/NCODA system used by the US Navy. An example of this validation is shown in Fig. 22.9 which shows the mean and RMS errors in SLD as a function of forecast time for three regions. This shows that the model forecast and persistence are both producing more accurate estimates of SLD than is available from climatological estimates throughout the 14-day forecast. The skill of the model is generally similar to that of persistence, although this result is regionally dependent. The RMS errors generally show a large amount of variability which is most likely due to vertical interpolation errors, and could also be due to observation sampling issues.

Forecast length (days) Forecast length (days)

Fig. 22.9 Error analysis of sonic layer depth (metre) as a function of forecast length based on 48 14-day forecasts by HYCOM/NCODA for regions MER4d (top), the western Pacific (middle) and the Arabian Sea (bottom). The left column shows mean error and the right column shows RMSD. The black curves are for HYCOM/NCODA forecasts, the blue curves are for persistence of the nowcast ocean state and the red curves are for the GDEM3 climatology. Note the y-axis differs between most plots

Forecast length (days) Forecast length (days)

Fig. 22.9 Error analysis of sonic layer depth (metre) as a function of forecast length based on 48 14-day forecasts by HYCOM/NCODA for regions MER4d (top), the western Pacific (middle) and the Arabian Sea (bottom). The left column shows mean error and the right column shows RMSD. The black curves are for HYCOM/NCODA forecasts, the blue curves are for persistence of the nowcast ocean state and the red curves are for the GDEM3 climatology. Note the y-axis differs between most plots

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