An important element of present oceanographic research is the assessment and quantification of uncertainty. These studies are challenging in the coastal ocean due to the wide variety of physical processes occurring on a broad range of spatial and temporal scales. In order to assess new methods for quantifying and predicting uncertainty, a joint Taiwan-US field program was undertaken in August/September 2009 to compare model forecasts of uncertainties in ocean circulation and acoustic propagation, with high-resolution in situ observations. The geographical setting was the continental shelf and slope northeast of Taiwan, where a feature called the “cold dome” frequently forms. Even though it is hypothesized that Kuroshio subsurface intrusions are the water sources for the cold dome, the dome’s dynamics are highly uncertain, involving multiple scales and many interacting ocean features. During the experiment, a combination of near-surface and profiling drifters, broad-scale and high-resolution hydrography, mooring arrays, remote sensing, and regional ocean model forecasts of fields and uncertainties were used to assess mean fields and uncertainties in the region. River runoff from Typhoon Morakot, which hit Taiwan August 7–8, 2009, strongly affected shelf stratification. In addition to the river runoff, a cold cyclonic eddy advected into the region north of the Kuroshio, resulting in a cold dome formation event. Uncertainty forecasts were successfully employed to guide the hydrographic sampling plans. Measurements and forecasts also shed light on the evolution of cold dome waters, including the frequency of eddy shedding to the north-northeast, and interactions with the Kuroshio and tides. For the first time in such a complex region, comparisons between uncertainty forecasts and the model skill at measurement locations validated uncertainty forecasts. To complement the real-time model simulations, historical simulations with another model show that large Kuroshio intrusions were associated with low sea surface height anomalies east of Taiwan, suggesting that there may be some degree of predictability for Kuroshio intrusions.

Gawarkiewicz, G., S. Jan, P.F.J. Lermusiaux, J.L. McClean, L. Centurioni, K. Taylor, B. Cornuelle, T.F. Duda, J. Wang, Y.J. Yang, T. Sanford, R.-C. Lien, C. Lee, M.-A. Lee, W. Leslie, P.J. Haley Jr., P.P. Niiler, G. Gopalakrishnan, P. Velez-Belchi, D.-K. Lee, and Y.Y. Kim. 2011. Circulation and intrusions northeast of Taiwan: Chasing and predicting uncertainty in the cold dome. Oceanography 24(4):110–121, https://doi.org/10.5670/oceanog.2011.99.

Auclair, F., P. Marsaleix, and P. De Mey. 2003. Space-time structure and dynamics of the forecast error in a coastal circulation model of the Gulf of Lions. Dynamics of Atmospheres and Oceans 36:309–346, https://doi.org/10.1016/S0377-0265(02)00068-4.
1. Chang, Y.-L., C.-R. Wu, and L.-Y. Oey. 2009. Bimodal behavior of the seasonal upwelling off the northeastern coast of Taiwan. Journal of Geophysical Research 114, C03027, https://doi.org/10.1029/2008JC005131.
2. Chassignet, E.P., H.E. Hurlburt, E.J. Metzger, O.M. Smedstad, J.A. Cummings, G.R. Halliwell, R. Bleck, R. Baraille, A.J. Wallcraft, C. Lozano, and others. 2009. US GODAE: Global ocean prediction with the HYbrid Coordinate Ocean Model (HYCOM). Oceanography 22(2):64–75, https://doi.org/10.5670/oceanog.2009.39.
3. Chern, C.-S., and J. Wang. 1992. The influence of Taiwan Strait waters on the circulation of the southern East China Sea. La mer 30:223–228.
4. Haley, P.J. Jr., and P.F.J. Lermusiaux. 2010. Multiscale two-way embedding schemes for free-surface primitive-equations in the Multidisciplinary Simulation, Estimation and Assimilation System. Ocean Dynamics 60:1,497–1,537, https://doi.org/10.1007/s10236-010-0349-4.
5. Heaney, K.D., G. Gawarkiewicz, T.F. Duda, and P.F.J. Lermusiaux. 2007. Nonlinear optimization of autonomous undersea vehicle sampling strategies for oceanographic data-assimilation. Journal of Field Robotics 24:437–448, https://doi.org/10.1002/rob.20183.
6. Jan, S., C.-C. Chen, Y.-L. Tsai, Y.J. Yang, J. Wang, C.-S. Chern, G. Gawarkiewicz, R.-C. Lien, L. Centurioni, and J.-Y. Kuo. 2011. Mean structure and variability of the cold dome northeast of Taiwan. Oceanography 24(4):100–109, https://doi.org/10.5670/oceanog.2011.98.
7. Johns, W.E., T.N. Lee, D.X. Zhang, R. Zantopp, C.T. Liu, and Y. Yang. 2001. The Kuroshio east of Taiwan: Moored transport observations from the WOCE PCM-1 array. Journal of Physical Oceanography 31:1,031–1,053, https://doi.org/10.1175/1520-0485(2001)031<1031:TKEOTM>2.0.CO;2.
8. Lee, H.-J., and S.-Y. Chao. 2003. A climatological description of circulation in and around the East China Sea. Deep-Sea Research Part II 50:1,065–1,084, https://doi.org/10.1016/S0967-0645(03)00010-9.
9. Lermusiaux, P.J.F. 1999. Data assimilation via Error Subspace Statistical Estimation: Part II. Mid-Atlantic Bight shelfbreak front simulations and ESSE validation. Monthly Weather Review 127:1,408–1,432, https://doi.org/10.1175/1520-0493(1999)127<1408:DAVESS>2.0.CO;2.
10. Lermusiaux, P.F.J. 2001. Evolving the subspace of the three-dimensional multiscale ocean variability: Massachusetts Bay. Journal of Marine Systems 29:385–422, https://doi.org/10.1016/S0924-7963(01)00025-2.
11. Lermusiaux, P.F.J. 2006. Uncertainty estimation and prediction for interdisciplinary ocean dynamics. Journal of Computational Physics 217:176–199, https://doi.org/ 10.1016/j.jcp.2006.02.010.
12. Lermusiaux, P.F.J. 2007. Adaptive modeling, adaptive data assimilation and adaptive sampling. Physica D 230:172–196, https://doi.org/10.1016/j.physd.2007.02.014.
13. Lermusiaux, P.F.J., C.-S. Chiu, G.G. Gawarkiewicz, P. Abbot, A.R. Robinson, R.N. Miller, P.J. Haley, W.G. Leslie, S.J. Majumdar, A. Pang, and F. Lekien. 2006. Quantifying uncertainties in ocean predictions. Oceanography 19(1):90–103, https://doi.org/10.5670/oceanog.2006.93.
14. Lermusiaux, P.F.J., and A.R. Robinson. 1999. Data assimilation via Error Subspace Statistical Estimation: Part I. Theory and schemes. Monthly Weather Review 127:1,385–1,407, https://doi.org/10.1175/1520-0493(1999)127<1385:DAVESS>2.0.CO;2.
15. Lermusiaux, P.F.J., A.R. Robinson, P.J. Haley, and W.G. Leslie. 2002. Advanced interdisciplinary data assimilation: Filtering and smoothing via error subspace statistical estimation. Pp. 795–802 in Proceedings of the OCEANS 2002 MTS/IEEE Conference. October 29–31, 2001, Biloxi, MS, Holland Publications.
16. Lermusiaux, P.F.J., J. Xu, C.F. Chen, S. Jan, L.Y. Chiu, and Y.-J. Yang. 2010. Coupled ocean-acoustic prediction of transmission loss in a continental shelfbreak region: Predictive skill, uncertainty quantification and dynamical sensitivities. IEEE Journal of Oceanic Engineering 35:895–916, https://doi.org/10.1109/JOE.2010.2068611.
17. Liang, W.-D., T.Y. Tang, Y.J. Yang, M.-T. Ko, and W.-S. Chuang. 2003. Upper-ocean currents around Taiwan. Deep-Sea Research Part II 50:1,085–1,105, https://doi.org/10.1016/S0967-0645(03)00011-0.
18. Liu, K.K., G.-C. Gong, S. Lin, C.Y. Yang, C.L. Wei, S.-C. Pai, and C.-K. Wu. 1992. The year-round upwelling at the shelf break near the northern tip of Taiwan as evidenced by chemical hydrography. Terrestrial Atmospheric and Oceanic Sciences 3:243–275.
19. Logutov, O.G., and P.F.J. Lermusiaux. 2008. Inverse barotropic tidal estimation for regional ocean applications. Ocean Modelling 25:17–34, https://doi.org/10.1016/j.ocemod.2008.06.004.
20. Maximenko, N., P.P. Niiler, L. Centurioni, M.-H. Rio, O. Melnichenko, D. Chambers, V. Zlotnicki, and B. Galperin. 2009. Mean dynamic topography of the ocean derived from satellite and drifting buoy data using three different techniques. Journal of Atmospheric and Oceanic Technology 26:1,910–1,919, https://doi.org/10.1175/2009JTECHO672.1.
21. Morimoto, A., S. Kojima, S. Jan, and D. Takahashi. 2009. Movement of the Kuroshio axis to the northeast shelf of Taiwan during typhoon events. Estuarine, Coastal, and Shelf Science 82:547–552, https://doi.org/10.1016/j.ecss.2009.02.022.
22. Niiler, P.P. 2001. The world ocean surface circulation. Pp. 193–204 in Ocean Circulation and Climate. G. Siedler, J. Church, and J. Gould, eds, Academic Press.
23. Rudnick, D., S. Jan, L. Centurioni, C.M. Lee, R.-C. Lien, J. Wang, D.-K. Lee, R.-S. Tseng, Y.Y. Kim, and C.-S. Chern. 2011. Seasonal and mesoscale variability of the Kuroshio near its origin. Oceanography 24(4):52–63, https://doi.org/10.5670/oceanog.2011.95.
24. Scott, R.B., B.K. Arbic, E.P. Chassignet, A.C. Coward, M. Maltrud, W.J. Merryfield, A. Srinivasan, and A. Varghese. 2010. Total kinetic energy in four global eddying ocean circulation models and over 5000 current meter records. Ocean Modelling 32:157–169, https://doi.org/10.1016/j.ocemod.2010.01.005.
25. Tang, T.Y., Y. Hsueh, Y.J. Yang, and J.C. Ma. 1999. Continental slope flow northeast of Taiwan. Journal of Physical Oceanography 29:1,353–1,362, https://doi.org/10.1175/1520-0485(1999)029<1353:CSFNOT>2.0.CO;2.
26. Tang, T.-Y., J.H. Tai, and Y.J. Yang. 2000. The flow pattern north of Taiwan and the migration of the Kuroshio. Continental Shelf Research 20:349–371, https://doi.org/10.1016/S0278-4343(99)00076-X .
27. Yang, Y., C.T Liu, J.-H. Hu, and M. Koga. 1999. Taiwan Current (Kuroshio) and impinging eddies. Journal of Oceanography 55:609–617.
28. Zhang, D.X., T.N. Lee, W.E. Johns, C.T. Liu, and R. Zantopp. 2001. The Kuroshio east of Taiwan: Modes of variability and relationship to interior ocean mesoscale eddies. Journal of Physical Oceanography 31:1,054–1,074, https://doi.org/10.1175/1520-0485(2001)031<1054:TKEOTM>2.0.CO;2.

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