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Development of Data Assimilation Schemes in Support of Coastal Ocean Observing Systems Zhijin Li , Yi Chao Jet Propulsion Laboratory, California Institute of Technology James C. McWilliams, Kayo Ide University of California, Los Angeles


  1. Development of Data Assimilation Schemes in Support of Coastal Ocean Observing Systems Zhijin Li , Yi Chao Jet Propulsion Laboratory, California Institute of Technology James C. McWilliams, Kayo Ide University of California, Los Angeles Mathematical Advancement in Geophysical Data Assimilation Banff, February 3-8, 2008 1

  2. Outline 1. Costal ocean observing systems 2. Assimilated observations 3. Three-dimensional variational data assimilation 4. Evaluation of analyses and forecasts 5. Observing system experiments (OSE) 6. Summary 2

  3. Coastal Oceans 3

  4. Integrated Ocean Observing System (IOOS): data assimilation, forecasting and adaptive sampling Theoretical Users: Understanding & Observations Managers (satellite, in situ) Numerical Education & Models Outreach Data Products Assimilation Information Observing System Design Feedback & Adaptive Sampling 4

  5. Regional Coastal Ocean Observing System (RCOOS) • Sea surface height SSH • Velocity u/v • Temperature T • Salinity S 5

  6. Assimilated Observations: satellite infrared SSTs Microwave, Low resolution (25km) Infrared, High resolution No cloud contamination Cloud contamination NOAA GOES NASA Aqua AMSR-E NASA TRIMM NOAA TMI AVHRR 6

  7. Assimilated observations: satellite SSHs along track JASON-1 ASON-1 Resolution: 120km cross track, 6km along track 7

  8. Real-Time High Frequency Radar Current Short distance: 100km, res of 1km, 5 MHz Long distance: 200km, res of 5km, 25 MHz 8

  9. Assimilated Current Observations Shipboard Buoy Acoustic Doppler Current Profiler (ADCP) Bottom 9

  10. Integrated Ocean Observing Systems * T/S profiles from gliders * Ship CTD profiles * Aircraft SSTs * AUV sections 10

  11. Modeling Approach 15-km 5-km 1.5-km Regional Ocean Modeling System (ROMS): From Global to Regional/Coastal 12-km Multi-scale (or “nested”) ROMS modeling approach is developed in order to simulate the 3D ocean at the spatial scale (e.g., 1.5-km) measured by in situ and remote sensors 11

  12. Model Inputs • Surface wind stress • Precipitation • Heat fluxes • Land water runoff • Topography • Tides (Royer, 2005) 12

  13. Tides Tide Gauge ROMS Simulation HF Radar Obs Sea Surface M2 Tidal Currents 13

  14. ROMS Analysis and Forecast Cycle: Incremental 3DVAR 3-day forecast x f 6-hour forecast 6-hour x a Initial assimilation condition cycle Time Aug.1 Aug.2 Aug.1 Aug.1 Aug.1 14 18Z 00Z 06Z 12Z 00Z

  15. Data Assimilation Formulation Variational methods (3Dvar/4Dvar):  prescribed B  optimization algorithm Sequential methods (Kalman filter/smoother)  dynamically evolved B  analytical solution 15

  16. Why a There-Dimensional Variational Data Assimilation • Real-time capability • Implementation with sophisticated and high resolution model configurations • Flexibility to assimilate various observation simultaneously • Development for more advanced scheme 16

  17. Inhomogeneous and anisotropic 3D Global Error Covariance Cross-shore and vertical section salinity correlation SSH correlations Kronecker Product 17

  18. Construction of 3D Corelations with Kronecker Product Kronecker product • Positive definiteness • Cholesky factorization • Computational efficiency (Li et al. 2008) 18

  19. Toward a Relocatable ROMS Forecasting System: Demonstration for Prince William Sound, Alaska 9-km 3-km 1-km 19

  20. Inhomogeneity and Anisotropy 20

  21. Construction of Correlation Matrix C Constructed locally a, b are two locations (e.g., Cummings, 2005) Schur product 21

  22. 3DVAR: Weak Geostrophic Constraint Geostrophic balance Geostrophic sea surface level ageostrophic streamfunction and velocity potential 22

  23. Forecast skills: AOSN-II Forecast Correlation " !(+ ,-../0123-4 !(' !(* !(& !() ! "# #$ %& 5-./,1627238/79:;<=> 23

  24. Observing System Experiment (OSE): Glider Data Denial Experiment Temperature RMS Error Salinity w/o CalPoly glider with CalPoly glider SIO CalPoly WHOI 1 st week 2 nd week 24

  25. Impact of HF radar HF Radar ROMS without ROMS with HF radar data HF radar data assimilation assimilation 25

  26. Real-Time SCCOOS Data Assimilation and Forecasting System http://ourocean.jpl.nasa.gov/SCB 26

  27. Observability Model configurations: Grids 280 by 400 Level 40 Averaged decorrelation scale: Horizontal: 20km Vertical: Complex structure Observation availability:  HF radar surface currents:10% coverage near shore  Glider T/S profiles: several daily  Satellite SSTs: cloudless days  Ship CDT: survey monthly to seasonally  ADCP: survey monthly to seasonally 27

  28. Summary • A coastal ocean observing system requires a data assimilation and forecasting system • Tremendous progresses have been made in observations • A developed data assimilation system has demonstrated forecast skills. • Limited numbers of observations will be a continuing challenge in coming years. • Significant model biases exist 28

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