ROMS 4DVar Progress

1
ROMS 4DVar Progress Mr. Hajoon Song, SIO Ph.D.
Student
High-resolution grid (10 km, 42 layers) for the
study area using the Regional Ocean Modeling
System (ROMS)
2
ROMS 4DVar Progress Mr. Hajoon Song, SIO Ph.D.
Student
Tests of the incremental strong constraints
4D-variational (IS4DVAR) assimilation procedure
using ROMS in the CalCOFI domain first executed
using real observations and wind forcing for a
weeklong test period. Data assimilation window
July 1-7, 2002 Data Advanced Microwave Scanning
Radiometer (AMSR-E) satellite SST data and
CalCOFI cruise hydrographic temperature and
salinity data IS4DVAR successfully reduced the
rms model-data misfit by approximately 75 after
eight inner loops and three outer loops Strong
nonlinearity of ROMS caused the fitting procedure
to fail for longer fitting time intervals.

• Better first guess of ocean state was needed
• Objective analysis or nudging to better represent
  observations
• Fits from Gregoire Brouquet and Chris Edwards
  (UCSC)

3
ROMS 4DVar Progress Mr. Hajoon Song, SIO Ph.D.
Student
Latest results Wind Stress Daily Regional
Spectral Model (RSM) downscaling to 10km Heat
Flux Corrected climatology using NOAA
SST Freshwater flux From 80 climatological run
nudged to observed SSS Initial state UCSC
Analysis (Excellent first guess) Boundary
Condition UCSC Analysis Data SST from
satellite, SLH from satellite, T-S from
CalCOFI
SST plot of assimilated July 1,
2002, CalCOFI/GLOBEC/satellite obs From Broquet
and Edwards (UCSC)
4
ROMS 4DVar Progress Mr. Hajoon Song, SIO Ph.D.
Student
July 1, 2002, SST from satellite and 33 misfit
reduction after 4DVAR
5
ROMS 4DVar Progress Mr. Hajoon Song, SIO Ph.D.
Student
Observed SST
Observed SST
Background SST
Data ssimilated SST
6
ROMS 4DVar Progress Mr. Hajoon Song, SIO Ph.D.
Student
CalCOFI temperature 40 misfit reduction
7
ROMS 4DVar Progress Mr. Hajoon Song, SIO Ph.D.
Student
CalCOFI salinity 14 misfit reduction
8
ROMS 4DVar Progress Mr. Hajoon Song, SIO Ph.D.
Student
ROMS fit captures the intrusion of cold SST down
to 31N and from 118 to 119 (Visible in CalCOFI
and AMSRE satellite observations) and the warm
coastal SST structure (seen only in CalCOFI)
9
Continuing Work

• Test how long the fits can extend in time
  (nonlinearity issues)
• Test adjustments of surface forcing to improve
  fits (intrinsic vs forced variability)
• Choose and fit best time intervals for sardine
  and squid analysis (only 2000-2004 is available
  from UCSC)