Title: U.S. GODAE: Global Ocean Prediction with the Hybrid Coordinate Ocean Model (HYCOM)
1Global Ocean Prediction with HYCOM
The NOPP GODAE project which developed and tested
the first global 1/12 HYCOM/NCODA
nowcast/forecast system ended in FY08. Global
1/12 system currently undergoing operational
trials at NAVOCEANO. Formal OPTEST expected in
FY10. An ONR sponsored follow-on to the NOPP
project started in FY09. Includes collaborations
with FSU and NCEP. The principal goal of the
ONR project is to perform the necessary RD to
prepare for the next generation global system at
higher horizontal resolution (1/25 on the
equator, 3.5 km at mid-latitudes, and 2 km in the
Arctic).
2Global Ocean Prediction with HYCOM
- New capabilities in the system will include
- sub-daily effects - diurnal cycle and tides,
including the internal tide (excluded in current
system) - CICE integration and coupling, including sea ice
data assimilation - 3D variational assimilation
- variational adjoint system for determining
observation impacts on selected measures of
forecast error
3Gulf Stream Sea Surface Height Variability
- Along-track from four satellite altimeters
(Hurlburt and Hogan, 2008) - b) 1/12? global model year 3
- c) 1/25? global model year 3
(a)
(c)
(b)
4Mean Simulated vs. Observed Velocity (top) and
Temperature (bottom) Along the Equator in the
Pacific Ocean
Earlier 1/12? HYCOM
Observations
New 1/25? HYCOM
m/s
?C
Observations from the TAO array (Johnson et al,
2007 Prog Oceanogr.)
5Global Ocean Prediction with HYCOM
Eight largest tidal constituents in a 32-layer
.08 global HYCOM simulation with NOGAPS
atmospheric forcing
Hourly steric SSH
Hourly non-steric SSH
Internal tidal signature seen in the steric SSH
signal
Propagation of tides is consistent with Robertson
and Ffield (2008)
6Difference in Steric SSH Over 6 Hours June 30
2006 06Z 00Z
7ESMF Coupled HYCOM/CICE/NCODA
Bering Sea Ice Thickness
no sea ice assimilation
with sea ice assimilation
Black line represents independent ice edge
analysis performed at the National Ice Center.
8HYCOM Assimilation NCODA
Raw Obs
Navy Coupled Ocean Data Assimilation operational
at Navy production centers (NAVOCEANO, FNMOC)
Automated QC w/condition flags
SST NOAA (GAC, LAC), METOP (GAC, LAC),
GOES, MSG, AATSR, AMSR-E, Ship/Buoy
Profile Temp/Salt XBT, CTD,
Argo Float, Fixed/Drifting Buoy SSH
Jason-1, Jason-2, ENVISAT, In situ Sea Ice
SSM/I, SSMIS Glider Slocum, Sea-glider, Spray
(T,S,U,V)
Ocean Data QC
Innovations
MVOI/3DVar - analysis of 5 ocean variables
temperature, salinity, geopotential, velocity
(u,v)
3D MVOI (3DVar)
Increments
HYCOM
Forecast Fields Prediction Errors
Adaptive Sampling Guidance
First Guess
QC Data Cut
Incremental Update Cycle
9Assimilation Sub-regions
10HYCOM/NCODA Runstream
Valid nowcast time
00Z
00Z
00Z
00Z
00Z
00Z
00Z
00Z
00Z
00Z
-120
-96
-72
-48
-24
0
tau
24
48
72
96
- 24 hour incremental update cycle
- IAU applied over the first 6 hrs of forecast (18Z
to 00Z) - 5-day hindcast followed by 4-day forecast
- Approximate run time (using 619 Cray XT5
processors) 13.4 hrs - six NCODA analyses, nine HYCOM hindcast/forecast
days - timing does not include PIPS sea ice coupling
11SSH Data Timeliness Jan-Apr, 2007Percent data
received by days before nowcast
Illustrates need for 5-day hindcast to obtain
synoptic altimeter SSH data
12NCODA 3D-Var Data Assimilation
- Observation Space Formulation
- same analysis equation as MVOI (solving the
equation is very different) - new HYCOM analysis variables (layer pressure and
layer thickness) - new non-separable formulation of correlation
functions new
preprocessing options (clustering, profile layer
averaging, etc)
based on NAVDAS atmospheric 3D-Var system
developed by Roger Daley and Ed Barker at NRL
Monterey
13So, why 3D-Var?
- global solution no data selection
- much reduced memory footprint over that of MVOI
important for global HYCOM 1/25? grid - greater flexibility for assimilating different
observation data types - general framework for using more sophisticated
background error covariance models - multi-incremental with an inner and an outer
loop - outer loop can assimilate observations
non-linearly related to the forecast state - valid approximation to 4DVar when assimilation
time window is short and dynamics are
quasi-stationary
14HYCOM Isopycnal Flow Dependent Correlations
Depth/distance cross section of temperature
(contour interval 1?C) and isopycnal following
correlations (color shaded) Observation is at
the surface in the frame on the left, and at 300
meters in the frame on the right
15END