| |
Home
Registration
Preparation of papers
Presenters
Programme
Contact
|
|
|
|
|
High resolution ensemble forecasting for the Gulf of Mexico eddies and fronts
|
Francois Counillon1
L. Bertino1,2
(1) Nansen Environmental and Remote Sensing Center (NERSC), Bergen, Norway
(2) Mohn-Sverdup Center for Global Ocean Studies and Operational Oceanography, Bergen, Norway
Main authors appear in bold
As oil production moves further into deeper waters, the costs related to
strong current hazards are increasing accordingly, and accurate three-dimensional forecasts of
currents are urgently needed. To be useful, models have to locate eddies and fronts to an
accuracy of 30 km at a nowcast stage, which is almost impossible to accomplish with the use of
satellite data of the same accuracy. The use of stochastic forecast allows us to give confidence
of our prediction.
We are using a nested configuration of the Hybrid coordinate ocean model (HYCOM), where the TOPAZ
system, which covers the Atlantic and the Artic, gives lateral boundary condition to a high-resolution
(5km) model of the Gulf of Mexico (GOM). TOPAZ is a real-time forecasting coupled ocean-ice model,
which assimilates sea level anomaly (SLA), sea surface temperature, and sea ice concentration, with
the ensemble Kalman filter. The high-resolution model assimilates SLA using the ensemble optimal
interpolation, which updates accordingly the currents, salinity, temperature, and layer interface
at all depths.
Here, we evaluate the ensemble forecast capabilities of our high- resolution model, for eddy
Extreme that has been observed from altimeters around the 15th of July.
We run 6 successive ensemble runs composed of 10 members of equal likelihood. Members differ by
perturbations of the initial state, of the lateral boundary conditions, and of the atmospheric
boundary conditions.
We have started the experiment 1 month prior to the shedding event, because it was the time necessary
for perturbation of boundary conditions to spread uniformly and reach a significant level across the GOM.
The ensemble reproduces well the dynamics of the eddy shedding and produces a significant spread at
the boundary of the eddy, but underestimates the RMS error of the SLA. Prior to the shedding time, the
error growth increase, induced by the highly non-linear growth of cyclonic eddies at the boundary of the
Loop Current.
Additionally, this ensemble has allowed for optimization of data assimilation parameters depending on
the range of the forecast.
Poster presentation
Back
|
