FY12-FY13 Semi-Annual GIMPAP Progress Report
Reporting Period: February 2013 – July 2013
Project Title: CIOSS Support to GOES Improvement and Product Application Program. GOES
SST Assimilation for Nowcasts and Forecasts of Coastal Ocean Conditions
PIs: P. Ted Strub, Alexander Kurapov, CIOSS, Oregon State University
Participants (NOAA Collaborators): Laury Miller, NOAA/NESDIS/STAR, Eileen Maturi,
NOAA/NESDIS/STAR/SOCD, Dave Foley, NOAA/NESDIS/CoastWatch
Brief Project Summary:
In this project, GOES sea surface temperature (SST) fields are assimilated in the threedimensional (3D) coastal ocean circulation model off Oregon (US West coast). As a result of this
research project, the following operational products can be developed:
o Continuous near-real time maps (“nowcasts”) of SST, sea surface topography, and surface
currents in the coastal ocean.
o 3-day forecasts of these fields.
The forecast model is based on the Regional Ocean Modeling System (ROMS,
www.myroms.org), a comprehensive nonlinear prediction model describing evolution of the
ocean currents, temperature, and salinity in three dimensions and time. Assimilation is done in a
series of 3-day intervals using a four-dimensional variational method (4DVAR) (Kurapov et al.,
2009, 2011, Yu et al., 2012). Our own tangent linear and adjoint codes AVRORA are utilized for
this purpose. Hourly GOES data obtained from the NOAA Coastwatch server are assimilated in
combination with alongtrack altimetry (currently Jason-2 and CryoSat, provided by Dr. L.
Miller, NOAA-STAR) and surface velocities from a series of high-frequency (HF) radars
operated along the Oregon coast by P. M. Kosro (OSU). The
4DVAR method provides dynamically based time and space
interpolation of the sparse and noisy GOES data and their synthesis
with other available data sources. Using the model dynamics, the
correction is propagated to subsurface fields. The ROMS model run
over the next window (using forecast winds and heat fluxes from the
NOAA NAM model) yields 3-day forecasts of the ocean state,
including surface currents and SST.
The current model domain is about 400×800 km, extended between
Figure 1. Model domains (smaller box: the present real-time forecast
model, larger box: a newer model including the Columbia River, currently
at a testing stage). Colors show model SST (08/31/2009) (range of colors
is between 8-18oC). White contours show 200 and 2000 m isobaths.
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41-47N and 129W-coast (Figure 1, smaller box). Forecasts are obtained at a 3-km horizontal
resolution.
The AVRORA-ROMS system has been run in the near real-time regime, providing every-day
updates of 3-day forecasts. These have been used by fishermen, who are interested in the
forecasts of the SST fronts, to guide their trips. The fields have been distributed to the public via
the NVS visualization system supported by the Northwest Association of Networked Ocean
Observing Systems (NANOOS, www.nanoos.org), a regional coastal ocean observing system
association supported by NOAA funding. We have demonstrated that assimilation of the GOES
SST impacts predictions of surface velocities (which are generally intensified along SST fronts).
The surface current forecast fields have been provided to the NOAA Office of Response and
Figure 2. Pre-assimilation quality control analysis of the hourly GOES SST product reveals noisy images,
appearing in summer months regularly during sunrise and sunset hours (as shown in a series of hourly
images here for July 29, 2013; times are UTC; images for 03, 04, and 05 hr UTC had to be removed
because of erroneously cold signal found offshore in the cloud-covered area).
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Restoration (ORR, Dr. Watabayashi), where they have been used with the NOAA GNOME oil
spill software. In particular, this software coupled with our forecasts has been used to track large
marine debris objects (e.g., docks) released in the ocean following the devastating tsunami in
Japan and spotted along the Oregon and Washington coasts by fishermen and Coast Guard.
The interpolated SST fields resulting from assimilation have been added to an OpenDAP server
and are ready to be posted on the NOAA Coastwatch site (in collaboration with D. Foley).
We have continued monitoring and assessing the quality of the hourly GOES SST data on a daily
basis, after we found erroneous and noisy images last summer during sunset and sunrise hours.
Suspicious images have been excluded from assimilation (Figure 2). These findings have been
reported to our NOAA collaborators, who provided guidance in using these fields.
Current efforts are directed to extend the model, to more fully utilize the GOES data, and to
improve the forecast model capabilities, to better reproduce variability in SST. In particular, the
Columbia River (CR) plume waters spread under the influence of the Earth rotation and local
winds to several hundred km north and south of the river mouth, 46.3N. They may contribute to
variability in SST due to the river’s distinct temperature (esp. the river water is colder than the
ocean in winter) and modifications in the surface boundary layer (e.g., solar heat may be
captured in a shallower layer in the CR in summer). To study the impact of CR on SST, we have
developed a 2-km resolution ROMS model in the domain that was extended to 41-50N (to
include both Oregon and Washington coastal areas, see the large box in Figure 1). Model
simulations with and without the CR discharge have been compared. We found that SST in the
area of the plume can be 1-3oC warmer, in part explaining spatial variability in the observed SST
between 43-47N in spring (Figure 3). At the same time, during strong upwelling events, water
inshore of the river plume edge may be relatively colder in the case with the CR than in the case
without CR. These effects may be enhanced if the vertical attenuation scale for the short wave
radiation is reduced in the area of the plume, based on the model sea surface salinity (such a
reduction would be justified since the Columbia River waters carrying sediments and nutrients
are more turbid than the ambient ocean waters). The manuscript on this topic has been written in
the reported period and is nearing submission to the J. Geophys. Res. (Kurapov et al., 2013).
Inclusion of the Columbia River discharge in the forecast model will potentially reduce the
model bias and improve the impact of the assimilated GOES SST data. At the same time, the
presence of a thin layer of anomalously lighter water will present new challenges to assimilation
(in particular, the initial condition error covariance will have to be modified to account for
horizontal and vertical inhomogeneity).
To improve presentation of the output fields, Dr. S. Erofeeva, the research associate in charge of
the real-time forecast model, has developed an interactive forecast viewer with features
convenient both for developers and users of the forecast product
(http://ingria.coas.oregonstate.edu/rtdav/, Figure 4). The main features of this viewer are a
calendar and a two-window graphical display. The viewer can select different daily fields in
windows 1 and 2 and compare them side-by-side. The list of mapped fields includes: model SST
and surface currents, the wind stress (calculated by the ocean model using NOAA NAM wind
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velocities), observed HF radar surface currents (provided by P. M. Kosro), AVHRR SST, and
MODIS SST. For instance, the viewer can compare available recent model fields to the
independent AVHRR and MODIS SST products (i.e., the fields that were not assimilated) and
view marine forecasts for today and the next 2 days. After the content of this new site is fully
verified, we will advertise this product to Oregon fisheries community and will collect feedback.
Tracking the number of visits to these web pages is also planned. This product will also be
demonstrated at NOAA NOS (Dr. F. Aikman).
Figure 3. The impact of the Columbia River on SST during a strong upwelling event (27 June 2009): (a)
SST, model without CR, (b) SST, model with CR and variable short wave radiation attenuation,
dependent on the surface salinity, (c) difference [(b) minus (a)]. Color is SST or difference in SST,
black contours are salinity [32.5, 30, and 28 psu; contours for case (b) are repeated in the difference
plot(c)]. The gray contour is the 200 m isobath. SST within the river plume area is relatively warmer
than in the case without CR (e.g., see panel (c)). SST inshore of the upwelling front (edge of the river
plume) is relatively colder.
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Figure 4. The new interactive viewer (developed by Dr. S. Erofeeva) is showing side-by-side (left) the
recent model forecast (SST and surface currents) and (right) the AVHRR SST composite for the same day
(July 11, 2013).
FY13 Milestones. Progress toward FY13 Milestones:
By July 2012: Set-up the model in a larger domain. Run it without the CR and tides. Provide
initial assessment of the SST, SSH, and velocity variability in the extension area (Washington
coast), using model outputs and available data (satellite SST, SSH, and moored velocities).
[DONE]
By October 2012: Assimilate GOES SST, RADS altimetry, and HF radar surface currents in the
Oregon-Washington model. Compare results against unassimilated data (glider, moored
velocities and temperature). Include the CR and tides in the model. Using model simulations
with and without the CR, assess the effect of the CR on SST. [Model assessments: DONE;
inclusion of the CR and tides in the model: DONE; assimilation: continued in the real time
old domain, without CR]
By January 2013: Run data assimilation experiments in the presence of the CR. Verify whether
forecast biases are reduced and data fit is improved as a result of adding fuller model dynamics.
[Initial assimilation tests have been run; analysis of outputs and impacts of the data in the
presence of CR is underway]
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By April 2013: Begin assimilation in a larger domain in near-real time. Provide information
(noise free SST maps, SST and velocity forecast) to the public via the NANOOS visualization
system. In collaboration with the NANOOS Data Management group, gauge information about
forecast products utilization (track a number of internet site visits, by month, by week, and by
day). If tests of the CR plume model prove to be successful, develop the forecast product of the
river plume edge. Collaborate with colleagues at NOAA-CoastWatch about adding assimilated
SST and surface velocity forecasts to a list of their products. [Forecast fields and noise free
maps of SST are provided via the NANOOS visualization system. The new interactive
viewer has been developed. Assimilation in the model incorporating the CR requires
careful re-evaluation of the data assimilation details, such as the in initial condition
covariance – these are being assessed in hindcast experiments. SST fields for adding our
forecasts have been prepared and stored at the OpenDAP server. Adding these to
CoastWatch sets has been postponed until additional quality control of the fields is
performed (e.g., noisy forecast behavior in June was attributed to bad boundary
conditions; we have used climatological boundary conditions; a better choice would be to
use 1/12th degree resolution NOAA RTOFS global model forecasts)]
Operational Transition Plans (if applicable)
Plans to develop an operational West Coast Coastal Ocean Forecast System have been
announced by NOAA NOS (Dr. F. Aikman). We are collaborating with NOS in a proposal
(submitted to NOAA as a part of a SURA omnibus proposal) that would establish a coastal ocean
testbed for the US West Coast. Dr. Aikman is a collaborator in that project. As a part of these
efforts, algorithms for assimilation and model assessment will be shared with NOS. The newly
developed interactive viewer will also be presented at NOAA NOS, and NOAA STAR.
Publications and Presentations
Publications:
Yu, P., A. L. Kurapov, G. D. Egbert, J. S. Allen, and P. M. Kosro, 2012: Variational assimilation
of HF radar surface currents in a coastal ocean model off Oregon, Ocean Modelling, 2012, 86104, doi: 10.1016/j.ocemod.2012.03.001
Kurapov A. L., P. Yu, R. K. Shearman, and J. S. Allen, 2013: Sea surface temperature variability
in the upwelling region off Oregon influenced by the Columbia River plume, in the final stage of
preparation (to be submitted to J. Geophys. Res. in August 2013).
Presentations:
Gordon Research Conference on Coastal Ocean Circulation, June 9-14, 2013, Biddeford, ME
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References
Kurapov, A. L., G. D. Egbert, J. S. Allen, and R. N. Miller, 2009: Representer-based analyses in the coastal
upwelling system, Dynamics of Atmosphres and Oceans, 48(1-3), 198-218, doi:10.1016/j.dynatmoce.2008.09.002.
Kurapov A. L., P. Yu, R. K. Shearman, and J. S. Allen, 2013: Sea surface temperature variability in the upwelling
region off Oregon influenced by the Columbia River plume, in the final stage of preparation (to be submitted to J.
Geophys. Res. in August 2013).
Kurapov, A. L., D. Foley, P. T. Strub, G. D. Egbert, and J. S. Allen, 2011: Variational assimilation of satellite
observations in a coastal ocean model off Oregon, J. Geophys. Res., 116, C05006, doi:10.1029/2010JC006909.
Yu, P., A. L. Kurapov, G. D. Egbert, J. S. Allen, and P. M. Kosro, 2012: Variational assimilation of HF radar
surface currents in a coastal ocean model off Oregon, Ocean Modelling, 2012, 86-104, doi:
10.1016/j.ocemod.2012.03.001.
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