2. Geophysical forcing data

ETMAES-I/Doc. 3.3(2)
ITEM 3.3
Original: ENGLISH
Support for Accidental Marine Pollution and Search and Rescue at the Norwegian
Meteorological Institute (met.no)
(Submitted by Mr Bruce Hackett and Mr Øyvind Breivik from the Norwegian Meteorological
Institute (met.no))
Summary and Purpose of Document
This document contains a report from the Norwegian Meteorological Institute
(met.no) that aims to describe its support for Accidental Marine Pollution and
Search and Rescue (SAR) operations.
The Expert Team on Marine Accident Emergency Support (ETMAES) is invited to note
and comment on the information provided, as appropriate, and generally to take it into account
when discussing relevant agenda items.
ETMAES-I/Doc. 3.3(2), p. 2
The Norwegian Meteorological Institute (met.no) has a national responsibility for weather
and ocean forecasting in Norwegian waters. The responsibilities extend to the support of Marine
Pollution Response (including oil spill fate and algal bloom forecasting), and to Search and
Rescue (SAR) operations. Norway has taken on the role of MSI Coordinator for NAVAREA XIX,
and has offered to take the responsibility as Coordinating Issuing Service for the corresponding
METAREA XIX; met.no will carry out the responsibilities for the latter. METAREA XIX
corresponds to the Arctic waters north of 71° N on MPI Area I.
Responsibility for forecast support to oil spill fate and search and rescue activities are
carried out by met.no's Forecasting Division for Western Norway (VV), located in Bergen.
Development of models and the forecasting systems is supported by the met.no Research and
Development Department, located in Oslo.
Geophysical forcing data
Forecasting the drift of oil and objects, as well as algal blooms, is founded on forcing
data from operational models for the atmosphere, ocean circulation and waves. The goal is to
apply the best available forcing data for a given area and time span. Given the complicated
terrain and rugged coastline, much effort is expended on developing fine-scale models that can
resolve the topographic features. For atmospheric forecasting, the HIRLAM and Unified Model
(UM) codes are run at met.no at various resolutions from 20 km (for Europe and the Arctic),
down to 1-4 km (for Norway proper). Lateral boundary conditions are obtained from the
ECMWF. The met.no-produced data are supplemented by ECMWF data for forecasting beyond
60 hours ahead. For ocean circulation, met.no runs the MIPOM code operationally on a range of
nested domains. A coupled ocean-ice model is run for the North Atlantic and Arctic Oceans at
20 km resolution. The main source of ocean data is the Nordic4 domain, a 4 km grid covering
the North and Nordic Seas (see Figure 1). This model is nearly eddy-resolving, and will be
coupled with an ice model for operational forecasting in 2007. Higher resolution domains
covering selected regions of the Norwegian coast are nested in Nordic4. For lateral boundary
conditions, data are obtained from global and basin-scale systems, such the UK FOAM, the
French Mercator and the Norwegian TOPAZ. For waves, the WAM code is applied on two
domains: a large scale model for the North Atlantic and Nordic Seas at 45 km resolution, and a
Nordic Seas mode at 10 km resolution. Lateral boundary forcing is obtained from the ECMWF
global WAM.
Figure 1: Nordic4 model domain. Met.no runs the MIPOM 3D hydrodynamic code on this domain with 4 km grid
ETMAES-I/Doc. 3.3(2), p. 3
intervals. Model runs are performed daily to produce forecasts of sea level and 3D currents, temperature and salinity
to +60 hours. Color shading shows bathymetry.
Drift forecast services
Met.no maintains three drift models to support marine emergency response: 1.) an oil
spill fate model, 2.) a model for surface drifting objects, and 3.) a model for ship drift. Technically
speaking, there are strong similarities between the models as well as the services for which they
are used. Therefore, the models are implemented in such a way that they share a common user
interface and dependence on a common processor for geophysical forcing data. Furthermore,
all three models are based on a “particle” representation of the object or substance, so that the
main difference lies in the particular characteristics of the particles. Met.no has cooperated with
leading centers of expertise on oil weathering and drift characteristics for floating objects, in an
effort to attain state-of-the-art models.
Oil spill fate model (OD3D)
Met.no's oil spill model system OD3D calculates the drift and chemical evolution of
surface and sub-surface oil in the guise of a cloud of "superparticles", each of which represents
a certain amount of oil or its by-products. The model is three-dimensional and features a novel
deep source module for handling, for example, bottom blowouts. It has been developed in
cooperation with SINTEF Chemistry (Trondheim, Norway). At present, over 60 different oil types
are implemented in the weathering module. The model is started by a user request and returns
a prognosis in the form of a time series of characteristics for each superparticle. The OD3D is
driven by ocean data (3D currents, temperature and salinity), atmospheric data (surface winds)
and wave data (Stokes drift), which are obtained from a variety of real-time or archive sources,
steered by the forcing processor.
Drifting objects model (LEEWAY)
The LEEWAY model simulates the drift of floating objects, and is aimed particularly at
supporting search and rescue operations. The model has been developed in cooperation with
the U.S. Coast Guard, who have provided leeway (“windage”) characteristics for an extensive
taxonomy of object types. In order to give the operational user an estimate of the uncertainty of
the predictions, the drifting object is represented by a cloud of particles, where the initial
distribution of the cloud is determined by the uncertainty in the last known position (location and
time) of the lost object. Furthermore, each particle is subjected to random fluctuations in drift.
The cloud representation is very similar to the representation of oil in OD3D, and the geophysical
forcing data are applied in the same manner. For LEEWAY, only surface currents and winds are
Ship drift model
The model for ship drift is closely-related to the LEEWAY model, the main difference
being the size of the object with respect to the length of the dominant surface waves. For large
floating objects - “ships” - wave effects become important for the drift velocity. In analogy with
the leeway characteristics of small objects, the hull characteristics of a ship are required to
model the ship drift. Met.no has cooperated with Det norske Veritas (Høvik, Norway), who
provide hull characteristics and wave effect algorithms for the ship drift model. At present, the
ship drift model calculates a single drift trajectory, but the implementation of Monte Carlo
ensemble methods is under development. Geophysical forcing data are surface currents,
surface winds and wave spectra, which again are obtained through the forcing processor.
Forcing processor
Over the past few years, met.no has recognized the similarities between the three drift
ETMAES-I/Doc. 3.3(2), p. 4
models described above, all of which were developed over the years as autonomous computer
programs. An effort is underway to isolate the application-specific algorithms (oil weathering,
leeway and ship drift) and to let them share the same methods for accessing geophysical forcing
data. Development of a forcing processor has been an ongoing activity, supported by the
Mersea Integrated Project (EU DG Enterprise).
The aim of the forcing processor is to provide a variety of available forcing data sets from
met.no and external operational models. Weather and wave forecast data for regional and
global scales are taken from met.no and the ECMWF. Ocean forecast data are obtained from
several sources, including met.no (for national services) and Mersea providers (see Figure 2). A
default list of prioritized sources is maintained and checked for availability when a simulation is
requested. An additional facility will allow the user to select specific forcing data sets (e.g., in
order to assess the sensitivity to forcing). Climatological ocean data from Mersea will be a
component of the ocean forcing data, to be used as a fall-back in cases when operational
sources fail and for making rough forecasts beyond 10 days ahead.
Figure 2: Schematic of data sources for the ocean forcing data processor for emergency drift models at met.no.
Accessed data include 3D currents, temperature and salinity.
Mersea operational ocean data: Currently, two types of access are being tested: daily
delivery by ftp from MetOffice FOAM and NERSC TOPAZ, and on-demand access to the Mersea
forecast TEPs’ (Thematic Portal) OpenDAP servers (cf. Figure 2). The daily delivery method has
the advantage of being quickly accessible and allowing nested operational models at met.no.
The disadvantages are storage and fixed geographical coverage. The Mersea TEPs offer a
range of data from shelf to global scales with a fairly consistent method of access. The TEPs
can be queried to determine what data are available at any time, and the data fetch can be
limited to just what is needed. The main disadvantage of the TEP OpenDAP service is that the
data products placed there are not optimal for many oil spill applications (e.g., only daily means).
User interface
The user enters information in web order forms which are accessed from a common
webpage (see example for oil spill in Figure 3). The order is submitted to a met.no server where
it is checked for consistency and given a unique identification. A simulation is then set up and
run, usually completing within a few minutes. The user can monitor the progress of the
simulation and view setup and log files. The models output their results in standard forms that
may be filtered to user-specified formats. Results may be delivered to the user as email
attachments or as downloads from the webpage. In addition, results are stored in an internal
ETMAES-I/Doc. 3.3(2), p. 5
format for viewing with met.no's graphical display tool DIANA (see http://met.no/diana/). This
allows the duty meteorologists to immediately view results in combination with other
environmental information, in order to provide expert advice to the user. It also facilitates display
of the results in a web mapping service client operating on the same web site as the order form,
thus enabling users with a web browser alone (see Figure 4).
Figure 3: Screen shot of web page at met.no showing an order form for oil spill fate forecasts at right (grey panels).
Menu at upper left shows common portal for three drift models (oil, leeway, ship drift) along with access to simple
visualization via a web mapping service (WMS) client. Access to the web page is restricted to registered users.
Figure 4: Screen shot of web page at met.no showing simple presentation of oil spill fate simulation using a WMS