North Sea - Baltic Sea ocean model
HBM
Dansk version

DMI operates a regional 3D ocean model HBM for the North Sea - Baltic, in order to provide information about the physical state of the Danish and nearby waters in the near future. The Figure to the right shows the model domain for the 3D grid. The parameter shown is the water depth.

Model code
The HBM code was developed in the early 1990'ies at Bundesamt für Seeschifffahrt und Hydrographie (BSH) in Hamburg, Germany. At the time the model was known as BSHcmod. It has undergone extensive revision in the DMI implementation, in co-operation between DMI, BSH, and other Baltic institutes. Basically the same code is used in the Baltic HIROMB co-operation.

Input
Three types of input is applied: surface fields, point sources, and open boundary conditions. Heat flux through the sea bed is parameterized. HBM is forced by DMI's numerical weather prediction model DMI-HIRLAM. The following parameters are used:
  • 10 metre wind speed and direction
  • mean sea level atmospheric pressure
  • surface (2 metre) air temperature
  • surface air (2 metre) humidity
  • cloud cover
HBM calculates surface energy fluxes (mechanical, radiative, thermodynamic) using bulk parameterisation formulae.
Point source data are
  • freshwater fluxes from 846 rivers and diffusive coastal sources
  • nutrient from the same rivers (optional)
Open boundary data are:
  • tidal sea surface elevation
  • monthly climatological hydrography

Data-assimilation
HBM optionally assimilates one or more types of observered or modelled data:
  • sea surface temperature from satellite
  • vertical profiles of hydrography
  • daily open boundary hydrography data
This facility has not been put in operational use as of yet.

Schedule
HBM runs every 6 hours, i.e. 4x/day. A run produces a 5 day forecast of the 3-dimensionelle state of the ocean.

Output
HBM calculates
  • sea level
  • water temperature
  • salinity
  • ocean currents
  • ice thickness and concentration
at 15 min.intervals. Temperature, salt and current is calculated for the entire water column, top to bottom, at ~ 50 fixed depth levels. Sea level at selected, coastal points is calculated in 10 minute time resolution.

Output parameter table.

Model set-up
The HBM model set-up consists of 5 model domains:
  • NOAMOD - 2-dimensional mesocale model, that calculates sea level as a function of wind speed and air pressure. Generates boundary data (external surge) for the regional 3-dimensionan model
  • North Sea - Baltic Sea - 3-dimensional regional model with subdomains
  • Transition Area - high resolution model of the waters south of Skagen and west of Bornholm
  • Wadden Sea - high resolution model of the Germasn Bight
  • Limfjord - high resolution fjord (appended) model

Model NOAMOD HBM
North Sea - Baltic Sea
HBM
Transition Area
HBM
Wadden Sea
HBM
Limfjord
Spatial resolution 6' lat 10' lon
(6 n.m.)
3' lat 5' lon
(3 n.m.)
30" lat 50" lon
(0.5 n.m.)
1' lat 1'24" lon
(1 n.m.)
12" lat 20" lon
(0.2 n.m.)
Vertical layers 1 50 52 24 9
Max. top layers thickness 900m 8m 2m 8m 2m
Time step:
Barotropic
Baroclinic:
Ice

15s
-
-

30s
90s
900s

15s
90s
900s

30s
90s
900s

10s
20s
900s
Atm. forcing ECMWF GLM Hirlam SKA
ECMWF GLM
Hirlam SKA
ECMWF GLM
Hirlam SKA
ECMWF GLM
Hirlam SKA
ECMWF GLM
Area: longitude 21W-13E 4W-30E 9E-15E 6E-10E 8E-10E
Area: latitude 48N-66N Baltic Sea: 48N-66N
North Sea: 48N-59N
53N-57½N 53N-56N 57N-58N
Open boundaries Radiation condition
  • Surge contribution from NOAMOD
  • tidal wave (17 constituents)
  • monthly climatology fields for T and S via a sponge layer
nested in regional model nested in regional model boundary data from regional and transition area model

Vibeke Huess & Jacob Woge Nielsen - Sept. 14th 2017