Mohid Ocean Downscalling
From MohidWiki
Contents
Download
MyOcean
To download my ocean solution go to http://www.myocean.eu/. and click in ACCES THE CATALOGUE. In block 1 choose "Global Ocean", in 2 the parameters and in 3 choose forecast products. After fill all the blocks click search and in the next web page choose DATA ACCES and then GO. Prescribe the user name and password and then choose the dates and area of interest.
NOOA : GFS, RTOFS
Conversion
grib-netcdf-hdf5
Bathymetry transition
Running tool SmoothBathymNesting.exe
Example of the input file SmoothBathymNesting.dat
! File bathymetry of the external 3D solution FATHER_BATIM : !Bathymetry File of MOHID solution SON_BATIM : !New Bathymetry File NEW_SON_BATIM : <begin_coef> NAME : generic property !Name of generic property INITIALIZATION_METHOD : sponge !Type of initialization used DEFAULTVALUE : 1 !0-external 3D solution, 1-MOHID solution SPONGE_OUT : 0 SPONGE_CELLS : 10 !sponge cells number SPONGE_EVOLUTION : 2 !1-exponential, 2-linear <end_coef>
Interpolation
z-level to MOHID geo
bilinear vs triangulation
linear horizontally and vertically
Boundary conditions
Open boundary
high frequency vs low frequency = mohid 2D + 3D external solution
radiation + flow relaxation scheme
Surface
To impose surface boundary conditions (e.g., wind stress, solar radiation, temperature, pressure etc.) in atmosphere module an example of the file is provided below.
OUTPUT_TIME : 0. 3600.
<begin_rugosity> INITIALIZATION_METHOD : CONSTANT DEFAULTVALUE : 0.0025 <end_rugosity>
<beginproperty> NAME : wind velocity X UNITS : m/s DESCRIPTION : wind velocity X interpolated from GFS model field DEFAULTVALUE : 0. FILE_IN_TIME : HDF FILENAME : ..\..\..\GeneralData\GFS\Abril2013\Level2_10-04-2013_25-04-2013.hdf5 TIME_SERIE : 0 OUTPUT_HDF : 1 <endproperty>
<beginproperty> NAME : wind velocity Y UNITS : m/s DESCRIPTION : wind velocity Y interpolated from GFS model field DEFAULTVALUE : 0. FILE_IN_TIME : HDF FILENAME : ..\..\..\GeneralData\GFS\Abril2013\Level2_10-04-2013_25-04-2013.hdf5 OUTPUT_HDF : 1 <endproperty>
<beginproperty> NAME : air temperature UNITS : ºC DESCRIPTION : Temperature interpolated from GFS model field DEFAULTVALUE : 15. FILE_IN_TIME : HDF FILENAME : ..\..\..\GeneralData\GFS\Abril2013\Level2_10-04-2013_25-04-2013.hdf5 TIME_SERIE : 0 OUTPUT_HDF : 1 <endproperty>
<beginproperty> NAME : solar radiation UNITS : W/m^2 DESCRIPTION : Solar radiation interpolated from GFS model field DEFAULTVALUE : 0.0 FILE_IN_TIME : HDF FILENAME : ..\..\..\GeneralData\GFS\Abril2013\Level2_10-04-2013_25-04-2013.hdf5 TIME_SERIE : 0 REMAIN_CONSTANT : 0 OUTPUT_HDF : 1 <endproperty>
<beginproperty> NAME : atmospheric pressure UNITS : Pa DESCRIPTION : Atmospheric pressure interpolated from GFS model field DEFAULTVALUE : 0. FILE_IN_TIME : HDF FILENAME : ..\..\..\GeneralData\GFS\Abril2013\Level2_10-04-2013_25-04-2013.hdf5 OUTPUT_HDF : 0 <endproperty>
<beginproperty> NAME : relative humidity UNITS : fraction DESCRIPTION : Constant value DEFAULTVALUE : 0.55 TIME_SERIE : 0 OUTPUT_HDF : 1 <endproperty>
<beginproperty> NAME : cloud cover UNITS : % DESCRIPTION : Constant value DEFAULTVALUE : 50. TIME_SERIE : 0 OUTPUT_HDF : 1 <endproperty>
Sensible/latent heat is computed in Module InterfaceWaterAir based in the atmospheric parameters (e.g.,wind stress, solar radiation, temperature, pressure etc.) prescribed in the atmosphere module. An example of the file is provided below.
OUTPUT_TIME : 0. 3600.
<begin_rugosity> INITIALIZATION_METHOD : CONSTANT DEFAULTVALUE : 0.0025 REMAIN_CONSTANT : 0 <end_rugosity>
<beginproperty> NAME : wind shear velocity UNITS : m/s DESCRIPTION : Computed wind shear velocity FILE_IN_TIME : NONE REMAIN_CONSTANT : 0 DEFAULTVALUE : 0. TIME_SERIE : 0 OUTPUT_HDF : 0 <endproperty>
<beginproperty> NAME : wind stress X UNITS : N/m2 DESCRIPTION : Computed wind stress X FILE_IN_TIME : NONE REMAIN_CONSTANT : 0 TIME_SERIE : 0 DEFAULTVALUE : 0. DEFINE_CDWIND : 0 OUTPUT_HDF : 0 <endproperty>
<beginproperty> NAME : wind stress Y UNITS : N/m2 DESCRIPTION : Computed wind stress Y FILE_IN_TIME : NONE REMAIN_CONSTANT : 0 TIME_SERIE : 0 DEFAULTVALUE : 0. DEFINE_CDWIND : 0 OUTPUT_HDF : 0 <endproperty>
<beginproperty> NAME : latent heat UNITS : W/m^2 DESCRIPTION : Computed latent heat FILE_IN_TIME : NONE REMAIN_CONSTANT : 0 DEFAULTVALUE : 0. TIME_SERIE : 0 OUTPUT_HDF : 0 <endproperty>
<beginproperty> NAME : sensible heat UNITS : W/m^2 DESCRIPTION : Computed sensible heat FILE_IN_TIME : NONE REMAIN_CONSTANT : 0 DEFAULTVALUE : 0. TIME_SERIE : 0 OUTPUT_HDF : 0 <endproperty>
<beginproperty> NAME : surface radiation UNITS : W/m^2 DESCRIPTION : Computed infrared radiation ALBEDO : 0.05 FILE_IN_TIME : NONE REMAIN_CONSTANT : 0 DEFAULTVALUE : 0. TIME_SERIE : 0 OUTPUT_HDF : 0 <endproperty>
<beginproperty> NAME : net long wave radiation UNITS : W/m^2 DESCRIPTION : Computed net long wave radiation FILE_IN_TIME : NONE REMAIN_CONSTANT : 0 DEFAULTVALUE : 0. TIME_SERIE : 0 OUTPUT_HDF : 0 <endproperty>
<beginproperty> NAME : downward long wave radiation UNITS : W/m^2 DESCRIPTION : Computed downward long wave radiation FILE_IN_TIME : NONE REMAIN_CONSTANT : 0 DEFAULTVALUE : 0. TIME_SERIE : 0 OUTPUT_HDF : 0 <endproperty>
<beginproperty> NAME : downward long wave radiation UNITS : W/m^2 DESCRIPTION : Computed downward long wave radiation FILE_IN_TIME : NONE REMAIN_CONSTANT : 0 DEFAULTVALUE : 0. TIME_SERIE : 0 OUTPUT_HDF : 0 <endproperty>
<beginproperty> NAME : upward long wave radiation UNITS : W/m^2 DESCRIPTION : Computed upward long wave radiation FILE_IN_TIME : NONE REMAIN_CONSTANT : 0 DEFAULTVALUE : 0. TIME_SERIE : 0 OUTPUT_HDF : 0 <endproperty>
<beginproperty> NAME : non solar flux UNITS : W/m^2 DESCRIPTION : Computed infrared radiation FILE_IN_TIME : NONE REMAIN_CONSTANT : 0 DEFAULTVALUE : 0. TIME_SERIE : 0 OUTPUT_HDF : 0 <endproperty>
Iinital condition and Spin up
For the spin-up procedure, a methodology based on a slow connection of the forcing terms (baroclinic force, windstress) is used. This methodology consists of defining an initial condition where the initial fields of salinity and temperature are interpolated from the external 3D solution (MyOcean or RTOFS), a null velocity field is assumed, and a SSH field with null gradient is also considered. A coefficient that varies linearly between 0 and 1 along the “connection” period of 5 days is multiplied by the baroclinic force and wind stress. Because the forces are slowly connected, the velocity reference solution of the OBC also needs to be slowly connected. The nudging term in the momentum equation is multiplied by a coefficient C given by:
In this way, the velocity field near the boundary also converges slowly to the reference solution. To minimize the perturbations suffered by the initial condition of salinity and temperature along the spin-up period, a relaxation period variable in time was also assumed for these properties. The idea is to assume a relaxation period that increases with time; this way, in the beginning of the run the temperature and salinity fields have a stronger nudging when the external and internal activity is more intense due to the spin-up process. In the end of the spin-up period, the nudging in the model interior (out of the FRS area) is null. For the forces, a connection coefficient was assumed with a linear evolution over 5 days. For the reference solution a quadratic evolution was imposed. For the slow connection of the forcing mechanisms, the methodology followed by Mellor (2004) for the baroclinic force was assumed. This evolution allows, in the first instants, a strong nudging across the entire domain. With time, the model tends to be free except in the flow relaxation scheme area.
Slow connection of tide, wind, pressure an baroclinic force in the hydrodynamic file:
SLOWSTART : 86400 TIDE : 1 TIDEPOTENTIAL : 1
RAMP : 1 RAMP_PERIOD : 259200
WIND : 2 WIND_SMOOTH_PERIOD : 259200
ATM_PRESSURE : 1 ATM_PERIOD : 259200
FLATHER_COLD_PERIOD : 432000
Slow connection of wind, tide, atmospheric pressure and baroclinc force
initial condition : salinity and temperature from external solutions, null sea level gradient and null velocities
initial strong relaxation of temperature and salinity in all domain
