opendrift.models.openberg

This code is initiated from the following reference with posterior modifications.

Reference: Keghouche, I., F. Counillon, and L. Bertino (2010), Modeling dynamics and thermodynamics of icebergs in the Barents Sea from 1987 to 2005, J. Geophys. Res., 115, C12062, doi:10.1029/2010JC006165.

Attributes

logger
rho_water
rho_air
rho_ice
rho_iceb
g
omega
csi
wave_drag_coef

Classes

IcebergObj	Extending Lagrangian3DArray with relevant properties for an Iceberg
OpenBerg	Generic trajectory model class, to be extended (subclassed).

Functions

ocean_force(iceb_vel, water_vel, Ao, rho_water, ...)	Ocean force
wind_force(iceb_vel, wind_vel, Aa, wind_drag_coef)	Wind force
wave_radiation_force(rho_water, wave_height, ...)	Wave radiation force
advect_iceberg_no_acc(f, water_vel, wind_vel)	Advect iceberg without acceleration
sea_ice_force(iceb_vel, sea_ice_conc, Ai, sea_ice_vel, ...)	Sea ice force
coriolis_force(iceb_vel, mass, lat)	Coriolis force
sea_surface_slope_force(sea_slope_x, sea_slope_y, mass)	This functions assumes you provide the sea surface slope from an external file
melwav(iceb_length, iceb_width, x_wind, y_wind, sst, ...)	Update the iceberg's dimensions (length and width) due to wave erosion
mellat(iceb_length, iceb_width, tempib, salnib, dt)	Update the iceberg's dimensions (length and width) due to lateral melting
melbas(iceb_draft, iceb_sail, iceb_length, salnib, ...)	Update the iceberg's dimensions (draft and sail) due to forced convection

Module Contents

opendrift.models.openberg.logger

opendrift.models.openberg.rho_water = 1027

opendrift.models.openberg.rho_air = 1.293

opendrift.models.openberg.rho_ice = 917

opendrift.models.openberg.rho_iceb = 900

opendrift.models.openberg.g = 9.81

opendrift.models.openberg.omega = 7.2921e-05

opendrift.models.openberg.csi = 1

opendrift.models.openberg.wave_drag_coef = 0.3

class opendrift.models.openberg.IcebergObj(**kwargs)

Bases: opendrift.elements.LagrangianArray

Extending Lagrangian3DArray with relevant properties for an Iceberg

Initialises a LagrangianArray with given properties.

Args:

Keyword arguments (kwargs) with names corresponding to the OrderedDict ‘variables’ of the class, and corresponding values. The values must be ndarrays of equal length, or scalars. All (or none) variables must be given, unless a default value is specified in the OrderedDict ‘variables’ An empty object may be created by giving no input.

variables

opendrift.models.openberg.ocean_force(iceb_vel, water_vel, Ao, rho_water, water_drag_coef)

Ocean force Args:

iceb_vel : Iceberg’s velocity at time t water_vel : Ocean current velocity Ao : Iceberg’s area in contact with ocean (length x draft) rho_water : Water density water_drag_coef : Co is the drag coefficient applied on the iceberg’s draft

opendrift.models.openberg.wind_force(iceb_vel, wind_vel, Aa, wind_drag_coef)

Wind force Args:

iceb_vel : Iceberg’s velocity at time t wind_vel : Wind velocity Aa : Iceberg’s area in contact with wind (length x sail) wind_drag_coef : Ca is the drag coefficient applied on the iceberg’s sail

opendrift.models.openberg.wave_radiation_force(rho_water, wave_height, wave_direction, iceb_length)

Wave radiation force Args:

rho_water : Water density wave_height : Wave significant height wave_direction : Wave direction iceb_length : Iceberg’s length

opendrift.models.openberg.advect_iceberg_no_acc(f, water_vel, wind_vel)

Advect iceberg without acceleration Args:

f : Wind drift factor water_vel : Ocean current velocity wind_vel : Wind velocity

Returns:

Iceberg’s velocity without acceleration

opendrift.models.openberg.sea_ice_force(iceb_vel, sea_ice_conc, Ai, sea_ice_vel, sum_force)

Sea ice force Args:

iceb_vel : Iceberg velocity at time t sea_ice_conc : Sea ice concentration Ai : Iceberg’s area in contact with ice (sea_ice_thickness x length) # (Alternatively: Test half length and half width) sea_ice_vel : Sea ice velocity sum_force : Effect of all other forces exerted on the iceberg (apart from the sea ice force)

opendrift.models.openberg.coriolis_force(iceb_vel, mass, lat)

Coriolis force Args:

iceb_vel : Iceberg velocity at time t mass: Mass of the iceberg lat : Latitude of the iceberg’s location in degrees

opendrift.models.openberg.sea_surface_slope_force(sea_slope_x, sea_slope_y, mass)

This functions assumes you provide the sea surface slope from an external file

opendrift.models.openberg.melwav(iceb_length, iceb_width, x_wind, y_wind, sst, sea_ice_conc, dt)

Update the iceberg’s dimensions (length and width) due to wave erosion Args:

iceb_length : Iceberg’s length iceb_width : Iceberg’s width x_wind : Wind speed in the x-direction y_wind : Wind speed in the y-direction sst : Sea surface temperature sea_ice_conc : Sea ice concentration dt : Timestep of the simulation

opendrift.models.openberg.mellat(iceb_length, iceb_width, tempib, salnib, dt)

Update the iceberg’s dimensions (length and width) due to lateral melting Args:

iceb_length : Iceberg’s length iceb_width : Iceberg’s width tempib : Water temperature salnib : Water salinity dt : Timestep of the simulation

opendrift.models.openberg.melbas(iceb_draft, iceb_sail, iceb_length, salnib, tempib, x_water_vel, y_water_vel, x_iceb_vel, y_iceb_vel, dt)

Update the iceberg’s dimensions (draft and sail) due to forced convection

class opendrift.models.openberg.OpenBerg(*args, **kwargs)

Bases: opendrift.models.basemodel.OpenDriftSimulation

Generic trajectory model class, to be extended (subclassed).

This as an Abstract Base Class, meaning that only subclasses can be initiated and used. Any specific subclass (‘model’) must contain its own (or shared) specific type of particles (ElementType), whose properties are updated at each time_step using method update() on basis of model physics/chemistry/biology and ‘required_variables’ (environment) which are provided by one or more Reader objects.

Attributes:

ElementType: the type (class) of particles to be used by this model

elements: object of the class ElementType, storing the specific particle properties (ndarrays and scalars) of all active particles as named attributes. Elements are added by seeding-functions (presently only one implemented: seed_elements).

elements_deactivated: ElementType object containing particles which

have been deactivated (and removed from ‘elements’)

elements_scheduled: ElementType object containing particles which

have been scheduled, but not yet activated

required_variables: list of strings of CF standard_names which is

needed by this model (update function) to update properties of particles (‘elements’) at each time_step. This core class has no required_elements, this is implemented by subclasses/modules.

environment: recarray storing environment variables (wind, waves,

current etc) as named attributes. Attribute names follow standard_name from CF-convention, allowing any OpenDriftSimulation module/subclass using environment data from any readers which can provide the requested variables. Used in method ‘update’ to update properties of elements every time_step.

time_step: timedelta object, time interval at which element properties

are updated (including advection).

time_step_output: timedelta object, time interval at which element

properties are stored in memory and eventually written to file

readers: Dictionary where values are Reader objects, and names are

unique reference keywords used to access a given reader (typically filename or URL)

priority_list: OrderedDict where names are variable names,

and values are lists of names (kewywords) of the reader, in the order of priority (user defined) of which the readers shall be called to retrieve environmental data.

Initialise OpenDriftSimulation

Args:

seed: integer or None. A given integer will yield identical

random numbers drawn each simulation. Random numbers are e.g. used to distribute particles spatially when seeding, and may be used by modules (subclasses) for e.g. diffusion. Specifying a fixed value (default: 0) is useful for sensitivity tests. With seed = None, different random numbers will be drawn for subsequent runs, even with identical configuration/input.

iomodule: name of module used to export data

default: netcdf, see opendrift.io for more alternatives. iomodule is module/filename without preceeding io_

loglevel: set to 0 (default) to retrieve all debug information.

Provide a higher value (e.g. 20) to receive less output.

logtime: if True, a time stamp is given for each logging line.

logtime can also be given as a python time specifier (e.g. ‘%H:%M:%S’)

logfile:

None (default) to send output to console. A string to send output to logfile. Or to get output to both terminal and file:

[<filename.log>, logging.StreamHandler(sys.stdout)]

ElementType

Any trajectory model implementation must define an ElementType.

required_variables

Any trajectory model implementation must list needed variables.

get_profile_masked(variable)

Apply a mask to extract data from the surface down to the iceberg’s draft.

get_basal_env(variable)

Get the basal layer of the variable for the icebergs

advect_iceberg()

melt()

Enable melting

roll_over()

Iceberg’s stability criterium

update()

Update positions and properties of particles