gnome.environment.waves

The waves environment object.

Computes the wave height and percent wave breaking

Uses the same approach as ADIOS 2

(code ported from old MATLAB prototype code)

Module Contents

Classes

Waves

class to compute the wave height for a time series

Attributes

g

gnome.environment.waves.g
class gnome.environment.waves.Waves(wind=None, water=None, **kwargs)

Bases: gnome.environment.environment.Environment

class to compute the wave height for a time series

At the moment, it only does a single point, non spatially variable, but may be extended in the future

wind and water must be set before running the model; however, these can be set after object construction

Parameters:

  • wind (A Wind type, or equivelent) – A wind object to get the wind speed. This should be a moving average wind object.

  • water (environment.Water object.) – water properties, specifically fetch and wave height

Note

must take **kwargs since base class supports more inputs like ‘name’. The new_from_dict() alternate constructor will invoke __init__ will arguments that supported by baseclass

property data_start

The Waves object doesn’t directly manage a time series of data, so it will not have a data range itself. But it depends upon a Wind and a Water object. The Water won’t have a data range either, but the Wind will. So its data range will be that of the Wind it is associated with.

property data_stop
_ref_as = 'waves'
_req_refs = ['wind', 'water']
_schema
validate()

All pygnome objects should be able to validate themselves. Many py_gnome objects reference other objects like wind, water, waves. These may not be defined when object is created so they can be None at construction time; however, they should reference valid objects when running in the model. If make_default_refs is True, then object is valid because the model will set these up at runtime. To raise an exception for missing references at runtime, directly call validate_refs(level=’error’)

‘wind’, ‘water’, ‘waves’ attributes also have special meaning. An object containing this attribute references the corresponding object.

Logs warnings:

Returns:

a tuple of length two containing: (a list of messages that were logged, isvalid bool) If any references are missing and make_default_refs is False, object is not valid

get_value(points, time)

return the rms wave height, peak period and percent wave breaking at a given time. Does not currently support location-variable waves.

Parameters:

time (datetime.datetime object) – the time you want the wave data for

Returns:

wave_height, peak_period, whitecap_fraction, dissipation_energy

Units:

wave_height: meters (RMS height) peak_period: seconds whitecap_fraction: unit-less fraction dissipation_energy: not sure!! # fixme!

get_wind_speed(points, model_time, coord_sys='r', fill_value=1.0)

Wrapper for the weatherers so they can extrapolate

get_emulsification_wind(points, time)

Return the right wind for the wave climate

If a wave height was specified, then you need the greater of the real or pseudo wind.

If not, then you need the actual wind.

The idea here is that if there is a low wind, but the user specified waves, we really want emulsification that makes sense for the waves. But if the actual wind is stronger than that for the wave height give, we should use the actual wind.

fixme: I’m not sure this is right – if we stick with the wave energy

given by the user for dispersion, why not for emulsification?

compute_H(U)
pseudo_wind(H)
whitecap_fraction(U)
mean_wave_period(U)
peak_wave_period(points, time)
Parameters:

time (datetime.datetime object) – the time you want the wave data for

Returns:

peak wave period (s)

dissipative_wave_energy(H)
energy_dissipation_rate(H, U)

c_ub = 100 = dimensionless empirical coefficient to correct for non-Law-of-the-Wall results (Umlauf and Burchard, 2003)

u_c = water friction velocity (m/s) sqrt(rho_air / rho_w) * u_a ~ .03 * u_a u_a = air friction velocity (m/s) z_0 = surface roughness (m) (Taylor and Yelland) c_p = peak wave speed for Pierson-Moskowitz spectrum w_p = peak angular frequency for Pierson-Moskowitz spectrum (1/s)

TODO: This implementation should be in a utility function. It should not be part of the Waves management object itself.