def EKE(ug, vg, grid, hboundary="extend", hfill_value=None):
"""Calculate EKE [m^2/s^2]
Inputs
------
ug: DataArray
Geostrophic or other xi component velocity [m/s]
vg: DataArray
Geostrophic or other eta component velocity [m/s]
grid: xgcm.grid
Grid object associated with ug, vg
hboundary: string, optional
Passed to `grid` method calls; horizontal boundary selection
for moving to rho grid.
From xgcm documentation:
A flag indicating how to handle boundaries:
* None: Do not apply any boundary conditions. Raise an error if
boundary conditions are required for the operation.
* 'fill': Set values outside the array boundary to fill_value
(i.e. a Neumann boundary condition.)
* 'extend': Set values outside the array to the nearest array
value. (i.e. a limited form of Dirichlet boundary condition.
hfill_value: float, optional
Passed to `grid` method calls; horizontal boundary selection
for moving to rho grid.
From xgcm documentation:
The value to use in the boundary condition with `boundary='fill'`.
Returns
-------
DataArray of eddy kinetic energy on rho grid.
Output is `[T,Y,X]`.
Notes
-----
EKE = 0.5*(ug^2 + vg^2)
Example usage
-------------
>>> ug, vg = xroms.uv_geostrophic(ds.zeta, ds.f, grid)
>>> xroms.EKE(ug, vg, grid)
"""
assert isinstance(ug, xr.DataArray), "ug must be DataArray"
assert isinstance(vg, xr.DataArray), "vg must be DataArray"
# make sure velocities are on rho grid
ug = xroms.to_rho(ug, grid, hboundary=hboundary, hfill_value=hfill_value)
vg = xroms.to_rho(vg, grid, hboundary=hboundary, hfill_value=hfill_value)
var = 0.5 * (ug**2 + vg**2)
var.attrs["name"] = "EKE"
var.attrs["long_name"] = "eddy kinetic energy"
var.attrs["units"] = "m^2/s^2"
var.attrs["grid"] = grid
var.name = var.attrs["name"]
return var
def speed(u, v, grid, hboundary="extend", hfill_value=None):
"""Calculate horizontal speed [m/s] from u and v components
Inputs
------
u: DataArray
xi component of velocity [m/s]
v: DataArray
eta component of velocity [m/s]
grid: xgcm.grid
Grid object associated with u, v
hboundary: string, optional
Passed to `grid` method calls; horizontal boundary selection
for moving to rho grid.
From xgcm documentation:
A flag indicating how to handle boundaries:
* None: Do not apply any boundary conditions. Raise an error if
boundary conditions are required for the operation.
* 'fill': Set values outside the array boundary to fill_value
(i.e. a Neumann boundary condition.)
* 'extend': Set values outside the array to the nearest array
value. (i.e. a limited form of Dirichlet boundary condition.
hfill_value: float, optional
Passed to `grid` method calls; horizontal boundary fill value
selection for moving to rho grid.
From xgcm documentation:
The value to use in the boundary condition with `boundary='fill'`.
Returns
-------
DataArray of speed calculated on rho/rho grids.
Output is `[T,Z,Y,X]`.
Notes
-----
speed = np.sqrt(u^2 + v^2)
Example usage
-------------
>>> xroms.speed(ds.u, ds.v, grid)
"""
assert isinstance(u, xr.DataArray), "var must be DataArray"
assert isinstance(v, xr.DataArray), "var must be DataArray"
u = xroms.to_rho(u, grid, hboundary=hboundary, hfill_value=hfill_value)
v = xroms.to_rho(v, grid, hboundary=hboundary, hfill_value=hfill_value)
var = np.sqrt(u**2 + v**2)
var.attrs["name"] = "speed"
var.attrs["long_name"] = "horizontal speed"
var.attrs["units"] = "m/s"
var.attrs["grid"] = grid
var.name = var.attrs["name"]
return var
def test_to_rho():
testvars = ["salt", "u", "v"]
for testvar in testvars:
var = xroms.to_rho(ds[testvar], grid)
# check for correct dims
assert "xi_rho" in var.dims
assert "eta_rho" in var.dims
def vertical_shear(dudz, dvdz, grid, hboundary="extend", hfill_value=None):
"""Calculate the vertical shear [1/s]
Inputs
------
dudz: DataArray
xi component of vertical shear [1/s]
dvdz: DataArray
eta compoenent of vertical shear [1/s]
grid: xgcm.grid
Grid object associated with dudz, dvdz
hboundary: string, optional
Passed to `grid` method calls; horizontal boundary selection
for moving dudz and dvdz to rho grid.
From xgcm documentation:
A flag indicating how to handle boundaries:
* None: Do not apply any boundary conditions. Raise an error if
boundary conditions are required for the operation.
* 'fill': Set values outside the array boundary to fill_value
(i.e. a Neumann boundary condition.)
* 'extend': Set values outside the array to the nearest array
value. (i.e. a limited form of Dirichlet boundary condition.
hfill_value: float, optional
Passed to `grid` method calls; horizontal boundary selection
for moving to rho grid.
From xgcm documentation:
The value to use in the boundary condition with `boundary='fill'`.
Returns
-------
DataArray of vertical shear on rho/w grids.
Notes
-----
vertical_shear = np.sqrt(u_z^2 + v_z^2)
Example usage
-------------
>>> xroms.vertical_shear(dudz, dvdz, grid)
"""
assert isinstance(dudz, xr.DataArray), "dudz must be DataArray"
assert isinstance(dvdz, xr.DataArray), "dvdz must be DataArray"
# make sure velocities are on rho grid
dudz = xroms.to_rho(dudz,
grid,
hboundary=hboundary,
hfill_value=hfill_value)
dvdz = xroms.to_rho(dvdz,
grid,
hboundary=hboundary,
hfill_value=hfill_value)
var = np.sqrt(dudz**2 + dvdz**2)
var.attrs["name"] = "shear"
var.attrs["long_name"] = "vertical shear"
var.attrs["units"] = "1/s"
var.attrs["grid"] = grid
var.name = var.attrs["name"]
return var