def SWdensityFromCTD(SA, t, p, potential=False):
"""Calculate seawater density at CTD depth
Args
----
SA: ndarray
Absolute salinity, g/kg
t: ndarray
In-situ temperature (ITS-90), degrees C
p: ndarray
Sea pressure (absolute pressure minus 10.1325 dbar), dbar
Returns
-------
rho: ndarray
Seawater density, in-situ or potential, kg/m^3
"""
import numpy
import gsw
CT = gsw.CT_from_t(SA, t, p)
# Calculate potential density (0 bar) instead of in-situ
if potential:
p = numpy.zeros(len(SA))
return gsw.rho(SA, CT, p)
def compute_mass_adjustment(self, f, w=None, **kwargs):
"""
\delta_m = V \delta \rho_w + \rho_w \delta V
"""
if w is not None:
z = -self.pressure
water_temperature = w.get_temp(z)
water_salinity = w.get_s(z)
lon, lat = w.lon, w.lat
else:
water_temperature = kwargs['temperature']
water_salinity = kwargs['salinity']
lon, lat = kwargs['lon'], kwargs['lat']
SA = gsw.SA_from_SP(water_salinity, self.pressure, lon, lat)
CT = gsw.CT_from_t(SA, water_temperature, self.pressure)
rho_water = gsw.density.rho(SA, CT, self.pressure) # new in situ density
for name, b in self._d.items():
delta_rho_water = rho_water - b['rho_water']
#
f.m = b['mass_in_air']*1e-3 # need to convert to kg
f.piston.update_d(b['piston_displacement']*1e-2) # need to convert to m
f.piston_update_vol()
f.V = b['V'] - f.v
V = f.volume(p=self.pressure, temp=water_temperature)
delta_V = V - b['V']
#
delta_m = V * delta_rho_water + rho_water * delta_V
print('According to balast %s, you need add %.1f g'
%(name, delta_m*1e3))
def calculate_n2(T, p, C, lat, long):
"""Calculates the buoyancy frequency N^2
All parameters and output are float or array-like.
:param T: temperature (deg C)
:param p: pressure (bar)
:param C: conductivity (S/m)
:param lat: latitude (decimal deg)
:param long: longitude (decimal deg)
:return: buoyancy (i.e. brunt-vaisala) frequency N^2 (s^-2)
"""
# pressure in dbars = pressure * 10
p_dbar = p * 10
# conductivity in mS/cm = conductivity * 10
C_mScm = C * 10
print(T.count())
print(p.count())
print(C.count())
print(lat.count())
print(long.count())
# calculate SP from conductivity (mS/cm), in-situ temperature (deg C), and gauge pressure (dbar)
SP = gsw.SP_from_C(C_mScm, T, p_dbar)
# calculate SA from SP (unitless), gauge pressure (dbar), longitude and latitude (decimal degrees)
SA = gsw.SA_from_SP(SP, p_dbar, long, lat)
# calculate CT from SA (g/kg), in-situ temperature (deg C), and gauge pressure (dbar)
CT = gsw.CT_from_t(SA, T, p_dbar)
# calculate N^2
nsquared, p_mid = gsw.Nsquared(SA, CT, p_dbar, lat=lat)
return nsquared
def o2pl2pkg(p_col, t_col, sal_col, dopl_col, dopkg_col, lat_col, lon_col,
inMat):
"""o2pl2pkg convert ml/l dissolved oxygen to umol/kg
Input:
- t_col, temperature column header deg c.
- sal_col, salinity column header psu.
- dopl_col, dissolved column header ml/l.
- dopkg_col, dissolved column header umol/kg
- lat_col, latitude for entire cast deg.
- lon_col, longitude for entire cast deg.
- inMat, dtype ndarray processed ctd time data.
Output:
- Converted Oxygen column umol/kg
Example:
>>> # linear interpolation of NaNs
>>> outArray = o2pl2kg(inArr)
"""
pkg = np.ndarray(shape=len(inMat), dtype=[(dopkg_col, np.float)])
# Absolute sailinity from Practical salinity.
SA = gsw.SA_from_SP(inMat[sal_col], inMat[p_col], inMat[lat_col],
inMat[lon_col])
# Conservative temperature from insitu temperature.
CT = gsw.CT_from_t(SA, inMat[t_col], inMat[p_col])
s0 = gsw.sigma0(
SA, CT
) # Potential density from Absolute Salinity g/Kg Conservative temperature deg C.
# Convert DO ml/l to umol/kg
for i in range(0, len(inMat[dopl_col])):
pkg[i] = inMat[dopl_col][i] * 44660 / (s0[i] + 1000)
return pkg
def compute_alpha_beta(data, temperature_var='SST', salinity_var='SSS'):
p = 0 * data['lon']
SA = gsw.SA_from_SP(data[salinity_var], p, data['lon'], data['lat'])
CT = gsw.CT_from_t(SA, data[temperature_var], p)
rho, alpha, beta = gsw.rho_alpha_beta(SA, CT, p)
return data.assign(alpha=xr.DataArray(alpha, dims='time'),
beta=xr.DataArray(beta, dims='time'))
def add_density(netCDFfile):
# loads the netcdf file
ds = Dataset(netCDFfile, 'a')
if 'DENSITY' in list(ds.variables):
ds.close()
return "file already contains density"
# extracts the variables from the netcdf
var_temp = ds.variables["TEMP"]
var_psal = ds.variables["PSAL"]
var_pres = ds.variables["PRES"]
var_lon = ds.variables["LONGITUDE"]
var_lat = ds.variables["LATITUDE"]
# extracts the data from the variables
t = var_temp[:]
psal = var_psal[:]
p = var_pres[:]
lon = var_lon[:]
lat = var_lat[:]
# calculates absolute salinity
SA = gsw.SA_from_SP(psal, p, lon, lat)
# calculates conservative temperature
CT = gsw.CT_from_t(SA, t, p)
# calculates density
density = gsw.rho(SA, CT, p)
# generates a new variable 'DENSITY' in the netcdf
ncVarOut = ds.createVariable(
"DENSITY", "f4", ("TIME", ), fill_value=np.nan,
zlib=True) # fill_value=nan otherwise defaults to max
# assigns the calculated densities to the DENSITY variable, sets the units as kg/m^3, and comments on the variable's origin
ncVarOut[:] = density
ncVarOut.units = "kg/m^3"
ncVarOut.long_name = "sea_water_density"
ncVarOut.standard_name = "sea_water_density"
ncVarOut.valid_max = np.float32(
1100
) # https://oceanobservatories.org/wp-content/uploads/2015/09/1341-10004_Data_Product_SPEC_GLBLRNG_OOI.pdf
ncVarOut.valid_min = np.float32(1000)
ncVarOut.comment = "calculated using gsw-python https://teos-10.github.io/GSW-Python/index.html"
# update the history attribute
try:
hist = ds.history + "\n"
except AttributeError:
hist = ""
ds.setncattr(
'history', hist + datetime.utcnow().strftime("%Y-%m-%d") +
" : added DENSITY from TEMP, PSAL, PRES, LAT, LON")
ds.close()
def derive_variables(dbase, which_ones='all'):
"""
Also include density, potential temp and density; and uncertainties!!
"""
SA_dat = [
gsw.SA_from_SP(dbase['sal'][n], dbase['pres'][n], dbase['lon'][n],
dbase['lat'][n]) for n in range(0, len(dbase))
]
CT_dat = [
gsw.CT_from_t(SA_dat[n], dbase['temp'][n], dbase['pres'][n])
for n in range(0, len(dbase))
]
N2_dat = [
gsw.Nsquared(
SA_dat[n],
CT_dat[n],
dbase['pres'][n],
dbase['lat'][n],
alphabeta=True,
) for n in range(0, len(dbase))
]
if which_ones == 'all':
return SA_dat, CT_dat, N2_dat
elif which_ones == 'N2':
return N2_dat
def rho(SP, t, p, lon=-45.401666, lat=-23.817233):
"""
Calculates in situ density from practical salinity, in situ
temperature and pressure (depth).
Parameters
----------
SP : array like
Salinity (PSS-78) [1e-3]
t : array like
Temperature (ITS-90) [degC]
p : array like
Pressure [dbar]
lon : array like, float, optional
Longitude, decimal degrees east
lat : array like, float, optional
Latitude, decimal degrees north
Returns
-------
rho : array like
In situ density [kg m-3]
"""
# Calculates Absolute Salinity from Practical Salinity
SA = gsw.SA_from_SP(SP, p, lon, lat)
# Calcualtes Conservative Temperature from in situ temperature
CT = gsw.CT_from_t(SA, t, p)
# Calculates and returns density
return gsw.rho(SA, CT, p)
def water_properties(sp, t, p, lon=0.0, lat=0.0):
"""
Calculates seawater density and sound speed using the TEOS-10 equations.
Uses the gsw toolbox, which is an implementation of the TEOS-10 equations.
Args:
:sp: Practical salinity [PSU]
:t: Temperature [degC]
:p: Pressure [dbar]
:lon: Longitude (optional - use named parameters) [decimal degrees]
:lat: Latitude (optional - use named parameters) [decimal degrees]
Returns:
:c: speed of sound in water [m/s]
:rho: density of water [kg/m^3]
Notes:
The accuracy of sound speed and density that we need is such that it
doesn't matter what latitude and longitude is used.
"""
sa = gsw.SA_from_SP(sp, p, lon, lat)
ct = gsw.CT_from_t(sa, t, p)
c = gsw.sound_speed(sa, ct, p)
rho = gsw.rho(sa, ct, p)
return c, rho
def get_hydro(my_file):
f = Dataset(my_file, mode='r')
eps = f.variables['EPSILON'][:]
eps = remove_bad_eps(eps)
lat = f.variables['LATITUDE'][:]
lon = f.variables['LONGITUDE'][:]
p = f.variables['PRESSURE'][:]
SP = f.variables['PSAL'][:]
T = f.variables['TEMPERATURE'][:]
z = gsw.z_from_p(p, lat) # m
SA = gsw.SA_from_SP(SP, p, lon, lat) # g/kg, absolute salinity
CT = gsw.CT_from_t(SA, T, p) # C, conservative temperature
SA = remove_bad_SA(SA)
CT = remove_bad_CT(CT)
[N2_mid, p_mid] = gsw.Nsquared(SA, CT, p, lat)
z_mid = gsw.z_from_p(p_mid, lat)
N2 = interp_to_edges(N2_mid, z, z_mid, 4)
N2 = np.append(np.append(N2, [np.nan]), [np.nan])
N2 = remove_bad_N2(N2)
return N2, SA, CT, eps, z
def _update_eos(self):
assert hasattr(self, 'd_depth'), \
'You need to run clean_and_depth_bin first'
d = self.d_depth
d['SA'] = gsw.SA_from_SP(d.salinity, d.index, d.longitude, d.latitude)
d['CT'] = gsw.CT_from_t(d.SA, d.temperature, d.index)
d['sound_speed'] = gsw.sound_speed(d.SA, d.CT, d.index)
def __init__(self, lon, lat, name=None):
self._woa=True
#
self._tfile = 'woa13_decav_t00_01v2.nc'
nc = Dataset(self._tfile,'r')
#
glon = nc.variables['lon'][:]
glat = nc.variables['lat'][:]
ilon = np.argmin(np.abs(lon-glon))
ilat = np.argmin(np.abs(lat-glat))
self.lon = glon[ilon]
self.lat = glat[ilat]
#
self.z = -nc.variables['depth'][:]
self.p = gsw.p_from_z(self.z,self.lat)
#
self.temp = nc.variables['t_an'][0,:,ilat,ilon]
nc.close()
#
self._sfile = 'woa13_decav_s00_01v2.nc'
nc = Dataset(self._sfile,'r')
self.s = nc.variables['s_an'][0,:,ilat,ilon]
nc.close()
# derive absolute salinity and conservative temperature
self.SA = gsw.SA_from_SP(self.s, self.p, self.lon, self.lat)
self.CT = gsw.CT_from_t(self.SA, self.temp, self.p)
# isopycnal displacement
self.eta=0.
#
if name is None:
self.name = 'WOA water profile at lon=%.0f, lat=%.0f'%(self.lon,self.lat)
def sound_speed_teos10(lats, lons, z, t, SP):
""" Compute sound speed from temperature, salinity, and depth
for a given latitude and longitude using the Thermodynamic
Equation of Seawater 2010.
https://teos-10.github.io/GSW-Python/
Args:
lats: numpy array
Latitudes (-90 to 90 degrees)
lons: numpy array
Longitudes (-180 to 180 degrees)
z: numpy array
Depths (meters)
t: numpy array
In-situ temperature (Celsius)
SP: numpy array
Practical Salinity (psu)
Returns:
c: numpy array
Sound speed (m/s)
"""
p = gsw.p_from_z(z=-z, lat=lats) # sea pressure (gsw uses negative z below sea surface)
SA = gsw.SA_from_SP(SP, p, lons, lats) # absolute salinity
CT = gsw.CT_from_t(SA, t, p) # conservative temperature
c = gsw.density.sound_speed(SA=SA, CT=CT, p=p)
return c
def _load_from_pts(self, pressure, temperature, salinity, lon, lat, name):
self._pts = True
#
if all([
isinstance(i, float)
for i in [pressure, temperature, salinity, lon, lat]
]):
#pressure = np.array([-1, 1e4])
#temperature = np.array([temperature, temperature])
#salinity = np.array([salinity, salinity])
#lon = np.array([lon,lon])
#lat = np.array([lat,lat])
pressure = [-1, 1e4]
temperature = [temperature, temperature]
salinity = [salinity, salinity]
lon = [lon, lon]
lat = [lat, lat]
#
self.lon, self.lat = lon, lat
#
self.p = pressure
self.z = gsw.z_from_p(self.p, self.lat)
#
self.temp, self.s = temperature, salinity
# derive absolute salinity and conservative temperature
self.SA = gsw.SA_from_SP(self.s, self.p, self.lon, self.lat)
self.CT = gsw.CT_from_t(self.SA, self.temp, self.p)
# isopycnal displacement and velocity
self.eta = 0.
self.detadt = 0.
#
if name is None:
self.name = 'Provided water profile at lon=%.0f, lat=%.0f' % (
self.lon, self.lat)
def aaoptode_sternvolmer(foil_coef, optode_phase, tempc, salin, press):
# %%%%%%%%%%%%%%%%%%%%%%%%%%%%
# %% AAOPTODE_STERNVOLMER: For Aanderaa optode 4XXX series, to interpret
# % calphase measurements based on the Stern Volmer equation. To be used in
# % combination with aaoptode_salpresscorr, which handles salinity and
# % pressure corrections.
#
# %% INPUTS
# % foil_coef: Struct of calibration coefficients
# % optode_phase: vector of optode phase measurements (calphase or dphase)
# % tempc: temperature in deg C
# % salin: Salinity
# % press: pressure (db) for pressure correction
#
# %% OUTPUTS
# % optode_uM: Oxygen concentration in uM
# % optode_umolkg: Oxygen concentration in umol/kg
# %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
# % H. Palevsky, 8/6/2019, based on sg_aaoptode.m
# % Uchida et al. 2008 Stern-Volmer based calbration mode
C = foil_coef;
Ksv = C[0] + C[1]*tempc+C[2]*tempc**2;
P0 = C[3] + C[4]*tempc;
PC = C[5] + C[6]*optode_phase;
optode_uM = ((P0/PC)-1)/Ksv;
# % note - this uses SR, reference salinity
SA = 35.16504/35*salin;
CT = gsw.CT_from_t(SA,tempc,press);
optode_umolkg = 1000*optode_uM/(1000+ gsw.sigma0(SA,CT));
return optode_uM, optode_umolkg
def common_thermodynamics(depth, lon, lat, SP, t):
"""Wrapper for various thermodynamic calculations.
Assumes input data is 1D with size N or M, or 2D with size N*M,
where M denotes profiles and N depths.
Parameters
----------
depth : numpy array
Depth (m), size N.
lon : numpy array
Longitude, size M.
lat : numpy array
Latitude, size M.
SP : numpy array
Practical salinity, size N*M.
t : numpy array
Temperature, size N*M.
"""
p = gsw.p_from_z(-depth, np.mean(lat))
SA = gsw.SA_from_SP(SP, p[:, np.newaxis], lon[np.newaxis, :],
lat[np.newaxis, :])
CT = gsw.CT_from_t(SA, t, p[:, np.newaxis])
sig0 = gsw.pot_rho_t_exact(SA, t, p[:, np.newaxis], 0)
N2, p_mid = gsw.Nsquared(SA, CT, p[:, np.newaxis], lat[np.newaxis, :])
return p, SA, CT, sig0, p_mid, N2
def calculate_density(T, p, C, lat, long):
"""Calculates density from temp, pressure, conductivity, and lat/long.
All parameters and output are float or array-like.
:param T: temperature (deg C)
:param p: pressure (bar)
:param C: conductivity (S/m)
:param lat: latitude (decimal deg)
:param long: longitude (decimal deg)
:return: density (kg/m^3)
"""
# pressure in dbars = pressure * 10
if type(p) == float:
p_dbar = p * 10
else:
p_dbar = [pi * 10 for pi in p]
# conductivity in mS/cm = conductivity * 10
if type(C) == float:
C_mScm = C * 10
else:
C_mScm = [Ci * 10 for Ci in C]
# calculate SP from conductivity (mS/cm), in-situ temperature (deg C), and gauge pressure (dbar)
SP = gsw.SP_from_C(C_mScm, T, p_dbar)
# calculate SA from SP (unitless), gauge pressure (dbar), longitude and latitude (decimal degrees)
SA = gsw.SA_from_SP(SP, p_dbar, long, lat)
# calculate CT from SA (g/kg), in-situ temperature (deg C), and gauge pressure (dbar)
CT = gsw.CT_from_t(SA, T, p_dbar)
# calculate density
return gsw.rho(SA, CT, p_dbar)
def convertToDictionary(refdata):
## gamma_n goes lon, lat, pres
data = {}
data["lats"] = np.asarray(refdata["lat_ref"])
data["lons"] = np.asarray(refdata["long_ref"])
p_ref = np.empty((91, 45, 33))
for i in range(p_ref.shape[0]):
for j in range(p_ref.shape[1]):
p_ref[i][j] = np.asarray(refdata["p_ref"]).flatten()
data["s"] = []
data["t"] = []
data["p"] = []
for j in range(refdata["SP_ref"].shape[0]):
data["s"].append(
np.asarray(
gsw.SA_from_SP(np.asarray(refdata["SP_ref"][j]), p_ref[j],
np.full_like(data["lats"], data["lons"][j]),
data["lats"])))
data["t"].append(
np.asarray(
gsw.CT_from_t(data["s"][-1], np.asarray(refdata["t_ref"][j]),
p_ref[j])))
data["p"].append(p_ref[j])
data["t"] = np.asarray(data["t"])
print(data["t"].shape)
data["p"] = np.asarray(refdata["p_ref"]).flatten()
data["lats"] = np.asarray(refdata["lat_ref"]).flatten()
data["lons"] = np.asarray(refdata["long_ref"]).flatten()
data["gamma"] = np.asarray(refdata["gamma_n_ref"])
return data
def add_ctd_params(df_in: MutableMapping[str, Sequence],
cfg: Mapping[str, Any],
lon=16.7,
lat=55.2):
"""
Calculate all parameters from 'sigma0', 'depth', 'soundV', 'SA' that is specified in cfg['out']['data_columns']
:param df_in: DataFrame with columns:
'Pres', 'Temp90' or 'Temp', and may be others:
'Lat', 'Lon': to use instead cfg['in']['lat'] and lat and -//- lon
:param cfg: dict with fields:
['out']['data_columns'] - list of columns in output dataframe
['in'].['b_temp_on_its90'] - optional
:param lon: # 54.8707 # least priority values
:param lon: # 19.3212
:return: DataFrame with only columns specified in cfg['out']['data_columns']
"""
ctd = df_in
params_to_calc = set(cfg['out']['data_columns']).difference(ctd.columns)
params_coord_needed_for = params_to_calc.intersection(
('depth', 'sigma0', 'SA', 'soundV')) # need for all cols?
if any(params_coord_needed_for):
# todo: load from nav:
if np.any(ctd.get('Lat')):
lat = ctd['Lat']
lon = ctd['Lon']
else:
if 'lat' in cfg['in']:
lat = cfg['in']['lat']
lon = cfg['in']['lon']
else:
print(
'Calc', '/'.join(params_coord_needed_for),
f'using MANUAL INPUTTED coordinates: lat={lat}, lon={lon}')
if 'Temp90' not in ctd.columns:
if cfg['in'].get('b_temp_on_its90'):
ctd['Temp90'] = ctd['Temp']
else:
ctd['Temp90'] = gsw.conversions.t90_from_t68(df_in['Temp'])
ctd['SA'] = gsw.SA_from_SP(
ctd['Sal'], ctd['Pres'], lat=lat,
lon=lon) # or Sstar_from_SP() for Baltic where SA=S*
# Val['Sal'] = gsw.SP_from_C(Val['Cond'], Val['Temp'], Val['P'])
if 'soundV' in params_to_calc:
ctd['soundV'] = gsw.sound_speed_t_exact(ctd['SA'], ctd['Temp90'],
ctd['Pres'])
if 'depth' in params_to_calc:
ctd['depth'] = np.abs(gsw.z_from_p(np.abs(ctd['Pres']), lat))
if 'sigma0' in params_to_calc:
CT = gsw.CT_from_t(ctd['SA'], ctd['Temp90'], ctd['Pres'])
ctd['sigma0'] = gsw.sigma0(ctd['SA'], CT)
# ctd = pd.DataFrame(ctd, columns=cfg['out']['data_columns'], index=df_in.index)
if 'Lat' in params_to_calc and not 'Lat' in ctd.columns:
ctd['Lat'] = lat
ctd['Lon'] = lon
return ctd[cfg['out']['data_columns']]
def derive_csv(data):
density = gsw.z_from_p(cast[6].values,lat)
absolute_sal=gsw.SA_from_SP(cast[10].values,density,lon,lat)
reference_sal=gsw.SR_from_SP(absolute_sal)
conservative_temp=gsw.CT_from_t(absolute_sal,cast[8],density)
potential_density=gsw.sigma0(absolute_sal,conservative_temp)
return density,absolute_sal,reference_sal,conservative_temp,potential_density
def insitu_to_absolute(Tis, SP, p, lon, lat, zref):
"""Transform in situ variables to TEOS10 variables
:rtype: float, float, float"""
# SP is in p.s.u.
SA = gsw.SA_from_SP(SP, p, lon, lat)
CT = gsw.CT_from_t(SA, Tis, p)
z = -gsw.z_from_p(p, lat)
return (CT, SA, z)
def brunt_vaisala(SP,
t,
p,
lon=-45.401666,
lat=-23.817233,
interpolate=True,
result='frequency'):
"""
Returns Brunt-Väisäla (or buoyancy) frequency/period from practical
salinity, in situ temperature and pressure (depth).
Parameters
----------
SP : array like
Salinity (PSS-78) [1e-3]
t : array like
Temperature (ITS-90) [degC]
p : array like
Pressure [dbar]
lon : array like, float, optional
Longitude, decimal degrees east
lat : array like, float, optional
Latitude, decimal degrees north
interpolate : boolean, optional
If True, interpolates calculated frequency to original pressure
(depth) levels. If False, returns results at mid pressure
between pressugre grid.
result : {'freuency', 'period'}, optional
Sets whether to return `frequency` [in
Returns
-------
N : array like
Brunt-Väisälä frequency [s-1] or period [s].
p : array like
Pressure levels [dbar].
"""
# Calculates Absolute Salinity from Practical Salinity
SA = gsw.SA_from_SP(SP, p, lon, lat)
# Calcualtes Conservative Temperature from in situ temperature
CT = gsw.CT_from_t(SA, t, p)
#
N2, p_mid = gsw.Nsquared(SA, CT, p, lat=lat)
N2[N2 < 0] = 0
#
if interpolate:
N2 = interp(p, p_mid, N2)
#
if result == 'frequency':
return N2**0.5, p_mid
elif result == 'period':
return 1. / N2**0.5, p_mid
else:
raise ValueError('Invalid result type {}.'.format(result))
def _update_eos(self):
# derive absolute salinity and conservative temperature
self.SA = gsw.SA_from_SP(self.s, self.p, self.lon, self.lat)
self.CT = gsw.CT_from_t(self.SA, self.temp, self.p)
# derive N2
self.N2, self.p_mid = gsw.Nsquared(self.SA,
self.CT,
self.p,
lat=self.lat)
self.z_mid = gsw.z_from_p(self.p_mid, self.lat)
def sigma0FromCTD(S, T, p, lon, lat):
"""
Rho from measured salinity and temperature values
"""
SA = gsw.SA_from_SP(S, p, lon, lat)
CT = gsw.CT_from_t(SA, T, p)
rho = gsw.density.sigma0(SA, CT)
return rho
def dens0(S, T, P):
# ctd file contain in situ temperature and practical salinity
# CT= conservative temperature
# SA= absolute salinity
# p is sea pressure (dbar)
SA = gsw.SA_from_SP(S, P, 6., 42.)
CT = gsw.CT_from_t(SA, T, P)
# sound speed
#C = gsw.sound_speed(SA, CT, P)
return gsw.sigma0(SA, CT) + 1000.
def compute_density(data):
p = 0 * data['lon']
SA = gsw.SA_from_SP(data['SSS'], p, data['lon'], data['lat'])
CT = gsw.CT_from_t(SA, data['SST'], p)
rho, alpha, beta = gsw.rho_alpha_beta(SA, CT, p)
#b = 9.81 * (1 - rho / 1025.)
data['SSS'].data = SA
data['SST'].data = CT
return data.assign(SSrho=xr.DataArray(rho, dims='time'),
SSalpha=xr.DataArray(alpha, dims='time'),
SSbeta=xr.DataArray(beta, dims='time'))
def sigma0(S, T, p, lat=None, lon=None):
ones = xr.ones_like(S)
p = ones * S['p']
if lat is None:
lat = ones * S['lat']
if lon is None:
lon = ones * S['lon']
SA = gsw.SA_from_SP(S, p, lon, lat)
CT = gsw.CT_from_t(SA, T, p)
rho = gsw.sigma0(SA, CT)
return rho
def Nsquared(S, T, p, lat=None, lon=None, dim='p'):
ones = xr.ones_like(S)
p = ones * S[dim]
if lat is None:
lat = ones * S['lat']
if lon is None:
lon = ones * S['lon']
SA = gsw.SA_from_SP(S, p, lon, lat)
CT = gsw.CT_from_t(SA, T, p)
N2, pmid = gsw.Nsquared(SA, CT, p, axis=S.get_axis_num(dim))
return N2, pmid
def test(self):
sal = np.array([0.1, 0.1]) #
temp = np.array([4., 21.]) # Celsius
pres = np.array([10., 20.])
rho = gsw.rho(sal, temp, pres)
print("density", rho)
lat = [43.2, 43.2]
CT = gsw.CT_from_t(sal, temp, pres)
N2, p_mid = gsw.Nsquared(sal, CT, pres, lat=lat)
print("N2", N2)
print("p_mid", p_mid)
def density_profile(Hydro_Dataframe):
for index, row in Hydro_Dataframe.iterrows():
t = row["CTDTMP"] #ITS-90
SP = row["CTDSAL"] # PSS-78
p = row["CTDPRS"] # decibar
lon = [row["LON"]]*t.size
lat = [row["LAT"]]*t.size
SA = gsw.SA_from_SP(SP, p, lon, lat) #gsw.SA_from_SP(SP, p, lon, lat)
CT = gsw.CT_from_t(SA,t,p) # gsw.CT_from_t(SA, t, p)
D = gsw.density.sigma0(SA, CT)# gsw.density.sigma0(SA, CT)
plt.plot(D+1000,-p,marker='.',linestyle='None',markersize=1)
plt.show()