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Commit 0b140fde authored by sbiri's avatar sbiri
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Update flux_subs.py

parent 60258065
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flux_subs.py
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......@@ -8,107 +8,9 @@ kappa = 0.4 # NOTE: 0.41
# ---------------------------------------------------------------------
def charnock_C35(wind, u10n, usr, seastate, waveage, wcp, sigH, lat):
""" Calculates Charnock number following Edson et al. 2013 based on
C35 matlab code (coare35vn.m)
Parameters
----------
wind : float
wind speed (m/s)
u10n : float
neutral 10m wind speed (m/s)
usr : float
friction velocity (m/s)
seastate : bool
0 or 1
waveage : bool
0 or 1
wcp : float
phase speed of dominant waves (m/s)
sigH : float
significant wave height (m)
lat : float
latitude (deg)
Returns
-------
ac : float
Charnock number
"""
g = gc(lat, None)
a1, a2 = 0.0017, -0.0050
charnC = np.where(u10n > 19, a1*19+a2, a1*u10n+a2)
A, B = 0.114, 0.622 # wave-age dependent coefficients
Ad, Bd = 0.091, 2.0 # Sea-state/wave-age dependent coefficients
charnW = A*(usr/wcp)**B
zoS = sigH*Ad*(usr/wcp)**Bd
charnS = (zoS*g)/usr**2
charn = np.where(wind > 10, 0.011+(wind-10)/(18-10)*(0.018-0.011),
np.where(wind > 18, 0.018, 0.011*np.ones(np.shape(wind))))
if waveage:
if seastate:
charn = charnS
else:
charn = charnW
else:
charn = charnC
ac = np.zeros((len(wind), 3))
ac[:, 0] = charn
ac[:, 1] = charnS
ac[:, 2] = charnW
return ac
# ---------------------------------------------------------------------
def cd_C35(u10n, wind, usr, charn, monob, Ta, hh_in, lat):
""" Calculates exchange coefficients following Edson et al. 2013 based on
C35 matlab code (coare35vn.m)
Parameters
----------
u10n : float
neutral 10m wind speed (m/s)
wind : float
wind speed (m/s)
charn : float
Charnock number
monob : float
Monin-Obukhov stability length
Ta : float
air temperature (K)
hh_in : float
input sensor's height (m)
lat : float
latitude (deg)
Returns
-------
zo : float
surface roughness (m)
cdhf : float
drag coefficient
cthf : float
heat exchange coefficient
cqhf : float
moisture exchange coefficient
"""
g = gc(lat, None)
zo = charn*usr**2/g+0.11*visc_air(Ta)/usr # surface roughness
rr = zo*usr/visc_air(Ta)
# These thermal roughness lengths give Stanton and
zoq = np.where(5.8e-5/rr**0.72 > 1.6e-4, 1.6e-4, 5.8e-5/rr**0.72)
zot = zoq # Dalton numbers that closely approximate COARE 3.0
cdhf = kappa/(np.log(hh_in[0]/zo)-psiu_26(hh_in[0]/monob))
cthf = kappa/(np.log(hh_in[1]/zot)-psit_26(hh_in[1]/monob))
cqhf = kappa/(np.log(hh_in[2]/zoq)-psit_26(hh_in[2]/monob))
return zo, cdhf, cthf, cqhf
# ---------------------------------------------------------------------
def cdn_calc(u10n, Ta, Tp, method="S80"):
def cdn_calc(u10n, Ta, Tp, lat, meth="S80"):
""" Calculates neutral drag coefficient
Parameters
----------
u10n : float
......@@ -117,39 +19,40 @@ def cdn_calc(u10n, Ta, Tp, method="S80"):
air temperature (K)
Tp : float
wave period
method : str
meth : str
Returns
-------
cdn : float
"""
if (method == "S80"):
if (meth == "S80"):
cdn = np.where(u10n <= 3, (0.61+0.567/u10n)*0.001,
(0.61+0.063*u10n)*0.001)
elif (method == "LP82"):
elif (meth == "LP82"):
cdn = np.where((u10n < 11) & (u10n >= 4), 1.2*0.001,
np.where((u10n <= 25) & (u10n >= 11),
(0.49+0.065*u10n)*0.001, 1.14*0.001))
elif (method == "S88" or method == "UA" or method == "ERA5"):
cdn = cdn_from_roughness(u10n, Ta, None, method)
elif (method == "YT96"):
elif (meth == "S88" or meth == "UA" or meth == "ERA5" or meth == "C30" or
meth == "C35" or meth == "C40"):
cdn = cdn_from_roughness(u10n, Ta, None, lat, meth)
elif (meth == "YT96"):
# for u<3 same as S80
cdn = np.where((u10n < 6) & (u10n >= 3),
(0.29+3.1/u10n+7.7/u10n**2)*0.001,
np.where((u10n <= 26) & (u10n >= 6),
(0.60 + 0.070*u10n)*0.001, (0.61+0.567/u10n)*0.001))
elif (method == "LY04"):
elif (meth == "LY04"):
cdn = np.where(u10n >= 0.5,
(0.142+(2.7/u10n)+(u10n/13.09))*0.001, np.nan)
else:
print("unknown method cdn: "+method)
print("unknown method cdn: "+meth)
return cdn
# ---------------------------------------------------------------------
def cdn_from_roughness(u10n, Ta, Tp, method="S88"):
def cdn_from_roughness(u10n, Ta, Tp, lat, meth="S88"):
""" Calculates neutral drag coefficient from roughness length
Parameters
----------
u10n : float
......@@ -158,42 +61,59 @@ def cdn_from_roughness(u10n, Ta, Tp, method="S88"):
air temperature (K)
Tp : float
wave period
method : str
meth : str
Returns
-------
cdn : float
"""
g, tol = 9.812, 0.000001
g, tol = gc(lat, None), 0.000001
cdn, usr = np.zeros(Ta.shape), np.zeros(Ta.shape)
cdnn = (0.61+0.063*u10n)*0.001
zo, zc, zs = np.zeros(Ta.shape), np.zeros(Ta.shape), np.zeros(Ta.shape)
for it in range(5):
cdn = np.copy(cdnn)
usr = np.sqrt(cdn*u10n**2)
if (method == "S88"):
if (meth == "S88"):
# .....Charnock roughness length (equn 4 in Smith 88)
zc = 0.011*np.power(usr, 2)/g
# .....smooth surface roughness length (equn 6 in Smith 88)
zs = 0.11*visc_air(Ta)/usr
zo = zc + zs # .....equns 7 & 8 in Smith 88 to calculate new CDN
elif (method == "UA"):
elif (meth == "UA"):
# valid for 0<u<18m/s # Zeng et al. 1998 (24)
zo = 0.013*np.power(usr, 2)/g+0.11*visc_air(Ta)/usr
elif (method == "ERA5"):
elif (meth == "C30"):
a = 0.011*np.ones(Ta.shape)
a = np.where(u10n > 10, 0.011+(u10n-10)/(18-10)*(0.018-0.011),
np.where(u10n > 18, 0.018, a))
zo = a*np.power(usr, 2)/g+0.11*visc_air(Ta)/usr
elif (meth == "C35"):
a = 0.011*np.ones(Ta.shape)
a = np.where(u10n > 18, 0.0017*19-0.0050,
np.where((u10n > 7) & (u10n <= 18),
0.0017*u10n-0.0050, a))
# charn = np.where(wind > 10, 0.011+(wind-10)/(18-10)*(0.018-0.011),
# np.where(wind > 18, 0.018, 0.011*np.ones(np.shape(wind))))
zo = 0.11*visc_air(Ta)/usr+a*np.power(usr, 2)/g
elif (meth == "C40"):
a = 0.011*np.ones(Ta.shape)
a = np.where(u10n > 22, 0.0016*22-0.0035, 0.0016*u10n-0.0035)
zo = a*np.power(usr, 2)/g+0.11*visc_air(Ta)/usr # surface roughness
elif (meth == "ERA5"):
# eq. (3.26) p.40 over sea IFS Documentation cy46r1
zo = 0.11*visc_air(Ta)/usr+0.018*np.power(usr, 2)/g
else:
print("unknown method for cdn_from_roughness "+method)
print("unknown method for cdn_from_roughness "+meth)
cdnn = (kappa/np.log(10/zo))**2
cdn = np.where(np.abs(cdnn-cdn) < tol, cdnn, np.nan)
return cdnn
# ---------------------------------------------------------------------
def ctcqn_calc(zol, cdn, u10n, zo, Ta, method="S80"):
def ctcqn_calc(zol, cdn, u10n, zo, Ta, meth="S80"):
""" Calculates neutral heat and moisture exchange coefficients
Parameters
----------
zol : float
......@@ -206,8 +126,8 @@ def ctcqn_calc(zol, cdn, u10n, zo, Ta, method="S80"):
surface roughness (m)
Ta : float
air temperature (K)
method : str
meth : str
Returns
-------
ctn : float
......@@ -215,27 +135,57 @@ def ctcqn_calc(zol, cdn, u10n, zo, Ta, method="S80"):
cqn : float
neutral moisture exchange coefficient
"""
if (method == "S80" or method == "S88" or method == "YT96"):
if (meth == "S80" or meth == "S88" or meth == "YT96"):
cqn = np.ones(Ta.shape)*1.20*0.001 # from S88
ctn = np.ones(Ta.shape)*1.00*0.001
elif (method == "LP82"):
elif (meth == "LP82"):
cqn = np.where((zol <= 0) & (u10n > 4) & (u10n < 14), 1.15*0.001,
np.nan)
ctn = np.where((zol <= 0) & (u10n > 4) & (u10n < 25), 1.13*0.001,
0.66*0.001)
elif (method == "LY04"):
cqn = 34.6*0.001*cdn**0.5
ctn = np.where(zol <= 0, 32.7*0.001*cdn**0.5, 18*0.001*cdn**0.5)
elif (method == "UA"):
usr = (cdn * u10n**2)**0.5
elif (meth == "LY04"):
cqn = 34.6*0.001*np.sqrt(cdn)
ctn = np.where(zol <= 0, 32.7*0.001*np.sqrt(cdn), 18*0.001*np.sqrt(cdn))
elif (meth == "UA"):
usr = np.sqrt(cdn*np.power(u10n, 2))
# Zeng et al. 1998 (25)
zoq = zo*np.exp(-(2.67*np.power(usr*zo/visc_air(Ta), 1/4)-2.57))
re=usr*zo/visc_air(Ta)
zoq = zo/np.exp(2.67*np.power(re, 1/4)-2.57)
zot = zoq
cqn = np.where((u10n > 0.5) & (u10n < 18), np.power(kappa, 2) /
(np.log(10/zo)*np.log(10/zoq)), np.nan)
ctn = np.where((u10n > 0.5) & (u10n < 18), np.power(kappa, 2) /
(np.log(10/zo)*np.log(10/zoq)), np.nan)
elif (method == "ERA5"):
elif (meth == "C30"):
usr = np.sqrt(cdn*np.power(u10n, 2))
rr = zo*usr/visc_air(Ta)
zoq = np.where(5e-5/np.power(rr, 0.6) > 1.15e-4, 1.15e-4,
5e-5/np.power(rr, 0.6)) # moisture roughness
zot=zoq # temperature roughness
cqn = kappa**2/np.log(10/zo)/np.log(10/zoq)
ctn = kappa**2/np.log(10/zo)/np.log(10/zot)
elif (meth == "C35"):
usr = np.sqrt(cdn*np.power(u10n, 2))
rr = zo*usr/visc_air(Ta)
zoq = np.where(5.8e-5/np.power(rr, 0.72) > 1.6e-4, 1.6e-4,
5.8e-5/np.power(rr, 0.72)) # moisture roughness
zot=zoq # temperature roughness
cqn = kappa**2/np.log(10/zo)/np.log(10/zoq)
ctn = kappa**2/np.log(10/zo)/np.log(10/zot)
elif (meth == "C40"):
usr = np.sqrt(cdn*np.power(u10n, 2))
rr = zo*usr/visc_air(Ta)
zot = np.where(1.0e-4/np.power(rr, 0.55) > 2.4e-4/np.power(rr, 1.2),
2.4e-4/np.power(rr, 1.2),
1.0e-4/np.power(rr, 0.55)) # temperature roughness
zoq = np.where(2.0e-5/np.power(rr,0.22) > 1.1e-4/np.power(rr,0.9),
1.1e-4/np.power(rr,0.9), 2.0e-5/np.power(rr,0.22))
# moisture roughness determined by the CLIMODE, GASEX and CBLAST data
# zoq = np.where(5e-5/np.power(rr, 0.6) > 1.15e-4, 1.15e-4,
# 5e-5/np.power(rr, 0.6)) # moisture roughness as in C30
cqn = kappa**2/np.log(10/zo)/np.log(10/zoq)
ctn = kappa**2/np.log(10/zo)/np.log(10/zot)
elif (meth == "ERA5"):
# eq. (3.26) p.40 over sea IFS Documentation cy46r1
usr = np.sqrt(cdn*np.power(u10n, 2))
zot = 0.40*visc_air(Ta)/usr
......@@ -243,14 +193,14 @@ def ctcqn_calc(zol, cdn, u10n, zo, Ta, method="S80"):
cqn = kappa**2/np.log(10/zo)/np.log(10/zoq)
ctn = kappa**2/np.log(10/zo)/np.log(10/zot)
else:
print("unknown method ctcqn: "+method)
print("unknown method ctcqn: "+meth)
return ctn, cqn
# ---------------------------------------------------------------------
def cd_calc(cdn, height, ref_ht, psim):
""" Calculates drag coefficient at reference height
Parameters
----------
cdn : float
......@@ -261,7 +211,7 @@ def cd_calc(cdn, height, ref_ht, psim):
reference height (m)
psim : float
momentum stability function
Returns
-------
cd : float
......@@ -274,7 +224,7 @@ def cd_calc(cdn, height, ref_ht, psim):
def ctcq_calc(cdn, cd, ctn, cqn, h_t, h_q, ref_ht, psit, psiq):
""" Calculates heat and moisture exchange coefficients at reference height
Parameters
----------
cdn : float
......@@ -295,7 +245,7 @@ def ctcq_calc(cdn, cd, ctn, cqn, h_t, h_q, ref_ht, psit, psiq):
heat stability function
psiq : float
moisture stability function
Returns
-------
ct : float
......@@ -307,24 +257,26 @@ def ctcq_calc(cdn, cd, ctn, cqn, h_t, h_q, ref_ht, psit, psiq):
# ---------------------------------------------------------------------
def psim_calc(zol, method="S80"):
def psim_calc(zol, meth="S80"):
""" Calculates momentum stability function
Parameters
----------
zol : float
height over MO length
method : str
meth : str
Returns
-------
psim : float
"""
coeffs = get_stabco(method)
coeffs = get_stabco(meth)
alpha, beta, gamma = coeffs[0], coeffs[1], coeffs[2]
if (method == "ERA5"):
if (meth == "ERA5"):
psim = np.where(zol < 0, psim_conv(zol, alpha, beta, gamma),
psim_stab_era5(zol, alpha, beta, gamma))
elif (meth == "C30" or meth == "C35" or meth == "C40"):
psim = psiu_26(zol, meth)
else:
psim = np.where(zol < 0, psim_conv(zol, alpha, beta, gamma),
psim_stab(zol, alpha, beta, gamma))
......@@ -332,24 +284,26 @@ def psim_calc(zol, method="S80"):
# ---------------------------------------------------------------------
def psit_calc(zol, method="S80"):
def psit_calc(zol, meth="S80"):
""" Calculates heat stability function
Parameters
----------
zol : float
height over MO length
method : str
meth : str
Returns
-------
psit : float
"""
coeffs = get_stabco(method)
coeffs = get_stabco(meth)
alpha, beta, gamma = coeffs[0], coeffs[1], coeffs[2]
if (method == "ERA5"):
if (meth == "ERA5"):
psit = np.where(zol < 0, psi_conv(zol, alpha, beta, gamma),
psi_stab_era5(zol, alpha, beta, gamma))
elif (meth == "C30" or meth == "C35" or meth == "C40"):
psit = psit_26(zol)
else:
psit = np.where(zol < 0, psi_conv(zol, alpha, beta, gamma),
psi_stab(zol, alpha, beta, gamma))
......@@ -357,26 +311,27 @@ def psit_calc(zol, method="S80"):
# ---------------------------------------------------------------------
def get_stabco(method="S80"):
def get_stabco(meth="S80"):
""" Gives the coefficients \\alpha, \\beta, \\gamma for stability functions
Parameters
----------
method : str
meth : str
Returns
-------
coeffs : float
"""
if (method == "S80" or method == "S88" or method == "LY04" or
method == "UA" or method == "ERA5"):
if (meth == "S80" or meth == "S88" or meth == "LY04" or
meth == "UA" or meth == "ERA5" or meth == "C30" or meth == "C35" or
meth == "C40"):
alpha, beta, gamma = 16, 0.25, 5 # Smith 1980, from Dyer (1974)
elif (method == "LP82"):
elif (meth == "LP82"):
alpha, beta, gamma = 16, 0.25, 7
elif (method == "YT96"):
elif (meth == "YT96"):
alpha, beta, gamma = 20, 0.25, 5
else:
print("unknown method stabco: "+method)
print("unknown method stabco: "+meth)
coeffs = np.zeros(3)
coeffs[0] = alpha
coeffs[1] = beta
......@@ -386,16 +341,16 @@ def get_stabco(method="S80"):
def psi_stab_era5(zol, alpha, beta, gamma):
""" Calculates heat stability function for stable conditions
""" Calculates heat stability function for stable conditions
for method ERA5
Parameters
----------
zol : float
height over MO length
alpha, beta, gamma : float
constants given by get_stabco
Returns
-------
psit : float
......@@ -406,16 +361,43 @@ def psi_stab_era5(zol, alpha, beta, gamma):
return psit
# ---------------------------------------------------------------------
def psit_26(zol):
""" Computes temperature structure function as in C35
Parameters
----------
zol : float
height over MO length
Returns
-------
psi : float
"""
b, d = 2/3, 0.35
dzol = np.where(d*zol > 50, 50, d*zol) # stable
psi = -((1+b*zol)**1.5+b*(zol-14.28)*np.exp(-dzol)+8.525)
psi = np.where(zol < 0, (1-(np.power(zol, 2)/(1+np.power(zol, 2))))*2 *
np.log((1+np.sqrt(1-15*zol))/2)+(np.power(zol, 2) /
(1+np.power(zol, 2))) *
(1.5*np.log((1+np.power(1-34.15*zol, 1/3) +
np.power(1-34.15*zol, 2/3))/3) -
np.sqrt(3)*np.arctan((1+2*np.power(1-34.15*zol, 1/3)) /
np.sqrt(3))+4*np.arctan(1)/np.sqrt(3)), psi)
return psi
# ---------------------------------------------------------------------
def psi_conv(zol, alpha, beta, gamma):
""" Calculates heat stability function for unstable conditions
Parameters
----------
zol : float
height over MO length
alpha, beta, gamma : float
constants given by get_stabco
Returns
-------
psit : float
......@@ -428,14 +410,14 @@ def psi_conv(zol, alpha, beta, gamma):
def psi_stab(zol, alpha, beta, gamma):
""" Calculates heat stability function for stable conditions
Parameters
----------
zol : float
height over MO length
alpha, beta, gamma : float
constants given by get_stabco
Returns
-------
psit : float
......@@ -445,43 +427,17 @@ def psi_stab(zol, alpha, beta, gamma):
# ---------------------------------------------------------------------
def psit_26(zol):
""" Computes temperature structure function as in C35
Parameters
----------
zol : float
height over MO length
Returns
-------
psi : float
"""
dzol = np.where(0.35*zol > 50, 50, 0.35*zol) # stable
psi = -((1+0.6667*zol)**1.5+0.6667*(zol-14.28)*np.exp(-dzol)+8.525)
k = np.where(zol < 0) # unstable
x = (1-15*zol[k])**0.5
psik = 2*np.log((1+x)/2)
x = (1-34.15*zol[k])**0.3333
psic = (1.5*np.log((1+x+x**2)/3)-np.sqrt(3)*np.arctan((1+2*x) /
np.sqrt(3))+4*np.arctan(1)/np.sqrt(3))
f = zol[k]**2/(1+zol[k]**2)
psi[k] = (1-f)*psik+f*psic
return psi
# ---------------------------------------------------------------------
def psim_stab_era5(zol, alpha, beta, gamma):
""" Calculates momentum stability function for stable conditions
""" Calculates momentum stability function for stable conditions
for method ERA5
Parameters
----------
zol : float
height over MO length
alpha, beta, gamma : float
constants given by get_stabco
Returns
-------
psim : float
......@@ -495,14 +451,14 @@ def psim_stab_era5(zol, alpha, beta, gamma):
def psim_conv(zol, alpha, beta, gamma):
""" Calculates momentum stability function for unstable conditions
Parameters
----------
zol : float
height over MO length
alpha, beta, gamma : float
constants given by get_stabco
Returns
-------
psim : float
......@@ -516,14 +472,14 @@ def psim_conv(zol, alpha, beta, gamma):
def psim_stab(zol, alpha, beta, gamma):
""" Calculates momentum stability function for stable conditions
Parameters
----------
zol : float
height over MO length
alpha, beta, gamma : float
constants given by get_stabco
Returns
-------
psim : float
......@@ -533,41 +489,54 @@ def psim_stab(zol, alpha, beta, gamma):
# ---------------------------------------------------------------------
def psiu_26(zol):
def psiu_26(zol, meth):
""" Computes velocity structure function C35
Parameters
----------
zol : float
height over MO length
Returns
-------
psi : float
"""
dzol = np.where(0.35*zol > 50, 50, 0.35*zol) # stable
a, b, c, d = 0.7, 3/4, 5, 0.35
psi = -(a*zol+b*(zol-c/d)*np.exp(-dzol)+b*c/d)
k = np.where(zol < 0) # unstable
x = (1-15*zol[k])**0.25
psik = 2*np.log((1+x)/2)+np.log((1+x**2)/2)-2*np.arctan(x)+2*np.arctan(1)
x = (1-10.15*zol[k])**0.3333
psic = (1.5*np.log((1+x+x**2)/3)-np.sqrt(3)*np.arctan((1+2*x)/np.sqrt(3)) +
4*np.arctan(1)/np.sqrt(3))
f = zol[k]**2/(1+zol[k]**2)
psi[k] = (1-f)*psik+f*psic
if (meth == "C30"):
dzol = np.where(0.35*zol > 50, 50, 0.35*zol) # stable
psi = -((1+zol)+0.6667*(zol-14.28)*np.exp(-dzol)+8.525)
k = np.where(zol < 0) # unstable
x = np.power(1-15*zol[k], 0.25)
psik = (2*np.log((1+x)/2)+np.log((1+np.power(x, 2))/2)-2*np.arctan(x) +
2*np.arctan(1))
x = np.power(1-10.15*zol[k], 0.3333)
psic = (1.5*np.log((1+x+np.power(x, 2))/3)-np.sqrt(3) *
np.arctan((1+2*x)/np.sqrt(3))+4*np.arctan(1)/np.sqrt(3))
f = np.power(zol[k], 2)/(1+np.power(zol[k], 2))
psi[k] = (1-f)*psik+f*psic
elif (meth == "C35" or meth == "C40"):
dzol = np.where(0.35*zol > 50, 50, 0.35*zol) # stable
a, b, c, d = 0.7, 3/4, 5, 0.35
psi = -(a*zol+b*(zol-c/d)*np.exp(-dzol)+b*c/d)
k = np.where(zol < 0) # unstable
x = np.power(1-15*zol[k], 0.25)
psik = 2*np.log((1+x)/2)+np.log((1+x**2)/2)-2*np.arctan(x)+2*np.arctan(1)
x = np.power(1-10.15*zol[k], 0.3333)
psic = (1.5*np.log((1+x+np.power(x, 2))/3)-np.sqrt(3) *
np.arctan((1+2*x)/np.sqrt(3))+4*np.arctan(1)/np.sqrt(3))
f = np.power(zol[k], 2)/(1+np.power(zol[k], 2))
psi[k] = (1-f)*psik+f*psic
return psi
# ------------------------------------------------------------------------------
def psiu_40(zol):
""" Computes velocity structure function C35
Parameters
----------
zol : float
height over MO length
Returns
-------
psi : float
......@@ -587,9 +556,9 @@ def psiu_40(zol):
# ---------------------------------------------------------------------
def get_skin(sst, qsea, rho, Rl, Rs, Rnl, cp, lv, usr, tsr, qsr, lat):
def get_skin(sst, qsea, rho, Rl, Rs, Rnl, cp, lv, tkt, usr, tsr, qsr, lat):
""" Computes cool skin
Parameters
----------
sst : float
......@@ -602,10 +571,14 @@ def get_skin(sst, qsea, rho, Rl, Rs, Rnl, cp, lv, usr, tsr, qsr, lat):
downward longwave radiation (W/m^2)
Rs : float
downward shortwave radiation (W/m^2)
Rnl : float
upwelling IR radiation (W/m^2)
cp : float
specific heat of air at constant pressure
lv : float
latent heat of vaporization
tkt : float
cool skin thickness
usr : float
friction velocity
tsr : float
......@@ -614,12 +587,12 @@ def get_skin(sst, qsea, rho, Rl, Rs, Rnl, cp, lv, usr, tsr, qsr, lat):
star humidity
lat : float
latitude
Returns
-------
dter : float
dqer : float
dqer : float
"""
# coded following Saunders (1967) with lambda = 6
g = gc(lat, None)
......@@ -629,30 +602,31 @@ def get_skin(sst, qsea, rho, Rl, Rs, Rnl, cp, lv, usr, tsr, qsr, lat):
# density of water, specific heat capacity of water, water viscosity,
# thermal conductivity of water
rhow, cpw, visw, tcw = 1022, 4000, 1e-6, 0.6
Al = 2.1e-5*(sst+3.2)**0.79
Al = 2.1e-5*np.power(sst+3.2, 0.79)
be = 0.026
bigc = 16*g*cpw*(rhow*visw)**3/(tcw*tcw*rho*rho)
wetc = 0.622*lv*qsea/(287.1*(sst+273.16)**2)
bigc = 16*g*cpw*np.power(rhow*visw, 3)/(np.power(tcw, 2)*np.power(rho, 2))
wetc = 0.622*lv*qsea/(287.1*np.power(sst+273.16, 2))
Rns = 0.945*Rs # albedo correction
hsb = -rho*cp*usr*tsr
hlb = -rho*lv*usr*qsr
qout = Rnl+hsb+hlb
tkt = 0.001*np.ones(np.shape(sst))
dels = Rns*(0.065+11*tkt-6.6e-5/tkt*(1-np.exp(-tkt/8.0e-4)))
qcol = qout-dels
alq = Al*qcol+be*hlb*cpw/lv
xlamx = 6*np.ones(sst.shape)
xlamx = np.where(alq > 0, 6/(1+(bigc*alq/usr**4)**0.75)**0.333, 6)
tkt = xlamx*visw/(np.sqrt(rho/rhow)*usr)
tkt = np.where(alq > 0, np.where(tkt > 0.01, 0.01, tkt), tkt)
tkt = np.where(alq > 0, xlamx*visw/(np.sqrt(rho/rhow)*usr),
np.where(xlamx*visw/(np.sqrt(rho/rhow)*usr) > 0.01, 0.01,
xlamx*visw/(np.sqrt(rho/rhow)*usr)))
dter = qcol*tkt/tcw
dqer = wetc*dter
return dter, dqer
return dter, dqer, tkt
# ---------------------------------------------------------------------
def get_gust(beta, Ta, usr, tsrv, zi, lat):
""" Computes gustiness
Parameters
----------
beta : float
......@@ -667,17 +641,15 @@ def get_gust(beta, Ta, usr, tsrv, zi, lat):
scale height of the boundary layer depth (m)
lat : float
latitude
Returns
-------
ug : float
"""
if (np.max(Ta) < 200): # convert to K if in Celsius
Ta = Ta+273.16
if np.isnan(zi):
zi = 600
g = gc(lat, None)
Bf = -g/Ta*usr*tsrv
Bf = (-g/Ta)*usr*tsrv
ug = np.ones(np.shape(Ta))*0.2
ug = np.where(Bf > 0, beta*np.power(Bf*zi, 1/3), 0.2)
return ug
......@@ -686,12 +658,12 @@ def get_gust(beta, Ta, usr, tsrv, zi, lat):
def get_heights(h):
""" Reads input heights for velocity, temperature and humidity
Parameters
----------
h : float
input heights (m)
Returns
-------
hh : array
......@@ -709,12 +681,12 @@ def get_heights(h):
def svp_calc(T):
""" Calculates saturation vapour pressure
Parameters
----------
T : float
temperature (K)
Returns
-------
svp : float
......@@ -729,17 +701,17 @@ def svp_calc(T):
def qsea_calc(sst, pres):
""" Computes specific humidity of the sea surface air
Parameters
----------
sst : float
sea surface temperature (K)
pres : float
pressure (mb)
Returns
-------
qsea : float
qsea : float
(kg/kg)
"""
if (np.nanmin(sst) < 200): # if sst in Celsius convert to Kelvin
......@@ -754,7 +726,7 @@ def qsea_calc(sst, pres):
def q_calc(Ta, rh, pres):
""" Computes specific humidity following Haltiner and Martin p.24
Parameters
----------
Ta : float
......@@ -763,7 +735,7 @@ def q_calc(Ta, rh, pres):
relative humidity (%)
pres : float
air pressure (mb)
Returns
-------
qair : float, (kg/kg)
......@@ -778,14 +750,14 @@ def q_calc(Ta, rh, pres):
def bucksat(T, P):
""" Computes saturation vapor pressure (mb) as in C35
Parameters
----------
T : float
temperature ($^\\circ$\\,C)
P : float
pressure (mb)
Returns
-------
exx : float
......@@ -800,14 +772,14 @@ def bucksat(T, P):
def qsat26sea(T, P):
""" Computes surface saturation specific humidity (g/kg) as in C35
Parameters
----------
T : float
temperature ($^\\circ$\\,C)
P : float
pressure (mb)
Returns
-------
qs : float
......@@ -824,14 +796,14 @@ def qsat26sea(T, P):
def qsat26air(T, P, rh):
""" Computes saturation specific humidity (g/kg) as in C35
Parameters
----------
T : float
temperature ($^\circ$\,C)
P : float
pressure (mb)
Returns
-------
q : float
......@@ -849,14 +821,14 @@ def qsat26air(T, P, rh):
def gc(lat, lon=None):
""" Computes gravity relative to latitude
Parameters
----------
lat : float
latitude ($^\circ$)
lon : float
longitude ($^\circ$, optional)
Returns
-------
gc : float
......@@ -879,22 +851,23 @@ def gc(lat, lon=None):
# ---------------------------------------------------------------------
def visc_air(Ta):
def visc_air(T):
""" Computes the kinematic viscosity of dry air as a function of air temp.
following Andreas (1989), CRREL Report 89-11.
Parameters
----------
Ta : float
air temperature ($^\circ$\,C)
Returns
-------
visa : float
kinematic viscosity (m^2/s)
"""
Ta = np.asarray(Ta)
if (np.nanmin(Ta) > 200): # if Ta in Kelvin convert to Celsius
Ta = Ta-273.16
visa = 1.326e-5 * (1 + 6.542e-3*Ta + 8.301e-6*Ta**2 - 4.84e-9*Ta**3)
T = np.asarray(T)
if (np.nanmin(T) > 200): # if Ta in Kelvin convert to Celsius
T = T-273.16
visa = 1.326e-5*(1+6.542e-3*T+8.301e-6*np.power(T, 2) -
4.84e-9*np.power(T, 3))
return visa
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