def Wavebreaking_modulation(kr, K, theta, azimuth, u_10, fetch, wind_dir, tsc,
polarization):
"""
:param kp:
:param kr:
:param theta:
:param azi:
:param u_10:
:param fetch:
:return:
"""
if polarization == 'VH':
print('no modulation cross-pol')
return
nphi = theta.shape[0]
ind = np.where(np.degrees(azimuth) == wind_dir)[0]
# divergence of the sea surface current
divergence = np.gradient(tsc[:, :, 0], 1e3, axis=1) + np.gradient(
tsc[:, :, 1], 1e3, axis=0)
# NRCS of plumes
wb0 = np.exp(-np.tan(theta)**2 / const.Swb) / (
np.cos(theta)**4 * const.Swb
) + const.yitawb / const.Swb # Kudryavstev 2003a equation (60)
knb = min(const.br * kr, const.kwb)
# tilting transfer function
dtheta = theta[1] - theta[0]
Mwb = np.gradient(wb0, dtheta) / wb0
# distribution function
# in radians azimuth of breaking surface area: -pi/2,pi/2
# phi1 = np.linspace(-np.pi/2, np.pi/2, nphi)
phi1 = np.linspace(-np.pi, np.pi, nphi)
nk = 1024
q = np.zeros([tsc.shape[0], tsc.shape[1]])
WB = np.zeros([tsc.shape[0], tsc.shape[1]])
for ii in np.arange(tsc.shape[0]):
for jj in np.arange(tsc.shape[1]):
KK = np.linspace(10 * spec_peak(u_10[ii, jj], fetch), knb, nk)
T = Trans_func(KK, K[ii, jj], u_10[ii, jj], fetch, azimuth,
divergence[ii, jj])
Bkdir = kudryavtsev05(KK.reshape(nk, 1), u_10[ii, jj], fetch,
phi1) * (1 + abs(T.reshape(nk, 1)))
n, alpha = param(KK, u_10[ii, jj], fetch)
lamda = (Bkdir / alpha.reshape(nk, 1))**(n.reshape(nk, 1) + 1) / (
2 * KK.reshape(nk, 1)
) # distribution of breaking front lengths
lamda_k = np.trapz(lamda, phi1, axis=1)
lamda = np.trapz(lamda, KK, axis=0)
lamda_k = np.trapz(lamda_k, KK)
q[ii, jj] = const.cq * lamda_k
Awb = np.trapz(np.cos(phi1 - azimuth[ind]) * lamda, phi1) / lamda_k
WB[ii, jj] = wb0[jj] * (1 + Mwb[jj] * const.theta_wb * Awb)
return WB, q
def eq_wb_mo(kr, K, theta_eq, eq_azi, u_10, fetch, div):
"""
:param kp:
:param kr:
:param theta:
:param azi:
:param u_10:
:param fetch:
:return:
"""
# NRCS of plumes
wb0 = np.exp(-np.tan(theta_eq)**2 / const.Swb) / (
np.cos(theta_eq)**4 * const.Swb
) + const.yitawb / const.Swb # Kudryavstev 2003a equation (60)
knb = min(const.br * kr, const.kwb)
# tilting transfer function
dtheta = theta_eq[1] - theta_eq[0]
Mwb = np.gradient(wb0, dtheta) / wb0
# distribution function
phi1 = np.linspace(-np.pi, np.pi, 37)
nk = 1024
q = np.zeros([div.shape[0], div.shape[1]])
WB = np.zeros([div.shape[0], div.shape[1]])
for ii in np.arange(div.shape[0]):
for jj in np.arange(div.shape[1]):
KK = np.linspace(10 * spec_peak(u_10[ii, jj], fetch), knb, nk)
T = Trans_func(KK, K[ii, jj], u_10[ii, jj], fetch, phi1, div[ii,
jj])
Bkdir = kudryavtsev05(KK.reshape(nk, 1), u_10[ii, jj], fetch,
phi1) * (1 + abs(T.reshape(nk, 1)))
n, alpha = param(KK, u_10[ii, jj], fetch)
lamda = (Bkdir / alpha.reshape(nk, 1))**(n.reshape(nk, 1) + 1) / (
2 * KK.reshape(nk, 1)
) # distribution of breaking front lengths
lamda_k = np.trapz(lamda, phi1, axis=1)
lamda = np.trapz(lamda, KK, axis=0)
lamda_k = np.trapz(lamda_k, KK)
q[ii, jj] = const.cq * lamda_k
Awb = np.trapz(np.cos(phi1 - eq_azi[jj]) * lamda, phi1) / lamda_k
WB[ii, jj] = wb0[jj] * (1 + Mwb[jj] * const.theta_wb * Awb)
return WB, q
def const_brmo(k, K, kr, theta, azimuth, u_10, fetch, wind_dir, ind_pi, div,
polarization):
"""
:param k:
:param kr:
:param theta:
:param azimuth:
:param u_10:
:param fetch:
:return:
"""
nk = k.shape[0]
# wind direction index
ind = np.where(np.degrees(azimuth) == wind_dir)[0]
# # Sea surface slope in the direction of incidence angle
ni2 = const_ni2_func(kr, k, K, u_10, fetch, azimuth, div, wind_dir)
nn = 89 * 2 * np.pi / 180
ni = (np.arange(nk) * nn / nk).reshape(1, nk) - nn / 2
ni = ni.reshape(nk, 1)
ni = np.tan(ni)
Br = np.zeros([div.shape[0], div.shape[1]])
for ii in np.arange(ni2.shape[0]):
for jj in np.arange(ni2.shape[1]):
P = np.exp(-0.5 * (ni - np.mean(ni))**2 / ni2[ii, jj]) / np.sqrt(
2 * np.pi * ni2[ii, jj])
# the range of the sea surface slope
angle_index = np.logical_and(
-3 * 180 * np.arctan(np.sqrt(ni2[ii, jj])) / np.pi <
np.arctan(ni) * 180 / np.pi,
np.arctan(ni) * 180 / np.pi <
3 * 180 * np.arctan(np.sqrt(ni2[ii, jj])) / np.pi)
P = P[angle_index]
nini = ni[angle_index]
nnk = nini.shape[0]
nini = nini.reshape(nnk, 1)
# local incidence angle
theta_l = np.abs(theta[jj] - np.arctan(nini).reshape(nnk, 1))
kbr = 2 * kr * np.sin(theta_l)
# geometric scattering coefficients [Plant 1997] equation 5,6
eps_sin = np.sqrt(const.epsilon_sw - np.sin(theta_l)**2)
kkbr = np.sort(kbr[:, 0])
T = Trans_func(kkbr, K[ii, jj], u_10, fetch, azimuth,
div[ii, jj])[np.argsort(kbr[:, 0])].reshape(nnk, 1)
spec_Skk = kudryavtsev05(kkbr.reshape(nnk, 1), u_10, fetch,
azimuth)[np.argsort(kbr[:, 0]), :] * (
1 + abs(T)) / kbr.reshape(nnk, 1)**4
Skb_r = (spec_Skk[:, ind] + spec_Skk[:, ind_pi]) / 2
if polarization == 'VV':
G = np.cos(theta_l)**2 * (const.epsilon_sw - 1) * (
const.epsilon_sw *
(1 + np.sin(theta_l)**2) - np.sin(theta_l)**2) / (
const.epsilon_sw * np.cos(theta_l) + eps_sin)**2
G = np.abs(G)**2
else:
G = np.cos(theta_l)**2 * (const.epsilon_sw -
1) / (np.cos(theta_l) + eps_sin)**2
G = np.abs(G)**2
# pure Bragg scattering NRCS
br0 = 16 * np.pi * kr**4 * G * Skb_r
# Bragg scattering composite model
BR = br0 * P.reshape(nnk, 1)
# integral over kbr >= kd
a = np.tan(theta[jj] - const.d / 2)
b = np.tan(theta[jj] + const.d / 2)
Br[ii, jj] = np.trapz(BR[nini <= a], nini[nini <= a]) + np.trapz(
BR[nini >= b], nini[nini >= b])
return Br
def const_eq_br_mo(k, K, kr, theta_eq, bist_ang_az, eq_azi, wind_dir, u_10,
fetch, div, polarization):
"""
all the angles are in radians
:param k:
:param kr:
:param theta:
:param azimuth:
:param u_10:
:param fetch:
:param spec_name:
:return:
"""
nk = k.shape[0]
# Set azimuth to compute transfer function
azimuth = np.linspace(-np.pi, np.pi, 37)
# # Sea surface slope in the direction of incidence angle
ni2 = const_ni2_func(kr, k, K, u_10, fetch, azimuth, div, wind_dir)
nn = 89 * 2 * np.pi / 180
ni = (np.arange(nk) * nn / nk).reshape(1, nk) - nn / 2
ni = ni.reshape(nk, 1)
ni = np.tan(ni)
Br = np.zeros([div.shape[0], div.shape[1]])
for ii in np.arange(ni2.shape[0]):
for jj in np.arange(ni2.shape[1]):
P = np.exp(-0.5 * (ni - np.mean(ni))**2 / ni2[ii, jj]) / np.sqrt(
2 * np.pi * ni2[ii, jj])
# the range of the sea surface slope
angle_index = np.logical_and(
-3 * 180 * np.arctan(np.sqrt(ni2[ii, jj])) / np.pi <
np.arctan(ni) * 180 / np.pi,
np.arctan(ni) * 180 / np.pi <
3 * 180 * np.arctan(np.sqrt(ni2[ii, jj])) / np.pi)
P = P[angle_index]
nini = ni[angle_index]
nnk = nini.shape[0]
nini = nini.reshape(nnk, 1)
# local incidence angle
theta_l = np.abs(theta_eq[jj] - np.arctan(nini).reshape(nnk, 1))
# geometric scattering coefficients [Plant 1997] equation 5,6
eps_sin = np.sqrt(const.epsilon_sw - np.sin(theta_l)**2)
# compute the wave number for bistatic geometry
kbr = 2 * kr * np.sin(theta_l) * np.cos(bist_ang_az[jj] / 2)
kkbr = np.sort(kbr[:, 0])
T = Trans_func(kkbr, K[ii, jj], u_10, fetch, azimuth,
div[ii, jj])[np.argsort(kbr[:, 0])].reshape(nnk, 1)
Skb = B_int_single(kkbr.reshape(nnk, 1), u_10, fetch,
eq_azi[jj])[np.argsort(kbr[:, 0]), :] * (
1 + abs(T)) / kbr.reshape(nnk, 1)**4
Skb_pi = B_int_single(kkbr.reshape(nnk, 1), u_10, fetch, np.pi +
eq_azi[jj])[np.argsort(kbr[:, 0]), :] * (
1 + abs(T)) / kbr.reshape(nnk, 1)**4
Skb_r = (Skb + Skb_pi) / 2 # Kudryavtsev 2003a equation 2
if polarization == 'VV':
G = np.cos(theta_l)**2 * (const.epsilon_sw - 1) * (
const.epsilon_sw *
(1 + np.sin(theta_l)**2) - np.sin(theta_l)**2) / (
const.epsilon_sw * np.cos(theta_l) + eps_sin)**2
G = np.abs(G)**2
else:
G = np.cos(theta_l)**2 * (const.epsilon_sw -
1) / (np.cos(theta_l) + eps_sin)**2
G = np.abs(G)**2
# pure Bragg scattering NRCS
br0 = 16 * np.pi * kr**4 * G * Skb_r
# Bragg scattering composite model
BR = br0 * P.reshape(nnk, 1)
# integral over kbr >= kd
a = np.tan(theta_eq[jj] - const.d /
(2 * np.cos(bist_ang_az[jj] / 2)))
b = np.tan(theta_eq[jj] + const.d /
(2 * np.cos(bist_ang_az[jj] / 2)))
Br[ii, jj] = np.trapz(BR[nini <= a], nini[nini <= a]) + np.trapz(
BR[nini >= b], nini[nini >= b])
return Br