backscatter_angle_zenith

At the zenith, singular point can be found.

''' At the zenith, singular point can be found.
'''

import os
import sys
import logging
logging.basicConfig()
import datetime
import math

import matplotlib.pyplot as plt
import numpy as np
import scipy as sp

from irfpy.cena import backscatter_angle

def main():

    sza = 0.
    scza = 0.

    # Prepare the phi values.
    phis = np.arange(0., 360)
    flist = np.zeros_like(phis)

    # From backscatter function implemented by me in Schaufelberger 2011
    for idx, phi in enumerate(phis):
        f = backscatter_angle.fs(sza, phi, scza)
        flist[idx] = f

    print('--- zn ---')
    print(backscatter_angle.z0(sza))
    print(backscatter_angle.z1(sza))
    print(backscatter_angle.z2(sza))
    print(backscatter_angle.z3(sza))

    print('--- fn at 0 ---')
    print(backscatter_angle.f0(sza, 90., scza))
    print(backscatter_angle.f1(sza, 90., scza))
    print(backscatter_angle.f2(sza, 90., scza))
    print(backscatter_angle.f3(sza, 90., scza))
    
    # From calculation manually
    phirad = phis * np.pi / 180.
    fhand = 0.007366 * (0.03002 * np.cos(phirad * 2) + 0.96998) * ( 0.06422 * np.cos(phirad) + 0.93578)

    fig = plt.figure()
    ax = fig.add_subplot(111)
    ax.plot(phis, flist, '-')
    ax.plot(phis, fhand, '-')

if __name__ == '__main__':
    main()