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ocbrdf/Raman.py

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+import numpy as np
+import xarray as xr
+
+''' 来自 Lee 等人 (2013) 的拉曼校正：
+      《全球海洋中紫外-可见太阳辐射的穿透：来自海洋水色遥感的见解》
+      J Geophys Res Oceans 2013;118:4241–55
+
+    光谱插值在最近波段进行
+'''
+
+""" 拉曼校正查找表的类 """ # TODO 存储并在 ADF 中读取
+class Raman():
+    def __init__(self):
+        bands = [412,443,488,531,551,667]
+        coords = {'bands': bands}
+        self.alpha = xr.DataArray([0.003,0.004,0.011,0.015,0.017,0.018], dims='bands', coords=coords)
+        self.beta1 = xr.DataArray([0.014,0.015,0.010,0.010,0.010,0.010], dims='bands', coords=coords)
+        self.beta2 = xr.DataArray([-0.022,-0.023,-0.051,-0.070,-0.080,-0.081], dims='bands', coords=coords)
+
+    def correct(self, Rrs):
+        # Interpolate coefficients at nearest bands
+        interp_opt = {'method':'nearest', 'kwargs':{'fill_value':'extrapolate'}}
+        alpha = self.alpha.interp(bands=Rrs.bands, **interp_opt)
+        beta1 = self.beta1.interp(bands=Rrs.bands, **interp_opt)
+        beta2 = self.beta2.interp(bands=Rrs.bands, **interp_opt)
+
+        # Select reference bands closest to 440 and 550
+        Rrs440 = Rrs.sel(bands=440, method='nearest')
+        Rrs550 = Rrs.sel(bands=550, method='nearest')
+
+        # Compute Raman factor
+        RF = alpha*Rrs440/Rrs550 + beta1*np.power(Rrs550,beta2)
+
+        # Correct
+        return Rrs/(1+RF)
+