Cloud Base Height Retrievals

This example shows how to calculate the cloud base heights using the sobel edge detection method. This can be used for vertical radar and lidar data.

Author: Adam Theisen

Average difference between ceilomter and sobel heights  84.37419

from arm_test_data import DATASETS
from matplotlib import pyplot as plt
import act
import numpy as np

# Read Ceilometer data for an example
filename_ceil = DATASETS.fetch('sgpceilC1.b1.20190101.000000.nc')
ds = act.io.arm.read_arm_netcdf(filename_ceil)

ds = act.retrievals.cbh.generic_sobel_cbh(
    ds, variable='backscatter', height_dim='range', var_thresh=1000.0, fill_na=0.0
)

# Plot the cloud base height data
display = act.plotting.TimeSeriesDisplay(ds, subplot_shape=(1, 2), figsize=(16, 6))
display.plot('backscatter', subplot_index=(0, 0))
title = 'SGP Ceilometer with Lidar-Calculated CBH Overplotted'
display.plot('first_cbh', subplot_index=(0, 0), color='k', set_title=title)

display.plot('backscatter', subplot_index=(0, 1))
title = 'SGP Ceilometer with CBH Overplotted'
display.plot('cbh_sobel_backscatter', color='k', subplot_index=(0, 1), set_title=title)

diff = ds['first_cbh'].values - ds['cbh_sobel_backscatter'].values

print("Average difference between ceilomter and sobel heights ", np.nanmean(diff))

ds.close()
plt.show()