If you use the single scattering lidar in uvspec

source sslidar

the vertical resolution of the lidar profile is typically much better than the vertical resolution of the provided atmospheric profiles. The optical properties are by default assumed to be constant within the atmospheric layers, which results in steps in the lidar profiles.

Steps due to molecules are unrealistic as the air density steadly decreases with height. The vertical resolution of the molecular profiles needs to be increased to make the profiles from the lidar simulator more realistic. The scripts in addlevel.tar.gz can be used for that purpose. Extract them in the libRadtran directory.

In the following we increase the vertical resolution of the provided UVSPEC_SSLIDAR.INP example:

cd example
../src/addlevel_for_sslidar ../data/atmmod/afglus.dat UVSPEC_SSLIDAR.INP > afglus_temp.dat

This script calculates the heights of the lidar range bins from the sslidar options provided in the input file and creates a new atmosphere file containing these heights. The profiles are linearly interpolated. Specify the new atmosphere_file in UVSPEC_SSLIDAR.INP

atmosphere_file afglus_temp.dat

and run it

../bin/uvspec < UVSPEC_SSLIDAR.INP

The steps due to molecules are removed, only steps due to aerosol and cloud layers remain visible. See the green line in the figure below, where the 'range-corrected signal' (number of photons multiplied with square of range in km) is plotted. The lidar is looking downward from a height of 8.55km.

 
 
user_area/adding_atmospheric_levels_for_single_scattering_lidar.txt ยท Last modified: 2013/10/18 11:40 by josef
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