Lufft CHM 15k Nimbus, Manual

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Data Evaluation/ Sky Condition Algorithm (SCA)
68 Revision R09, November 2016
9.6 Parameters for data evaluation
A set of parameters controls the data evaluation routine. The system dependent
values are stored on the laser optical unit. User accessible data are listed within
the table 4 and table 5. Additional parameters are listed in table 26.
9.7 Determination of Maximum Detection Range (MXD)
The maximum detection range defines the maximum distance at which signifi-
cant signals can still be measured. It derives from averaged signal/noise ratios
versus the distance range. At heights which are beyond the planetary boundary
layer, significant signals are only generated by clouds or aerosol layers. The max-
imum detection range is calculated independently from the cloud detection
algorithm and can be used to cross check that result, e.g. in a case when the
ceilometer can not detect a cloud layer nor a vertical visibility the MXD can be
used for verification if the clear sky result is correct.
s
Fig. 26: Diagram to illustrate the evaluation process for different cloud parameters. In case the
instrument is operated in tilted mode the ranges are corrected by the zenith angle.
signal (Pr ) 2
cloud base height
(cbh)
threshold
threshold − 10%
cloud penetration depth
(cpd)
cbe
distance
cde