Campbell SkyVUE 8, Руководство по эксплуатации продукта

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Appendix B. Cloud height
calculation
The scatter profile is inverted (using the Klett inversion technique) and an extinction profile is
calculated.
Cloud base heights are identified using two criteria as follows (cloud is detected if either of them
is met).
Criterion 1: likely cloud bases are estimated based on increasing slope of the extinction profile of
at least 7 m (22.9 ft) per bin (bin width is 5 m (16.4 ft) and an extinction threshold. This threshold
is based on an extinction coefficient (EXCO) of 3, equivalent to a horizontal visibility (MOR) of
1000 m (3280 ft). This results in a number of possible cloud bases at different heights.
Criterion 2: horizontal visibility falls below an average of 4800 m (15,748 ft) over 300 m (984 ft)
starting at an altitude of 1000 m (3280 ft).
To report a cloud layer above a lower one the scatter coefficient first has to fall below the
extinction threshold used for cloud definitions (less a small hysteresis offset). The scatter profile
must then again meet the criteria above.
If rain is detected, the sensitivity of detection is increased by a factor of 3.
To avoid many very narrow close layers being reported when they have little significance a
minimum separation based on WMO reporting intervals is applied. The separation is ± 30 m
(98 ft) below 1500 m (4921 ft) and 300 m (984 ft) above 1500 m (4921 ft). The lowest cloud height
is used. If a thin cloud identified by Criterion 2 above is within ±150 m (492 ft) of a cloud
identified by criterion 1, then the thin cloud is ignored.
SkyVUE™8 (CS136) LIDAR Ceilometer 95