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Where N
i
and N
j
are the sum of hits of each bin and H
i
and H
j
the respective heights.
Find the pair with the minimum distance D and combine into one bin with the height of the
lowest and number of hits of the combined total.
This process is repeated until 5 or less bins remain. These are now taken as cloud layers.
Finally, if cloud layers are closer than the distances below, then they are merged with the height
of the lowest and combined total number of hits.
Height range
Distance (D)
Height ≤ 300 m
(1000 ft)
≤ 90 m
(300 ft)
300 m < Height ≤ 900 m
(1000 ft < Height ≤ 3000 ft)
≤ 120 m
(400 ft)
900 m < Height ≤ 1500 m
(3000 ft < Height ≤ 5000 ft)
≤ 180 m
(600 ft)
1500 m < Height ≤ 2400 m
(5000 ft < Height ≤ 8000 ft)
≤ 300 m
(1000 ft)
Height > 2400 m
(8000 ft)
≤ 480 m
(1600 ft)
Weights per layer are used to calculate number of oktas per layer.
If the total possible is W
max
, then the cover is (W
i
/W
max
) x 8.
Cloud amounts are rounded up to the next highest whole oktas.
For layers above the lowest this is based on the maximum possible weights. If the lower layers
have W
1
hits and the next layer has W
2
hits, then the cover of the higher layer is given by:
(W
2
/(W
max
-W
1
)) x 8
For example, taking weighting into account, if lower layers of cloud only allow 4/8 of clear sky
above and the cover is 2/8 out of those 4/8, then the layer above is taken as 4/8.
Finally, only layers meeting the following criteria are reported:
Layer 1 ≥ 1/33 oktas
Layer 2 ≥ 3 oktas
Layer 3 ≥ 5 oktas
Layer 4 ≥ 7 oktas
Layer 5 ≥ 7 oktas
Any layer > (8 – 1/33) oktas is reported as 8 oktas
SkyVUE™8M Tactical LIDAR Ceilometer
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