Concentration Reclassification Scheme:
Stage Reclassification Scheme:
If V ≤ 0.5, then V = 0
If V ≤ 0.25, then V = 0
If 0.5 < V ≤ 1.5, then V = 1
If 0.25 < V ≤ 1.5, then V = 1
If 1.5 < V ≤ 2.5, then V = 2
If 1.5 < V ≤ 2.5, then V = 2
If 2.5 < V ≤ 3.5, then V = 3
If 2.5 < V ≤ 3.5, then V = 3
If 3.5 < V ≤ 4.5, then V = 4
If 3.5 < V ≤ 4.5, then V = 4
If 4.5 < V ≤ 5.5, then V = 5
If 4.5 < V, then V = 5
If 5.5 < V ≤ 6.5, then V = 6
If 6.5 < V ≤ 7.5, then V = 7
If 7.5 < V ≤ 8.5, then V = 8
If 8.5 < V ≤ 9.5, then V = 9
If 9.5 < V, then V = 10
We used ArcView's Spatial Analyst extension to convert the grid data sets into vec-
tor polygon representations and to consolidate contiguous cells with the same value
into a single polygon. This step was done separately for both the concentration values
and the stage values. Finally, we hand-edited on screen to smooth the polygon shapes
and to consolidate orphaned polygon fragments.
Probability distribution ranges were determined for 1) any occurrence of ice and 2)
ice of at least 5/10ths concentration (Map Sets 2 and 3, respectively). The calculations
were accomplished using the map algebra tools of ArcInfo Grid. Grids for each two-
week period were reclassified to create a set of binary grids for any ice and a set for
5/10ths or greater. Cell values were then calculated for the percent occurrence for the
selected condition for each respective two-week period from:
N
Gi
Gp = ∑
i =1 N
Gi = selected condition individual two-week binary grid
N = total number of grids for the two-week period.
The grid for the two-week period, Gp, was reclassified according to the following
scheme:
0 ≤ V ≤ 0.01
0.01 < V ≤ 25
25 < V ≤ 50
50 < V ≤ 75
75 < V ≤ 100.
This produced a grid that depicted probabilities stratified at 25% intervals. This entire
procedure is diagrammed in Figure C1.
93
Previous Page
