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.

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:

The grid for the two-week period, *G*p, 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.

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