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Lake Ice Symbols
Two International Egg Code Eggs

Row A

Total concentration: the ice coverage of an area determined by its concentration and expressed in tenth (in this example, 7/10)

Row B

Partial concentration: the break-down of the total ice coverage expressed in tenths and graded by thickness. The thickest starting from the left and in this example, 2/10 is the thickest.

Row C

Stage of development: the type of ice in each of the grades, determined by its age, that is 1/10 is thick lake ice (7), 2/10 is medium lake ice (5) and 3/10 is thin lake ice (4).

Row D

Floe Size: the form of the ice determined by its floe size for each section. In this example, big floes (5) for thick lake ice (7); medium floes (4) for medium lake ice (5); and small floes (3) for thin lake ice (4).

ColumnDescription
ETrace of ice thicker/older then Sa
FThickest
GSecond thickest
HThird thickest
IAdditional groups

Lake Ice Symbols

open water symbolOpen Water ice free symbolIce Free fast ice symbolFast Ice

Stage of Development (SoSaSbScSdSe)

Description Thickness Code
New Ice < 5 cm 1
Thin Lake Ice 5 - 15 cm 4
Medium Lake Ice 15-30 cm 5
Thick Lake Ice 30-70 cm 7
Very Thick Lake Ice > 70 cm 1.
Undetermined/Unknown   X

Floe Size (FaFbFc)

Description Width Code
Pancake ice   0
Small ice cake; brash ice < 2m 1
Ice cake 2 - 20m 2
Small floe 20 - 100m 3
Medium floe 100 - 500m 4
Big floe 500 - 2000m 5
Vast floe 2 - 10 km 6
Giant floe > 10 km 7
Fast Ice   8
Undetermined or unknown   X
Ice in strips   SC

Concentration of Ice

Open water < 1/10Open Water
Very open drift 1-3/10Very open drift
Open drift 4-6/10Open drift
Close pack/drift 7-8/10Close pack
Very close pack 9/10Very close pack
Very close pack 9+/10Very close pack
Compact/Consolidated ice10/10Compact/Consolidated ice

WMO Concentration Colour Code - Lake Ice

Colour* Description
Ice Free
< 1 Tenth Ice
1-3 Tenths Ice
4-6 Tenths Ice
7-8 Tenths Ice
9-10 Tenths Ice
Fast Ice of Unspecified Stage of Development
Undefined Ice
Optional
No Information Areas for which no information is known are identified accordingly.

* Colour is based on total ice concentration.



WMO Stage of Development Colour Code - Lake Ice

Colour Description Thickness
Ice Free  
Ice of Unspecified Stage of Development (open water)  
New Lake Ice <5 cm
Thin Lake Ice 5-15 cm
Medium Lake Ice 15-30 cm
Thick Lake Ice 30-70 cm
Very Thick Lake Ice > 70 cm
Fast Ice of Unspecified Stage of Development  
Undefined Ice  

Colour is based on stage of development of predominant ice.