Ice
and iceberg charts serve tactical or strategic planning and operational
purposes. They illustrate ice or iceberg conditions at a particular moment in
time. The ice information is presented using a standard international code The
World Meteorology Organization (WMO) system for sea ice symbology is referred
to as the "Egg Code" due to the oval shape of the symbol.
The basic data concerning concentrations, stages of development (age)
and form (floe size) of ice are contained in a simple oval form. A maximum of
three ice types is described within the oval. This oval and the coding
associated with it are referred to as the "Egg Code". To
indicate ice observations interpreted from radar imagery, the oval shall be
omitted.
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| Common Practice |
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| Canadian Practice |
Above figures are shown for thickness, floe sizes or other dimensions, a report
coinciding with the end point of a range shall be coded as the higher value.
This code conforms to international
convention and shall be used in coding all visual sea ice and lake ice
observations without exception.
The symbols Ca Cb Cc and Fa Fb Fc correspond
to Sa Sb Sc respectively.
In common practice Cd Se and Fe are no included but in
Canada they are using Cd Se and Fe to enable
the reporting of additional classes, especially during freeze-up and
break up.
The specific details and rules for
completing each level of information within the egg are given below.
CONCENTRATION (C)
Ct - Total concentration of ice in area, reported in tenths. May be
expressed as a single number or as a range, not to exceed two tenths (3-5, 5-7
etc.)
Ca Cb Cc - Partial concentration (Ca,
Cb, Cc) are
reported in tenths, as a single digit. These are reported in order of
decreasing thickness. Ca is the
concentration of the thickest ice and Cc is the concentration of the thinnest ice.
Less than 1/10 (i.e. traces) shall not be reported within the
oval except to describe open water. When only one ice
type is present, the partial concentration shall not be indicated. When one ice type is present with a trace of a thinner type, only total
concentration of the major ice type shall be indicated
STAGE OF DEVELOPMENT (S)
Stage of development of thickest (So), second thickest (Sa ), third thickest (Sb ) fourth thickest (Sc ) ice fifth thickest (Sd ) and the thinner
ice types Se, of which the concentrations are reported by Ca Cb Cc Cd respectively.
NOTE: If there is a dot (.), all stages of development codes
to the left of the dot (.) are assumed to carry the dot (.)) These codes
correspond directly with the partial concentrations above. Ca is the concentration of stage Sa, Cb is the concentration of stage Sb, and Cc is the concentration of Sc.
So Sd Se - Development stage (age) of remaining ice types. So if reported is a trace of ice type thicker/older than Sa. Se is a thinner ice type which is reported when there are four or more
ice thickness types.
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| Coding for Sea-Ice Stages of Development (So Sa Sb Sc Sd Se) |
FORM OF ICE (F)
Floe Size
corresponding to Sa Sb Sc Sd and Se (when Sd and Se are
greater than a trace).
World Meteorological
Organization International procedures also permit reporting of Fp and Fs as the
primary and secondary forms of all the ice without reference to stage of
development.
It
is Canadian practice to report Fa Fb Fc as predominant floe sizes of Sa Sb Sc respectively. This makes it necessary, when only Sa and Sb are present, that Fa and Fb shall be followed by a dash (-) where Fc would normally appear.
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| Coding for Forms of Ice (Fa Fb Fc Fd Fe) |
Example
Description:
9+/10 total ice concentration. 3/10
old ice in small floes, 2/10 thick first-year ice in medium floes, 1/10 thin
first-year ice in small floes, 2/10 grey-white ice in small floes, and the
remaining 2/10 is new ice with no floe form.
Reference:
US / Canada Met Department
