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Format for Gridded Sea Ice Information (SIGRID)


Thomas Thompson. 1981. Proposed Format for Gridded Sea Ice Information (SIGRID). Unpublished report prepared for the World Climate Programme.


Contents

1. Introduction
2. Encoding of Sea Ice Information
The Charts
General Layout of the Tape Format
3. Header File
Layout
4. Chart Data File
Header Record
Grid Line Record
Record of Data Groups
5. Coding Procedures
General
Chart Data File (SIGRIDNN)
Specification of symbolic letters
6. Data Groups
Categories of Parameters
Identification of Parameters Within a Data Group
Dynamic Processes
Water Openings
Topography features (ridges and rafting)
Thickness of Ice
Surface Features And Melting Forms
Icebergs or Ice of Land Origin
Sea Surface Temperature
Source of Information
Land area
7. The Grid
General
Positioning of the grid
Variation of Grid Resolution
8. Examples
Example 1. Digitized Norwegian Ice Chart of 1 February 1979
Example 2. Digitized Norwegian Ice Chart of 1 February 1979
Explanation of the Code Figures
List of Parameter Identifiers and Parameters
List of Sea Ice Parameters

Code Tables
Code Table 1 - Concentration
Code Table 2 - Thickness of Ice or Stage of Development
Code Table 3 - Form of Ice
Code Table 4 - Dynamic Processes
Code Table 5 - Direction Indicator
Code Table 6 - Form of Water Opening
Code Table 7 - Number of Water Openings
Code Table 8 - Nature of Topography Feature (deformation)
Code Table 9 - Age of Topography Feature
Code Table 10 - Snow Depth
Code Table 11 - Melting Forms
Code Table 12 - Ice of Land Origin
Code Table 13 - Number of Icebergs
Code Table 14 - Observational Methods
Code Table 15 - Grid subdivision Indicator

1. Introduction

A vast amount of sea ice information is today available at the various ice services in the world. Almost all of this information is stored in the form of ice charts for operational purposes. For statistical or climatological use the chart format is however not convenient and the information needs to be digitized. This is done by assigning numerical values to the ice parameters and to read these values at given grid points on the chart. The values read at each grid point is representative for the ice conditions in a well defined area around the point.

The charts prepared by the various ice services do not all contain the same number of parameters. The resolution and accuracy also vary according to the use for which the charts are intended. A large degree of flexibility has therefore to be built into the design of both code, format and grid. it should allow digitization of historical ice charts as well as current ones in order to obtain a comprehensive computer-compatible sea ice data bank which is currently updated. The SIGRID format is mainly designed to meet larger scale climate requirements but it may also be used by national services for other purposes.

This report concentrates on conventional sea ice parameters as this is considered most important in the light of present operational practices and the large amount of historical sea ice charts that need to be digitized. It is however realized that remote sensing methods are gradually becoming more and more sophisticated and that automatic interpreted remotely sensed data may supplement some of the conventional sea ice parameters. Provisions have therefore been made to allow for these types of data to be included in the code when required.

2. Encoding of Sea Ice Information

The Charts

On sea ice charts the ice parameters are represented by symbols and accompanying numbers giving the actual values of the parameters. The various sea ice services have up to now used their own symbols and one of the problems encountered when designing a coding system for sea ice information is this lack of uniformity. A new international system of sea ice symbols has however recently been developed and approved by WMO. This symbology forms the basis for the coding system proposed for digitizing sea ice charts. The symbology covers most parameters contained in the various sea ice charts and as the parameters are basically the same on all charts irrespective of symbology used it is possible to digitize charts based on the old as well as the new international sea ice symbols.

As the various ice charts do not contain the same number of parameters and as these may have different accuracy and resolution the code has been designed to allow for an arbitrary number of parameters to be digitized. The grid system can further be varied to cover the required resolution. As an example it will be possible to digitize only the total ice concentration with a resolution of say 4 degrees longitude X 2 degrees latitude. It will also be possible to digitize 20 parameters for each grid point with a resolution of for instance 0 degrees, 30 minutes longitude by 0 degrees 15 minutes latitude. The grid will be geographical but it can easily be expanded to a Cartesian if such a requirement occurs.

General Layout of the Tape Format

It is assumed that the digitized sea ice charts will be registered on magnetic tape. The individual sea ice services will be responsible for the digitizing and punching procedures and these problems have therefore not been taken up in this study. Control procedures etc. will have to be agreed upon but this will be taken up at a later stage.

A magnetic tape containing digitized sea ice data should include Header files and chart data files. The header file will contain information relevant to the whole or major portions of the tape. Each chart data file will contain information relevant to one ice chart and will include a header record, grid line records and data groups. See figure 1.

Figure 1

Organization of digitized sea ice information on magnetic tape

3. Header File

Layout

The DS-name of the file should be :SIGRIDINF." The header file should contain all information relevant to a set of uniform ice charts from the dame ice services using the same grid. Any changes in grid, grid area of parameters should be preceded by a new header file. The header file contains the following information:

  • Type of information identifier (SIGRID)
  • Originating country
  • Originating Service
  • Meshwidth of grid
  • Starting point of grid
  • Size of gridded area
  • Total number and types of parameters included

Further should any information pertinent to the whole tape be included. This may refer to new parameters in which case they should be clearly defined as well as any other deviation from the coding procedures internationally agreed upon. The header file may also contain information on control procedures used and any other background information facilitating the use of the data. The header file should always include information on the maximum number of grid lines, grid points and parameters than can occur in any one chart on the tape. This will allow for the appropriate space to be allocated in the computer. The record length should be 80 characters.

4. Chart Data File

Layout

The DS-name of this file should be "SIGRIDNN," where NN is the sequential number of file starting from 01. This file contains all information relevant to the individual ice charts and is divided into three records as follows:

  • Reader record
  • Grid line record
  • Data group records

Header Record

Contains all information required for the identification of the chart:

  • Date and time
  • Serial number of chart
  • Number and types of parameters included

Grid Line Record

This record contains information necessary for the identification of the information in grid points lying on the same grid line:

  • Start of grid line indicator
  • Configuration of grid area (longitude/latitude ratio)
  • Coordinates of starting point of grid line
  • Number of grid points along grid line

Record of Data Groups

The record of a data group will contain the actual sea ice information for each grid point as read from the chart. It will contain:

  • Start of data group indicator
  • Grid subdivision indicator (if required)
  • Indicator for number of following consecutive points for which identical data is repeated (if required)
  • Ice parameters

5. Coding Procedures

General

All information is coded for easy identification of all background information, as well as all data for the digitized ice charts. One exception is the possibility of including plain language information on the header file for additional information. This plain language information should follow after the coded information.

Header File	SIGRINF

		:AAFcFcNNN
		(:AQcLaLaLaLaLoLoLoLoLo :Bn_n_n_n_n-n:Cd2d2d2d2)
			   :DNtNtPtPt...PtPt

Chart Data File (SIGRIDNN)

Header Record	:EJJJMMYYGGGpGp:FNsNsNs
		:GNpNpP2P2:HP=P=NpNn
Grid Line Record:KZZ:Lmmmppp:MNpNpNp
Data Group	:NGIRNrNrP2P2

Specification of Symbolic Letters

In this report the symbolic letters are typed in italics: letters used as indicators on the tape record are printed in normal letter style. The following specifications of identifiers and symbolic letters are given in the order in which they appear in the record.

SIGRIDINF - identifier of header file

: - start of a new information group

AA - area or country from which the data originate (See WMO Pub No. 365, Part 11, Attachment 11-6, Table 8)

FcFc - Centre, Service or institution from which the data originate (table to be established)

NN - Catalogue number of grid used (See WMO Pub. No. 9, Volume 3). If the grid specification is not included in this publication, the grid can be defined by the following groups identified by the letters A, B and C. Use in this case NN = 099

( ) - If the grid is specified by means of a WMO catalogue number, groups within parentheses are omitted.

A B C ...R - indicators

QcLaLaLaLaLoLoLoLoLo - latitude and longitude of origo (starting point) of a geographical grid. The grid lines are scanned towards increasing latitudes (south to north in the Northern Hemisphere and north to south in the Southern). The grid points are scanned from west to east along grid lines (applies to the Southern as well as the Northern Hemisphere)

nlnlnl - maximum number of grid lines (along meridian)

npnpnp - maximum number of grid points (along parallels)

dldldldl - mesh width of grid (distance between grid lines along meridians) in degrees and minutes.

NtNt - total number of sea ice parameters occurring on the charts

PtPt...PtPt - identifiers of all sea ice parameters occurring on the charts

SIGRIDNN - identifier of Chart Data File with sequential number (NN)

JJJ - century, decade and year (e.g. 982 = 1982)

MM - month of the year; from 01 to 12

YY - day of the month, from 01 to 31

GG - time of chart in whole hours, GMT

GpGp - period (+/- whole hours)of observations on which chart is based

NsNs - serial number of chart (determined by national centre)

NpNp - number of sea ice parameters included in each grid point without being separately identified in these points (see note 1).

PiPi...PiPi - identifiers of sea ice parameters and order in which they are included in each grid point without being separately identified in these points (see note 1).

PIPI - identifier of sea ice parameters defined individually for actual chart

Np - number of parameters defined by PIPI

Nn - number of digits per parameter defined by PIPI

= - sign that identifies the start of grid line record

ll - longitude/latitude mesh width ratio (example: distance between grid lines (N-S) 2 degrees, distance between grid points (E-W) 4 degrees, ll = 2).

mmmppp - coordinates of first grid point of a grid line, expressed as the number of grid points along the meridian (mmm) and along the parallel (ppp) counted from the origo (the origo has the coordinates 001001)

NpNpNp - number of grid points on grid line

: - start of data group indicator, used to separate data groups

GI - grid subdivision indicator (see Code table 14)

NrNr - number of consecutive grid points for which the identical information is repeated. (The RNrNr should not occur when the information only refers to one point). When, for instance RnrNr = RO2, the actual and the following point contain identical information.

PiPi - identifier of sea ice parameter within a data group. The data group may include one or several sea ice parameters all identified by PiPi, unless all grid points contain the same parameters in which case the parameters are identified in the Header Record (see Note 1).

6. Data Groups

Categories of Parameters

A data group consist of one or several sea ice parameters which correspond to a grid point. The parameters in a data group are representative for one mesh rectangle (for instance a geographical rectangle where the length along the parallels is 2 degrees and along the meridians 1 degree). the grid point is in the middle of the rectangle. The parameters are divided into nine main categories which contain one or several sub-elements.

The sea ice parameters are defined according to the new International System of Sea Ice Symbols. Each parameter is identified in the record by two letters, e.g. CT (total concentration of ice). The first letter identifies the category of the parameter while the second identifies parameters within the category. In the following tables the letters B,C,D,E,L,O,R,S,T and W are used as category indicators; the rest of the alphabet is left for future use.

The letters X, Y and Z are however reserved for use by individual services should they wish to include parameters not contained in the internationally agreed list. The X, Y, and Z may be used together with any other letter of the alphabet. The use of X, Y, Z should be clearly explained in the Tape Header File at the beginning of each tape. The number of parameters defined in the following tables is 53.

The following categories are proposed for general use:

Category   Elements
Indicator

   c	Concentration, stage of development and form of ice
	  (including strips  and  patches) 
   D	Dynamic processes
   v	Water openings
   R	Topography  features
   E	Thickness of ice
   s	Surface features and melting forms
   B	Ice bergs or ice of land origin
   T	Sea surface temperature
   0	Source of information on which chart is based
   L	Land area

Identification of parameters within a data group

In order to identify unambiguously a parameter within a data group, each parameter is defined by an identifier. The identifier can be used in the header record to define the parameter or parameters and the order in which they appear at each grid point. The identification of parameters in the header record shall be used when they occur at all or most of the grid points. Parameters not occurring at most of the grid points could preferably be identified at each grid point.

It should be noted that the recording of parameters on a tape record is less subject to space restrictions as are their coding for telecommunicated reports or plotting in the form of symbols on a sea ice chart. For archiving purposes, there is a greater freedom of choice of the number of digits to be used to record a parameter; this facilitates later processing of the data. Thus, for the recording of for instance, sea ice concentration, two digits are proposed.

The following parameter identifiers are defined:

  • Concentration
  • Stage of development
  • Form of ice

According to the New International System of Sea Ice Symbols, seven cases need to be distinguished:

  1. CT- Total concentration, CC (code table 1)
  2. CA - Partial concentration, stage of development (or thickness) and form of thickest ice CaCaSaSaFaFa (code tables 1, 2 and 3)
  3. CB - Partial concentration, stage of development, and form of second thickest ce,CbCbSbSbFbFb (code tables 1, 2 and 3)
  4. CC - Partial concentration, stage of development and form of third thickest ice, cCcScScFcFc (code tables 1, 2 and 3)
  5. CF - Predominant FpFp and secondaryFsFs form of ice (code table 3)
  6. CN - Stage of development of ice thicker than reported by SaSc, but with a concentration less than 1/10, SoSo (code table 2)
  7. CD - Stage of development of any remaining class of ice, SdSd, not reported under CA, CB or CC (code table 2); note that no concentration or form of ice is reported for SoSo and SdSd
	
Coding:	CTCC CACaCaSaSaFaFa  CBCbCbSbSbFbFb
	CCCcCcScScFcFc   (CFFpFpFsFs)   CNSoSo CDSdSd

Dynamic Processes

DP- Dynamic processes dp (code table 4)
DD - Direction of dynamic processes,D(code table: 5)
DR - Rate of ice drift in tenths of knots (ViVi).
DO - Source of information, Op (code table 14)
Coding: - DPdp DDD DRViVi DOOp

Water Openings

WF - Form of water openings, Wj (code table 6)
WN - Number of water openings, No (code table 7)
WD - Orientation (direction) of water openings, D (code table 5)
WW - Width of water openings, WwWw (in hundreds of meters)
WO - Source of information, Op (code table 14)
Coding: WFWf WDD WWWwWw WNNo WOOp

Topography Features (Ridges And Rafting)

RN - Nature of topography feature, Rn (code table 8)
RA - Age of topography feature, Ra (code table 9)
RD - Orientation of topography feature, D (code table 5)
RC - Concentration of topography feature, CrCr (code table 1)
RF - Frequency of topography feature, RfRf (number per nautical mile)
RH - Height (mean) of topography feature, RhRh in tenths of meters
RO - Source of information, Op (code table 14)
RX - Maximum height of topography feature, RxRx in tenths of meters
Coding: RNRn RARa RDD RCCrCr RFRfRf
RHRhRh RXR=R= ROOp

*Drift of icebergs to be reported under "Icebergs or ice of land origin"

Thickness of Ice

EM - Mean thickness of level ice in cm, tEtEtE
EX - Maximum thickness of level ice in cm, TxTxTx

To indicate whether the thickness is estimated or measured, the following convention may be used:

  • last digit of tEtEtE T=T=T= is 0 or 5: estimated
  • last digit is any other number: measured
EI - Thickness interval, tntntnt=t=t=
  • tntntn = lower limit in centimeters
  • t=t=t= = upper limit in centimeters
EX 35 - 50 EIO35050 (tntntn = 35 cm, t=t=t= = 50 cm)
EO - Source of information, Op (code table 14)
Coding: EM tEtEtE Xt=t=t=EItntntnt=t=t=EOOp

Surface features and melting forms

SC - Concentration of snow (areal coverage) in tenths, CsCs
SN - Snow depth, s (code table 10)
SD - Orientation (direction) of sastrugies, D(code table 5)
SM - Melting forms, ms (code table 11)
SA - Area coverage of water on ice in tenths, mcmc
SO - Source of information, Op (code table 14)
Coding: SCCsCs Sns SDD SMms SAmama SOOP

Icebergs or ice of land origin

BL - type of iceberg, BiBs (code table 12)
BD - direction of drift of iceberg, D (code table 5)
BE - rate of drift in tenths of knots, ViVi
BN - number of icebergs, nBnB (code table 13)
BY - day of month (YY) when iceberg(s) was (were) sighted
BO - source of information, Op (code table 14)
Coding: BLBiBs BDD BRViVi BNnBnB BYYY BOOp

Sea surface temperature

TT - sea surface temperature in tenths of degrees, TwTwTw
TO - source of information, Op (code table 14)
Coding: TTTwTwTw TOOp

Note: If the temperature is negative, the first digit should be coded by a minus sign.

Source of information

OP - primary source of information on which the chart is based, Op (code table 14)
OS - secondary source of information on which the chart is based, Os (code table 14)
OT - tertiary source of information on which the chart is based, Ot (code table 14)
Coding: OPOp OSOs OTOt

Land area

LL - grid point over land A list of parameter identifiers and parameters is given in Annex 1 and a list of parameters with definitions in Annex 2. Code tables are given in Annex 3

7. The Grid

General

Provision is only made for one type of grid, the geographical. This in order to facilitate the compilation of data from different centres, which cover over-lapping geographical areas. The following definitions are used in this report:

Grid Line: Line connecting all grid points having the same latitude

Grid Point: A point in the middle of a square or rectangle where the dimension corresponds to the mesh width along parallels and meridians. The distance between the grid points corresponds to the above mesh width. The ice information for a grid point is representative for the grid square in which the grid point lies.

Data Group: Group which contains information on one or several ice parameters relative to one grid point (or several consecutive grid points with identical information on a grid line).

Mesh Width: The length of the sides of the rectangles, in the middle of which the grid point lies. The sides of the rectangle will in most cases have different lengths in a geographical grid (e.g. 2 degrees along parallels and 1 degree along meridians).

Scanning Mode: the order in which the grid points are scanned. In a geographical grid the grid points are scanned along grid lines from west to east (0 to 360 degrees). The grid lines are scanned towards increasing latitudes (south to north in the Northern Hemisphere and north to south in the Southern).

Positioning of the Grid

A grid will consist of a number of sequential grid lines along which lie a number of sequential grid points. An example of a geographical grid is given in figure 3. The grid covers an area from 67 degrees N to 83 degrees N and 33 degrees W to 40 degrees E corresponding to the Norwegian ice chart shown in figure 4. The grid squares have a mesh width of 2 degrees Long. X 1 degree Lat from 67 degrees N to 75 degrees N and 4 degrees Long. X 1 degree Lat. from 76 degrees N to 83 degrees N. The origo is placed in the lower left corner. The grid lines are numbered and scanned from south to north and the grid points from west to east. When digitizing a chart, the "coordinates" of the first point on each grid line shall be given, e.g. 008007. This would mean that the first point on grid line 008 to be scanned is No. 007. This point is marked with x in figure 3.

To identify a grid the following information is needed:

  • the coordinates of the origo
  • the mesh width (grid distance) along meridians which is constant for each chart
  • the longitude/latitude ratio for each grid line (this will allow the ratio long/lat to be changed when moving along the meridians)

The following ratio (Long/Lat) is recommended:
Latitude	Long/Lat	Mesh width along parallels
intervals			if mesh width along meridians
				is 60 nm (1 degree lat)

00 - 50		1		60 nm - 39 nm
50 - 75		2		77 nm - 31 nm
75 - 80		4		52 nm - 42 nm	
80 - 85		6		63 nm - 31 nm
85 - 87		12		63 nm - 38 nm
87 - 89		20		63 nm - 21 nm
89 - 895	40		42 nm - 21 nm
895 - 90	80		42 nm

Variation of Grid Resolution

The information contained in an ice chart will generally not be evenly distributed. Over large areas the conditions may be fairly uniform and a course grid may suffice here. In other areas more detailed information may be shown, especially along coast lines and along the ice edges. A more detailed recording of information in such limited areas without having to use a fine grid for the entire chart is made by the insertion of local subdivisions of the grid. The subdivision is then indicated by a "subdivision indicator."

Three levels of subdivisions have been provided for, with a view to dividing the original grid square into four, nine or 16 areas according to figure 2. The basic grid may be defined as :first order" and the following finer meshes as second, third and fourth respectively. The number of sub-areas for each of these orders will be 12 =1, 22 =4, 32 =9 and 42 =16.

Example: a geographical grid has a basic mesh width of 1 latitude by 2 longitude; the second order will have 4 grid squares with a mesh width of 1/2 latitude by 1 longitude, the third order 9 grid squares with a mesh width of 1/3 latitude by 2/3 longitude, and the fourth order 16 grid squares with a mesh width of 1/4 latitude by 1/2 longitude. Expressed in degrees and minutes this would be 1 x 2, 30'x 1, 20' x 40', and 15' x 30'. The grid subdivision is indicated by a subdivision indicator which for the basic grid is set to 1, second order to 2, third order to 3 and fourth order to 4.

Grid Square Subdivision

Figure 2, Subdivision of a Grid Square

8. Examples

As an example of gridding and digitizing a sea ice chart, the Norwegian ice chart from 1 October 1979 was chosen. The mesh width of the grid is constant 1 degree along the meridians and 2 degrees along the parallels south of 75 degrees N and 4 degrees north of 75 degrees N. The origo of the grid lies at 67 degrees north, 33 degrees west. The grid is shown in figure 3. The sea ice information has only been digitized for two grid lines 009 and 010. In Example 1 each parameter is identified at each grid point, while in Example 2 the parameter CT (total concentration of ice) is defined in the Header Record and identified at each grid point by its position.

Example 1. Digitized Norwegian Ice Chart of 1 February 1979

	SIGRIDINF
	:NOMI:099:A7670003300:B018036:C0100:D05CTCAWFWDTT
	SIGRID01
	:E97902011200:F009
	=K02:L009007:M032
	:R02CT92CA929908:RO3CT90:407CT80:N2CT80:CT402F6WD3
	:CT00:CT60Wf6WD7:CT00:TT000:TT010:TT015:N2CT10:TT000:TT005
	:CT40WF6WD7:CT50WF6WD7:RO3CT80:N2CT40:CT20WF6WD5:CT80:CT70
	:CT30WF6WD1:R02 CT20WF6WD2:CT60WF6WD3:CT70:RC2CT90:R02CT80
	=K04:L010004:M016
	:CT92CA929908:R02CT90:CT90:CT80:CT60WF6WD3:CT0CTT005
	:CT01TT005:N2CT0155005:CT40WF6WD4:CT60WF6WD7:CT00
	:CT70WF6WD3:R02CT80:CT90:R04CT90
	=k04:L011004:M016
	:99:99:99

Example 2. Digitized Norwegian Ice Chart of 1 February 1979

	SIGRIDINF
	:NOMI:099:A7670003300:B018036:C0100:D05CTCAWFWDTT
	SIGRID01
	:E97902011200:F0009:G01CT
	=KD2:L009007:M032
	:R0292CA929908:R0390:R0780:N280:40WF6WD3:00:60WF6WD7:00
	:00TT000:00TT01000TT015:N210:00TT000:00TT005:40WF6WD7
	:50WF6WD7:R0380:N240:20WF6WD5:80:70:30WF6WD1:R0220WF6WD2
	:60WF6WD2:70:R0290:R0280
	=k04:L010004:M016
	:92CA929908:R0290:90:80:60WF6WD3:00TT005:01TT005:N201TT005
	:40WF6WD4:60WF6WD7:00:70WF6WD3:R0280:90:R0490
	=K04:L011004:M016
	:99:99:99
		

Explanation of the Code Figures

NO		= Norway
MI		= Meteorological Institute
099		= Geographical Grid with definitions
A7670003300	= Coordinates of origo (67 00' N, 3300' W)
B0018036	= Maximum number of grid lines (18) and maximum number 
			of grid points along grid line (36)
C0100		= Grid mesh (1 degree along meridians)
D05CTCAWFWDTT	= Total number of parameters digitized (5)
			and identifiers of these parameters
E97902011200	= Date of chart (1 February 1979 12 GMT)
F009		= Serial number of chart (no 9/1979)
G01CT (example 2) = Number of parameters (1) and parameter
			not identified in each grid point
=		= Start of grid line
K02		= Ratio between longitude and latitude
			(2 long/1 lat)
L009007		= coordinates of starting point of grid line
M032		= number of grid points along grid line
:		= start of first data group
R02		= number of grid points for which the same data
			apply (two grid points)
CT92 (example 1) = total concentration = 10/10
92 (example 2)	= total concentration = 10/10
CA92		= Partial concentration of thickest ice = 10/10
99		= stage of development of ice unknown
08		= form of ice = fast ice
:		= start of second data group (applies to third grid point)
R03		= number of grid points for which the same data
			apply (three grid points)
CT90 (example 1) = total concentration = 9/10
90 (example 2)	= total concentration = 9/10
:		= start of third data group (sixth grid point)
RO7		= seven consecutive grid points are identical
CT80 (example 1)= total concentration = 8/10
80 (example 2)	= total concentration = 8/10
:		= start of fourth data group (thirteenth grid point)
N2		= grid square subdivided into four subsquares
CT80 (example 1)= total concentration in first subsquare = 8/10
80 (example 2)	= total concentration in first subsquare = 8/10
:		= start of fifth data group (subsquare 2)
CT40 (example 1)= total concentration = 4/10
40 (example 2)	= total concentration = 4/10
WF6		= form of water opening = ice edge (6)
WD3		= orientation of ice edge = SE - NE (3)
:		= start of sixth data group (subsquare_3)
CT00 (example 1)= open water
00 (example 2)	= open water
:		= start of seventh data group (subsquare 4)
CT60 (example 1)= total concentration = 6/10
60 (example 2)	= total concentration = 6/10
WF6		= form of water opening = ice edge (6)
WD7		= orientation of ice edge = NW - SE (7)
:		= start of eighth data group (fourteenth grid point)
CT00 (example 1)= open water
00 (example 2)	= open water
:		= start of ninth data group (fifteenth grid point)
00 (example 2)	= open water
TT000		= sea surface temperature = 00.0 c

List of Parameter Identifiers and Parameters

Parameter        Parameter(s)       Number of         Digits per     Total number of   
   Identifier                          Parameters        parameter           digits       
       CT                CC         	1                 2                 2                 
       CA           CaCaSaSaFaFa    	3                 2                 6                 
       CB           CbCbSbSbFbFb    	3                 2                 6                 
       CC           CcCcScScFcFc    	3                 2                 6                 
       CF             FpFpFsFs      	2                 2                 4                 
       CN               SoSo       	1                 2                 2                 
       CD               SdSd        	1                 2                 2                 
       DP                dp        	1                 1                 1                 
       DD                D          	1                 1                 1          
       DR               ViVi        	1                 2                 2          
       DO                Op         	1                 1                 1          
       WF                Wf         	1                 1                 1          
       WN                No         	1                 1                 1          
       WD                D          	1                 1                 1          
       WW               WwWw        	1                 2                 2          
       WO                Op         	1                 1                 1          
       RN                Rn         	1                 1                 1          
       RA                Ra         	1                 1                 1          
       RD                D          	1                 1                 1          
       RC               CrCr        	1                 2                 2          
       RF               RfRf        	1                 2                 2          
       RH               RhRh        	1                 2                 2          
       RO                Op             1                 1                 1          
       RX               RIRI            1                 2                 2          
       EM              tEtEtE           1                 3                 3          
       EX              txtxtx           1                 3                 3          
       EI           tntntntxtxtx        2                 3                 6          
       EO                Op             1                 1                 1          
       SC               CsCs            1                 2                 2          
       SN                s              1                 1                 1          
       SD                D              1                 1                 1          
       SM                ms             1                 1                 1          
       SA               mama            1                 1                 1          
       SO                Op             1                 1                 1          
       BL               BiBs            1                 2                 2          
       BD                D              1                 1                 1          
       BR               ViVi            1                 2                 2          
       BN               nBnB            1                 2                 2          
       BY                YY             1                 2                 2          
       BO                Op             1                 1                 1          
       TT              TwTwTw           1                 3                 3          
       TO                Op             1                 1                 1          
       OP                Op             1                 1                 1          
       OS                Os             1                 1                 1          
       OT                Ot             1                 1                 1          
       LL                               0                                   0          
   Total: 46                        	53                                  88                

List of Sea Ice Parameters

BiBs		-type and size of iceberg (code table 12)

CC -total concentration of all ice in the area, reported in tenths (code table 1)

CaCa -Partial concentration of respectively thickest, CbCb second thickest and third thickest ice, reported in CcCc tenths (code table 1)

CrCr -concentration of topography features, in tenths (code table 1)

CsCs -concentration of snow coverage in tenths (code table 1)

D -1) Direction of dynamic processes (code table 5) -2) Orientation of water openings (code table 5) -3) Orientation of sastrugies (code table 5) -4) Orientation of topography feature (code table 5) Note: compacting of ice in for instance NE-SW direction is recorded either as 1 or 5

dp -dynamic processes (code table 4)

FaFa FbFb FcFc -form of ice corresponding to SaSa, SbSb, andScSc respectively (code table 3)

FpFp - predominant (FpFp) and secondary (FsFs) form FsFs of ice (code table 3)

MaMa -area coverage of melt water in tenths

Ms -melting forms (code table 11)

No -number of water openings (code table 7)

nBnB -number of icebergs (code table 13) (WMO code 2877)

Op -Observational method for individual parameters (code table 14)

Op -primary (Op), secondary (Os) and tertiary (Ot) Os source of observation on which the ice chart is Ot based (code table 14)

Ea -age of topography feature (code table 9)

RfRf -frequency of topography feature, in number per nautical mile

EhEh -mean height of topography feature, in tenths of meters

RxRx -maximum height of topography feature, in tenths of meters

Rn -nature of topography feature (code table 8)

SaSa -stage of development of respectively thickest, SbSb second thickest and third thickest ice, of which ScSc the concentration is reported by CaCa, CbCb and CcCc respectively (code table 2)

SdSd -stage of development of any remaining class of ice not reported by SaSa, SbSb, ScSc or SoSo (code table 2)

SoSo -stage of development of ice thicker than SaSa but with a concentration less than 1/10 (code table 2)

s -snow depth (code table 10) (WMO code )

TwTwTw -sea surface temperature, in tenths of degrees

tEtEtE -mean thickness of ice in centimeters

tntntn -minimum thickness in thickness interval

txtxtx -maximum thickness of ice, in centimeters

ViVi -rate of ice drift, in tenths of knots

Wf -form of water openings (code table 6)

WwWw -width of water openings, in hundreds of meters

YY -day of month when icebergs were sighted

Code Tables


Code Table 1 - Concentration (CC, CaCa, CbCb, CcCc, CrCr, CsCs)

					Code Figure

Ice free 00 Less than 1/10 (open water) 01 Bergy water 02 1/10 10 2/10 20 . . . . . . 9/10 90 more than 9/10 less than 10/10 (9+) 91 10/10 92 concentration intervals ClCh

(Cl = lowest concentration in interval) Ch = highest concentration in interval)

Examples:

1/10 - 3/10 13

4/10 - 6/10 46

7/10 - 9/10 79

7/10 - 10/10 71

Unknown 99


Code Table 2 - Thickness of ice or stage of development (SaSa, SbSb, ScSc, SdSd, SoSo)

					Code Figure

Ice free 00 Ice thickness in cm 01 . . 50 55 cm 51 60 cm 52 65 cm 53 70 cm 54 thickness 80 cm 56 interval, 5 cm 85 57 90 58 95 59 -------------- 100 60 110 61 120 62 130 63 thickness 140 64 interval 10 cm 150 65 160 66 170 67 180 68 190 69 --------------- 200 70 thickness 250 71 interval 50 cm 300 72 350 73 --------------- 400 74 thickness 500 75 interval, 600 76 100 cm 700 77 800 78 --------------- 900 79 No stage of development 80 new ice 81 nilas, ice rind less than 10 cm 82 young ice 10 - 30 cm 83 gray ice 10 - 15 cm 84 gray-white ice 15 - 30 cm 85 first year ice 30 - 200 cm 86 thin first year ice 30 - 70 cm 87 thin first year stage 1 30 - 50 cm 88 thin first year stage 2 50 - 70 cm 89 for later use 90 medium first year ice 70 - 120 cm 91 for later use 92 thick first year ice greater than 120 cm 93 for later use 94 old ice 95 second year ice 96 multiyear ice 97 glacier ice 98 undetermined/unknown 99


Code Table 3 - Form of ice (FaFa, FbFb, FcFc, FpFp, FsFs)

						Code Figure
Pancake ice			30 mm -3 m		00
Shuga/small ice cake, brash ice	less than 2 m across		01
Ice cake			less than 20 m across		02
Small floe			20 m - 100 m		03
Medium floe			100 m - 500 m		04
Big floe			500 m - 2 km		05
Vast floe			2 km - 10 km		06
Giant floe			greater than 10 km across		07
Fast ice						08
Growlers, floebergs or floebits				09
Icebergs						10
Strips and patches					11
Level ice						12
Undetermined or unknown					99

Code Table 4 - Dynamic processes (dp)

					Code Figure

Compacting ice, no intensity given 0 Compacting ice, slight 1 Compacting ice, considerable 2 Compacting ice, strong 3 Diverging ice 4 Shearing ice 5 Ice drift, rate 0,1 - 0,9 knots 6 Ice drift, rate 1,0 - 1,9 knots 7 Ice drift, rate 2,0 - 2,9 knots 8 Ice drift, rate 3,0 knots or more 9

Note: When actual rates of ice drive (ViVi) are given, code figure ViVi = 99 is used for rate unknown


Code Table 5 - Direction indicator (D) (see WMO code 0700)

Direction Indicator Schematic

The direction is identified in relation to the grid. In a geographical grid, 1 would indicate northeast, 2 east, 3 southeast, etc.


Code Table 6 - Form of water opening (Wf)

	
					Code Figure

cracks 1 crack at specific location 2 lead 3 frozen lead 4 polynia ` 5 ice edge 6


Code Table 7 - Number of water openings (No)

					Code Figure

1 1 2 2 3 - 5 3 5 - 10 4 > 10 5


Code Table 8 - Nature of topography feature (deformation) (Rn)

					Code Figure

rafting 1 hummocks 2 ridges 3 jammed brash barrier 4


Code Table 9 - Age of topography feature (Ra)

					Code Figure

New 1 weathered 2 very weathered 3 aged 4 consolidated 5


Code Table 10 - Snow depth (s) (see WMO code)


Code Table 11 - Melting forms (ms)

	
		Code Figure			Code Figure

no melt 0 many thaw holes 5 few puddles 1 dried ice 6 flooded ice 3 rotten ice 7 few thaw holes 4 few frozen puddles 8 all frozen puddles 9


Code Table 12 - Ice of land origin (BiBs)

Type (Bi) Code Figure Size (Bs) Code Figure

growler and/or
bergy bit		1	unspecified		0
iceberg unspecified	2	small			1
iceberg, glacier berg	3	medium			2
iceberg, dome		4	large			3
iceberg, pinnacled	5	very large		4
iceberg, tabular	6
ice island		7
floeberg		8
radar target		9
(suspected iceberg)


Code Table 13 - Number of icebergs (nBnB) (see WMO code 2877)


Code Table 14 - Observational methods (Op, Os, Ot)

					Code Figure

visual surface observation 1 visual aircraft observation 2 visual and infrared satellite observation 3 passive microwave satellite observation 4 radar surface or airborne observation 5 radar satellite observation (SAR) 6 laser/scatterometer/sonar 7 data buoys 8 estimated (temporal and/or spatial) 9 unknown 0


Code Table 15 - Grid subdivision indicator (GI)

					Code Figure

second order subdivision (4 squares) 2 third order subdivision (9 squares) 3 fourth order subdivision (16 squares) 4