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NMC Office Note 84
Packing and Identification
of
NMC Grid-Point Data
INTRODUCTION
The purpose of this Office Note is to provide information
related to NMC grid point data fields. It describes the data
structure used and presents the rationale and details involved in
identifying and packing the fields. Because of the availability
and efficiency of existing software as well as the convenience of
augmenting existing data sets, a large number of requirements have
been accommodated since the procedures were first introduced years
ago. As might be expected, some exceptions to these procedures
have crept into usage. These involve a minor amount of non-
conformity to the ON84 standard units and to the usual packing
procedures. These exceptions, where known, are indicated.
NMC PACKED BINARY DATA FORMAT
Most NMC grid point data fields are packed by transforming
32-bit IBM floating point numbers into 16-bit IBM halfword
integers using a scaling algorithm which will be described later.
A 12-word label which prefaces each data array serves two
purposes: 1) it uniquely identifies the data field for retrieval
of the data set from where it is stored, and 2) it contains count
and scaling information so that the data, which follows the label,
may be unpacked and converted back into an array of floating point
numbers. Spectral coefficients are stored without packing. In
this case, each complex coefficient is composed of two 32-bit IBM
floating point real numbers.
DATA PACKING AND UNPACKING
The most common method for scaling and packing the data is
as follows.
First, compute a reference value A by finding the maximum
and minimum data values, QMAX and QMIN, respectively. Use
these two values to determine the mid-range of the data array:
A = (QMAX + QMIN) / 2.0
Next, find the binary scaling value n, the least integer
such that:
(QMAX - A) < 2**n
88-01-01 1 NMC Office Note 84
The reference value A is stored as a 32-bit IBM floating
point number in word 10 of the 12-word label. The binary scaling
value n is stored as an IBM halfword integer in the right half
of word 11. (See Figure 1.)
Then the data array is scaled according to:
H(j) = (Q(j) - A) * 2**(15 - n), j=1,J
where Q(j) is a 32-bit IBM floating point number to be packed,
and J is the number of data points to be packed. The scaled
values H(j) are rounded, converted to halfword integers, and
stored in sequence following word 12 of the label. If the field
is of two dimensions or more, the points are taken in the order
they occur in storage. J will be the product of the dimensions.
Negative values of n as well as negative values of H(j) are
stored in standard IBM two's complement form.
NMC data fields can be packed and unpacked following the
method just described with library subroutines W3AI00 and W3AI01.
The casual users of NMC packed fields need not concern themselves
further with the packing details except to note that signed values
with 15-bit precision are maintained. The precision of the data
that is retained by the scaling algorithm depends inversely on the
range of values in the original array; i.e., the smaller the
range, the greater the precision retained. The procedure of using
a reference value which is the mid-range of the data array and
forming anomalies for packing yields the same precision as using a
reference level which is the minimum value of the data array and
forming positive anomalies packed into 16-bit halfwords. The
functions IW3GET and IW3PUT have the unpacking and packing
subroutines built in for the convenience of the user.
In packing a data field, the reference value A and the
scaling factor n can, of course be preset by the creator of the
field rather than using the packing subroutine (W3AI00). This
procedure affects only the precision of the data generated and
does not prohibit the use of the unpacking subroutine (W3AI01), as
long as all 12 label words are properly set.
IDENTIFYING THE DATA FIELDS
Each packed data field is uniquely identified in the first 5
words of its 12-word label. These 5 words specify the data type,
the type and value of the (constant) surface on which the data are
given, the forecast (projection) time (including the value zero),
the grid type, and any other parameters needed.
Most NMC data fields can be thought of as some quantity Q
on a horizontal or quasi-horizontal surface S at some level
value L. For example, a 500-mb height field would be identified
by specifying Q = height, S = pressure, and L = 500. Another
example is Q = pressure, S = mean sea level, and L = 0 (not
88-01-01 2 NMC Office Note 84
applicable). If the quantity Q is for a layer, the domain of
the layer is given by S1 at L1 and S2 at L2. In this case,
the surface of S1 is the one physically above the surface of S2.
For example, the thickness of the (500/1000)-mb layer is specified
by Q = height, S1 and S2 = pressure, L1 = 500, and L2 = 1000.
Another possibility is that the quantity Q is formed by
differencing two fields of the same data type, e.g., constant
pressure height for different levels (thickness) or constant
pressure height for the same level for different times (tendency).
The identifications for these examples, as well as for many other
possibilities, can be constructed by carefully considered
combinations of the markers T, M, X, and N, as described in
Tables 2 through 5, below.
The numerical value of the level L for the corresponding
surface S is coded in words 2 and 4 of the label as follows.
Represent L as:
L = C * 10**E
where C is a 5-digit signed decimal integer whose high-
order digit is non-zero unless L itself is zero, and E is a
signed integer, zero if L is zero. For example, if L = 500:
C = 50000
E = -2
so that:
L = 50000 * 10**(-2)
Again, if L = 0.83333
C = 83333
E = -5
so that:
L = 83333 * 10**(-5)
LABEL ELEMENT VALUES
Table 1 gives the code figures for Q and S, the data type
and surface.
Table 2 gives the values for the marker T which is used to
specify time intervals. It also explains how the values of F1
and F2 are to be specified.
88-01-01 3 NMC Office Note 84
Table 3 gives values for the marker M which is used to
specify data fields involving layers, and to indicate whether
fields have been initialized.
Table 4 gives values to be used for the exception marker X,
which is used to specify a data field whose date/time (YYMMDDII)
precedes that of the date/time found in the data set identifier
table. (This option is used, for example, to store first guess
fields from an earlier cycle in a current cycle data set).
Table 5 gives values for the miscellaneous marker N, which
is used to specify types of spectral coefficient data and also to
indicate that forecast times are in units of half days rather than
hours.
Table 6 gives values for the markers CM and CD which
specify climatological data fields.
Table 7 gives values for the marker K which identifies the
grid for which the data are given. Table 7 lists a combination of
grids currently in operational use at NMC as well as others which
have been used in the past. The grids thought to be active as of
the date of this Office Note are so indicated in the table.
The vertical grid lines of an NMC grid can be considered
columns (i) and the horizontal grid lines can be considered rows
(j). The coordinate system is the normal right-hand cartesian
system in which i increases from left to right and j increases
from bottom to top. Grid point values for the columns are stored
in consecutive array locations starting with the bottom row.
Succeeding rows are stored in a like manner progressing from the
bottom to the top of the grid. This follows the usual FORTRAN
indexing procedure for a two-dimensional array.
For polar stereographic projection grids, the orientation is
defined as the longitude value 1) which parallels the vertical
grid lines and 2) for which latitude increases as j increases.
This longitude may lie within or without the domain of the grid
and may or may not coincide with a grid line.
Table 8 gives the values for the marker KS which
identifies how the field was derived; e.g., by spectral methods,
by departures from climatological normals, etc.
Values from the tables described above, used in combination
with values for surfaces (C1,E1 and C2,E2) and values for
forecast hours F1 and F2, are sufficient to identify a data
field.
Word 6 is for internal (computer) use and can be ignored.
Word 7 gives the date and time of either the nominal
observation time of the data used in the analysis, or the initial
time of the forecast. The time II is specified in Universal
88-01-01 4 NMC Office Note 84
Coordinated Time (UTC) in hours: 00-23. For example, for
midnight UTC II = 00, for noon UTC II = 12. YY is the year of
the century, 00-99, MM is the month of the year, 1-12, and DD
is the day of the month, 1-31. The date and time are entered as
8-bit integers in the format YYMMDDII.
The remainder of the label should be filled out as shown in
Figure 1. Note that most users rely upon standard NMC library
subroutines to accomplish packing the data. These subroutines
will also initialize words 9 and 10 and the scaling value in word
11. The user must supply J, the number of data points, in word 8
for the packing subroutine (W3AI01).
Table 9 gives the values of the marker R which specifies
the run within the cycle.
Table 10 gives the values for the marker G which specifies
the program which generated the field. Programs which are
currently in operational use as of the date of this Office Note
are so indicated.
Tables 9 and 10 are intended primarily for internal NMC use.
The markers R and G in some data fields may have these
parameters specified in a manner other than that given in this
Office Note.
Table 11 contains the hexadecimal representations of some
commonly used values of C. Negative values of C and E are
indicated by turning on the high-order bit of these parameters,
thus using sign-and-magnitude representation.
Table 12 shows some examples of identifying some commonly
generated data fields.
Table 13 gives the values for the marker P which specifies
the number of bits which have been used to pack each grid point
value. While the most common number of bits used is 16 (for which
P = 0), there are some fields which have been packed using fewer
bits. In these cases, the data array is scaled according to:
H(j) = (Q(j) - A) * 2**((P-1) - n), j=1,J
88-01-01 5 NMC Office Note 84
Table 1 - Q and S
PARAMETERS AND SURFACES
Number Abbreviation Item Units
Hex Dec (*)
-----------------------------------------------------------------
Height wrt mean sea level
1 1 -HGT-- Geopotential gpm
2 2 -P-ALT Pressure altitude gpm
Distance wrt Earth's surface
6 6 -DIST- Geometric distance above m
7 7 -DEPTH Geometric distance below m
8 8 -PRES- Atmospheric pressure mb
9 9 -PTEND Pressure tendency mb/sec
Temperature
10 16 -TMP-- Atmospheric temperature degree K
11 17 -DPT-- Dewpoint temperature degree K
12 18 -DEPR- Dewpoint depression degree K
13 19 -POT-- Potential temperature degree K
14 20 -T-MAX Maximum temperature degree K
15 21 -T-MIN Minimum temperature degree K
16 22 -TSOIL Soil temperature degree K
Vertical motion
28 40 -V-VEL Vertical velocity dp/dt mb/sec
29 41 -NETVD Net vertical displacement mb
2A 42 -DZDT- Vertical velocity dz/dt m/sec
2B 43 -OROW- Orographic component dz/dt m/sec
2C 44 -FRCVV Frictional component dz/dt m/sec
Wind
30 48 -U-GRD U comp. of wind wrt grid m/sec
31 49 -V-GRD V comp. of wind wrt grid m/sec
32 50 -WIND- Wind speed m/sec
33 51 -T-WND Thermal wind speed m/sec
34 52 -VW-SH Vertical speed shear 1/sec
35 53 -U-DIV Divergent u comp wrt grid m/sec
36 54 -V-DIV Divergent v comp wrt grid m/sec
88-01-01 6 NMC Office Note 84
Number Abbreviation Item Units
Hex Dec (*) Table 1 - Q and S (cont)
-----------------------------------------------------------------
37 55 -WDIR- Direction from which wind is degree
blowing (wrt North)
38 56 -WWND- Westerly comp. of wind m/sec
39 57 -SWND- Southerly comp. of wind m/sec
3A 58 -RATS- Ratio of speeds non-dim.
3B 59 -VECW- Vector wind (spectral) m/sec
3C 60 -SFAC- Steadiness factor percent
3D 61 -GUST- Wind gustiness m/sec
3E 62 D-DUDT Diffusive u-comp. accel. m/sec**2
3F 63 D-DVDT Diffusive v-comp. accel. m/sec**2
Fluid flow functions
48 72 -ABS-V Absolute vorticity 1/sec
49 73 -REL-V Relative vorticity 1/sec
4A 74 -DIV-- Divergence 1/sec
50 80 -STRM- Stream function m**2/sec
51 81 -V-POT Velocity potential m**2/sec
52 82 -U-STR Westerly comp. of wind stress N/m**2
53 83 -V-STR Southerly comp. of wind stress N/m**2
54 84 -TUVRD Westerly wind comp. accelera- N/m**2
tion by vertical diffusion
55 85 -TVVRD Southerly wind comp. accelera- N/m**2
tion by vertical diffusion
56 86 XGWSTR x-component of gravity wave N/m**2
drag
57 87 YGWSTR y-component of gravity wave N/m**2
drag
Moisture
58 88 -R-H-- Relative humidity percent
59 89 -P-WAT Precipitable water kg/m**2
5A 90 -A-PCP Accumulated total precip meter
5B 91 -P-O-P Probability of precipitation percent
5C 92 -P-O-Z Prob. of frozen precipitation percent
5D 93 -SNO-D Snow depth m
5E 94 -ACPCP Accumulated convective precip m
5F 95 -SPF-H Specific humidity kg/kg
60 96 -L-H2O Liquid water kg/kg
61 97 -RRATE Rainfall rate kg/m**2/sec
62 98 -TSTM- Probability of thunderstorm percent
63 99 -CSVR- Conditional probability of percent
severe local storm
64 100 -CTDR- Conditional probability of percent
major tornado outbreak
65 101 -MIXR- Mixing ratio kg/kg
66 102 -PSVR- Unconditional probability percent
of severe local storm
88-01-01 7 NMC Office Note 84
67 103 -MCONV Moisture convergence kg/kg/sec
88-01-01 8 NMC Office Note 84
Number Abbreviation Item Units
Hex Dec (*) Table 1 - Q and S (cont)
-----------------------------------------------------------------
68 104 -VAPP- Vapor pressure mb
69 105 -NCPCP Accumulated non-convective m
precipitation
6A 106 -ICEAC Ice accretion rate m/s
6B 107 -NPRAT Non-convective precip rate kg/m**2/sec
6C 108 -CPRAT Convective precipitation rate kg/m**2/sec
6D 109 -TQDEP Deep conv. moisture tndcy. kg/kg/sec
6E 110 -TQSHL Shallow conv. moisture tndcy. kg/kg/sec
6F 111 -TQVDF Vertical diffusion moisture kg/kg/sec
tendency
Stability
70 112 -LFT-X @Lifted index degree K
71 113 -TOTOS @Total totals degree K
72 114 -K-X-- @K-index degree K
73 115 -C-INS @Convective instability degree K
74 116 -4LFTX 4-layer lifted index degree K
75 117 -A-EVP Accumulated evaporation meters
Wave components
78 120 -L-WAV Long wave component of gpm
geopotential
79 121 -S-WAV Short wave component of gpm
geopotential
Miscellaneous surfaces/levels
80 128 -MSL-- Mean sea level -----
81 129 -SFC-- Earth's surface (base of -----
atmosphere)
82 130 -TRO-- Tropopause -----
83 131 -MWSL- Maximum wind speed level -----
84 132 -PLYR- Oceanographic primary layer -----
85 133 -A-LEV Anemometer Level -----
86 134 -T-AIL Top of Aircraft Icing Layer
87 135 -B-AIL Bottom of Aircraft Icing Layer
Sigma domain
90 144 -BDY-- Boundary -----
91 145 -TRS-- Troposphere -----
92 146 -STS-- Stratosphere -----
93 147 -QCP-- Quiet cap -----
94 148 -SIG-- Entire atmosphere -----
88-01-01 9 NMC Office Note 84
Number Abbreviation Item Units
Hex Dec (*) Table 1 - Q and S (cont)
-----------------------------------------------------------------
Miscellaneous parameters
A0 160 -DRAG- Drag coefficient non-dim.
approx. range:
100-1200 (on maps 5&27)
.001-.009 (on maps 29&30)
A1 161 -LAND- Land/sea flag non-dim.
values: land=-1; sea=0
A2 162 -KFACT K factors (700 mb to 500 mb non-dim.
normal ratio)
A3 163 -10TSL Conversion consts (1000 mb to mb/m
sea level pressure)
A4 164 -7TSL- Sea level pressure specifi- mb/m
cation from 700 mb heights
A5 165 -RCPOP Regression coefficients for percent/m
probability of precip.
A6 166 -RCMT- Regression coefficients for deg K/m
mean temperature
A7 167 -RCMP- Regression coefficients for m(precip)/m
mean precipitation
A8 168 -ORTHP Orthogonal pressure function mb
A9 169 -ALBDO Albedo non-dim.
approx. range: 0.06 - 0.80
AA 170 -ENFLX Energy flux watt/m**2
AB 171 -TTHTG Temperature tendency from deg K/sec
heating
AC 172 -ENRGY Energy statistics (various)
AD 173 -TOTHF Total heat flux downward watt/m**2
AE 174 -SPEHF Sensible + evaporative heat watt/m**2
flux upward
AF 175 -SORAD Solar heat flux downward watt/m**2
B0 176 -LAT-- Latitude degree N
B1 177 -LON-- Longitude degree W
B2 178 -RADIC Radar intensity non-dim.
B3 179 ------ @@Ceiling Height (TDL) m
B4 180 ------ ##Visibility (TDL) m
B5 181 ------ Liquid Precip. (Y/N) (TDL) binary
B6 182 ------ Freezing Precip. (Y/N) (TDL) binary
B7 183 ------ Frozen Precip. (Y/N) (TDL) binary
B8 184 -PROB- Probability percent
B9 185 -CPROB Conditional probability percent
BA 186 -USTAR Surface friction velocity m/sec
BB 187 -TSTAR Surface friction temperature degree K
BC 188 -MIXHT Mixing height m
88-01-01 10 NMC Office Note 84
Number Abbreviation Item Units
Hex Dec (*) Table 1 - Q and S (cont)
-----------------------------------------------------------------
BD 189 -MIXLY Number of mixed layers next (integer)
to the surface
BE 190 -DLRFL Downward flux of long-wave watt/m**2
radiation
BF 191 -ULRFL Upward flux of long-wave watt/m**2
radiation
C0 192 -DSRFL Downward flux of short-wave watt/m**2
radiation
C1 193 -USRFL Upward flux of short-wave watt/m**2
radiation
C2 194 -UTHFL Upward turbulent flux of watt/m**2
sensible heat
C3 195 -UTWFL Upward turbulent flux of water kg/m**2/sec
C4 196 -TTLWR Temperature tendency from deg K/sec
long-wave radiation
C5 197 -TTSWR Temperature tendency from deg K/sec
short-wave radiation
C6 198 -TTRAD Temperature tendency from deg K/sec
all radiation
C7 199 -MSTAV Moisture availabililty non-dim.
C8 200 -RDNCE **Radiance watt/m**2/sr/m
C9 201 -BRTMP **Brightness temperature degree K
CA 202 -TCOZ- **Total column ozone kg/m**2
CB 203 -OZMR- **Ozone mixing ratio kg/kg
CC 204 -SWABS Rate of absorption of short- watt/m**2
wave radiation
CD 205 -TTLRG Temperature tendency from deg K/sec
large scale precipitation
CE 206 -TTSHL Temperature tendency from deg K/sec
shallow convection
CF 207 -TTDEP Temperature tendency from deg K/sec
deep convection
D0 208 -TTVDF Temperature tendency from deg K/sec
vertical diffusion
D1 209 -STCOF Soil thermal coefficient joules/m**2/deg
88-01-01 11 NMC Office Note 84
Number Abbreviation Item Units
Hex Dec (*) Table 1 - Q and S (cont)
-----------------------------------------------------------------
Cloud-cover variables
D2 210 -CDLYR Amount of non-convective cloud non-dim.
D3 211 -CDCON Amount of convective cloud non-dim.
D4 212 -PBCLY Pressure at the base of a mb
non-convective cloud
D5 213 -PTCLY Pressure at the top of a mb
non-convective cloud
D6 214 -PBCON Pressure at the base of a mb
convective cloud
D7 215 -PTCON Pressure at the top of a mb
convective cloud
D8 216 -SFEXC Exchange coefficient at (kg/m**3)*m/sec
surface
D9 217 -ZSTAR Surface roughness length m
DA 218 -STDZG Standard deviation of ground m
height
Oceanographic variables
130 304 -UOGRD U comp. of current wrt grid m/sec
131 305 -VOGRD V comp. of current wrt grid m/sec
180 384 -WTMP- Water temperature degree K
181 385 -WVHGT Height of wind-driven waves m
182 386 -SWELL Height of sea swells m
183 387 -WVSWL Combined height of waves and m
swell
184 388 -WVPER Period of wind-driven waves sec
185 389 -WVDIR Direction from which waves degree
are moving (wrt North)
186 390 -SWPER Period of sea swells sec
187 391 -SWDIR Direction from which swells degree
are moving (wrt North)
188 392 -ICWAT Ice-free water surface percent
190 400 -HTSGW Significant wave height m
191 401 -PERPW Primary wave period sec
88-01-01 12 NMC Office Note 84
Number Abbreviation Item Units
Hex Dec (*) Table 1 - Q and S (cont)
-----------------------------------------------------------------
192 402 -DIRPW Direction from which primary degree
waves are moving (wrt North)
193 403 -PERSW Secondary wave period sec
194 404 -DIRSW Direction from which secondary degree
waves are moving (wrt North)
195 405 -WCAPS White cap coverage percent
-----------------------------------------------------------------
* Abbreviations are 6 characters. A dash (-) is used to
indicate a blank when printed.
** These data types do not use the standardized ON84
identification scheme and may have been stored in non-
standard units. Contact NMC/CAC/AIB for further infor-
mation.
@ 273.15 degrees has been added to the original data values.
@@ Has been stored in units of 100s of feet.
## Has been stored in the units of miles.
wrt means "with respect to"
--------------------------------------------------------------
88-01-01 13 NMC Office Note 84
Table 2 - T
TIME MARKER
(4 bits)
T (Dec) Meaning F1 (*) F2 (*)
----------------------------------------------------------------
0 Instantaneous field. E.g., 500-mb Fcst time 0
height forecast: Q of Q
F1 = 0 denotes an analysis unless
M set equal to 8, 9, or 10. See Table 3.
1 Field formed from 2 fields whose Fcst time Fcst time
valid times are equal but whose of Q2 of Q2 minus
forecast times may or may not be fcst time
equal. E.g., difference between 2 of Q1
analyses (times equal), or diff-
erence between a forecast and the
verifying analysis (times unequal):
Q2 - Q1
2 Field formed from 2 fields whose Fcst time Valid time
forecast times are equal but whose of Q1 and of Q2 minus
valid times are unequal. E.g., a Q2 valid time
tendency field formed by differ- of Q1
encing 2 analyses which are 12
hours apart: Q2 - Q1
3 Field formed from 2 fields whose Fcst time Fcst time
initial times are equal but whose of Q2 of Q2 minus
forecast times are unequal. E.g., fcst time
a forecast tendency field: Q2 - Q1 of Q1
4 Field of normal values averaged Days used 0
over a number of days, where F1 in average
= number of days and F2 = 0, or
averaged over a number of years, -or- -or-
where F1 = 0 and F2 = number of
years. 0 Years used
in average
5 Non-instantaneous field. E.g., a Fcst time Fcst time
field of forecast probability of at end of at end of
precipitation during some time period period minus
period. fcst time
at bgng.
88-01-01 14 NMC Office Note 84
T (Dec) Meaning F1 (*) F2 (*)
----------------------------------------------------------------
6 Field of time-averaged values. Fcst time Length of
E.g., a 5-day height mean: of bgng of period in
(Q1+Q2+Q3+Q4+Q5)/5 period in half days
with F1 the fcst time of Q1 in half days,
half days and F2 = 8 half days. high-order
bit on if
negative
7 Field of differences between 2 Fcst time Fcst time
fields of time-averaged values of of Q2 in of Q2 minus
type T=6. E.g., the difference of half days fcst time
two 5-day height means Q2 - Q1, of Q1 in
Q2 centered at D+8, Q1 centered at half days
D+3.
10 Same meaning as case T=2 except F1
and F2 are in days.
(*) F1 and F2 are in hours unless N=15 (Table 5) or unless half
days, days or years are specified.
----------------------------------------------------------------
88-01-01 15 NMC Office Note 84
Table 3 - M
LEVEL DIFFERENCE AND INITIALIZATION MARKER
(4 bits)
M Value
-----------------------------------------------
0 Indicates S2 and L2 are not applicable.
(In this case S2 = L2 = 0)
1 Indicates a field formed by taking the
value of Q at S1 minus the value of Q
at S2.
2 Indicates a field of Q for a layer
bounded by S1 and S2.
3 - 7 Available
8 - 10 Same meanings as 0-2 above except the
field has been initialized by a model
identified by the Generating Code in Table 10.
Such initialized fields are often referred to
as "00-hour forecasts".
11 - 15 Available
-----------------------------------------------
88-01-01 16 NMC Office Note 84
Table 4 - X
EXCEPTION MARKER
(8 bits)
X Value
-------------------------------------------------------------
0 Indicates the date/time of the field is the
same as the date/time of the file in which
the field is stored.
1 Indicates the date/time of the field is 6
hours prior to the date/time of the file
in which the field is stored.
2 Indicates the date/time of the field is 12
hours prior to the date/time of the file
in which the field is stored.
... ...
n Indicates the date/time of the field is 6*n
hours prior to the date/time of the file
which the field is stored.
... ...
80 Special use marker to indicate a field produced with
spectral wave truncation.
100 Field formed from NMC field and ECMWF field
101 Field formed from NMC field and UKMET field
255 Not applicable. The exception marker does not apply
to this field.
-------------------------------------------------------------
88-01-01 17 NMC Office Note 84
Table 5 - N
MISCELLANEOUS MARKER
(4 bits)
N Value
--------------------------------------------
0 None of the following
1 Spectral specification
2 Zonal coefficient
3 Spectral amplitude
4 Spectral phase angle
5 Summation over wave numbers 0 - 5
15 F1 and/or F2 are in half days
--------------------------------------------
88-01-01 18 NMC Office Note 84
Table 6 - CM and CD
CLIMATOLOGY MARKERS
(8 bits each)
CM Month-Hour
-------------------------
00 Not applicable
01 JAN - 0000 UTC
02 FEB - 0000 UTC
... ...
12 DEC - 0000 UTC
13 JAN - 1200 UTC
14 FEB - 1200 UTC
... ...
24 DEC - 1200 UTC
-------------------------
CD Day of Month
-------------------------
00 Not applicable
01 1st day of month
02 2nd day of month
... ...
31 31st day of month
-------------------------
88-01-01 19 NMC Office Note 84
Table 7 - K
GRID TYPE
K Grid Grid
Hex Dec Increment
-----------------------------------------------------------------
0 0 A 1977-point N. Hemisphere polar stereo- 381 km
graphic grid (octagon) oriented 80W; at 60N
Pole at (24,26).
1 1 A 1679-point (73x23) Mercator grid with 5 degs of
(1,1) at (0W,48.09S), (73,23) at (0W, longitude
48.09N); I increasing eastward, Equator
at J=12.
2 2 1752-point (73x24) Mercator grid for 5 degs of
latitudes 49.73S to 49.73N. longitude
3 3 3021-point (53x57) N. Hemisphere polar 381 km
stereographic grid oriented 80W; Pole at 60N
(27,29).
4 4 reserved
5 5 A 3021-point (53x57) N. Hemisphere polar 190.5 km
stereographic grid oriented 105W; Pole at 60N
at (27,49).
6 6 1977-point octagonal subset of grid 190.5 km
type 5; Pole at (24,46). at 60N
7 7 2329-point N. Hemisphere polar stereo- 381 km
graphic grid (octagon) oriented 80W. at 60N
8 8 5104-point (116x44) Mercator grid with 3.1035
(1,1) at (0W,48.67S) and (116,44) at degs of
(3.1035W,61.05N); I increasing eastward, longitude
Equator at J=19.
9 9 A Station grid (US and Canada) for TDL
wind, cloud, flight weather, sunshine,
dewpoint, temperature, and max/min
products. Number of stations varies
from product to product, but usually
ranges from 143 to over 200.
88-01-01 20 NMC Office Note 84
K Table 7 - K (cont) Grid
Hex Dec GRID TYPE Increment
-----------------------------------------------------------------
A 10 A Station grid (US cities) for TDL prob-
ability of precipitation type (POPT).
B 11 286 US cities for TDL precipitation
amount.
C 12 1702-point (74x23) Mercator grid for 5 degs of
latitudes 48.09S to 48.09N. longitude
D 13 576-point (36x16) N. Hemisphere
longitude/latitude LRPG diamond array--
pole stored at top of every 10 degs of
longitude--for latitudes 15S to 90N.
E 14 108 U.S. stations for TDL max/min
temperatures.
F 15 40 U.S. stations for TDL max/min
temperatures.
10 16 1560-point (39x40) N. Hemisphere polar 95.25 km
stereographic grid (Eastern U.S.) at 60N
oriented 80W.
11 17 A 221-point (17x13) N. Hemisphere polar 381 km
stereographic grid oriented 105W; Pole at 60N
at (7,21). US grid used for TDL
trajectory model.
12 18 Reserved.
13 19 1977-point S. Hemisphere polar stereo- 381 km
graphic grid (octagon) oriented 100E; at 60S
Pole at (24,26).
14 20 2655-point (45x59) Mercator grid for 1.5 degs of
latitudes 30S to 30N. longitude
15 21 A 1387-point (73x19) N. Hemisphere lon- 5 degs
gitude/latitude grid for latitudes 0N
to 90N.
88-01-01 21 NMC Office Note 84
K Table 7 - K (cont) Grid
Hex Dec GRID TYPE Increment
-----------------------------------------------------------------
16 22 A 1387-point (73x19) S. Hemisphere lon- 5 degs
gitude/latitude grid for latitudes 90S
to 0S.
17 23 783-point (29x27) N. Hemisphere polar 190.5 km
stereographic grid oriented 105W. at 60N
US grid is used for NMC/TDL boundary
layer model.
18 24 A 651-point (31x21) N. Hemisphere polar 190.5 km
stereographic grid oriented 98W; Pole at 60N
at (15,41). US grid is used for TDL
probability of precipitation, max/min
temperature, dewpoint, surface temp-
erature, and sunshine.
19 25 3021-point (53x57) S. Hemisphere polar 381 km
stereographic grid oriented 100E; Pole at 60S
at (27,29).
1A 26 A 2385-point (53x45) N. Hemisphere polar 190.5 km
stereographic grid oriented 105W; Pole at 60N
at (27,49).
1B 27 A 4225-point (65x65) N. Hemisphere polar 381 km
stereographic grid oriented 80W; Pole at 60N
at (33,33).
1C 28 A 4225-point (65x65) S. Hemisphere polar 381 km
stereographic grid oriented 100E; Pole at 60S
at (33,33).
1D 29 A 5365-point (145x37) N. Hemisphere lon- 2.5 degs
gitude/latitude grid for latitudes 0N
to 90N; (1,1) at (0E,0N).
1E 30 A 5365-point (145x37) S. Hemisphere lon- 2.5 degs
gitude/latitude grid for latitudes 90S
to 0S; (1,1) at (0E,90S).
88-01-01 22 NMC Office Note 84
K Table 7 - K (cont) Grid
Hex Dec GRID TYPE Increment
-----------------------------------------------------------------
1F 31 A 327-point TDL field composed of 4 grids: 381 km
US, Alaska, Hawaii, and Puerto Rico. at 60N
The US grid is a 255-point (17x15)
N. Hemisphere polar stereographic grid
oriented 80W; Pole at (13,22). Alaska
grid is a 56-point (7x8) N. Hemisphere
polar stereographic grid oriented 80W;
pole at (11,8). The Hawaii grid is a
12-point (3x4) N. Hemisphere polar
stereographic grid oriented 80W; Pole
at (23,7). The Puerto Rico grid is a
4-point (2x2) N. Hemisphere polar stereo-
graphic grid oriented 80W; Pole at (-4,23).
(These grids are used to archive MRF
Model data).
20 32 A 744-point (31x24) N. Hemisphere polar 190.5 km
stereographic grid oriented 105W; at 60N
Pole at (13,42). The TDL grid (US)
is used to archive LFM data.
21 33 A 8326-point (181x46) N. Hemisphere lon- 2 degs
gitude/latitude grid for latitudes 0N
to 90N; (1,1) at (0E,0N).
22 34 A 8326-point (181x46) S. Hemisphere lon- 2 degs
gitude/latitude grid for latitudes 90S
to 0S; (1,1) at (0E,90S).
23 35 228 U.S. cities for TDL MOS max/min
temperatures.
24 36 A 1558-point (41x38) N. Hemisphere polar 190.5 km
stereographic grid oriented 105W; Pole at 60N
at (19,42). The TDL grid (N. America)
is used to archive LFM and NGM data.
25 37 5365-point (145x37) N. Hemisphere lon- 2.5 degs
gitude/latitude grid for latitudes
1.25 to 88.75N; (1,1) at (1.25E,1.25N);
row 37 is fictitious.
88-01-01 23 NMC Office Note 84
K Table 7 - K (cont) Grid
Hex Dec GRID TYPE Increment
-----------------------------------------------------------------
26 38 5365-point (145x37) S. Hemisphere lon- 2.5 degs
gitude/latitude grid for latitudes
88.75S to 1.25S; (1,2) at
(1.25E,88.75S); row 1 is fictitious.
27 39 8326-point (181x46) N. Hemisphere lon- 2 degs
gitude/latitude grid for latitudes 1N
to 89N, (1,1) at (1E,1N); row 46 is
fictitious.
28 40 8326-point (181x46) S. Hemisphere lon- 2 degs
gitude/latitude grid for latitudes 89S
to 1S, (1,2) at (1E,89S); row 1 is
fictitious.
29 41 850-point (34x25) N. Hemisphere lon- 1 deg
gitude/latitude grid for latitudes 22N
to 46N; (1,1) at (87W,22N).
2A 42 Reserved.
2B 43 4225-point (65x65) N. Hemisphere polar 381 km
stereographic grid oriented 105W; Pole at 60N
at (33,33).
2C 44 4225-point (65x65) S. Hemisphere polar 381 km
stereographic grid oriented 75E; Pole at 60S
(33,33).
2D 45 2425-point (97x25) N. Hemisphere lon- 3.75 degs
gitude/latitude grid for latitudes
0N to 90N; (1,1) at (0E,0N).
2E 46 2425-point (97x25) S. Hemisphere lon- 3.75 degs
gitude/latitude grid for latitudes
90S to 0N; (1,1) at (0E,90S).
2F 47 A 10057-point (113x89) N. Hemisphere 47.625 km
polar stereographic grid oriented 105W; at 60N
Pole at (41,161).
88-01-01 24 NMC Office Note 84
K Table 7 - K (cont) Grid
Hex Dec GRID TYPE Increment
-----------------------------------------------------------------
30 48 3477-point (61x57) N. Hemisphere 190.5 km
polar stereographic grid oriented 105W; at 60N
Pole at (27,49).
31 49 16641-point (129x129) N. Hemisphere 190.5 km
polar stereographic grid oriented 80W; at 60N
Pole at (65,65).
32 50 16641-point (129x129) S. Hemisphere 190.5 km
polar stereographic grid oriented 100E; at 60S
Pole at (65,65).
33 51 A 16641-point (129x129) N. Hemisphere 190.5 km
polar stereographic grid oriented 105W; at 60N
Pole at (65,65).
34 52 Reserved.
35 53 5967-point (117x51) Mercator grid with 3.1035
(1,1) at (0W,61.05S) and (117,51) at degs of
(0W,61.05N); I increasing eastward, longitude
Equator at J=26.
36 54 A 1050-point (35x30) N. Hemisphere polar 95.25 km
stereographic grid oriented 80W; Pole at 60N
at (1,75). The TDL grid (eastern US)
is used for a boundary layer model.
37 55 A 6177-point (87x71) N. Hemisphere polar 254 km
stereographic grid oriented 105W; Pole at 60N
at (44,38).
38 56 A 6177-point (87x71) N. Hemisphere polar 127 km
stereographic grid oriented 105W; Pole at 60N
at (40,73).
39 57 Reserved
3A 58 100 U.S. cities for 24-hour accumulated
precipitation.
88-01-01 25 NMC Office Note 84
K Table 7 - K (cont) Grid
Hex Dec GRID TYPE Increment
-----------------------------------------------------------------
3B 59 5293-point (79x67) subset of grid type 127 km
56 (used for LFM-II mountains); Pole at 60N
at (40,73).
3C 60 A 3249-point (57x57) N. Hemisphere polar 190.5 km
stereographic grid oriented 105W; Pole at 60N
at (29,49).
3D 61 A Spectral coefficients, scalar fields. 30 modes
(961 COMPLEX*8 words).
3E 62 A Spectral coefficients, U- or V- 30 modes
component fields.
(992 COMPLEX*8 words).
3F 63 A 1095-point (73x15) longitude/latitude 5 degs
grid for latitudes 35S to 35N; (1,1)
at (0,35S) and I increasing eastward.
40 64 Available
41 65 Available
42 66 2701-point (73x37) longitude/latitude 5 degs
grid for latitudes 90S to 90N; (1,1)
at (0,90S); I increasing eastward.
43 67 A 13689-point (117x117) N.W. Atlantic 23.8125 km
polar stereographic grid oriented 80W; at 60N
Pole at (9,317).
44 68 A 13689-point (117x117) Gulf of Mexico 23.8125 km
polar stereographic grid oriented 105W; at 60N
Pole at (-35,361).
45 69 A 13689-point (117x117) Gulf of Alaska 23.8125 km
polar stereographic grid oriented 105W; at 60N
Pole at (177,209).
88-01-01 26 NMC Office Note 84
K Table 7 - K (cont) Grid
Hex Dec GRID TYPE Increment
-----------------------------------------------------------------
46 70 A 13689-point (117x117) Calif. Pacific 23.8125 km
polar stereographic grid oriented 105W; at 60N
Pole at (169,285).
47 71 A 13689-point (117x117) Mexican Pacific 23.8125 km
polar stereographic grid oriented 105W; at 60N
Pole at (137,377).
48 72 406-point (29x14) Mercator grid with 2.5 degs of
(1,1) at (170.00E,46.40N) and (29,14) longitude
at (120.00W,64.40N).
49 73 13056-point (128x102) global gaussian R40 trans
longitude/latitude grid.
4A 74 A 10800-point (180x60) N. Hemisphere 2.0 deg lon
longitude/latitude grid for latitudes 1.5 deg lat
0N to 90N; (1,1) at (0E,0N).
4B 75 A 12321-point (111x111) N. Hemisphere 40 km at
Lambert Conformal grid. No fixed 30&60 deg N
location; used by QLM Hurricane model.
4C 76 A 12321-point (111x111) S. Hemisphere 40 km at
Lambert Conformal grid. No fixed 30&60 deg S
location; used by QLM Hurricane model.
4D 77 A 12321-point (111x111) N. Hemisphere 40 km at
Mercator grid. No fixed location; equator
used by QLM Hurricane model.
51 81 A 7921-point (89x89) N. Hemisphere polar 190.5 km
stereographic grid oriented 105W; pole at 60N
at (44.5,44.5)
52 82 A 15066-point (243x62) N. Hemisphere variable
T80 gaussian transform lat/lon grid
53 83 A 15066-point (243x62) S. Hemisphere variable
T80 gaussian transform lat/lon grid
64 100 A 6889-point (83x83) N. Hemisphere polar 91.452 km
stereographic grid oriented 105W; Pole at 60N
at (40.5,88.5). (NGM Original Grid C)
65 101 A 10283-point (113x91) N. Hemisphere 91.452 km
stereographic grid oriented 105W; Pole at 60N
at (58.5,92.5). (NGM Expanded Grid C)
88-01-01 27 NMC Office Note 84
99 153 A 240-point (16x15) N. Hemisphere polar 190.5 km
stereographic grid oriented 105W; Pole at 60N
at (-2,47). TDL grid (Gulf of Mexico)
used for wind wave forecasts.
FF 255 Not applicable.
-----------------------------------------------------------------
Footnote: "A" indicates a currently active Grid Type
88-01-01 28 NMC Office Note 84
Table 8 - KS
DERIVATION MARKER
(8 bits)
KS Derivation method
----------------------------------------------------
0 None of the following
1 Hough spectral method
2 Field formed by subtracting a climatological
normal from each data value; e.g., a field
of departure from normal heights.
----------------------------------------------------
Table 9 - R
RUN MARKER
(8 bits)
R Run
----------------------------------------------------
0 Early run (ERL)
1 Initializing run (NMC)
2 Regional run (RGL)
3 Aviation run (AVN)
4 Medium Range Forecast run (MRF)
5 Final operational run in a given
observational cycle (FNL)
6 Hurricane Run (HCN)
15 Runs from non-NMC networks
255 Not applicable
----------------------------------------------------
88-01-01 29 NMC Office Note 84
Table 10 - G
GENERATING PROGRAM
(8 bits)
G Name of program generating data Map
Hex Dec Label
-----------------------------------------------------------------
0 0 Objective analysis (Cressman octagon)
1 1 A Barotropic fcst model BATROP
2 2 Mesh model 1958
3 3 Mesh model 1964 (imprv. terr.)
4 4 Reed 1000-mb fcst model
5 5 3-level baroclinic fcst model
6 6 4-level baroclinic fcst model
7 7 4-layer Primitive Equation model (PE)
8 8 6-layer PE model
9 9 A Maximum and minimum temperature fcst
A 10 Sea height and swell fcst
B 11 Tropical analysis
C 12 Tropical fcst
D 13 Bat analysis
E 14 Tropical fcst
F 15 Tropical fcst with satellite modification
10 16 Sub-synoptic advection model
11 17 Compute long wave components
12 18 A Trajectory forecast
13 19 A Successive Correction Method analysis SCM
14 20 Limited-area successive correction method LFM1
15 21 Perfect prog precipitation fcst
16 22 A Hough analysis HOUGH
17 23 Eddy analysis and SANBAR fcst (NHC Miami)
18 24 NWRC/NCAR climatology data
19 25 A Snow cover
1A 26 Planetary boundary layer analysis and fcst
1B 27 Extended fcst data processor
1C 28 PE and trajectory model output statistics
1D 29 9-layer global PE model (5-deg mesh)
1E 30 9-layer N.H. PE model (2.5-deg mesh)
1F 31 6-layer PE model (360/195 version) 6LPE
88-01-01 30 NMC Office Note 84
G Table 10 - G (cont) Map
Hex Dec GENERATING PROGRAM Label
-----------------------------------------------------------------
20 32 Sea surface temp., satellite derived
21 33 Land shelter temperature analysis
22 34 Energy statistics code
23 35 9-layer global PE model (2.5-deg mesh)
24 36 As above except used for 6-hour cycle
25 37 3-layer global PE model
26 38 7-layer PE Hemis. fine mesh model, 190.5 km 7LPE
27 39 A Nested Grid Model NGM
28 40 9-layer N. H. PE model (2-deg mesh)
29 41 LFM with 127-km grid increment LFM2
2A 42 7-layer PE model (381 km grid) 7LCM
2B 43 A Global Optimum Interpolation analysis GOI
2C 44 A Sea surface temperature analysis
2D 45 A Spectral Model Global 24-mode 12-layer SMG2C
2E 46 A Spectral Model Global 30-mode 12-layer SMG3C
2F 47 Spectral Model Hemis. 24-mode-12 layer SMH2C
30 48 Spectral model Hemis. 30-mode-12 layer SMH3C
31 49 Ozone Analysis Tiros Operational TOVS
32 50 Spectral model Global 24-mode 6-layer SMG26
33 51 Spectral model Global 30-mode 6-layer SMG36
34 52 Ozone Analysis Nimbus 7 SBUV
35 53 A LFM with Fourth-Order differencing LFM
36 54 Spectral model Hemis. 24-mode 6-layer SMH26
37 55 A N. American sea level pressure analysis
38 56 A N. H. sea level pressure analysis
39 57 A European Center for Medium-range Wea. Fcst. ECMWF
3A 58 Fleet Numerical Oceanography Center FNOC
3B 59 Air Force Global Weather Central AFGWC
3C 60 NWS Central Region CRGN
3D 61 NWS Western Region WRGN
3E 62 NWS Eastern Region ERGN
3F 63 A Spectral model Global 40-mode 12-layer SMG4C
40 64 A Regional Optimum Interpolation Analysis ROI
41 65 A Spectral model Global 40-mode 18-layer SMG4I
42 66 A U.K. Meteorological Office UKMET
43 67 A Statistical correction by linear regression SCLR
44 68 A 10-layer hurricane model HCN
45 69 A Medium Range Forecast Model w/ GFDL Physics MRF
46 70 A Quasi-Lagrangiam Hurricane Model QLM
47 71 A Stastical Blending (MRFG)
48 72 A Isentropic Analysis
-----------------------------------------------------------------
Footnote: "A" indicates a currently active Generating Program
88-01-01 31 NMC Office Note 84
Table 11
HEXADECIMAL EQUIVALENTS FOR FREQUENTLY
USED VALUES OF C
(Coding of L)
Decimal Hexadecimal
-----------------------
10000 02710
16667 04116
15000 03A98
15240 03B88
18290 04772
20000 04E20
21340 0535C
25000 061A8
27315 06AB3
27430 06B26
30000 07530
30480 07710
33333 08235
35000 088B8
36580 08EE4
40000 09C40
41667 0A2C3
42670 0A6AE
45000 0AFC8
50000 0C350
55000 0D6D8
58333 0E3DD
60000 0EA60
65000 0FDE8
66667 1046B
70000 11170
75000 124F8
80000 13880
83333 14585
85000 14C08
90000 15F90
91400 16508
91667 16613
95000 17318
99000 182B8
-----------------------
88-01-01 32 NMC Office Note 84
Table 12
EXAMPLES OF IDENTIFIER WORDS FOR COMMON FIELDS
(1) 1000-mb height analysis for N.H. (grid type 27):
00100800 00271081 00000000 00000000 0000001B
(2) 500-mb height analysis for N.H. (grid type 27):
00100800 00C35082 00000000 00000000 0000001B
(3) 500-mb temperature analysis for N.H. (grid type 27):
01000800 00C35082 00000000 00000000 0000001B
(4) 500-mb 12-hour height forecast for LFM (grid type 26):
0010080C 00C35082 00000000 00000000 0000001A
(5) 12-hour forecast of potential temperature for the
boundary layer, expressed in sigma coordinates,
for the N.H. 2.5 long/lat (grid type 29):
0130900C 00000000 20009000 00271084 0000001D
(6) 100-mb forecast height tendency, for 6 to 18 hours
after an initial time, which is 12 hours prior
to the date/time of the file (grid type 27):
00100812 30271082 0020000C 00000000 0000001B
(7) Precipitation at the surface which is forecast to be
accumulated between 24 and 30 hours after the initial
time (grid type 27):
05A0811E 30000000 00000006 00000000 0000001B
88-01-01 33 NMC Office Note 84
Table 13 - P
PACKING MARKER
(4 bits)
P Value
--------------------------------------------
0 16 bits used for packing
2 2 bits used for packing
4 4 bits used for packing
8 8 bits used for packing
12 12 bits used for packing
--------------------------------------------
DJDE FORMS=JOY,END;
88-01-01 34 NMC Office Note 84
Figure 1 - NMC Format for Packed Data Fields
W Upper left: Table reference, if any
o Upper right: Field size in bits
r Bit . . . .
d 0 3 4 7 8 11 12 15 16 23 24 31
1 12 1 12 8
1 Q Data type S1 Type of surface 1 F1 Time 1
2 T 4 Numerical value of 20 8
2 Marker C1 Surface 1 = C1 * 10**E1 E1
3 M 4 4 Exception 8 1 12 8
3 Marker X Marker S2 Type of surface 2 F2 Time 2
5 N 4 Numerical value of 20 8
4 Marker C2 Surface 2 = C2 * 10**E2 E2
6 Climat day 8 6 Climat 8 8 Derivation 8 7 8
5 CD of month CM Month Hour KS Method K Grid type
=0,1 4 For internal 12 For internal use 16
6 1st GES RN use by I/O only NW by I/O routines only
8 8 8 Initial 8
7 YY Year MM Month DD Day II Hour
9 Run 8 10 Generating 8 16
8 R Marker G Program J Number of data points
Number of bytes 16 Exclusive OR 16
9 B in Record Z Checksum
1 32
0 A Reference value, REAL*4 floating point
1 13 P 4 # of 4 reserved 08 Scaling value 16
1 Marker add.rec n (INTEGER*2)
1 32
2 Reserved
1 16 16
3 Data point 1 Data point 2
1 16 16
4 Data point 3 Data point 4
In word 6, first byte indicates source of GES ...
0 = AVN run 1 = FNL run
In word 11, byte 2 is used by VSAM for logical records
that exceed 32,768 bytes
88-01-01 35 NMC Office Note 84
