ON388 - TABLE B

GRID IDENTIFICATION
(PDS Octet 7)
MASTER LIST OF NCEP STORAGE GRIDS
GRIB Edition 1 (FM92)


Revised 04/09/2008
Red text depicts changes made since 02/12/2008


VALUE GRID GRID INCREMENT GRID
Image
1 1679-point (73x23) Mercator grid with (1,1) at (0W,48.09S), (73,23) at (0W,48.09N); I increasing eastward, Equator at J=12.
See GRIB Specifications		 5 degs of Longitude GIF
 PS
2 10512-point (144x73) global longitude-latitude grid. (1,1) at (0E, 90N), matrix layout. N.B.: prime meridian not duplicated. 2.5 deg GIF PS
3 65160-point (360x181) global longitude-latitude grid. (1,1) at (0E, 90N), matrix layout. N.B.: prime meridian not duplicated.
See GRIB Specifications		 1.0 deg GIF PS
4 259920-point (720x361) global Lon/Lat grid. (1,1) at (0E, 90N); matrix layout; prime meridian not duplicated 0.5 deg GIF PS
5 3021-point (53x57) N. Hemisphere polar stereographic grid oriented 105W; Pole at (27,49). (LFM analysis) 190.5 km at 60N GIF PS
6 2385-point (53x45) N. Hemisphere polar stereographic grid oriented 105W; Pole at (27,49). (LFM Forecast) 190.5 km at 60N GIF PS
8 5104-point (116x44) Mercator grid with (1.1) at (3.1035E,48.67S) and (116,44) At (0.000W,61.05N); I increasing eastward, Equator at j=19. 3.105 degs of longitude GIF PS
10
 25020-point (180x139) longitude-latitude ocean grid with (1,1) at (1E,64N), (180,139) at (1W,74S); I increasing eastward, Equator at J=65
See GRIB Specifications		 2 degs of Lon and 1 deg of Lat

11
 Global 0.5 degree Latitude/Longitude grid
(Used by Global Multi-Grid Wave Model) See GRIB Specifications		 0.5 degree

12
 0.167 degree Latitude/Longitude grid - US East Coast
(Used by Global Multi-Grid Wave Model) See GRIB Specifications		 0.167 degree

13
 0.167 degree Latitude/Longitude grid - US West Coast
(Used by Global Multi-Grid Wave Model) See GRIB Specifications		 0.167 degree

14
 0.167 degree Latitude/Longitude grid
US Eastern Pacific - includes Hawaii and extends to the Pacific islands of Guam
(Used by Global Multi-Grid Wave Model) See GRIB Specifications		 0.167 degree

15
 0.250x0.167 degree Latitude/Longitude grid - Alaska
(Used by Global Multi-Grid Wave Model) See GRIB Specifications		 0.25 degree Lat and 0.167 degree Lon

16
 0.133x0.067 degree Latitude/Longitude grid - Alaska
(Used by Global Multi-Grid Wave Model) See GRIB Specifications		 0.133 degree Lat and 0.067 degree Lon

17
 0.067 degree Latitude/Longitude grid - US West Coast (includes Hawaii)
(Used by Global Multi-Grid Wave Model) See GRIB Specifications		 0.067 degree

18
 0.067 degree Latitude/Longitude grid - US East Coast
(Used by Global Multi-Grid Wave Model) See GRIB Specifications		 0.067 degree

21-26 International Exchange and Family of Services (FOS) grids.
See GRIB Specifications


27 4225-point (65x65) N. Hemisphere polar stereographic grid oriented 80W; Pole at (33,33). 381 km at 60N GIF PS
28 4225-point (65x65) S. Hemisphere polar stereographic grid oriented 280E ( 80W ); Pole at (33,33). 381 km at 60S GIF PS
29 5365-point (145x37) N. Hemisphere longitude/latitude grid for latitudes 0N to 90N; (1,1) at (0E,0N). 2.5 degs GIF PS
30 5365-point (145x37) S. Hemisphere longitude/latitude grid for latitudes 90S to 0S; (1,1) at (0E,90S). 2.5 degs GIF PS
33 8326-point (181x46) N. Hemisphere longitude/latitude grid for latitudes 0N to 90N; (1,1) at (0E,0N). 2 degs GIF PS
34 8326-point (181x46) S. Hemisphere longitude/latitude grid for latitudes 90S to 0S; (1,1) at (0E,90S). 2 degs GIF PS
37-44 Eight Lat-Lon 1.25x1.25 "thinned" grids, covering the globe by octants of 3447 points. For WAFS, ICAO, Family of Services (FOS), and International exchange.
See GRIB Specifications


45 Global latitude/longitude 1.25 deg Resolution.
See GRIB Specifications
GIF PS
50 Family of Services "regional grid".
See GRIB Specifications


53 5967-point (117x51) Mercator grid with (1,1) at (0.000W,61.05S) and (117,51) At (0.000W,61.05N); I increasing eastward, Equator at j=26. 3.105 degs of longitude GIF PS
55 6177-point (87x71) N. Hemisphere polar stereographic grid oriented 105W; Pole at (44,38). (2/3 bedient NH sfc anl) 254 km at 60N GIF PS
56 6177-point (87x71) N. Hemisphere polar stereographic grid oriented 105W; Pole at (40,73). (1/3 bedient NA sfc anl) 127 km at 60N GIF PS
61-64 International Exchange & FOS grids.
See GRIB Specifications


75 12321-point (111x111) N. Hemisphere Lambert Conformal grid. No fixed location; used by QLM Hurricane model. 40 km at 30&60 deg N

76 12321-point (111x111) S. Hemisphere Lambert Conformal grid. No fixed location; used by QLM Hurricane model. 40 km at 30&60 deg S

77 12321-point (111x111) N. Hemisphere Mercator grid. No fixed location; used by QLM Hurricane model. 40 km at 22.5 deg N&S

85 32400-point (360x90) N. Hemisphere longitude/latitude grid; longitudes: 0.5E to 359.5E (0.5W); latitudes: 0.5N to 89.5N; origin (1,1) at (0.5E,0.5N) 1 deg GIF PS
86 32400-point (360x90) S. Hemisphere longitude/latitude grid; longitudes: 0.5E to 359.5E (0.5W); latitudes: 89.5S to 0.5S; origin (1,1) at (0.5E,89.5S) 1 deg GIF PS
87 5022 point (81x62) N. Hemisphere polar stereographic grid oriented at 105W. Pole at (31.91, 112.53) Used for RUC. (60 km at 40N).
See GRIB Specifications		 68.153 km at 60N GIF PS
88 317840 point (580x548) N. American polar stereographic grid oriented at 105W. Pole at (260.853, 613.176) Used for RSAS. (15 km at 60N).
See GRIB Specifications		 15 km at 60N GIF PS
90 111723-point (223x501) Arakawa staggered E-grid on rotated latitude/longitude grid (used by the 8 km Non-hydrostatic Meso Model (NMM) - Eastern US).
See GRIB Specifications


91 111723-point (223x501) Arakawa staggered E-grid on rotated latitude/longitude grid (used by the 8 km NMM model - Central US).
See GRIB Specifications


92 111723-point (223x501) Arakawa staggered E-grid on rotated latitude/longitude grid (used by the 8 km NMM model - Western US).
See GRIB Specifications


93 111723-point (223x501) Arakawa staggered E-grid on rotated latitude/longitude grid (used by the 8 km NMM model - Alaska).
See GRIB Specifications


94 196305-point (345x569) Arakawa staggered E-grid on rotated latitude/longitude grid.
See GRIB Specifications


95 36062-point (146x247) Arakawa staggered E-grid on rotated latitude/longitude grid (Northwest US).
See GRIB Specifications


96 646602-point (606x1067) Arakawa staggered E-grid on rotated latitude/longitude grid.
See GRIB Specifications


97 12727-point (89x143) Arakawa staggered E-grid on rotated latitude/longitude grid (used by the 8 km NMM model - Puerto Rico).
See GRIB Specifications


98 Global Gaussian T62 grid.
See GRIB Specifications


99 779385-point (669x1165) Arakawa staggered E-grid on rotated latitude/longitude grid (Used by the 12km NAM Model - expanded domain).
See GRIB Specifications


100 6889-point (83x83) N. Hemisphere polar stereographic grid oriented 105W; Pole at (40.5,88.5). (NGM Original C-Grid) 91.452 km at 60N GIF PS
101 10283-point (113x91) N. Hemisphere polar stereographic grid oriented 105W; Pole at (58.5,92.5). (NGM "Big C-Grid") 91.452 km at 60N GIF PS
103 3640-point (65x56) N. Hemisphere polar stereographic grid oriented 105W; Pole at (25.5,84.5) (used by ARL) 91.452 km at 60N GIF PS
104 16170-point (147x110) N. Hemisphere polar stereographic grid oriented 105W; pole at (75.5,109.5). (NGM Super C grid) 90.75464 km at 60N GIF PS
105 6889-point (83x83) N. Hemisphere polar stereographic grid oriented 105W; pole at (40.5,88.5). (U.S. area subset of NGM Super C grid, used by NAM model) 90.75464 km at 60N GIF PS
106 19305 point (165x117) N. Hemisphere polar stereographic grid oriented 105W; pole at (80,176) Hi res. NAM (2 x resolution of Super C) 45.37732 km at 60N GIF PS
107 11040 point (120x92) N. Hemisphere polar stereographic grid oriented 105W; pole at (46,167) subset of Hi res. NAM; for NAM & MAPS/RUC 45.37732 km at 60N GIF PS
110 LDAS Grid over CONUS (longitude/latitude grid)
See GRIB Specifications		 1/8 degree GIF PS
119
 83160-point(360x231) Curvi-linear Orthogonal Tri-Polar grid
See GRIB Specifications
GIF PS
120
 2020800-point(1200X1684) Curvi-linear Orthogonal Grid of the Atlantic sector within 25.0S to 76.0N & -105.0W to 67.0E. 
See GRIB Specifications		 2.40km - 25.25 km
 GIF PS
122
 162750-point(350X465) Curvi-linear Orthogonal Grid of the Gulf of Mexico sector within 18.0N to 33.0N & -99.0W to -77.0W. 
See GRIB Specifications		 3.13km - 5.67km
 GIF PS
123
 100800-point(280X360) Curvi-linear Orthogonal Grid of the North West Atlantic sector within 33.0N to 54.0N & -77.0W to -46.0W. 
See GRIB Specifications		 4.3km - 6.89km
 GIF PS
124
 75360-point(240X314) Curvi-linear Orthogonal Grid of the Middle West Atlantic sector within 26.0N to 42.0N & -84.0W to 63.0W. 
See GRIB Specifications		 4.12 km - 6.28km
 GIF PS
125
 102000-point(300X340) Curvi-linear Orthogonal Grid of the South West Atlantic sector within 15.0N to 34.0N & -82.0W to -59.0W. 
See GRIB Specifications		 4.59km - 7.67km
 GIF PS
126 Global Gaussian T126 grid
See GRIB Specifications


127 Global Gaussian T254 grid
See GRIB Specifications


130
 Regional (CONUS) Lambert Conformal grid
See GRIB Specifications
 13 km
 GIF PS
138 Air-Quality Forecasting CONUS
See GRIB Specifications		 12 km

145 Air-Quality Forecasting Northeast Intermediate Domain
See GRIB Specifications		 12 km GIF PS
146 Air-Quality Forecasting Northeast Output Domain
See GRIB Specifications		 12 km GIF PS
147
 Air-Quality Forecasting Eastern "3x" Output Domain
See GRIB Specifications		 12 km GIF PS
148
 Air-Quality Forecasting CONUS "5x" Output Domain
See GRIB Specifications		 12 km GIF PS
150 Grid over Central America - LAT/LON grid (for CPC)
See GRIB Specifications		 12 km

151 Grid over North America - Polar Stereographic
(Used by the 32-km NAM Model - Expanded domain)
See GRIB Specifications		 32 km

160
 North Polar Stereographic grid for Alaska (Quadruple grid 203)
See GRIB Specifications
 47.5 km
 GIF PS
161
 Lat/Lon grid for Puerto Rico
See GRIB Specifications
 0.5 degree
 GIF PS
163
 Regional (CONUS) Lambert Conformal grid
See GRIB Specifications
 5 km

170 Global Gaussian T170 grid
See GRIB Specifications


171 Northern Hemisphere High Resolution Sea Ice grid (polar stereographic)
See GRIB Specifications		 12.7 km
 GIF PS
172 Southern Hemisphere High Resolution Sea Ice grid (polar stereographic)
See GRIB Specifications		 12.7 km GIF PS
173
 1/12 degree global Lat/Lon grid
See GRIB Specifications
 0.5 degree

174
 Global High Resolution Sea Ice grid (longitude/latitude grid)
See GRIB Specifications		 0.125 degree

175  Lat/Lon grid over Guam
See GRIB Specifications		 10 km lon/lat GIF PS
176
 Lat/Lon grid for the US Great Lakes
See GRIB Specifications		 0.050 x 0.035 degree

180
 CONUS - Lat/Lon grid (for AFWA product)
See GRIB Specifications		 12 km

181
 Central America/Caribbean - Lat/Lon grid (for AFWA product)
See GRIB Specifications		 12 km

182
 Hawaii/North Pacific - Lat/Lon grid (for AFWA product)
See GRIB Specifications		 12 km

183
 Alaska - Lat/Lon grid (for AFWA product)
See GRIB Specifications		 12 km

185
 Limited domain CONUS Lambert Conformal (used by the DGEX)
See GRIB Specifications
 12 km

186
 Limited domain Alaska Polar Stereographic (used by the DGEX)
See GRIB Specifications		 12 km

190 12972-point (92x141) Arakawa staggered E-grid on rotated latitude/longitude grid.
See GRIB Specifications


192 91719-point (237x387) Arakawa staggered E-grid on rotated latitude/longitude grid.
See GRIB Specifications


194 12727-point (89x143) Arakawa staggered E-grid on rotated latitude/longitude grid (used by the 8 km NMM model over Hawaii).
See GRIB Specifications


195 Grid over Puerto Rico - Mercator
(Used by RTMA and NAM smartinit output for NDFD grids)
See GRIB Specifications		 2.50 km

196 Grid over Hawaii - Mercator
(Used by RTMA and NAM smartinit output for NDFD grids)
See GRIB Specifications		 2.50 km

197 Grid over CONUS - 16X Resolution (5 km) Lambert Conformal
(Used by the Radar Stage IV precipitation analyses and Satellite-derived Precipitation Estimates and NAM DNG grids and RTMA NDFD grids)
See GRIB Specifications		 2.50 km

198 Grid over Alaska - Polar Stereographic
(Used by RTMA and NAM smartinit output for NDFD grids)
See GRIB Specifications		 5.953 km

199 Grid over Guam - Mercator
(Used by RTMA and GFS smartinit output for NDFD grids)
See GRIB Specifications		 2.50 km

201 Northern Hemispheric (polar stereographic).
See GRIB Specifications		 381.000 km GIF PS
202 National - CONUS (polar stereographic).
See GRIB Specifications		 190.500 km GIF PS
203 National - Alaska (polar stereographic).
See GRIB Specifications		 190.500 km GIF PS
204 National - Hawaii (Mercator).
See GRIB Specifications		 160.000 km GIF PS
205 National - Puerto Rico (polar stereographic).
See GRIB Specifications		 190.500 km GIF PS
206 Regional - Central US MARD (Lambert Conformal).
See GRIB Specifications		 81.2705 km GIF PS
207 Regional - Alaska (polar stereographic).
See GRIB Specifications		 95.250 km GIF PS
208 Regional - Hawaii (Mercator).
See GRIB Specifications		 80.000 km GIF PS
209 Regional - NOAMIM - Intermediate Resolution North American Master Grid (Lambert Conformal).
See GRIB Specifications		 44.000 km GIF PS
210 Regional - Puerto Rico (Mercator).
See GRIB Specifications		 80.000 km GIF PS
211 Regional - CONUS (Lambert Conformal).
See GRIB Specifications		 80 km
 GIF PS
212 Regional - CONUS - Double Resolution (Lambert Conformal).
See GRIB Specifications		 40.63525 km GIF PS
213 National - CONUS - Double Resolution (polar stereographic).
See GRIB Specifications		 95.250 km GIF PS
214 Regional - Alaska - Double Resolution (polar stereographic).
See GRIB Specifications		 47.625 km GIF PS
215 Regional grid over the contiguous United States - Quadruple Resolution (used by the 29-km NAM Model) (Lambert Conformal).
See GRIB Specifications		 20.317625 km GIF PS
216 Regional grid over Alaska (polar stereographic).
See GRIB Specifications		 45.000 km GIF PS
217 Grid over Alaska - Double Resolution (polar stereographic).
See GRIB Specifications		 22.500 km GIF PS
218 Grid over the Contiguous United States (used by the 12-km NAM Model) (Lambert Conformal).
See GRIB Specifications		 12.19058 km GIF PS
219 Grid over the Northern Hemisphere to depict SSMI-derived ice concentrations (polar stereographic).
See GRIB Specifications		 25.4 km GIF PS
220 Grid over the Southern Hemisphere to depict SSMI-derived ice concentrations (polar stereographic).
See GRIB Specifications		 25.4 km GIF PS
221 Regional - NOAMHI - High Resolution North American Master Grid (Lambert Conformal).
See GRIB Specifications		 32.46341 km GIF PS
222 Regional - NOAMLO - Low Resolution North American Master Grid (Lambert Conformal).
See GRIB Specifications		 88.00000 km GIF PS
223 Hemispheric - Double Resolution (polar stereographic).
See GRIB Specifications		 190.500 km GIF PS
224 Southern Hemispheric (polar stereographic).
See GRIB Specifications		 381.000 km GIF PS
225 National Double Resolution - Hawaii (Mercator).
See GRIB Specifications		 80.000 km GIF PS
226 Regional grid over the contiguous United States - 8X Resolution (10 km) (Used by the Radar mosaics) (Lambert Conformal).
See GRIB Specifications		 10.1588125 km GIF PS
227 Regional grid over the contiguous United States - 16X Resolution (5 km) (Used by the Radar Stage IV precipitation analyses and Satellite-derived Precipitation Estimates and SMOKE grids) (Lambert Conformal).
See GRIB Specifications		 5.079 km

228 Global (longitude/latitude grid).
See GRIB Specifications		 2.500 degrees GIF PS
229 Global (longitude/latitude grid).
See GRIB Specifications		 1.000 degrees GIF PS
230 Global (longitude/latitude grid).
See GRIB Specifications		 0.500 degrees GIF PS
231 Northern Hemisphere (longitude/latitude grid).
See GRIB Specifications		 0.500 degrees GIF PS
232 Northern Hemisphere (longitude/latitude grid).
See GRIB Specifications		 1.000 degree GIF PS
233 Regional (longitude/latitude grid).
See GRIB Specifications		 1.250 X 1.000 degrees GIF PS
234 Regional (longitude/latitude grid).
See GRIB Specifications		 0.250 degrees GIF PS
235 Global (longitude/latitude grid).
See GRIB Specifications
GIF PS
236 Regional - CONUS (Lambert Conformal)
See GRIB Specifications		 40.63525 km GIF PS
237 Puerto Rico FAA Regional Grid (Lambert Conformal)
See GRIB Specifications		 32.46341 km GIF PS
238 Western North Atlantic (longitude/latitude grid)
See GRIB Specifications
GIF PS
239 Alaska Regional (longitude/latitude grid)
See GRIB Specifications
GIF PS
240 HRAP Grid over the Contiguous United States and Puerto Rico (polar stereographic)
See GRIB Specifications		 4.7625 km

241 Regional - NOAMHI - High Resolution North American Grid (Lambert Conformal)
See GRIB Specifications		 22.00000 km GIF PS
242 Grid over Alaska - Quadruple Resolution Grid (polar stereographic)
See GRIB Specifications		 11.25 km GIF PS
243 Eastern North Pacific (longitude/latitude grid)
See GRIB Specifications
GIF PS
244 North Atlantic Hurricane (longitude/latitude grid)
See GRIB Specifications		 0.250 degrees
 GIF PS
245 Regional - NOAMHI - High Resolution over Eastern US (Lambert Conformal for 8 km NMM)
See GRIB Specifications		 8.00000 km GIF PS
246 Regional - NOAMHI - High Resolution over Western US (Lambert Conformal for 8 km NMM)
See GRIB Specifications		 8.00000 km GIF PS
247 Regional - NOAMHI - High Resolution over Central US (Lambert Conformal for 8 km NMM)
See GRIB Specifications		 8.00000 km GIF PS
248 Puerto Rico (longitude/latitude grid)
See GRIB Specifications
GIF PS
249 Grid over Alaska for 10-km Alaska nest (Polar Stereographic)
See GRIB Specifications		 9.86789 km GIF PS
250 Grid over Hawaii for 8 km NMM (longitude/latitude grid)
See GRIB Specifications
GIF PS
251 Coastal Ocean Forecast System Grid - North Atlantic Region (longitude/latitude grid)
See GRIB Specifications
GIF PS
252 Regional - CONUS (Lambert Conformal)
See GRIB Specifications		 20.317625 km GIF PS
253 Eastern North Pacific Regional (longitude/latitude grid)
See GRIB Specifications
GIF PS
254
 Mercator grid for Pacific Region
See GRIB Specifications
 40 km
 GIF PS
255 (non-defined grid - specified in the GDS)





NOTE ON NCEP STORAGE GRIDS:

On the polar stereographic grids, the vector wind is resolved into u and v components with respect to the grid coordinates, i.e., u represents motion in the direction of increasing x (i) coordinate, v in the direction of increasing y (j). On the latitude-longitude grids, u and v are true eastward and northward components, respectively. However, take note of Table 7, below, which allows for the specification of other possibilities when the Grid Description Section is included in the message.



INTERNATIONAL EXCHANGE AND FAMILY OF SERVICES (FOS) GRIDS


VALUE RESOLUTION
lon x lat (degrees)		 AREA COVERAGE
(degrees)		 GRID SHAPE
cols rows		 GRID POINTS
21 5.0 x 2.5 0-180E, 0-90N 37 36 + pole 1333
22 5.0 x 2.5 180W-0, 0-90N 37 36 + pole 1333
23 5.0 x 2.5 0-180E, 90S-0 pole + 37 36 1333
24 5.0 x 2.5 180W-0, 90S-0 pole + 37 36 1333
25 5.0 x 5.0 0-355E, 0-90N 72 18 + pole 1297
26 5.0 x 5.0 0-355E, 90S-0 pole + 72 18 1297
50 2.5 x 1.25 (see note iv)

964
61 2.0 x 2.0 0-180E, 0-90N 91 45 + pole 4096
62 2.0 x 2.0 180W-0, 0-90N 91 45 + pole 4096
63 2.0 x 2.0 0-180E, 90S-0 pole + 91 45 4096
64 2.0 x 2.0 180W-0, 90S-0 pole + 91 45 4096



NOTES ON INTERNATIONAL EXCHANGE/FOS GRIDS:

(i) The grid points are laid out in a linear array such that the longitude index (the columns) is the most rapidly varying. For the northern hemisphere grids the first point in the record is at the intersection of the western-most meridian and southern-most circle of latitude; the last point is the single polar value (see note iii, below). For the southern hemisphere grids the first point in the record is the single polar value (see note iii, below); the last point is at the intersection of the eastern-most meridian and northern-most circle of latitude. For those familiar with FORTRAN subscripting conventions, longitude is the first subscript, latitude the second.

(ii) In grids 21 through 26, and 61 through 64, the values on the shared boundaries are included in each area.

(iii) The datum for the pole point is given only once in each grid. The user must expand, if desired, the single pole point value to all the pole "points" at the pole row of a latitude-longitude grid. Scalar quantity values are the same for all pole points on a the grid. Wind components at the poles are given by the formulae:
u = -speed * sin(dd) & v = -speed * cos(dd)

where dd is the direction of the wind as reported according to the specification of wind direction at the poles (refer to WMO Manual on Codes, code table 878).

The WMO convention can be given this operational definition: At the North Pole, face into the wind and report the value of the west longitude meridian along which the wind is coming at you; at the South Pole do likewise but report the east longitude meridian value. This is equivalent to placing the origin of a right-handed Cartesian coordinate system on the North Pole with the y-axis pointing to the prime (0 degree) meridian and the x-axis pointing to the 90 degrees west meridian, and then resolving any vector wind at the pole point into components along those axes. At the South Pole the coordinate axes are oriented such that the y-axis points toward 180 degrees west. Those components are the u- and v-values given as the single pair of pole point winds in the GRIB format.

In terms of a longitude/latitude grid these are the wind components for the pole point at the 180 degree meridian. For example, on a 2.5x2.5 degree northern hemisphere grid (145x37 points), with the abscissa along the equator and the ordinate along the prime meridian, the transmitted north pole wind components are those that belong at the gridpoint (73,37). The wind components at the other grid points along the pole row may be obtained through suitable rotation of the coordinate system. All the components at the pole row are, of course, simply representations of the same vector wind viewed from differing (rotated) coordinate systems. In the southern hemisphere the analogous situation holds; the single set of transmitted pole point wind components belong at the gridpoint (73,1).

(iv) Grid 50 is a set of points over the contiguous United States and environs on a grid extending from 20N (row No. 1) to 60N (row No. 33) in 1.25 degree intervals. The grid increases in longitudinal extent from south to north in the following manner:

ROWS NO. POINTS LONGITUDINAL EXTENT
1-4 22 122.5W - 70.0W
5-8 24 125.0W - 67.5W
9-12 26 127.5W - 65.0W
13-16 28 130.0W - 62.5W
17-20 30 132.5W - 60.0W
21-24 32 135.0W - 57.5W
25-28 34 137.5W - 55.0W
29-33 36 140.0W - 52.5W

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WAFS/ICAO/INTERNATIONAL EXCHANGE/FOS GRIDS

(Grids 37 - 44)

Global Coverage of Grids
Octants of the Globe

90N
37
I		 38
J		 39
K		 40
L
41
M		 42
N		 43
O		 44
P
0
90S

330E 60E 150E 240E 330E

In the figure the coordinates indicate the location of the octants of the globe, the numbers are the corresponding grid identification numbers (PDS Octet 7), and the letters are the grid identification used in the WMO heading (see Appendix A).

The left and right meridional columns of each octant/grid are shared with the neighbors.

The basic grid point separation is 1.25x1.25 deg. on a latitude/longitude array, but the grid is "thinned" by reducing the number of points in each row as one goes northward (or southward) away from the equator. In GRIB terms, this is referred to as a "quasi-regular" grid.

The latitudinal increment is always 1.25 deg.; this results in 73 rows where the pole is included as a "row", not a single gridpoint.

The longitudinal spacing at the equator is also 1.25 deg.; thus there will be 73 gridpoints at the equator in each octant.

The number of points on each latitudinal row, other than the equator, is given by (using FORTRAN notation):

NPOINTS = IFIX(2.0 + (90.0/1.25) * COS(LATITUDE))

Thus at the pole there will be two gridpoints, one each at the meridians that delineate the edges of the octant. The formula was worked out so that there is (approximately) equal geographic separation between the grid points uniformly across the globe.

Because of variations in precision and roundoff error in different computers, the value of NPOINTS may vary by 1 at "critical" latitudes when calculated on various hardware platforms. Here is a table of the exact values of NPOINTS as a function of latitude as used in the internationally exchanged grids. These numbers will, of course, be found in the Grid Description Section of each GRIB bulletin.

Latitude Range
inclusive
(north or south)		 NPOINTS Latitude Range
inclusive
(north or south)		 NPOINTS
0.00 - 8.75 73 55.00 43
10.00 - 12.50 72 56.25 42
13.75 - 16.25 71 57.50 40
17.50 - 18.75 70 58.75 39
20.00 - 21.25 69 60.00 38
22.50 68 61.25 36
23.75 - 25.00 67 62.50 35
26.25 66 63.75 33
27.50 - 28.75 65 65.00 32
30.00 64 66.25 30
31.25 63 67.50 29
32.50 62 68.75 28
33.75 61 70.00 26
35.00 - 36.25 60 71.25 25
37.50 59 72.50 23
38.75 58 73.75 22
40.00 57 75.00 20
41.25 56 76.25 19
42.50 55 77.50 17
43.75 54 78.75 16
45.00 52 80.00 14
46.25 51 81.25 12
47.50 50 82.50 11
48.75 49 83.75 9
50.00 48 85.00 8
51.25 47 86.25 6
52.50 45 87.50 5
53.75 44 88.75 3


90.00 2

When all this is put together the result is that there are 3447 points of data actually transmitted in any individual GRIB bulletin containing one octant of the globe.

In the GRIB bulletins all of this information will be included in the Grid Description Section (GDS); the GDS must be included in order to describe the thinned or "quasi-regular" grid structure. See Section 2 and Table C for the general description of the GDS; what follows are the specific values of the variables in the GDS that describe these eight grids.

GDAS Contents
Octets Value or variable
1-3 178 (length of GDS)
4 0 (or 255, either indicating no PV)
5 33 (pointer to start of PL list)
6 0
7-32 Grid description - see below
33-178 number of points in each of 73 rows (2 octets per point)


Details of Octets 7-32 - Grid Description

Octets Variable & Value
7-8 Ni = all bits set to 1 (missing)
9-10 Nj = 73

GRID: 37 38 39 40 41 42 43 44
La1 = 0 0 0 0 90S 90S 90S 90S
Lo1 = 330 60 150 240 330 60 150 240
11-13
14-16
17 Resolution & Component Flag = [10000000] (binary)

GRID: 37 38 39 40 41 42 43 44
La2 = 90N 90N 90N 90N 0 0 0 0
Lo2 = 60 150 240 330 60 150 240 330
18-20
21-23
24-25 Di = all bits set to 1 (missing)
26-27 Dj = 1.25 deg
28 Scan Mode = [01000000] (binary)
29-32 Set to 0 (unused)

Note that the scanning direction is from the bottom (south edge) to the top of the octant grids, regardless of the hemisphere. Thus in the northern hemisphere the first 73 data points (in the BDS) will be the equatorial values and the last two will be the polar values. The PL counts in the GDS octets 33-178 will, of course, indicate contain these numbers.

In the southern hemisphere, the first two data points will be the south pole values, and the last 73 points will be the equatorial values. Octets 33-34 in the GDS will contain "2", octets 35-36 will contain a "3", and so on to octets 177-178 which will contain "73".

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SELECTED NCEP GRIDS DEFINED USING GRIB SPECIFICATIONS
(See Table C, in Section 2, for definition of symbols)

VALUE GRID DESCRIPTIONS
1 Tropical Strip (Mercator)

Ni 73
Nj 23
La1 48.09S
Lo1 0.000E
Res. & Comp. Flag 1 0 0 0 0 0 0 0
La2 48.090N
Lo2 0.000W
Latin 22.5
Di 513.669 km
Dj 513.669 km
Scanning Mode (bits 1 2 3) 0 1 0


The longitudinal grid spacing is 5.00 degrees.


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VALUE GRID DESCRIPTIONS
3 Global Latitude/Longitude 1 deg Resolution

Ni 360
Nj 181
La1 90.000N
Lo1 0.0E
Res. & Comp. Flag 1 0 0 0 0 0 0 0
La2 90.000S
Lo2 359.000E = 1.000W
Di 1.000 degrees
Dj 1.000 degrees
Scanning Mode 00000000(NB: matrix style)


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VALUE GRID DESCRIPTIONS
10 Latitude/Longitude Ocean grid
with (1,1) at (1E,64E) and (180,139) at (1W,74S)
I increasing Eastward, Equator at J=65

Ni 180
Nj 139
La1 64.000N
Lo1 1.0E
Res. & Comp. Flag 1 0 0 0 0 0 0 0
La2 74.000S
Lo2 359.000E = 1.000W
Di 2.000 degrees
Dj 1.000 degrees
Scanning Mode 0 0 0(NB: matrix style)


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VALUE GRID DESCRIPTIONS
11 Global 0.5 degree Latitude/Longitude grid
(Used by Global Multi-Grid Wave Model (Static Grids)

Ni 720
Nj 311
La1 77.500N
Lo1 0.0E
Res. & Comp. Flag 1 0 0 0 0 0 0 0
La2 77.500S
Lo2 359.500E = 0.500W
Di 0.500 degrees
Dj 0.500 degrees
Scanning Mode 0 0 0(NB: matrix style)
Lat/lon values of the corners of the grid
(1,1) 77.500N, 0.000E
(1,311) 77.500S, 0.000E
(720,311) 77.500S, 359.500E
(720,1) 77.500N, 359.500E


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VALUE GRID DESCRIPTIONS
12 0.167 degree Latitude/Longitude for the US East Coast grid
(Used by Global Multi-Grid Wave Model (Static Grids)

Ni 301
Nj 331
La1 55.000N
Lo1 260.000E
Res. & Comp. Flag 1 0 0 0 0 0 0 0
La2 0.00N
Lo2 310.000E = 50.000W
Di 0.167 degrees
Dj 0.167 degrees
Scanning Mode 0 0 0(NB: matrix style)
Lat/lon values of the corners of the grid
(1,1) 55.000N, 260.000E
(1,331) 0.000N, 260.000E
(301,331) 0.000N, 310.000E
(301,1) 55.000N, 310.000E


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VALUE GRID DESCRIPTIONS
13 0.167 degree Latitude/Longitude for the US West Coast grid
(Used by Global Multi-Grid Wave Model (Static Grids)

Ni 241
Nj 151
La1 50.000N
Lo1 210.000E
Res. & Comp. Flag 1 0 0 0 0 0 0 0
La2 25.000N
Lo2 250.000E = 110.000W
Di 0.167 degrees
Dj 0.167 degrees
Scanning Mode 0 0 0(NB: matrix style)
Lat/lon values of the corners of the grid
(1,1) 50.000N, 210.000E
(1,151) 25.000N, 210.000E
(241,151) 25.000N, 250.000E
(241,1) 50.000N, 250.000E


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VALUE GRID DESCRIPTIONS
14 0.167 degree Latitude/Longitude grid
(for the Easter Pacific; includes Hawaii and extends to the Pacifici islands of Guam etc.)
(Used by Global Multi-Grid Wave Model (Static Grids)

Ni 511
Nj 301
La1 30.000N
Lo1 130.000E
Res. & Comp. Flag 1 0 0 0 0 0 0 0
La2 20.000S
Lo2 215.000E = 145.000W
Di 0.167 degrees
Dj 0.167 degrees
Scanning Mode 0 0 0(NB: matrix style)
Lat/lon values of the corners of the grid
(1,1) 30.000N, 130.000E
(1,301) 20.000S, 130.000E
(511,301) 20.000S, 215.000E
(511,1) 30.000N, 215.000E


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VALUE GRID DESCRIPTIONS
15 0.25 x 0.167 degree Latitude/Longitude grid for Alaska
(Used by Global Multi-Grid Wave Model (Static Grids)

Ni 401
Nj 187
La1 75.000N
Lo1 140.000E
Res. & Comp. Flag 1 0 0 0 0 0 0 0
La2 44.000N
Lo2 240.000E = 120.000W
Di 0.250 degrees
Dj 0.167 degrees
Scanning Mode 0 0 0(NB: matrix style)
Lat/lon values of the corners of the grid
(1,1) 75.000N, 140.000E
(1,187) 44.000N, 140.000E
(401,187) 44.000N, 240.000E
(401,1) 75.000N, 240.000E


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VALUE GRID DESCRIPTIONS
16 0.133 x 0.067 degree Latitude/Longitude grid for Alaska
(Used by Global Multi-Grid Wave Model (Static Grids)

Ni 548
Nj 391
La1 74.000N
Lo1 165.000E
Res. & Comp. Flag 1 0 0 0 0 0 0 0
La2 48.000N
Lo2 237.933E = 122.067W
Di 0.133 degrees
Dj 0.067 degrees
Scanning Mode 0 0 0(NB: matrix style)
Lat/lon values of the corners of the grid
(1,1) 74.000N, 165.000E
(1,391) 48.000N, 165.000E
(548,391) 48.000N, 237.933E
(548,1) 74.000N, 237.933E


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VALUE GRID DESCRIPTIONS
17 0.067 degree Latitude/Longitude grid for the US West Coast ; includes Hawaii
(Used by Global Multi-Grid Wave Model (Static Grids)

Ni 736
Nj 526
La1 50.000N
Lo1 195.000E
Res. & Comp. Flag 1 0 0 0 0 0 0 0
La2 15.000N
Lo2 244.000E = 116.000W
Di 0.067 degrees
Dj 0.067 degrees
Scanning Mode 0 0 0(NB: matrix style)
Lat/lon values of the corners of the grid
(1,1) 50.000N, 195.000E
(1,526) 15.000N, 195.000E
(736,526) 15.000N, 244.000E
(736,1) 50.000N, 244.000E


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VALUE GRID DESCRIPTIONS
18 0.067 degree Latitude/Longitude grid for the US East Coast
(Used by Global Multi-Grid Wave Model (Static Grids)

Ni 586
Nj 481
La1 47.000N
Lo1 261.000E
Res. & Comp. Flag 1 0 0 0 0 0 0 0
La2 15.000N
Lo2 300.000E = 60.000W
Di