U. S. DEPARTMENT OF COMMERCE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION NATIONAL WEATHER SERVICE NATIONAL METEOROLOGICAL CENTER OFFICE NOTE 84 (REVISED) (see overleaf) Packing and Identification of NMC Grid-Point Data Automation Division Staff February 10, 1994 Changes, additons, and corrections since the last full printing, dated January 19, 1993: January 1993 p.10 interpretation of parameter 159 clarified p.11-13 units of 179,199,210,211 new parameters 219 & 220 p.27ff new grid types: 87, 88, 89, 90, 91, 92, 93, 98, 104, 105, 106, 107; 153 deleted p.28 RUC added to run marker table. p.29ff new generating programs:80,81,83,84,85,86 March 1993 p.10ff Added parameters 138, 157, 158 p.9 Deleted parameter 118 (redundant with 157) November 1993 p.20 Added Grid 4 February 1994 p.4 Correction to specification of location of T p.21 Added grid 18 (12 hex) p.30 Model 78 (4E hex) changed to indicate 28 layers p.30.1 Added model No. 87, 88 Then reprinted in entirety with new pagination, one hopes for the last time, as this identification system will not be carried over to UNIX based operating systems. GRIB will be used instead. Note: This publication is available via Internet on the NOAA Information Center server. Do an "anonymous FTP" into nic.fb4.noaa.gov, with a password of your e-mail address; check the /Readme file in the root directory for further directions. INTRODUCTION This Office Note provides information related to NMC grid point data fields. It describes the structure and packing of the data and the system used to identify the fields. A large number of requirements have been accommodated since these procedures were introduced many years ago and, as might be expected, some exceptions have crept into usage. These generally involve a minor amount of non-conformity to the standard units and to the packing procedures. The exceptions, where known, are indicated. The "Office Note 84" packing and identification method, as it is known locally, is an internal NMC standard; external transmissions generally use one or more World Meteorological Organization (WMO) code forms. In particular, grid-point data are represented in Code FM 92 GRIB (GRIdded Binary). Documentation on GRIB is available from the NMC Automation Division as Office Note 388. The documentation is also available on the nic.fb4.noaa.gov server. An effort is under way to convert NMC's internal data storage to GRIB to avoid the necessity of routinely changing data from one representation form to another and to bring NMC into line with the international standards. NMC PACKED BINARY DATA FORMAT Most NMC grid point data fields are packed by transforming 32-bit full-word floating point numbers into 16-bit half-word integers using a scaling algorithm which will be described later. A 12-word label is prefixed to each packed data array, serving two purposes: 1) to uniquely identify the data field; and 2) to hold count and scaling information so that the data 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 full- word floating point numbers. DATA PACKING AND UNPACKING The 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 ("**" denotes exponentiation.) 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 a 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 floating point number to be packed, and J is the number of data points. The scaled values H(j) are rounded, converted to halfword integers, and stored in sequence following word 12 of the label. The points are taken in the order they occur in storage. Negative values of n and H(j) are stored in two's complement form. NMC data fields can be packed and unpacked by this method with NMC 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 15-bit precision is maintained. The precision 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. Using a reference value which is the mid-range of the data array and forming departures from that value yields the same precision as using a reference value which is the minimum of the data array and then forming positive departures with 16-bit precision. 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 ID label words are properly set. IDENTIFYING THE DATA FIELDS Each packed data field is uniquely identified by 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. See Figure 1. Most NMC data fields can be thought of as some quantity Q on a horizontal or quasi-horizontal surface S at some level of value L. For example, a 500-hPa 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 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 geometrically above the surface of S2. For example, the thickness of the 500 to 1000-hPa 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 zero unless L is a negative number, and E is a signed integer. The convention for representing the signed integers C and E is to set the high-order bit on for negative values. 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, both in word 1 (and possibly word 3) of the label. 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 interpreted. T is found in word 2; F1 and F2 are in words 1 and 3 respectively. 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. M is in word 3. Table 4 gives values to be used for the exception marker X, found in word 3, 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. N is in word 4. Table 6 gives values for the markers CM and CD, word 5, which specify climatological data fields. Table 7 gives values for the marker K which identifies the grid for which the data are given. K is in word 7. Table 7 lists the 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 indicated in the table with an "A". 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 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 which parallels the vertical grid lines and 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. The first 4 bits of Word 6 indicate the source of the first guess for the analysis: 0 for the AVN run, 1 for the FNL run. The next 4 contain a count of number of additional physical records that constitute one (large) logical record. The physical record size and the number is set with the data set is initially allocated with VSAM I/O. If the number of physical records is likely to exceed the number of logical records (individual packed fields) because of the use of large logical records, this must be taken into account during the original allocation of the files. The remaining portions of the word are 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 Coordinated Time (UTC) in hours: 00-23 (midnight UTC II = 00, 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. 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 the right-hand (low-order) side of word 8 for the packing subroutine (W3AI01). Note that there are only 16 bits available to specify the number of data points. This means that a single field is limited to no more than approximately 65,000 data points. Special versions of the packer/unpacker are available to take care of such very large records. They make use of the "reserved" word 12 to hold the data point count. Note also, for records larger that about 32,000 data points that the number of bytes in the record (word 9) will be incorrect. Generally there are approximately two times as many bytes in the record as data points; for byte counts that are too large to fit into word 9, the number will simply be truncated at the high end. Neither the packer nor the unpacker make any use of the byte count. Table 9 gives the values of the marker R, word 8, which specifies the run within a cycle. Table 10 gives the values for the marker G, word 8, which specifies the program which generated the field. Programs which are currently in operational use as of the date of this Office Note are indicated by an "A". Table 10, incidentally, is a concise history of operational numerical weather prediction at NMC. 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 examples of identifying some common data fields. Table 13 gives the values for the marker P, word 11, 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 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 hPa 9 9 -PTEND Pressure tendency hPa/sec Temperature 10 16 -TMP-- Sensible air 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 17 23 -EPOT- Equivalent potential temp. degree K 18 24 -VTMP- Virtual temperature degree K Vertical motion 28 40 -V-VEL Vertical velocity dp/dt hPa/sec 29 41 -NETVD Net vertical displacement hPa 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 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 47 71 MGSTRM Montgomery Stream Function m**2/sec**2 48 72 -ABS-V Absolute vorticity 1/sec 49 73 -REL-V Relative vorticity 1/sec 4A 74 -DIV-- Divergence 1/sec 4B 75 -POT-V Potential vorticity deg K/hPa/sec 50 80 -STRM- Stream function m**2/sec 51 81 -V-POT Velocity potential m**2/sec 52 82 -U-STR Westerly comp. wind stress N/m**2 53 83 -V-STR Southerly comp. wind stress N/m**2 54 84 -TUVRD Westerly wind comp. N/m**2 acceleration by vert. diffusion 55 85 -TVVRD Southerly wind comp. N/m**2 acceleration by vert. 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 67 103 -MCONV Moisture convergence kg/kg/sec 68 104 -VAPP- Vapor pressure hPa 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 77 119 -CIN-- Convective inhibition m**2/sec**2 (negative buoyant energy) 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 ----- (NWS reduction) 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 Ship Anemometer Level ----- (19.5m) 86 134 -T-AIL Top of Aircraft Icing Layer --- -- 87 135 -B-AIL Bottom of Aircraft Icing Layer --- -- 88 136 -MSLSA Mean sea level (Standard ----- Atmosphere Reduction) 89 137 -MSLMA Mean sea level (MAPS ----- System Reduction) 8A 138 -MSLET Mean Sea Level (ETA, ----- Fedor Messinger reduction method) Sigma domain 90 144 -BDY-- Boundary ---- 91 145 -TRS-- Troposphere ----- 92 146 -STS-- Stratosphere ----- 93 147 -QCP-- Quiet cap ----- 94 148 -SIG-- Entire atmosphere ----- Miscellaneous parameters 9D 157 -CAPE- Convective Available J/kg Potential Energy 9E 158 -TKE-- Turbulent Kinetic Energy J/kg 9F 159 -CONDP Condensation pressure hPa of parcel lifted from indicated level/surface (S). A0 160 -DRAG- Drag coefficient non-dim. approx. range: 100-1200 (on maps 5&27) 0.001-0.009 (on maps 29&30) A1 161 -LAND- Land/sea flag non-dim. values... on map 5: land=-1, sea=0; on maps 29,30,33,34: land=+1, sea=0 A2 162 -KFACT K factors (700 hPa to 500 hPa non- dim. normal ratio) A3 163 -10TSL Conversion consts hPa/m (1000 hPa to sea level pressure) A4 164 -7TSL- Sea level pressure specifi- hPa/m cation from 700 hPa 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 hPa 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) hft@@ B4 180 ------ Visibility 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 BD 189 -MIXLY Number of mixed layers next (integer) to the surface Radiation Parameters 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 availability fractional: 1.0- 0.0 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 Tendency Parameters 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 Cloud-cover variables D2 210 CDLYR Amount of non-convective fract:1.0-0.0 cloud D3 211 CDCON Amount of convective cloud fract:1.0-0.0 D4 212 PBCLY Pressure at the base of a hPa non-convective cloud D5 213 PTCLY Pressure at the top of a hPa non-convective cloud D6 214 PBCON Pressure at the base of a hPa convective cloud D7 215 PTCON Pressure at the top of a hPa 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 DB 219 height of bottom of lowest hft cloud layer DC 220 height of bottom of highest hft cloud layer 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 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 (combined sea and swell) 191 401 -PERPW Primary wave period sec 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 degree secondary waves are moving (wrt North) 195 405 -WCAPS White cap coverage percent Notes: * 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. wrt means "with respect to" Table 2 - T TIME MARKER (4 bits) T (Dec) Meaning F1 (*) F2 (*) 0 Instantaneous field. E.g., 500-hPa 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 beginning. 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. 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 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 combination of NMC and ECMWF fields. 101 Field formed from combination of NMC and UKMET fields. 255 Not applicable. 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 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 Table 7 - K GRID TYPE ("A" indicates a currently active Grid Type) K GRID TYPE 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 A 259920-point (720x361) global lon/lat 0.5 deg grid;(1,1) at 0E, 90N; matrix layout; prime meridian not duplicated 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 (3.1035E,48.67S) and (116,44) degs of at (0W,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. 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 temps. F 15 40 U.S. stations for TDL max/min temps. 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 4205-point (129x29) lat/lon tropical 2.5 degs strip (35S to 35N) (0 - 360E) (1,1) at 35S, 0 deg. (from ECMWF) 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. 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 90.5 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). 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. 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 available. 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). 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 available. 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). (2/3 bedient NH sfc anl) 38 56 A 6177-point (87x71) N. Hemisphere polar 127 km stereographic grid oriented 105W; Pole at 60N at (40,73). (1/3 bedient NA sfc anl) 39 57 available 3A 58 100 U.S. cities for 24-hour accumulated precipitation. 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 64 875-point (35x25) longitude/latitude 0.5 deg grid; lat: 18.5N to 30.5N, long: 97.5W to 80.5W; Gulf of Mexico wave forecasts. 41 65 available 42 66 2701-point (73x37) longitude/latitude 5 deg 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). 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.& S. Hemisphere 40 km at Mercator grid. No fixed location; equator used by QLM Hurricane model. 50 80 A 2976-point (62x48) N. Hemisphere polar 80.0 km stereographic grid oriented 105W; Pole at 40N at (24.683025,85.27335). (MAPS analysis/forecast grid.) 51 81 A 7921-point (89x89) N. Hemisphere polar 190.5 km stereographic grid oriented 80W; at 60N pole at (44.5,44.5) 52 82 15372-point (244x63) N. Hemisphere variable T80 Gaussian transform lat/lon grid 53 83 15372-point (244x63) S. Hemisphere variable T80 Gaussian transform lat/lon grid 54 84 1344-point (42x32) N. Hemisphere polar 111.0 km stereographic grid oriented 105W; Pole at 40N at (16.08811,61.33562). (AFOS B03 p-s projection) 55 85 A 32400-point (360x90) N. Hemisphere 1 deg 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) 56 86 A 32400-point (360x90) S. Hemisphere 1 deg 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) 57 87 A 5022-point (81x62) N. Hemisphere polar 68.153 km stereographic grid oriented 105W. Pole at 60N at (31.91,112.53) (60 km at 40N) Used in MAPS/Rapid Update Cycle 58 88 A 262144-point (512x512) N. Hemisphere 47.625 km polar stereographic grid oriented 80W. at 60N Pole at (257,256) Shared Processing Net. 59 89 A 262144-point (512x512) S. Hemisphere 47.625 km polar stereographic grid oriented 100E. at 60S Pole at (257,256) Shared Processing Net. 5A 90 A 12902 point (92x141 semi-staggered) lat. 14/26 deg lat. long., rotated such that center lon. 15/26 deg located at 52.0N, 111.0W; LL at 37.5W, 35S Unfilled E grid for 80 km ETA model 5B 91 A 25803 point (183x141) lat. 14/26 deg lat. long., rotated such that center lon. 15/26 deg located at 52.0N, 111.0W; LL at 37.5W,35S Filled E grid for 80 km ETA model 5C 92 A 24162 point (127x191 semi-staggered) lat. 15/57 deg lat. long., rotated such that center lon. 5/18 deg located at 41.0N, 97.0W; LL at 35W,25S Unfilled E grid for 40 km ETA model 5D 93 A 48323 point (253x191) lat. 15/57 deg lat. long., rotated such that center lon. 5/18 deg located at 41.0N, 97.0W; LL at 35W ,25S Filled E grid for 40 km ETA model 62 98 A 18048-point (192x94) global T62 spectral variable Gaussian transform grid. Matrix layout. Origin at 0.0E and Gaussian lat 88.542N 192 columns (long.); 94 rows (lat.) 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 C Grid ) 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 C Grid ) 66 102 A 14375-point (115x125) N. Hemisphere 31.75 km stereographic grid oriented 105W; Pole at 60N at (13,241). (HPB precip. analysis) 67 103 A 3640-point (65x56) N. Hemisphere polar 91.452 km stereographic grid oriented 105W; Pole at 60N at (25.5,84.5) (Used by ARL) 68 104 A 16170-point (147x110) N.Hemisphere 90.75464 km polar stereographic grid oriented 105W; at 60N pole at (75.5,109.5). (NGM Super C grid) 69 105 A 6889-point (83x83) N.Hemisphere polar 90.75464 km stereographic grid oriented 105W; at 60N pole at (40.5,88.5). (Subset of NGM Super C grid) 6A 106 A 19305 point (165x117) N. Hemisphere 45.37732 km stereographic grid oriented 105W; at 60N pole at (80,176) Hi res ETA (2 x resolution of Super C) 6B 107 A 11040 point (120x92) N. Hemisphere 45.37732 km stereographic grid oriented 105W; at 60N pole at (46,167) subset of Hi res ETA; for ETA & MAPS/RUC 7E 126 A 72960-point (384x190) global T126 spectral variable Gaussian transform grid. Matrix layout. Origin at 0.0E and Gaussian lat 89.277N 384 columns (long.); 190 rows (lat.) D6 214 A 6693-point (97x69) N. Hemisphere polar 47.625 km stereographic grid oriented 150W; at 60N Pole at (49,101); AWIPS Alaskan area. FF 255 Not applicable. 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) 7 Rapid Update Cycle (RUC) 15 Runs from non-NMC networks 255 Not applicable Table 10 - G GENERATING PROGRAM (8 bits) "A" indicates a currently active Generating Program G Name of program generating data Map Hex Dec Label 0 0 Objective analysis (Cressman octagon) 1 1 A Barotropic fcst model BATRO 2 2 Mesh model 1958 3 3 Mesh model 1964 (imprv. terr.) 4 4 Reed 1000-hPa 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 A Sea height and swell fcst NOWAV 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 SNOW 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 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 NOW 2D 45 Spectral Model Global 24-mode 12-layer SMG2C 2E 46 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 NMSFC 38 56 A N. H. sea level pressure analysis NHSFC 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 10-layer hurricane model HCN 45 69 A T80 L18 Spectral Forecast Model MRF 46 70 A Quasi-Lagrangian Hurricane Model QLM 47 71 A Statistical Blending (MRFG) SBLND 48 72 A Isentropic Analysis ISENA 49 73 A Statistical Fog & Visibility (MPB) SFVSB 4A 74 A Gulf of Mexico Wind/Wave GMEXW 4B 75 A Gulf of Alaska Wind/Wave GAKWV 4C 76 A Bias Corrected MRF MRFBC 4D 77 A Japanese Meteorological Agency JMET 4E 78 A T126 L28 Spectral Forecast Model SM126 4F 79 A Backup from Earlier Run BCKUP 50 80 A T62 L18 Spectral Forecast Model SMT62 51 81 A Spectral Statistical Interpolation Analysis SSI 53 83 A ETA Model - 80 km version ETA80 54 84 A ETA Model - 40 km version ETA40 55 85 A ETA Model - 30 km version ETA30 56 86 A RUC/MAPS Model, from Forecast Systems Lab RUC60 (Isentropic; scale: 60km at 40N) 57 87 A Ensemble Forecasts (CAC) ENSMB 58 88 A Wave model with additional physics (MPB) PWAV 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 Table 12 EXAMPLES OF IDENTIFIER WORDS FOR COMMON FIELDS (1) 1000-hPa height analysis for N.H. (grid type 27): 00100800 00271081 00000000 00000000 0000001B (2) 500-hPa height analysis for N.H. (grid type 27): 00100800 00C35082 00000000 00000000 0000001B (3) 500-hPa temperature analysis for N.H. (grid type 27): 01000800 00C35082 00000000 00000000 0000001B (4) 500-hPa 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-hPa 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 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 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|# of 4| Internal I/O 8| For internal use 16| 6 |1st GES|add.rec| use 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| 12| Scaling value 16| 1 | Marker| Reserved | 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 | etc. Notes: next page... In word 6, bits 0-3 indicate source of GES ... 0 = AVN run 1 = FNL run In word 6, bits 4-7 are used to accommodate logical records that exceed the maximum physical record length set when the file was allocated. Such records are split into additional physical records. You must account for those additional records in the original allocation of the data set.