McIDAS User's Guide
Version 2016.2

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GRDLIST

Lists grids in a dataset.

Format

GRDLIST dataset [keywords]

Parameter

dataset

ADDE dataset name and absolute position; specify one of the following formats:

group/descriptor.position

alias.position

use only positive integers or ALL (all positions) for position (no default for group/descriptor or alias; default=ALL for position)

Search Keywords

DAY=	d1 . . dn	lists grids with the specified days
DERive=	lists derived grids with the specified parameter, for example, DST or VOR; the grid listed does not exist, but the components needed to derive such a grid do; do not use with the PARAM keyword; see the Remarks
DRAnge=	bday eday inc	lists grids in the range of days bday through eday, incremented by inc days (no default for bday; eday default=bday; inc default=1)
ENSemble=	e1 . . en	lists grids with the specified ensemble numbers; each ensemble number must include a + or - sign, e.g., -1 -0 +0 +1
FDAy=	lists grids with the specified forecast day; a grid's forecast day is determined by adding the forecast hour to the day and time; for example, a 12 UTC grid from day 95300 with a forecast hour of 72 has a forecast day of 95303; you cannot use FDAY with the FHOUR, FRANGE or MATH keyword
FHOur=	h1 . . hn	lists grids with the specified forecast hours; you cannot use FHOUR with the FRANGE, FDAY or FTIME keyword
FRANge=	bhr ehr inc	lists grids in the range of forecast hours bhr through ehr, incremented by inc hours; you cannot use FRANGE with the FHOUR, FDAY or FTIME keyword (no default for bhr; ehr default=bhr; inc default=1)
FTIme=	lists grids with the specified forecast time; a grid's forecast time is determined by adding the forecast hour to the time; for example, a 12 UTC grid with a forecast hour of 18 has a forecast time of 6 on the following day; you cannot use FTIME with the FHOUR, FRANGE or MATH keyword
GPRo=	g1 . . gn	lists grids with the specified projection, for example, MERC, PS, LAMB, EQUI
GRIB=	geo par model level lists grids with the specified GRIB codes; the four values are the geographic, parameter, model and level codes that can be listed with the FORM=ALL keyword; values specified as an X (a placeholder) or not specified at all will match any GRIB code
GRId=	bgrid egrid	lists grids bgrid through egrid in the grid file specified in the dataset parameter; enter a grid number or LAST (last grid) for bgrid and egrid; see the Remarks (no default for bgrid; egrid default=bgrid)
LEV=	l1[u1] . . ln[un]	lists grids with the specified levels and units, e.g., SFC, 850[MB], 5000[M]; units are optional but must be in square brackets if specified; if [MB] or [HPA] is specified for units then grids with either of those units are listed
PARam=	p1 . . pn	lists grids with the specified parameters, for example, T, Z, RH; do not use with the DERIVE keyword; see the Remarks
SRC=	s1 . . sn	lists grids with the specified sources, for example, MDX, GFS, ETA
TIMe=	t1 . . tn	lists grids with the specified times
TRAnge=	btim etim inc	lists grids in the range of times btim through etim, incremented by inc (no default for btim; etim default=btim; inc default=1, meaning one hour)

Mathematical Operations Keywords

Gn=

'clause1; clause2; . .; clausen'

lists grids to be used with the MATH keyword; separate select clauses with semicolons; single quotes are mandatory; specify clause using the following format:

searchkeyword value

valid options for searchkeyword are DAY, FHOUR, GPRO, GRID, LEV, PARAM, SRC, TIME; you can specify numbers between 1 and 99 in the keyword name (G1, G2, . . , G99); see the Remarks

MATh=

'expression'

mathematical operation to be performed on the grids specified with the Gn keywords; single quotes are mandatory; see the Remarks

Output Keywords

BYTecount=	YES	lists the number of bytes received from the server
	NO	does not list the number of bytes (default)
FORm=	SHORT	lists a one-line summary for each grid (default)
	ALL	lists all information for each grid
	FILE bpos epos
		lists only the grid file directories; none of the grids in the grid files are listed; all other keywords are ignored; bpos is the beginning position number or ALL; epos is the ending position number or LAST; bpos and epos override the position specified in the dataset parameter (bpos default=position specified in the dataset parameter, epos default=bpos)
NUM=	number of grids matching the criteria defined with the search keywords to list; for example, if you specify NUM=50, the first 50 grids matching the search keywords are listed (default=1)
	ALL	lists all grids matching the search keywords
PUNit=	units to assign to the pressure grids that are listed; the valid options are MB or HPA and will be used regardless of which of the two units appear in the source grids (default=units in source grids)

Remarks

Individual grids are stored in grid files. Each dataset position points to a single grid file. GRDLIST lists grids in one or more grid files in a dataset. The listing includes the parameter, level, day, time, source, forecast hour, forecast day, forecast time, grid number and projection. Use the search keywords to limit the output to the desired grids.

The GRID keyword lists grids in the grid file specified in the dataset position number; the default position value, ALL, is not valid. When using the GRID keyword, do not specify additional search keywords, PARAM, LEV, DAY, etc., or NUM.

If you specify PARAM=STREAML, WINDB or WINDV, GRDLIST does not search for grids with that parameter. Instead, it locates the u-component grids that match the other search keywords, then locates the matching v-component grids, and lists both sets of grids. These grids may be used to draw streamlines, plot wind barbs or plot wind vectors with the GRDDISP command. If you specify any other parameter with the PARAM keyword, the value entered is the value searched for in the grid's parameter field.

The DERIVE keyword lists a virtual grid: a grid that could be derived. GRDLIST searches for grids with the components needed to derive a grid with the specified parameter. The listing is for the grid that would be created using the GRDCOPY command. Use GRDCOPY with the DERIVE keyword to create derived grids. Once the derived grid is created, use GRDLIST with the PARAM keyword to list the output grid.

Use the Gn keywords to specify the grids to be used with the MATH keyword. GRDLIST lists the grids but the mathematical operation is not performed. Each Gn keyword specifies a single grid. Gn is followed by a list of select clauses in single quotes. By default, subsequent Gn keywords have the same select clauses, unless specified differently. For example, to request 850 and 1000 mb height grids from the 0:00 UTC GFS run, specify G1='LEV 850;PARAM Z;TIME 0;SRC GFS' G2='LEV 1000'.

The MATH keyword defines the operation to be performed on the specified grids, for example, MATH='G1**(SQRT(G2))'. Even though the math is not done, the MATH keyword must be used with the Gn keywords.

Examples

GRDLIST NCEP/GFS

This entry lists the first grid in the first grid file in dataset NCEP/GFS.

GRDLIST NCEP/GFS.5

This entry lists the first grid in the grid file in position 5 of dataset NCEP/GFS.

GRDLIST NCEP/GFS.5 LEV=850 NUM=10

This entry lists the first 10 grids with a level of 850 mb in the grid file in position 5 of dataset NCEP/GFS.

GRDLIST NCEP/GFS.5 NUM=ALL

This entry lists all grids in the grid file in position 5 of dataset NCEP/GFS. Be careful when using NUM=ALL; grid files can contain thousands of grids. Use the search keywords to limit the output to the desired grids, as shown in the following examples.

GRDLIST NMC/ETA.ALL LEV=500 PARAM=Z T TD RH ABV DAY=#Y TIME=0 NUM=ALL

This entry lists all 500 mb height, temperature, dew point temperature, relative humidity and absolute vorticity grids from today's 00 UTC run in all grid files in dataset NMC/ETA.

GRDLIST NMC/ETA.1 LEV=TRO PARAM=Z T FHOUR=12 36 NUM=ALL

This entry lists all 12- and 36-hour forecast tropopause height and temperature grids in the grid file in position 1 of dataset NMC/ETA.

GRDLIST NMC/ETA.1 LEV=TRO PARAM=Z T FRANGE=12 36 6 NUM=ALL

This entry lists all 12-, 18-, 24-, 30- and 36-hour forecast tropopause height and temperature grids in the grid file in position 1 of dataset NMC/ETA.

GRDLIST NMC/ETA.10 LEV=TRO PARAM=Z T FDAY=#Y FTIME=18 NUM=ALL

This entry lists all forecast tropopause height and temperature grids valid at 18 UTC today in the grid file in position 10 of dataset NMC/ETA.

GRDLIST LOCAL/GRIDS.2 GRID=1 20

This entry lists grids 1 through 20 in the grid file in position 2 of dataset LOCAL/GRIDS.

GRDLIST MYGRIDS.2 GRID=LAST

This entry lists the last grid in the grid file in position 2 of the dataset with the alias name MYGRIDS. This information may be useful for subsequent GRDLIST or GRDCOPY commands, as it usually indicates about how many grids are in the grid file. For example, if this command shows that grid 800 is the last grid, then the grid file contains 800 or less grids. There are less than 800 grids only if there are "holes" in the grid file. For example, if grid 800 is the last grid, but there are no grids between 600 and 649, the grid file contains 750 grids.

GRDLIST STORM/FORECAST.ALL FORM=FILE

This entry lists the directories for all grid files in dataset STORM/FORECAST. None of the grids in the dataset are listed. If the grid file directories contain useful information such as day, time and contents, you can determine which grid file has the grids you want to list, copy or display. Then you can specify that grid file in the dataset parameter's position in your GRDLIST, GRDCOPY and GRDDISP commands to limit the search to that grid file.

GRDLIST MYGRIDS.1 DERIVE=SPD LEV=500 FHOUR=48

This command lists the wind speed grids that could be derived from 500 millibar, 48 hour forecast time component grids in position 1 of the dataset with the alias MYGRIDS.

GRDLIST MYGRIDS.1 G1='SRC GFS;PARAM Z;LEV 500;FHOUR 12' G2='FHOUR 24' G3='FHOUR 36' MATH='(G1+G2+G3)/3'

This command lists the three 500 millibar geopotential height grids from the GFS model needed for an average of the 12, 24, and 36 forecast hours. The grids listed are from position 1 of the dataset with the alias MYGRIDS.