McIDAS User's Guide
Version 2010.2

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GRDCOPY

Copies grids from one dataset to another.

Format

GRDCOPY sdataset ddataset [keywords]

Parameters

sdataset	source ADDE dataset name and absolute position; specify one of the following formats:
		group/descriptor.position alias.position
	only positive integers or ALL (all positions) are valid for position (no default for group/descriptor or alias; default=ALL for position)
ddataset	destination ADDE dataset name and absolute position; specify one of the following formats:
		group/descriptor.position alias.position
	use only positive integers for position

Search Keywords

DAY=	d1 . . dn	copies grids with the specified days
DRAnge=	bday eday inc	copies 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	copies grids with the specified ensemble numbers; each ensemble number must include a + or - sign, e.g., -1 -0 +0 +1
FDAy=	copies 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	copies grids with the specified forecast hours; you cannot use FHOUR with the FRANGE, FDAY or FTIME keyword
FRANGe=	bhr ehr inc	copies 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=	copies grids with this 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	copies grids with the specified projection, for example, MERC, PS, LAMB, EQUI
GRIB=	geo par model level copies grids with the specified GRIB codes; the four values are the geographic, parameter, model and level codes that can be listed with GRDLIST FORM=ALL; values specified as an X (a placeholder) or not specified at all will match any GRIB code
GRId=	bgrid egrid	copies grids bgrid through egrid; 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]	copies 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
PARam=	p1 . . pn	copies grids with the specified parameters, for example, T, Z, RH; see the Remarks
SRC=	s1 . . sn	copies grids with the specified sources, for example, MDX, GFS, ETA
TIMe=	t1 . . tn	copies grids with the specified times
TRAnge=	btim etim inc	copies grids in the time range of btim through etim, incremented by inc (no default for btim; etim default=btim; inc default=1, meaning one hour)

Derived Grid Keywords

DERive=	derives a grid of the specified parameter, for example, DST or VOR; searches for the component grids using the search keywords, derives the grid, and copies it to the ddataset; do not use with the PARAM keyword; see the Remarks
MERidional=	YES	adds a correction term to account for the convergence of longitude lines at the poles
	NO	does not add a correction term; only valid with DERIVE=ABV, DSH, DST, DVG, or VOR; see the Remarks (default)
PLAnet=	planet for which derive calculations are done; valid options are MERCURY, VENUS, EARTH, MARS, JUPITER, SATURN, NEPTUNE, URANUS (default=EARTH)

Mathematical Operations Keywords

Gn=	'clause1; clause2; . .; clausen' 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
INFo=	'text'		string placed in the header of the copied grid when the MATH keyword is used; maximum of 48 characters
MATh=	'expression'		mathematical operation to perform on the grids specified with the Gn keywords; single quotes are mandatory; see the Remarks
NEWpar=	param punit level lunit src header information for the grid copied with the MATH keyword; parameter and level values, and associated units
		param	grid parameter; four characters maximum (default=MATH)
		punit	units of grid parameter; four characters maximum (default=NONE)
		level	grid level (default=from grid)
		lunit	units of grid level; two characters maximum (default=from grid)
		src	grid source; four characters maximum (default=from grid)

Output Keywords

BYTecount=	YES	lists the number of bytes received from the server
	NO	does not list the number of bytes (default)
DEL=	YES	delete the destination grid file before copying; see the Remarks
	NO	do not delete the destination grid file (default)
DGRid=	beginning grid number in the destination grid file to place the copied grids; this keyword may overwrite existing grids; see the Remarks (default=append after the last grid in the grid file)
MAXgrd=	maximum number of grids the newly created destination grid file can store; see the Remarks (default=1000)
NUM=	number of grids matching the criteria defined with the search keywords to copy; for example, if you specify NUM=50, the first 50 grids matching the search keywords are copied (default=1)
	ALL	copies all grids matching the search keywords
SUBsect=	slat nlat elon wlon incrow inccol geographic region to subsect from the source grid, and row and column reduction intervals to use within the subsect region; see the Remarks
	slat, nlat		southern and northern latitudes of the subsect region
	elon, wlon		eastern and western longitudes of the subsect region (slat, nlat, elon, wlon defaults=source grid bounds)
	incrow, inccol		row and column reduction intervals; 1 means copy every row/column of grid points in the subsect region, 2 means copy every other row/column, etc.; when subsecting a conformal projection grid, the incrow and inccol values must be the same (default=1 for both)
	Note: If the source grid is a McIDAS grid, you can subsect it by row and column instead of latitude and longitude. To do so, specify row and column numbers instead of latitudes and longitudes in the first four parameters, and specify ROWCOL as the seventh parameter. For example, SUBSECT=10 40 80 160 1 2 ROWCOL uses rows 10, 11, 12, ..., 40 and columns 80, 82, 84, ..., 160 for the subsect region. (If you don't include the ROWCOL at the end, it will treat 10 and 40 as latitudes, and 80 and 160 as longitudes.)
TITLE=	'text'	title of the newly created destination grid file; 32 characters maximum; see the Remarks

Remarks

Individual grids are stored in grid files. Each dataset position points to a single grid file. GRDCOPY copies grids from one or more grid files in the source dataset to a single grid file in the destination dataset.

If you specify DEL=YES or a position number of a nonexistent grid file in the ddataset parameter, the grids are copied into a newly created grid file with the attributes specified in keywords MAXGRD and TITLE.

Using the DGRID keyword may result in grids being overwritten in the destination grid file. For example, if the destination grid file has 50 grids (in grids 1 to 50) and you specify NUM=10 DGRID=25, the new grids will overwrite grids 25 to 34 in the destination grid file.

The GRID keyword copies grids from the grid file specified with the sdataset 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, GRDCOPY 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 copies both sets of grids to the destination dataset. 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.

Use command GRDLIST to preview the grids to be copied with GRDCOPY.

Use the SUBSECT keyword to copy a portion of the source grid. This keyword is useful because the subsected grid is smaller and can be copied more quickly than the source grid.

Use the DERIVE keyword to create grids of a variety of common meteorological parameters. The valid options are defined in the table below. In these equations, the following variables appear often:

u = u-component of the wind

v = v-component of the wind

x = grid point distance in the east-west direction

y = grid point distance in the north-south direction

DERIVE=	Description	Equation
ABV	absolute vorticity	f =coriolis parameter: 2ΩsinΦ (see COR)
BETA	beta parameter	f =coriolis parameter: 2ΩsinΦ (see COR) Ω=angular speed of the rotation of the planet (7.292 × 10^-5 radians/second for Earth) Φ=latitude in degrees a=radius of the planet
COR	coriolis parameter	2ΩsinΦ Ω=angular speed of the rotation of the planet (7.292 × 10^-5 radians/second for Earth) Φ=latitude in degrees
DIR	wind direction	atan2(-u,-v)
DSH	shearing deformation
DST	stretching deformation
DVG	divergence
SPD	wind speed
TD	dew point temperature	T =temperature in Kelvin RH =relative humidity Rv=moist gas constant: 461.5 Joules per kilogram per degree Kelvin
VOR	relative vorticity

Use the MERIDIONAL keyword to correct for the convergence of longitude lines at the poles. When deriving divergence and stretching deformation grids (DVG and DST), specify MERIDIONAL=YES to subtract the following correction term from the calculation.

When deriving vorticity, absolute vorticity, or shear deformation grids (VOR, ABV, or DSH), specify MERIDIONAL=YES to add the following correction term to the calculation.

For both the correction terms above:

u = u-component of the wind

v = v-component of the wind

Φ = latitude in degrees

r = radius, in kilometers, of the planet at Φ latitude

The MERIDIONAL keyword has no effect with other DERIVE keyword options.

Use the Gn keywords to specify the grids to be used with the MATH keyword. 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 perform on the specified grids, for example, MATH='G1**(SQRT(G2))'. The table below shows the operations available with the MATH keyword.

MATH= option	Function
+	addition
–	subtraction
*	multiplication
/	division
**	power
SQRT	square root
EXP	exponential (the number e raised to a power)
LOG	natural logarithm
LOG10	base 10 logarithm
SIN	sine
COS	cosine
TAN	tangent
ASIN	arcsine
ACOS	arccosine
ATAN	arctangent
ABS	absolute value
MIN	minimum of two grids
MAX	maximum of two grids
DDX	derivative with respect to x
DDY	derivative with respect to y
DELSQ	laplacian
COR	coriolis parameter (2ΩsinΦ)
BETA	beta parameter
LAT	creates a grid of latitude
LON	creates a grid of longitude

When specifying powers of ten, such as 10² or 10^-3 in the MATH keyword, use one of the two methods shown in the examples below.

MATH='2*7.292*(1e-5)*(SIN(G1))'

MATH='2*7.292*(10**(-5))*(SIN(G1))'

In these entries both 1e-5 and 10**(-5) represent 10^-5. You must include the parentheses with 10**(-5); 10**-5 will not be interpreted correctly.

When using the MATH keyword and the range of output data values is larger than five orders of magnitude, the output grid is scaled based on the maximum end of the range. This means that small data values may be replaced by zeros in the output grid.

Grids created using GRDCOPY and those created using IGG MAKE with the DERIVE or MATH keyword may not yield numerically identical results. However, the values for both are correct. The differences are the result of one of the following:

Grids created using GRDCOPY will be in Standard International units, whereas grids created using IGG MAKE may not be. For example, a grid created using the TADV (temperature advection) function in IGG MAKE will be in degrees per day, while a similar grid created using GRDCOPY with the MATH keyword will be in degrees per second unless a factor is added to the equation to compute it in degrees per day.
By default, IGG MAKE applies a smoothing function and, if applicable, a meridional correction term to the data. GRDCOPY does not do this by default. You can override the IGG MAKE defaults by specifying SMO=NO and ADD=NO.

Examples

GRDCOPY NCEP/GFS MYDATA/GRIDS.1

This entry copies the first grid in the first grid file in dataset NCEP/GFS to the grid after the last grid in position 1 of dataset MYDATA/GRIDS.

GRDCOPY NCEP/GFS.5 MYDATA/GRIDS.2 LEV=850 NUM=10 DGRID=5

This entry copies the first 10 grids with a level of 850 mb in position 5 of dataset NCEP/GFS to grids 5 through 14 in position 2 of dataset MYDATA/GRIDS.

GRDCOPY NCEP/GFS.5 MYDATA/GRIDS.1 NUM=ALL DEL=YES TITLE='All grids in NCEP/GFS position 5'

This entry copies all grids in position 5 of dataset NCEP/GFS to position 1 of dataset MYDATA/GRIDS. The keyword DEL=YES deletes the existing destination grid file and creates a new file with the title All grids in NCEP/GFS position 5 for the copied grids. Since the destination grid file is new, the copied grids begin in grid 1. Be careful when using NUM=ALL; grid files can contain thousands of grids. Use the search keywords to copy only the desired grids, as shown in the following examples.

GRDCOPY NMC/ETA.ALL G/SCRATCH.10 LEV=500 PARAM=Z T TD RH ABV DAY=#Y TIME=0 NUM=ALL

This entry copies 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 to position 10 of dataset G/SCRATCH. The grids are appended after the last grid in the destination grid file.

GRDCOPY NMC/ETA.1 G/MODEL.2 LEV=TRO PARAM=Z T FHOUR=12 36 NUM=ALL DGRID=1

This entry copies all 12- and 36-hour forecast tropopause height and temperature grids in position 1 of dataset NMC/ETA to position 2 of dataset G/MODEL. The copied grids begin in grid 1 of the destination grid file.

GRDCOPY NMC/ETA.1 G/MODEL.2 LEV=TRO PARAM=Z T FRANGE=12 36 6 NUM=ALL DGRID=100

This entry copies all 12-, 18-, 24-, 30-, and 36-hour forecast tropopause height and temperature grids in position 1 of dataset NMC/ETA to position 2 of dataset G/MODEL. The copied grids begin in grid 100 of the destination grid file.

GRDCOPY NMC/ETA.1 G/MODEL.2 LEV=TRO PARAM=Z T FDAY=#Y FTIME=18 NUM=ALL

This entry copies all forecast tropopause height and temperature grids valid at 18 UTC today in position 1 of dataset NMC/ETA to position 2 of dataset G/MODEL. The grids are appended after the last grid in the destination grid file.

GRDCOPY MODEL.5 GRD.1 GRID=1 20 DGRID=1

This entry copies grids 1 through 20 in position 5 of the dataset with the alias name MODEL to grids 1 through 20 in position 1 of the dataset with the alias name GRD.

GRDCOPY GRIDS/GFS CASE/STUDY.1 DAY=#Y TIME=12 PARAM=U V LEV=200 SUBSECT=-20 20 -180 -120 1 2 NUM=ALL

This entry copies all 200 mb height u- and v-component grids from today's 12 UTC run in dataset GRIDS/GFS to position 1 of dataset CASE/STUDY. The copied grids contain every source grid point in the row direction and every other source grid point in the column direction in the region 20°S to 20°N and 180°E to 120°E.

GRDCOPY GG.1 GRD.4000 DERIVE=SPD LEV=500 FHOUR=48

The entry creates a 500 mb wind speed grid using component grids in position 1 of the dataset with the alias GG. The grids used to derive wind speed are the u- and v-components of the wind with 48-hour forecast times. The derived grid is copied to position 4000 of the dataset with the alias GRD.

GRDCOPY RTGRIDS/GFS LOCAL/MYGRIDS.10 DERIVE=VOR LEV=500 DAY=96284 TIME=12 FHOUR=12 24 36 48 NUM=ALL

This entry creates 500 mb relative vorticity grids using component grids from dataset RTGRIDS/GFS. The grids used to derive relative vorticity are the u- and v-components of the wind from day 96284 at 12:00 UTC with 12-, 24-, 36-, and 48-hour forecast times. The derived grids are copied to position 10 of the dataset LOCAL/MYGRIDS.

GRDCOPY GRD.8000 GRD.4000 G1='PARAM Z;LEV 850;FHOUR 48' G2='LEV 1000' MATH='G1-G2' NEWPAR=THCK

This entry finds two 48-hour forecast geopotential height grids in position 8000 of the dataset with the alias GRD. The 1000 mb grid is subtracted from the 850 mb grid and the result is copied to position 4000 of the dataset with the alias GRD. The copied grid is labeled with the new parameter name THCK and units NONE.

GRDCOPY GRD.4004 GRD.4004 G1='PARAM T;LEV 1000' G2='LEV 850' G3='PARAM U;LEV 1000' G4='LEV 850' NEWPAR=M DEG MATH='(COR(G1))/9.8*((G1+G2)/2)*((G3-G4)/(G1-G2))'

This entry creates a grid of frontal slope (Margules equation) from the 1000 and 850 mb temperature grids, and the 1000 and 850 mb u-component grids in position 4004 of the dataset with the alias GRD. The grid is copied into the same dataset, and labeled M with units DEG.

GRDCOPY G/G.4000 G/G.4000 G1='PAR T;LEV 1000;TIME 12; DAY 93070;SRC GFS' G2='PAR U;SRC ROI' G3='PAR V; SRC ROI' MATH='-(G2*(DDX(G1))+G3*(DDY(G1)))' INFO='Temperature Advection at 1000 MB' NEWPAR=TADV K/S

This entry creates a grid of 1000 mb temperature advection using the 1000 millibar GFS model temperature grid, and the 1000 mb ROI model u- and v-component grids in position 4000 of the dataset G/G. The grid is copied into the same dataset, and labeled TADV with units of degrees Kelvin per second. The string Temperature Advection at 1000 MB is placed in the header of the new grid.

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