McIDAS User's Guide
Version 2010.1

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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:


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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