GEMPAK Online Tutorial

13. Radar Programs

GDRADR - NEXRAD to Grid

GDRADR samples NEXRAD Level III (NIDS) products to a common grid projection.

GDFILE specifies the output grid file. If the file does not already exist, the file is created using the grid defined by CPYFIL, or if CPYFIL is not defined then by PROJ, GRDAREA, and KXKY.

CPYFIL may provide either an existing grid file to read the projection information from, or a grid number (#nnn) defined in grdnav.tbl.

STNFIL is the station table which supplies radar IDs to be searched for the composite. If STNFIL is blank, then nexrad.tbl is used by default.

GDPFUN is a list of data parameters for which composites are created. The NEXRAD file naming is assumed to be such that the site identifier and the product type are both present in the directory/file naming structure.

Exercise #23 (Create a NEXRAD N0Q Grid)

Create a National composite of NEXRAD base reflectivity (N0Q). Use the current time with a 30 minute window for data. Use the nexrad.tbl station table. Create the grid output file using the YYYYMMDD_radar.gem file name template. Accept data only from radars operating in precipitation mode.

PROJ     = lcc/25;-103;60
GRDAREA  = 23.0;-120.0;47.0;-65.0
KXKY     = 720;500
GDPFUN   = n0q
GDFILE   = YYYYMMDD_radr.gem
RADTIM   = current
RADDUR   = 30
RADFRQ   = 
CPYFIL   =  
STNFIL   = nexrad.tbl
MAXGRD   = 1000
RADMODE  = P

Examine the contents with GDINFO:

GDFILE   = 20121102_radr.gem
LSTALL   = YES
OUTPUT   = T
GDATTIM  = all
GLEVEL   = all
GVCORD   = all
GFUNC    = n0q
GEMPAK-GDINFO>

Now color-fill the N0Q reflectivity contours with GDPLOT2:

GDFILE   = 20121102_radr.gem
GDATTIM  = last
GLEVEL   = 0
GVCORD   = none
PANEL    = 0
SKIP     = l
SCALE    =  
GDPFUN   = n0q
TYPE     = f
CONTUR   = 2
CINT     = l
LINE     =  
FINT     = 5/5
FLINE    = 0;30-7
HILO     =  
HLSYM    =  
CLRBAR   = 1
WIND     = 0
REFVEC   =  
TITLE    = @
TEXT     = 1/2//hw
CLEAR    = y
GAREA    = us
IJSKIP   = 0
PROJ     = lcc/25;-103;60
MAP      = 1
MSCALE   = 0
LATLON   = 0
DEVICE   = xw
STNPLT   =  
SATFIL   =  
RADFIL   =  
IMCBAR   = 1
LUTFIL   =  
STREAM   =  
POSN     = 0
COLORS   =  
MARKER   = 0
GRDLBL   = 0
FILTER   = YES

image

NEX2GINI - GINI File from NEXRAD Composite

NEX2IMG samples NEXRAD Level III (NIDS) products to a common grid projection, and then creates a GIF format image raster. NEX2IMG is not limited by the traditional LLMXGD limitation for grid files.

NEX2GINI Input Variables

GRDAREA    Area covered by grid
PROJ       Map projection/angles/margins|drop flag
KXKY       Number of grid points in x;y
CPYFIL     Grid file whose navigation is to be used in new grid file | subarea
GFUNC      Scalar grid
RADTIM     Radar composite current/dattim
RADDUR     Radar time window (minutes prior to RADTIM)
RADFRQ     Update Frequency
STNFIL     Station information file
RADMODE    Radar operational mode
SATFIL     Satellite image filename(s)
COMPRESS   output in compressed format

NEX2GINI uses a suplemental table $GEMTBL/unidata/nex2gini.tbl to specify configurations for data to pixel mappings.

SATFIL specifies the output file. If the file already exists, it is overwritten.

CPYFIL may provide either an existing grid file to read the projection information from, or a grid number (#nnn) defined in grdnav.tbl.

PROJ, GRDAREA, and KXKY define a grid navigation as in GDCFIL if CPYFIL is blank.

STNFIL is the station table which supplies radar IDs to be searched for the composite. If STNFIL is blank, then nexrad.tbl is used by default.

GFUNC is the data parameter which the composite is created for. The NEXRAD file naming is assumed to be such that the site identifier and the product type are both present in the directory/file naming structure.

Exercise #24 (NEX2GINI N0Q Composite)

Create a 1km National composite of NEXRAD base reflectivity (N0Q). Use the current time with a 30 minute window for data. Use the nexrad.tbl station table. Create the GINI output file using the rad_YYYYMMDD_HHNN file name template. Accept data from radars operating in precipitation and clear air mode.

GRDAREA  = 25;-128;50;-65
PROJ     = mer
KXKY     = 4000;2400
CPYFIL   =  
GFUNC    = n0q
RADTIM   = current
RADDUR   = 5
RADFRQ   = 0
STNFIL   = nexrad.tbl
RADMODE  = PC
SATFIL   = rad_YYYYMMDD_HHNN
COMPRESS =  
GEMPAK-NEX2GINI>r

You now have the rad_YYYYMMDD_HHNN in your working directory.

Display the NEXRAD composite as a satellite image in GPMAP:

MAP      = 1
MSCALE   = 0
GAREA    = 25;-128;50;-65
PROJ     = sat
SATFIL   = rad_20121102_0349
RADFIL   = 
IMCBAR   = 1/V/LL/0.05;0.04/0.925;0.0125/-5
LATLON   =  
PANEL    = 0
TITLE    = 1/-2
TEXT     = 1/2//hw
CLEAR    = y
DEVICE   = xw
LUTFIL   = upc_ref256.tbl
STNPLT   =  
VGFILE   =  
AFOSFL   =  
AWPSFL   =  
LINE     =  
WATCH    =  
WARN     =  
HRCN     =  
ISIG     =  
LTNG     =  
ATCF     =  
AIRM     =  
GAIRM    =  
NCON     =  
CSIG     =  
SVRL     =  
BND      = lakes/24
TCMG     =  
QSCT     =  
WSTM     =  
WOU      =  
WCN      =  
WCP      =  
ENCY     =  
FFA      =  
WSAT     =  
ASCT     =  
TRAK1    =  
TRAKE    =  
TRAK2    =  
GEMPAK-GPMAP>r

image

Exercise #25 (NEX2IMG N0Q Composite)

nex2img operates the exact same way as nex2gini , only it outputs the radar data directly to a GIF image.

To create a composite of NEXRAD base reflectivity (N0Q), use the current time with a 30 minute window for data. Create the GIF output file using the YYYYMMDD_HHNN.gif file name template. Accept data from radars operating in precipitation and clear air mode.

    GRDAREA  = 25;-125;50;-65
    PROJ     = MER
    KXKY     = 4000;2400
    CPYFIL   =  
    GFUNC    = n0q
    RADTIM   = current
    RADDUR   = 30
    RADFRQ   =  
    STNFIL   = nexrad.tbl
    RADMODE  = PC
    RADFIL   = YYYYMMDD_HHNN.gif
    LUTFIL   = upc_rad24.tbl
    GEMPAK-NEX2IMG>r

GPNIDS - NEXRAD Level III Plotting

GPNIDS plots NEXRAD Level III products.

RADFIL is the NEXRAD Level III input file. A template may be specified, with an optional site name and product type (eg NEXRIII|DDC|NWV). If a site name is provided, it will be used to replace the %SITE% alias in the template name. If a product type is provided, it will be used to replace the %PROD% alias in the template string if present. Products will br plotted in graph or map coordinates depending on the type of product. For VAD wind profile products (NVW) the display is graph coordinates, while raster and radial images, and overlay products (eg mesocyclone, storm track, tvs etc) are displayed in map coordinates. The NEXRIII template is provided for NEXRAD Level III files.

GPNIDS Input Parameters

RADFIL    Radar image filename(s)
RADTIM    Radar composite current/dattim
TITLE     Title color/line/title
PANEL     Panel loc/color/dash/width/regn
DEVICE    Device|name|x size;y size|color type
CLEAR     Clear screen flag
TEXT      Size/fnt/wdth/brdr/N-rot/just/hw flg
COLORS   Color list
WIND      Wind symbol/siz/wdth/typ/hdsz
LINE      Color/type/width/label/smth/fltr
CLRBAR   Color/ornt/anch/x;y/ln;wd/freq|text_info
IMCBAR    Color/ornt/anch/x;y/ln;wd/freq
GAREA     Graphics area
MAP       Map color/dash/width/filter flag
LATLON    Line color/dash/width/freq/inc/label/format
OUTPUT    Output device/filename

WIND can be used to select the type and plot size of barbs or arrows for the vectors in the VAD display.

Exercise #26 (Level 3 Reflectivity)

Plot the High Resolition Reflectivity (N0Q) product for RTX:

RADFIL   = NEXRIII|RTX|N0Q
RADTIM   = last
TITLE    = 1/-2
PANEL    = 0
DEVICE   = xw
CLEAR    = Y
TEXT     = 1/2/2/hw
COLORS   = 7
WIND     =  
LINE     =  
CLRBAR   =  
IMCBAR   = 5/v/LL/.005;.6/.4;.01
GAREA    = dset
$mapfil  = lorvus.usg + hicnus.nws + hipona.nws + louhus.nws + loisus.nws
MAP      = 24 + 23 + 1/1/2 + 14 + 15/1/2
LATLON   = 0
OUTPUT   = t
GEMPAK-GPNIDS>r

image

GPNEXR2 - NEXRAD Level II Plotting

GPNEXR2 displays NEXRAD Level II products in ARCHIVE2 format.

RADFIL specifies the input level II file. A template may be specified, with an optional site name (eg NEXRII|KDDC). If a site name is provided, it will be used to replace the %SITE% alias in the template name. The NEXRII template is provided for ARCHIVE2 format files.

RADPARM is the Radar parameter to be displayed.

Valid values are:

GPNEXR2 Input Parameters

MAP       Map color/dash/width/filter flag
GAREA     Graphics area
PROJ      Map projection/angles/margins|drop flag
RADFIL    Radar image filename(s)
LATLON    Line color/dash/width/freq/inc/label/format
PANEL     Panel loc/color/dash/width/regn
TITLE     Title color/line/title
TEXT      Size/fnt/wdth/brdr/N-rot/just/hw flg
CLEAR     Clear screen flag
DEVICE    Device|name|x size;y size|color type
LUTFIL    Enhancement lookup table filename
IMCBAR    Color/ornt/anch/x;y/ln;wd/freq|text_info
TILT      Radar beam elevation/tilt number
RADPARM  Radar parameter (dz, vr, sw)
RADTIM    Radar composite current/dattim

Exercise #27 (Level 2 Reflectivity)

Display the most recent reflectivity for KRTX using the sweep with mean elevation angle is closest to .5 degrees.

    MAP      = 6/1/1+3/1/2
    GAREA    = dset
    PROJ     = rad
    RADFIL   = NEXRII|KRTX
    LATLON   = 0
    PANEL    = 0
    TITLE    = 31
    TEXT     = 1
    CLEAR    = YES
    DEVICE   = xw
    LUTFIL   = default
    IMCBAR   = 31/V/LL/.005;.05/.85;.01|.7/1/1/hw
    TILT     = .5
    RADPARM  = dz
    RADTIM   = last
    GEMPAK-GPNEXR2>r

image

GPVAD - NEXRAD Level III Wind Profile

GPVAD plots the NEXRAD Level III wind profile product.

RADFIL is used the same as in GPNIDS (eg NEXRIII|DDC|NWV).

RADFIL    Radar image filename(s)
RADTIM    Radar composite current/dattim
WIND      Wind symbol/siz/wdth/typ/hdsz
TITLE     Title color/line/title
PANEL     Panel loc/color/dash/width/regn
DEVICE    Device|name|x size;y size|color type
CLEAR     Clear screen flag
TEXT      Size/fnt/wdth/brdr/N-rot/just/hw flg
CLRBAR    Color/ornt/anch/x;y/ln;wd/freq|text_info
OUTPUT    Output device/filename

Exercise #28 (VAD Time Series)

Plot the VAD profile for radar location RTX using the NEXRIII template for the most recent time. Use wind barbs, and plot the RMS bar along the altitude axis.

RADFIL   = NEXRIII|RTX|NVW
RADTIM   = last
WIND     = bk1
TITLE    = 1/-2/VAD DISPLAY ~
PANEL    = 0
DEVICE   = XW
CLEAR    = y
TEXT     = 1/1/1/hw
CLRBAR   = 1/v/cl/.05;.5/.3;.01
GEMPAK-GPVAD>r

image

NEXR2RHI - NEXRAD Level II Vertical Cross-Section

NEXR2RHI displays NEXRAD Level II vertical cross sections for data in ARCHIVE2 format. This program is adopted from GDCROSS to create a volume rendering of NEXRAD data along a specified axis.

CXSTNS    Cross-section station line
GVCORD    Grid vertical coordinate
PTYPE     Plot type/h:w ratio/margins
YAXIS     Ystrt/ystop/yinc/lbl;gln;tck
CINT      Contour interval/min/max
SCALE     Scalar scale / vector scale
LINE      Color/type/width/label/smth/fltr
BORDER    Background color/type/width
TITLE     Title color/line/title
CLEAR     Clear screen flag
DEVICE    Device|name|x size;y size|color type
TEXT      Size/fnt/wdth/brdr/N-rot/just/hw flg
PANEL     Panel loc/color/dash/width/regn
CLRBAR    Color/ornt/anch/x;y/ln;wd/freq|text_info
CONTUR    Subbox/smooth
FINT      Fill interval/min/max
FLINE     Fill colors/fill types
CTYPE     Contour type: C/F
RADFIL    Radar file
RADPARM  Radar parameter (dz, vr, sw)
RADTIM    Radar date/time
INTERP    Interpolation flag
 

RADPARM is the Radar parameter to be displayed. Valid values are dz (reflectivity), vr (radial velocity), sw (spectrum width).

RADTIM is a valid GEMPAK date/time string or abbreviation. A time range may be specified.

INTERP is a logical variable which determines whether interpolation between sweeps will occur.

CXSTNS is the cross section axis (as in GDCROSS). A grid coordinate can be used with row and colums 1 to 920.

GVCORD is the vertical coordinate of the radar data (always HGHT).

PTYPE is the plot type. A value of LIN is generally the only useful setting.

Exercise #29 (Reflectivity RHI)

Display an East-West RHI which passes through the radar location for reflectivity data from KRTX. Display the RHI from 0 to 6km using color filled contours. Use a contour interval of 4 dBZ with a minimum value of -12 dBZ. Grid point 460;460 is the radar center. Interpolate contours between beam scans.

CXSTNS   = @300;460>@620;460
GVCORD   = hght
PTYPE    = lin
YAXIS    = 0/6000
CINT     = 0
SCALE    = 0
LINE     = 1
BORDER   = 1
TITLE    = 1/-2/RHI Base Reflectivity Level II ^
CLEAR    = YES
DEVICE   = xw
TEXT     = .8/1/1/111/hw
PANEL    = 0
CLRBAR   = 1
CONTUR   = 3/2
FINT     = 4
FLINE    = 0;30-7
CTYPE    = f
RADFIL   = NEXRII|KRTX
RADPARM  = dz
RADTIM   = last
INTERP   = y

image

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