[gradsusr] how to find typhoon center via minloc function

Charles Seman Charles.Seman at noaa.gov
Wed Jul 20 12:44:56 EDT 2011


Sushant and Diallo,

I found a confusing comment in the maxwind.gs and maxwind2.gs scripts 
referring to "plotting track of hurricane center" (not sure, but 
possibly left over from code copied from another script?), and changed 
the comment to "plotting location of max wind". Please find attached 
updated GrADS scripts maxwind.gs, maxwind2.gs.

Sorry for this confusion,
Chuck

Charles Seman wrote:
> Sushant,
> 
> Glad to hear the script was helpful.
> 
> An updated script "maxwind.gs" (attached) for a single wind file and 
> wind variable (e.g. ucomp or vcomp) is now able to search over a 
> user-specified domain.
> 
> Another script "maxwind2.gs" (attached) has been coded based on 
> "maxwind.gs" to find the max wind magnitude of 2 wind variables (e.g. 
> ucomp, vcomp) over a user-specified domain (although the wind magnitude 
> is defined over all (x,y,z) points at each time level).
> 
> The scripts were run over a subset of the total (x,y,z,t) domain to 
> verify they work for a limited domain (note, you can set these in the 
> scripts yourself):
>   x1 = 2 ; x2 = nx-1
>   y1 = 2 ; y2 = ny-1
>   z1 = 2 ; z2 = nz-1
>   t1 = 2 ; t2 = nt-1
> 
> Run commands:
> cjs: /home/cjs/grads/Sushant_Puranik/ --> set wind_file = ( 
> ucomp.1981-2000.climatology.nc vcomp.1981-2000.climatology.nc )
> cjs: /home/cjs/grads/Sushant_Puranik/ --> set wind_var = ( ucomp vcomp )
> cjs: /home/cjs/grads/Sushant_Puranik/ --> set wind_units = m/s
> cjs: /home/cjs/grads/Sushant_Puranik/ --> set lev_units = hPa
> cjs: /home/cjs/grads/Sushant_Puranik/ --> grads -lcx "maxwind.gs 
> $wind_nc_file[1] $wind_var[1] $wind_units $lev_units"
> ...
> cjs: /home/cjs/grads/Sushant_Puranik/ --> grads -lcx "maxwind.gs 
> $wind_nc_file[2] $wind_var[2] $wind_units $lev_units"
> ...
> cjs: /home/cjs/grads/Sushant_Puranik/ --> grads -lcx "maxwind2.gs 
> $wind_nc_file[1] $wind_var[1] $wind_nc_file[2] $wind_var[2] $wind_units 
> $lev_units"
> ...
> 
> Please find attached sample plot files: maxwind_ucomp.pdf, 
> maxwind_vcomp.pdf, maxwind2.pdf
> 
> The scripts were tested and appear to be working OK.  Please let me know 
> if you find any problems and/or have any questions.
> 
> Thanks,
> Chuck
> 
> sushant puranik wrote:
>> Thanks again It works fine. Since i am interested in low level wind so 
>> can you please tell me how to make it to check for low levels only(i 
>> have data at 17 pressure levels). Also i have uwind and vwind data in 
>> separate files, how to run script with two files?
>>
>>
>> thank you
>> On Mon, May 2, 2011 at 11:04 PM, Charles Seman <Charles.Seman at noaa.gov 
>> <mailto:Charles.Seman at noaa.gov>> wrote:
>>
>>     Sushant,
>>
>>     Following Kun-Hsuan Chou in the "hurricane_tracking.txt" file (or
>>     plot_hurricane_center3.gs <http://plot_hurricane_center3.gs>),
>>     please find attached a revised version "maxwind.gs
>>     <http://maxwind.gs>" which plots the wind and its max for each time
>>     level.
>>
>>     To run:
>>
>>     % grads -lcx "maxwind.gs <http://maxwind.gs> nc_file wind wind_units"
>>
>>     or
>>
>>     ga-> run maxwind.gs <http://maxwind.gs> nc_file wind wind_units
>>
>>     Where a new argument "wind_units" has been added which is plotted in
>>     a title.  Be sure there are no blank spaces in the "wind_units" so
>>     that GrADS gets the correct string to plot (e.g. m/s or knots,
>>     etc.).  Note, the script as it is clears the screen before each time
>>     level (it plots the wind field itself at the level of maximum wind
>>     and an "x" at the location of the max wind).  I'm not sure if this
>>     is what you want?  If not, I would suggest adapting the code from
>>     maxwind.gs <http://maxwind.gs> into a modified version of
>>     plot_hurricane_center3.gs <http://plot_hurricane_center3.gs> (and
>>     rename it to something more appropriate like plot_maxwind.gs
>>     <http://plot_maxwind.gs> or whatever you choose).  One thing I found
>>     when running the script several times on the GrADS command line is
>>     that at some point the script exits with a "Memory allocation
>>     error!" condition.  I'm not sure why this happens.  In an attempt to
>>     prevent this, 'c events' and 'close 1' statements were added in
>>     addition to the previous 'reinit' command, but this did not prevent
>>     the problem.
>>
>>     I hope this helps,
>>     Chuck
>>
>>     sushant puranik wrote:
>>
>>         Hello Charles
>>         I tried maxwind.gs <http://maxwind.gs> <http://maxwind.gs> it
>>         works fine as per your suggestion. But i want to know at which
>>         lat lon maximum value is instead of x and y location. So can you
>>         please tell me how to convert x y in lat lon.
>>
>>         Thanks
>>
>>         Sushant
>>         On Sat, Apr 30, 2011 at 11:43 AM, sushant puranik
>>         <sushantpuranik at gmail.com <mailto:sushantpuranik at gmail.com>
>>         <mailto:sushantpuranik at gmail.com
>>         <mailto:sushantpuranik at gmail.com>>> wrote:
>>
>>            Thank you for help i will try it. Please don't mind if error
>>         occurs
>>            i'll mail you.     Thanks again
>>
>>
>>            On Sat, Apr 30, 2011 at 1:32 AM, Charles Seman
>>            <Charles.Seman at noaa.gov <mailto:Charles.Seman at noaa.gov>
>>         <mailto:Charles.Seman at noaa.gov <mailto:Charles.Seman at noaa.gov>>>
>>         wrote:
>>
>>                Hello Sushant,
>>
>>                I think it should be possible.  Please find attached an 
>> email
>>                exchange to this List from several years ago
>>                "hurricane_tracking.txt" in which Kun-Hsuan Chou gave a
>>         method
>>                to track the maximum wind speed using maxloc and max.  
>> This
>>                technique works on a 2D field.  To find the location of
>>         the max
>>                wind in 4D wind dataset, a short script "maxwind.gs
>>         <http://maxwind.gs>
>>                <http://maxwind.gs>" was coded that blends the technique
>>         used in
>>
>>                a local script "plot_hurricane_center3.gs
>>         <http://plot_hurricane_center3.gs>
>>                <http://plot_hurricane_center3.gs>" and the technique in
>>
>>                Kun-Hsuan Chou's "hurricane_tracking.txt".
>>                ("plot_hurricane_center3.gs
>>         <http://plot_hurricane_center3.gs>
>>         <http://plot_hurricane_center3.gs>"
>>
>>                itself was developed using Joe Covert's script
>>         "plot_tc_shi.gs <http://plot_tc_shi.gs>
>>                <http://plot_tc_shi.gs>" and Kun-Hsuan Chou's
>>                "hurricane_tracking.txt".)  "maxwind.gs
>>         <http://maxwind.gs> <http://maxwind.gs>"
>>
>>                loops over the time levels and finds the value of the max
>>         wind
>>                and its (x,y,z) location for each time level.  These
>>         values are
>>                printed out to the screen.  Here is a copy of what the
>>                "maxwind.gs <http://maxwind.gs> <http://maxwind.gs>"
>>         script printed out using GrADS
>>
>>                1.9b4 for a local model "ucomp" climatology dataset:
>>                ---
>>                ...
>>                (nx,ny,nz,nt) = (144,90,23,12)
>>                tt = 1
>>                 max ucomp = 81.833
>>                 xc = 137
>>                 yc = 71
>>                 zc = 23
>>                 ucomp(x=137,y=71,z=23) = 81.833
>>                tt = 2
>>                 max ucomp = 68.9826
>>                 xc = 57
>>                 yc = 61
>>                 zc = 10
>>                 ucomp(x=57,y=61,z=10) = 68.9826
>>                tt = 3
>>                 max ucomp = 62.7262
>>                 xc = 56
>>                 yc = 60
>>                 zc = 11
>>                 ucomp(x=56,y=60,z=11) = 62.7262
>>                tt = 4
>>                 max ucomp = 61.6225
>>                 xc = 10
>>                 yc = 15
>>                 zc = 23
>>                 ucomp(x=10,y=15,z=23) = 61.6225
>>                tt = 5
>>                 max ucomp = 85.5501
>>                 xc = 4
>>                 yc = 18
>>                 zc = 23
>>                 ucomp(x=4,y=18,z=23) = 85.5501
>>                tt = 6
>>                 max ucomp = 109.233
>>                 xc = 4
>>                 yc = 19
>>                 zc = 23
>>                 ucomp(x=4,y=19,z=23) = 109.233
>>                tt = 7
>>                 max ucomp = 119.698
>>                 xc = 143
>>                 yc = 17
>>                 zc = 23
>>                 ucomp(x=143,y=17,z=23) = 119.698
>>                tt = 8
>>                 max ucomp = 117.018
>>                 xc = 2
>>                 yc = 16
>>                 zc = 22
>>                 ucomp(x=2,y=16,z=22) = 117.018
>>                tt = 9
>>                 max ucomp = 98.7713
>>                 xc = 63
>>                 yc = 9
>>                 zc = 20
>>                 ucomp(x=63,y=9,z=20) = 98.7713
>>                tt = 10
>>                 max ucomp = 74.1137
>>                 xc = 65
>>                 yc = 7
>>                 zc = 19
>>                 ucomp(x=65,y=7,z=19) = 74.1137
>>                tt = 11
>>                 max ucomp = 77.7408
>>                 xc = 137
>>                 yc = 67
>>                 zc = 23
>>                 ucomp(x=137,y=67,z=23) = 77.7408
>>                tt = 12
>>                 max ucomp = 84.3092
>>                 xc = 16
>>                 yc = 70
>>                 zc = 23
>>                 ucomp(x=16,y=70,z=23) = 84.3092
>>                ...finished.
>>                ---
>>
>>                It seems the script is working OK.  You can give it a 
>> try for
>>                one of your datasets.  To run the script as it is coded,
>>         run it
>>                in batch mode as follows:
>>                % grads -blcx "maxwind.gs <http://maxwind.gs>
>>         <http://maxwind.gs> nc_file wind"
>>
>>                or on the GrADS command line
>>                http://grads.iges.org/grads/gadoc/gradcomdrun.html as (no
>>         quotes
>>                as with the batch command):
>>                ga-> run maxwind.gs <http://maxwind.gs>
>>         <http://maxwind.gs> nc_file wind
>>
>>                where "nc_file" is the netCDF file containing the "wind"
>>                variable name (the "nc_file" and "wind" are generic names;
>>                please replace them with the actual netCDF file and wind
>>                variable in the netCDF file).  Note, please also 
>> include the
>>                quotes surrounding "maxwind.gs <http://maxwind.gs>
>>         <http://maxwind.gs> nc_file wind"
>>
>>                for the batch command or else the batch command won't 
>> work.
>>
>>                I hope this helps.  Please let me know if you have any
>>         questions.
>>
>>                Thanks,
>>                Chuck
>>
>>                sushant puranik wrote:
>>
>>                    Hello Charles
>>                    I want to make a jet stream plot. Can i make it 
>> with the
>>                    help of hurricane center script by changing minloc
>>         and min
>>                    to maxloc and max.
>>                    any suggestion?
>>
>>                    thanks
>>
>>                    Sushant
>>                    On Wed, Jan 5, 2011 at 1:01 AM, Charles Seman
>>                    <Charles.Seman at noaa.gov
>>         <mailto:Charles.Seman at noaa.gov> <mailto:Charles.Seman at noaa.gov
>>         <mailto:Charles.Seman at noaa.gov>>
>>                    <mailto:Charles.Seman at noaa.gov
>>         <mailto:Charles.Seman at noaa.gov>
>>                    <mailto:Charles.Seman at noaa.gov
>>         <mailto:Charles.Seman at noaa.gov>>>> wrote:
>>
>>                       Jie,
>>
>>                       Attached is a file
>>         File_Error_1_Grads_1.9-Plot_tc_shi.gs.txt
>>                       containing the text from an email exchange to the
>>         GrADS
>>                    Listserv
>>                       between Joe Covert and Diane Stokes on 9/13/2004 
>> -- on
>>                    4/27/06,
>>                       found via a Google search for "plot_tc_shi.gs
>>         <http://plot_tc_shi.gs>
>>                    <http://plot_tc_shi.gs>
>>                       <http://plot_tc_shi.gs>":
>>                    http://caos.iisc.ernet.in/gslib/plot_tc_shi.gs
>>
>>
>>                       The attached GrADS script
>>         plot_hurricane_center3.gs <http://plot_hurricane_center3.gs>
>>                    <http://plot_hurricane_center3.gs>
>>                       <http://plot_hurricane_center3.gs> (along with
>>         pause.gsf,
>>                    aGrADS
>>
>>                       script function used by the plot script) is a 
>> locally
>>                    modified
>>                       version derived from Joe Covert's script
>>         "plot_tc_shi.gs <http://plot_tc_shi.gs>
>>                    <http://plot_tc_shi.gs>
>>                       <http://plot_tc_shi.gs>" (Joe.Covert at noaa.gov
>>         <mailto:Joe.Covert at noaa.gov>
>>                    <mailto:Joe.Covert at noaa.gov 
>> <mailto:Joe.Covert at noaa.gov>>
>>                       <mailto:Joe.Covert at noaa.gov
>>         <mailto:Joe.Covert at noaa.gov>
>>                    <mailto:Joe.Covert at noaa.gov
>>         <mailto:Joe.Covert at noaa.gov>>>) which was posted to the GrADS
>>                    Listserv
>>
>>                       on 9/13/2004 (his script was named plot_tc_shi.gs
>>         <http://plot_tc_shi.gs>
>>                    <http://plot_tc_shi.gs>
>>                       <http://plot_tc_shi.gs>) and code from
>>                    hurricane_tracking.txt (taken
>>
>>                       from an email exchange posted to the GrADS 
>> Listserv by
>>                    Kun-Hsuan
>>                       Chou and Arturo Caracas Uribe in Oct, 2004)...
>>
>>                       Please find below code from hurricane_tracking.txt
>>         (taken
>>                    from an
>>                       email exchange posted to the GrADS Listserv by
>>         Kun-Hsuan
>>                    Chou and
>>                       Arturo Caracas Uribe in Oct, 2004) illustrating a
>>                    technique for
>>                       finding max wind in a 2D field... and below that 
>> some
>>                    code from
>>                       attached script plot_hurricane_center3.gs
>>         <http://plot_hurricane_center3.gs>
>>                    <http://plot_hurricane_center3.gs>
>>                       <http://plot_hurricane_center3.gs> to find the min
>>         sea-level
>>
>>                       pressure in a 2D field...
>>
>>                       code from Kun-Hsuan Chou to find maximum wind
>>         speed from
>>                       hurricane_tracking.txt:
>>                       ---
>>                       'd
>>         maxloc(max(mag(u,v),lon=120,lon=130),lat=15,lat=25)'
>>                        line=sublin(result,2)
>>                        ygrd=subwrd(line,4)
>>                       'd
>>         maxloc(max(mag(u,v),lat=15,lat=25),lon=120,lon=130)'
>>                        line=sublin(result,2)
>>                        xgrd=subwrd(line,4)
>>                       'set x 'xgrd
>>                       lonval = subwrd(result,4)
>>                       'set y 'ygrd
>>                       latval = subwrd(result,4)
>>                       'q w2xy 'lonval' 'latval
>>                       xpos = subwrd(result,3)
>>                       ypos = subwrd(result,6)
>>                       'draw mark 1 'xpos' 'ypos' .2'
>>                       ---
>>
>>                       sample code from plot_hurricane_center3.gs
>>         <http://plot_hurricane_center3.gs>
>>                    <http://plot_hurricane_center3.gs>
>>                       <http://plot_hurricane_center3.gs> to find 
>> hurricane
>>                    center (see
>>
>>                       script for supporting code):
>>                       ---
>>                       *
>>                       * find minimum "pressure" within box area (x1,x2),
>>         (y1,y2)...
>>                       *
>>                           'set x 'x1
>>                           'set y 'y1
>>                           'set z 1'
>>                           'set t 'tt
>>                           'set gxout print'
>>                           nxp = x2-x1+1
>>                       *      say '    nxp = 'nxp
>>                           nyp = y2-y1+1
>>                       *      say '    nyp = 'nyp
>>                           'd 
>> minloc(min(psl,y='y1',y='y2'),x='x1',x='x2')'
>>                             rec=sublin(result,nxp+3)
>>                             xc=subwrd(rec,1)
>>                           'd 
>> minloc(min(psl,x='x1',x='x2'),y='y1',y='y2')'
>>                             rec=sublin(result,nyp+3)
>>                             yc=subwrd(rec,1)
>>                           say
>>                           say 'location of minimum "pressure"...'
>>                           say
>>                           say ' (xc,yc) = ('xc','yc')'
>>                       *
>>                       * find "world" coordinates of (xc,yc) and convert
>>         "world"
>>                    coordinates
>>                       * to "xy" coordinates for plotting track of 
>> hurricane
>>                    center...
>>                       *
>>                           'set x 'xc
>>                           lonval = subwrd(result,4)
>>                           'set y 'yc
>>                           latval = subwrd(result,4)
>>                           say ' (lonval,latval) = ('lonval','latval')'
>>                           'q w2xy 'lonval' 'latval
>>                           xpos = subwrd(result,3)
>>                           ypos = subwrd(result,6)
>>                           say ' (xpos,ypos) = ('xpos','ypos')'
>>                       *
>>                       * write (xpos,ypos) to output file...
>>                       *
>>                           res = write (''hurricane.nf
>>         <http://hurricane.nf> <http://hurricane.nf>
>>                    <http://hurricane.nf>'','t = 'tt'
>>
>>                       xpos = 'xpos' ypos = 'ypos'')
>>
>>                           pause()
>>                       ---
>>
>>                       Please let me know if you have any questions.
>>
>>                       Hope this helps,
>>                       Chuck
>>
>>                       Jie TANG wrote:
>>
>>
>>                           hi,grads folks ,
>>                            I am using grads v1.9, trying to find the
>>         center of
>>                    typhoon via
>>                           minloc function.
>>                           the key script is shown as below:
>>                           slplat=min(slp,lat=19,lat=26)                
>>                                   
>> tclon=minloc(slplat,lon=119,lon=126)  
>>                                                  
>> slplon=min(slp,lon=119,lon=126)                                
>>                  tclat=minloc(slplon,lat=19,lat=26)
>>
>>                           but grads tell me that "function not found min
>>         " and
>>                    when i
>>                           changed my script to be :
>>                           tclat=min(minloc(slpt,lon=119,lon=126),
>>         lat=19,lat=26)
>>                           tclon=min(minloc(slpt, lat=19,lat=26
>>         )lon=119,lon=126)
>>
>>
>>                           how can i finx my scrpit ? thank you .:)
>>                           --
>>                           TANG Jie
>>                           Email: totangjie at gmail.com
>>         <mailto:totangjie at gmail.com>
>>                    <mailto:totangjie at gmail.com
>>         <mailto:totangjie at gmail.com>> <mailto:totangjie at gmail.com
>>         <mailto:totangjie at gmail.com>
>>                    <mailto:totangjie at gmail.com
>>         <mailto:totangjie at gmail.com>>>
>>                           <mailto:totangjie at gmail.com
>>         <mailto:totangjie at gmail.com>
>>                    <mailto:totangjie at gmail.com
>>         <mailto:totangjie at gmail.com>> <mailto:totangjie at gmail.com
>>         <mailto:totangjie at gmail.com>
>>                    <mailto:totangjie at gmail.com
>>         <mailto:totangjie at gmail.com>>>>
>>
>>
>>                           Tel: 0086-2154896104
>>                           Shanghai Typhoon Institute,China
>>                                             
>> ------------------------------------------------------------------------
>>
>>                           _______________________________________________
>>                           gradsusr mailing list
>>                           gradsusr at gradsusr.org
>>         <mailto:gradsusr at gradsusr.org> <mailto:gradsusr at gradsusr.org
>>         <mailto:gradsusr at gradsusr.org>>
>>                    <mailto:gradsusr at gradsusr.org
>>         <mailto:gradsusr at gradsusr.org> <mailto:gradsusr at gradsusr.org
>>         <mailto:gradsusr at gradsusr.org>>>
>>
>>
>>                           http://gradsusr.org/mailman/listinfo/gradsusr
>>                                                --
>>                       Please note that Charles.Seman at noaa.gov
>>         <mailto:Charles.Seman at noaa.gov>
>>                    <mailto:Charles.Seman at noaa.gov
>>         <mailto:Charles.Seman at noaa.gov>>
>>                       <mailto:Charles.Seman at noaa.gov
>>         <mailto:Charles.Seman at noaa.gov>
>>                    <mailto:Charles.Seman at noaa.gov
>>         <mailto:Charles.Seman at noaa.gov>>> should be considered my NOAA
>>                       email address, not cjs at gfdl.noaa.gov
>>         <mailto:cjs at gfdl.noaa.gov>
>>                    <mailto:cjs at gfdl.noaa.gov <mailto:cjs at gfdl.noaa.gov>>
>>         <mailto:cjs at gfdl.noaa.gov <mailto:cjs at gfdl.noaa.gov>
>>
>>                    <mailto:cjs at gfdl.noaa.gov 
>> <mailto:cjs at gfdl.noaa.gov>>>.
>>
>>
>>                                         
>> ********************************************************************
>>                       Charles Seman                                    
>>               Charles.Seman at noaa.gov <mailto:Charles.Seman at noaa.gov>
>>         <mailto:Charles.Seman at noaa.gov <mailto:Charles.Seman at noaa.gov>>
>>                       <mailto:Charles.Seman at noaa.gov
>>         <mailto:Charles.Seman at noaa.gov>
>>                    <mailto:Charles.Seman at noaa.gov
>>         <mailto:Charles.Seman at noaa.gov>>>
>>
>>                       U.S. Department of Commerce / NOAA / OAR
>>                       Geophysical Fluid Dynamics Laboratory         
>> voice:
>>                    (609) 452-6547
>>                       201 Forrestal Road                              
>> fax:
>>                    (609) 987-5063
>>                       Princeton, NJ  08540-6649                      
>>         http://www.gfdl.noaa.gov/~cjs/
>>                                         
>> ********************************************************************
>>
>>                       "The contents of this message are mine personally
>>         and do
>>                    not reflect any
>>                       official or unofficial position of the United 
>> States
>>                    Federal Government,
>>                       the United States Department of Commerce, or NOAA."
>>
>>
>>
>>                       worked great ... thanks.  joe
>>
>>                       Diane Stokes wrote:
>>
>>                        > Joe,
>>                        >
>>                        > Read works fine for me in 1.9.
>>                        >
>>                        > I think this is the issue where 'pull' in 1.9
>>         throws
>>                    in a carriage
>>                        > return.  The read statement is not getting the
>>         exact
>>                    filename.
>>                        >
>>                        > Try adding:
>>                        >   file=sublin(file,1)
>>                        > after each:
>>                        >   pull file
>>                        >
>>                        > Diane
>>                        >
>>                        > Joe Covert wrote:
>>                        >
>>                        >> There appears to be a problem with version 
>> 1.9 of
>>                    GrADS "read"
>>                       function.
>>                        >>
>>                        >> The plot_tc_shi.gs <http://plot_tc_shi.gs>
>>         <http://plot_tc_shi.gs>
>>                    <http://plot_tc_shi.gs> script (see below)
>>
>>                       uses the read function to open the
>>                        >> track data file and the program gives the 
>> subject
>>                    error message
>>                       "File
>>                        >> Error 1".
>>                        >>
>>                        >> jc
>>                        >>
>>                        >>
>>                        >> *  Script to draw an hurricane-track plot.
>>                        >> *  Does little error checking on the input 
>> file.
>>                        >> *  Assumes the input file is set up as follows:
>>                        >> *
>>                        >> *    Line 1:  Title
>>                        >> *    Line 2:  Drawing primitives for marks:
>>         marktype size
>>                        >> *    Line 3:  Drawing primitives for lines: 
>> color
>>                    style thickness
>>                        >> *    Line 4:  Starting hour and the interval of
>>                    plotting points
>>                        >> *             e.g., 0 6 means that track
>>         starts at 0
>>                    hour and mark
>>                        >> *                   will be plotted every 6 
>> hours.
>>                        >> *    Rest of lines:  hour  long.  lat.
>>                        >> *             e.g.,   0    -70.5  25.0
>>                        >> *                     6    -71.8  25.2
>>                        >> *                            :
>>                        >> *                            :
>>                        >> *
>>                        >> *  Also assumes that a file has been opened 
>> (any
>>                    file, doesn't
>>                        >> *  matter -- the set command doesn't work 
>> until a
>>                    file has been
>>                        >> *  opened).
>>                        >> *
>>                        >>
>>                        >> function main()
>>                        >>
>>                        >> *  'clear'
>>                        >>
>>                        >>   'open dummy.ctl'
>>                        >>   'set lat 20 50'
>>                        >>   'set lon -90 -30'
>>                        >>   'set mpdset hires'
>>                        >>   'set poli on'
>>                        >>   'draw map'
>>                        >>
>>                        >>
>>                        >> say 'Enter File Name: (type q to stop)'
>>                        >> pull fname
>>                        >>
>>                        >> while (fname != 'q')
>>                        >>
>>                        >> *  Read the 1st record: Title
>>                        >>
>>                        >>   ret = read(fname)
>>                        >>   rc = sublin(ret,1)
>>                        >>   if (rc>0)
>>                        >>       say 'File Error 1'
>>                        >>       return
>>                        >>   endif
>>                        >>   title = sublin(ret,2)
>>                        >>   say title
>>                        >>
>>                        >> *  Read the drawing primitives
>>                        >>
>>                        >>   ret = read(fname)
>>                        >>   rc = sublin(ret,1)
>>                        >>   if (rc>0)
>>                        >>      say 'File Error 2'
>>                        >>      return
>>                        >>   endif
>>                        >>   dpline = sublin(ret,2)
>>                        >>   marktype = subwrd(dpline,1)
>>                        >>   marksize = subwrd(dpline,2)
>>                        >>   ret = read(fname)
>>                        >>   rc = sublin(ret,1)
>>                        >>   if (rc>0)
>>                        >>      say 'File Error 3'
>>                        >>      return
>>                        >>   endif
>>                        >>   dpline = sublin(ret,2)
>>                        >>   lcolor = subwrd(dpline,1)
>>                        >>   lstyle = subwrd(dpline,2)
>>                        >>   lthick = subwrd(dpline,3)
>>                        >>   say ' marktype, marksize, lcolor, lstyle and
>>         lthick:'
>>                        >>   say ' 'marktype ' ' marksize ' ' lcolor ' '
>>         lstyle
>>                    ' ' lthick
>>                        >>
>>                        >> * Read starting hour and the interval hours of
>>                    plotting points
>>                        >>
>>                        >>   ret = read(fname)
>>                        >>   rc = sublin(ret,1)
>>                        >>   if (rc>0)
>>                        >>      say 'File Error 4'
>>                        >>      return
>>                        >>   endif
>>                        >>   dhour = sublin(ret,2)
>>                        >>   start = subwrd(dhour,1)
>>                        >>   jump = subwrd(dhour,2)
>>                        >>   say ' starting hour and the interval hours of
>>                    plotting points:'
>>                        >>   say '  'start' 'jump
>>                        >>
>>                        >> *  Read all data points
>>                        >>
>>                        >>   ret = read(fname)
>>                        >>   rc = sublin(ret,1)
>>                        >>   while (rc = 0)
>>                        >>       loc = sublin(ret,2)
>>                        >>       hour = subwrd(loc,1)
>>                        >>       dlong.hour = subwrd(loc,2)
>>                        >>       dlat.hour = subwrd(loc,3)
>>                        >> *      prompt ' hour ' hour ' are read,'
>>                        >> *      say ' long=' dlong.hour '    lat='
>>         dlat.hour
>>                        >>       ret = read(fname)
>>                        >>       rc = sublin(ret,1)
>>                        >>   endwhile
>>                        >>
>>                        >>   if (rc!=2 & rc!=0)
>>                        >>          say 'File Error 5, rc=' rc
>>                        >>          return
>>                        >>   endif
>>                        >>
>>                        >>   endhour = hour
>>                        >>   say ' endhour=' endhour
>>                        >>
>>                        >> * Plotting
>>                        >>
>>                        >>   'set line 'lcolor' 'lstyle' 'lthick
>>                        >>   'query w2xy 'dlong.start' 'dlat.start
>>                        >>   xprev = subwrd(result,3)
>>                        >>   yprev = subwrd(result,6)
>>                        >>   'draw mark 'marktype' 'xprev' 'yprev' 
>> 'marksize
>>                        >>   next = start+jump
>>                        >>   while (next <= endhour)
>>                        >> *      say ' 'dlong.start' 'dlat.start
>>                        >>       'query w2xy 'dlong.next' 'dlat.next
>>                        >>       xnext = subwrd(result,3)
>>                        >>       ynext = subwrd(result,6)
>>                        >>       'draw line 'xprev' 'yprev' 'xnext' 'ynext
>>                        >> *      say ' 'xprev' 'yprev' 'xnext' 'ynext
>>                        >>       'draw mark 'marktype' 'xnext' 'ynext'
>>         'marksize
>>                        >>       next = next+jump
>>                        >>       xprev = xnext
>>                        >>       yprev = ynext
>>                        >>   endwhile
>>                        >>
>>                        >>   say fname ' is working fine.'
>>                        >>
>>                        >> * read in the filename to be plotted next
>>                        >>
>>                        >>   say 'Enter File Name: (type q to stop)'
>>                        >>   pull fname
>>                        >>
>>                        >> endwhile
>>                        >>
>>
>>
>>                                         
>> *----------------------------------------------------------------------
>>                       *
>>                       *  Adapted from plot_hurricane_center2c.gs
>>         <http://plot_hurricane_center2c.gs>
>>                    <http://plot_hurricane_center2c.gs>
>>                       <http://plot_hurricane_center2c.gs>, which was
>>         adapted from:
>>
>>                       *
>>                       *  (1) "plot_hurricane_center2[a][b].gs" (from
>>                       "plot_hurricane_center.gs
>>         <http://plot_hurricane_center.gs>
>>                    <http://plot_hurricane_center.gs>
>>                    <http://plot_hurricane_center.gs>"),
>>
>>                       *      locally modified versions derived from Joe
>>                    Covert's script
>>                       *      "plot_tc_shi.gs <http://plot_tc_shi.gs>
>>         <http://plot_tc_shi.gs>
>>                    <http://plot_tc_shi.gs>" (Joe.Covert at noaa.gov
>>         <mailto:Joe.Covert at noaa.gov>
>>                    <mailto:Joe.Covert at noaa.gov 
>> <mailto:Joe.Covert at noaa.gov>>
>>                       <mailto:Joe.Covert at noaa.gov
>>         <mailto:Joe.Covert at noaa.gov>
>>                    <mailto:Joe.Covert at noaa.gov
>>         <mailto:Joe.Covert at noaa.gov>>>), which was posted to the
>>
>>                       *      GrADS Listserv on 9/13/2004 (his script was
>>         named
>>                       plot_tc_shi.gs <http://plot_tc_shi.gs>
>>         <http://plot_tc_shi.gs>
>>                    <http://plot_tc_shi.gs>)
>>
>>                       *      on 4/27/06, found via a Google search for
>>                    "plot_tc_shi.gs <http://plot_tc_shi.gs>
>>         <http://plot_tc_shi.gs>
>>                       <http://plot_tc_shi.gs>":
>>
>>                       *      
>> http://caos.iisc.ernet.in/gslib/plot_tc_shi.gs
>>                       *
>>                       *  (2) code in "hurricane_tracking.txt" (taken 
>> from an
>>                    email exchange
>>                       *      posted to the GrADS Listserv by Kun-Hsuan
>>         Chou and
>>                       *      Arturo Caracas Uribe in Oct, 2004)
>>                       *
>>                       *
>>                       *  To use: grads -l
>>                       *
>>                                         
>> *----------------------------------------------------------------------
>>
>>                       function main()
>>
>>                        'reinit'
>>
>>                                         
>> ************************************************************************
>>                       *  Allow external GrADS functions
>>                                         
>> ************************************************************************
>>
>>                        rc = gsfallow("on")
>>
>>                                         
>> ************************************************************************
>>                       *  Define dataset file information and plotting 
>> limits
>>                    for base map...
>>                                         
>> ************************************************************************
>>
>>                       **  nc_file1 = ''
>>                       **  nc_file2 = ''
>>                       **  nc_file3 = ''
>>                       **  nc_file = ''nc_file1' 'nc_file2' 'nc_file3''
>>                        nc_file = 'your_netCDF_file'
>>
>>                        lon1 = 298 ; lon2 = 308
>>                        lat1 =  20 ; lat2 =  25
>>
>>                                         
>> ************************************************************************
>>                       *  Legend captions, colors, and marks for the plots
>>                                         
>> ************************************************************************
>>
>>                       **  nmodels = 1
>>                       **  model.1 = 'isabel_ras'
>>                       **  model.2 = 'isabel_isotke'
>>                       **  model.3 = 'isabel_my25'
>>
>>                       **  titles.1 = model.1 ; colors.1 = 2 ; marks.1 = 2
>>                       **  titles.2 = model.2 ; colors.2 = 3 ; marks.2 = 2
>>                       **  titles.3 = model.3 ; colors.3 = 4 ; marks.3 = 2
>>                       ***
>>                       ***  Define the legend plotter input...
>>                       ***
>>                       **  titles = '-t' ; colors = '-c' ; marks = '-m' ;
>>         lines
>>                    = '-l'
>>                       **  n=1
>>                       **  while ( n <= nmodels )
>>                       **    titles = ''titles' "'titles.n'"'
>>                       **    colors = ''colors' 'colors.n
>>                       **    marks = ''marks' "'marks.n'"'
>>                       **    lines = ''lines' 1'
>>                       **    n=n+1
>>                       **  endwhile
>>
>>                       **  legend_info = ''colors' 'lines' 'marks'
>>         'titles' -p'
>>
>>                        nmodels = 1
>>                        model.1 = 'title_name_for_your_netCDF_dataset'
>>
>>                        titles.1 = model.1 ; colors.1 = 2 ; marks.1 = 2
>>                       *
>>                       *  Define the legend plotter input...
>>                       *
>>                        titles = '-t' ; colors = '-c' ; marks = '-m' ;
>>         lines = '-l'
>>                        n=1
>>                        while ( n <= nmodels )
>>                          titles = ''titles' "'titles.n'"'
>>                          colors = ''colors' 'colors.n
>>                          marks = ''marks' "'marks.n'"'
>>                          lines = ''lines' 1'
>>                          n=n+1
>>                        endwhile
>>
>>                        legend_info = ''colors' 'lines' 'marks' 
>> 'titles' -p'
>>
>>                       *  ...other drawing primitives
>>
>>                        marksize = 0.1
>>
>>                        lstyle = 1 ; lthick = 5
>>
>>                                         
>> ************************************************************************
>>                       *  Use "cbar_line" or "cbar_line_box"?
>>                                         
>> ************************************************************************
>>
>>                        legend_plotter = 'cbar_line'
>>                       *  legend_plotter = 'cbar_line_box'
>>
>>                                         
>> ************************************************************************
>>                       *  Plot page limits
>>                                         
>> ************************************************************************
>>
>>                        plot_vpage = '0 11 0 8.5'
>>                        plot_area  = '1 10 1 7.5'
>>
>>                        xl = subwrd(plot_area,1) ; xr = 
>> subwrd(plot_area,2)
>>                        yb = subwrd(plot_area,3) ; yt = 
>> subwrd(plot_area,4)
>>
>>                        xc = xl + (xr-xl)/2
>>
>>                                         
>> ************************************************************************
>>                       *  GrADS metafile output...
>>                                         
>> ************************************************************************
>>
>>                        'enable print hurricane_track.gx'
>>
>>                                         
>> *-----------------------------------------------------------------------
>>                       *  Define and plot track of minimum surface
>>         pressure for
>>                    each dataset...
>>                                         
>> *-----------------------------------------------------------------------
>>
>>                        nf=1
>>                        while ( nf <= nmodels )
>>
>>                       * Open dataset file and define parameters...
>>
>>                          fname = subwrd(nc_file,nf)
>>                          'sdfopen 'fname
>>                          'set dfile 'nf
>>                          'q file'
>>                          rec3 = sublin(result,3) ; binary_file =
>>         subwrd(rec3,2)
>>                          say
>>                          say
>>                          say '*** 'binary_file' ***'
>>                          say
>>                          rec5 = sublin(result,5)
>>                          nx = subwrd(rec5,3) ; ny = subwrd(rec5,6) ; nz =
>>                    subwrd(rec5,9) ;
>>                       nt = subwrd(rec5,12)
>>
>>                          if( nf = 1 )
>>
>>                       * Plot base map...
>>
>>                                   
>> plot_base_map(plot_vpage,plot_area,lon1,lon2,lat1,lat2)
>>
>>                          endif
>>
>>                       * Define locations of "hurricane center" for 
>> plotting
>>                    points, and write
>>                       * locations out to ASCII text file for read-in for
>>                    plotting track
>>                       later...
>>
>>                          hurricane.nf <http://hurricane.nf>
>>         <http://hurricane.nf>
>>                    <http://hurricane.nf> = 'hurricane_'nf'.txt'
>>
>>
>>                          ts=2
>>                          tt=ts
>>                          while ( tt <= nt )
>>                            'set t 'tt
>>                            say
>>                            say '---------'
>>                            say ' tt = 'tt
>>                            say '---------'
>>                            say
>>                            'set lon 'lon1' 'lon2
>>                            'set lat 'lat1' 'lat2
>>                            'set z 1'
>>                       *
>>                       * here is where you put in the name of your 
>> sea-level
>>                    pressure variable:
>>                       *
>>                            'define psl =
>>         name_of_your_sea_level_pressure_variable'
>>                            'set gxout shaded'
>>                            'd psl'
>>                       *
>>                       * following interactive "box location" code
>>         adapted from
>>                       "cbar_line_box.gs <http://cbar_line_box.gs>
>>         <http://cbar_line_box.gs>
>>                    <http://cbar_line_box.gs>"...
>>
>>                       *
>>                            say 'Click where you want the left upper
>>         corner of
>>                    the box'
>>                            'query bpos'
>>                            xb1o = subwrd(result,3)
>>                            yb2o = subwrd(result,4)
>>                            say 'Click where you want the right lower
>>         corner of
>>                    the box'
>>                            'query bpos'
>>                            xb2o = subwrd(result,3)
>>                            yb1o = subwrd(result,4)
>>
>>                            say
>>                            say '...left upper corner of the box at X Y:
>>         'xb1o'
>>                    'yb2o
>>                            say '...right lower corner of the box at X Y:
>>         'xb2o'
>>                    'yb1o
>>                       *
>>                       * draw box to show specified area for defining
>>         hurricane
>>                    center...
>>                       *
>>                            'set line 1 1'
>>                            'draw rec 'xb1o' 'yb1o' 'xb2o' 'yb2o
>>                       *
>>                       * convert box "xy" coordinates to "grid" 
>> coordinates
>>                       * for finding minimum "pressure" (hurricane 
>> center)...
>>                       *
>>                            'q xy2gr 'xb1o' 'yb2o
>>                            x1o = subwrd(result,3) ; x1 = 
>> math_int(x1o+0.5)
>>                            y2o = subwrd(result,6) ; y2 = 
>> math_int(y2o+0.5)
>>                            'q xy2gr 'xb2o' 'yb1o
>>                            x2o = subwrd(result,3) ; x2 = 
>> math_int(x2o+0.5)
>>                            y1o = subwrd(result,6) ; y1 = 
>> math_int(y1o+0.5)
>>                            say
>>                            say 'Specified grid coordinates (x1o,x2o),
>>         (y1o,y2o)
>>                    from box,'
>>                            say 'rounded to (x1,x2), (y1,y2) for finding
>>         minimum
>>                    "pressure"...'
>>                            say
>>                            say ' (x1o,x2o) = ('x1o','x2o')  -->  
>> (x1,x2) =
>>                    ('x1','x2')'
>>                            say ' (y1o,y2o) = ('y1o','y2o')  -->  
>> (y1,y2) =
>>                    ('y1','y2')'
>>                       *
>>                       * find minimum "pressure" within box area (x1,x2),
>>         (y1,y2)...
>>                       *
>>                            'set x 'x1
>>                            'set y 'y1
>>                            'set z 1'
>>                            'set t 'tt
>>                            'set gxout print'
>>                            nxp = x2-x1+1
>>                       *      say '    nxp = 'nxp
>>                            nyp = y2-y1+1
>>                       *      say '    nyp = 'nyp
>>                            'd 
>> minloc(min(psl,y='y1',y='y2'),x='x1',x='x2')'
>>                              rec=sublin(result,nxp+3)
>>                              xc=subwrd(rec,1)
>>                            'd 
>> minloc(min(psl,x='x1',x='x2'),y='y1',y='y2')'
>>                              rec=sublin(result,nyp+3)
>>                              yc=subwrd(rec,1)
>>                            say
>>                            say 'location of minimum "pressure"...'
>>                            say
>>                            say ' (xc,yc) = ('xc','yc')'
>>                       *
>>                       * find "world" coordinates of (xc,yc) and convert
>>         "world"
>>                    coordinates
>>                       * to "xy" coordinates for plotting track of 
>> hurricane
>>                    center...
>>                       *
>>                            'set x 'xc
>>                            lonval = subwrd(result,4)
>>                            'set y 'yc
>>                            latval = subwrd(result,4)
>>                            say ' (lonval,latval) = ('lonval','latval')'
>>                            'q w2xy 'lonval' 'latval
>>                            xpos = subwrd(result,3)
>>                            ypos = subwrd(result,6)
>>                            say ' (xpos,ypos) = ('xpos','ypos')'
>>                       *
>>                       * write (xpos,ypos) to output file...
>>                       *
>>                            res = write (''hurricane.nf
>>         <http://hurricane.nf> <http://hurricane.nf>
>>                    <http://hurricane.nf>'','t = 'tt'
>>
>>                       xpos = 'xpos' ypos = 'ypos'')
>>
>>                            pause()
>>                       *
>>                       * erase box showing area for defining hurricane
>>         center...
>>                       *
>>                       *      'set line 0 1'
>>                       *      'draw rec 'xb1o' 'yb1o' 'xb2o' 'yb2o
>>                            tt=tt+1
>>                          endwhile
>>
>>                          res = close (''hurricane.nf
>>         <http://hurricane.nf> <http://hurricane.nf>
>>                    <http://hurricane.nf>'')
>>
>>
>>                          nf=nf+1
>>                        endwhile
>>
>>                       *  Clear frame and re-plot base map...
>>
>>                               
>> plot_base_map(plot_vpage,plot_area,lon1,lon2,lat1,lat2)
>>
>>                       *  Plot track(s)...
>>
>>                        nf=1
>>                        while ( nf <= nmodels )
>>
>>                       *  Specify drawing primitives
>>
>>                          marktype = marks.nf <http://marks.nf>
>>         <http://marks.nf> <http://marks.nf>
>>                          lcolor = colors.nf <http://colors.nf>
>>         <http://colors.nf> <http://colors.nf>
>>
>>
>>
>>                          say ' marktype, marksize, lcolor, lstyle and
>>         lthick:'
>>                          say ' 'marktype ' ' marksize ' ' lcolor ' '
>>         lstyle ' '
>>                    lthick
>>
>>                          tt=ts
>>                       *
>>                       *  read (xpos,ypos) from ASCII text input file...
>>                       *
>>                          res = read(''hurricane.nf <http://hurricane.nf>
>>         <http://hurricane.nf>
>>                    <http://hurricane.nf>'') ; rc =
>>
>>                       sublin(res,1)
>>                          if( rc != 0 )
>>                            say '"read" status = 'rc
>>                            exit
>>                          endif
>>                          rec = sublin(res,2) ; say '"hurricane.'nf'"
>>         record: 'rec
>>                          xc = subwrd(rec,6) ; yc = subwrd(rec,9)
>>
>>                          'set line 'lcolor' 'lstyle' 'lthick
>>                          'draw mark 'marktype' 'xc' 'yc' 'marksize
>>                          tt = tt+1
>>                          while ( tt <= nt )
>>                            res = read(''hurricane.nf
>>         <http://hurricane.nf> <http://hurricane.nf>
>>                    <http://hurricane.nf>'') ; rc =
>>
>>                       sublin(res,1)
>>                            if( rc != 0 )
>>                              say '"read" status = 'rc
>>                              exit
>>                            endif
>>                            rec = sublin(res,2) ; say '"hurricane.'nf'"
>>         record: 'rec
>>                            xn = subwrd(rec,6) ; yn = subwrd(rec,9)
>>                            say ' 'xc' 'yc' 'xn' 'yn
>>                            'draw line 'xc' 'yc' 'xn' 'yn
>>                            'draw mark 'marktype' 'xn' 'yn' 'marksize
>>                            tt=tt+1
>>                            xc = xn
>>                            yc = yn
>>                          endwhile
>>
>>                          nf=nf+1
>>                        endwhile
>>
>>                        say
>>                        say '...plot legend'
>>                        ''legend_plotter' -x 3 -y 6 'legend_info
>>                        say
>>
>>                        'print'
>>                        'disable print'
>>
>>                        say
>>                        say
>>         '************************************************'
>>                        say ' Finished with this script.'
>>                        say
>>         '************************************************'
>>                        say
>>
>>                       return
>>
>>                       function
>>                    
>> plot_base_map(plot_vpage,plot_area,lon1,lon2,lat1,lat2)
>>
>>                       *  Plots base map...
>>
>>                        'c'
>>                        'set vpage 'plot_vpage
>>                        'set parea 'plot_area
>>                        'set lon 'lon1' 'lon2
>>                        'set lat 'lat1' 'lat2
>>                        'set mproj latlon'
>>                        'set mpt * 1 1 5'
>>                        'set mpdset hires'
>>                        'set poli on'
>>                       *  'set grid on'
>>                        'set grads off'
>>                        'set gxout contour'
>>                        'draw map'
>>
>>                       *  add lon/lat lines...
>>
>>                        'set ccolor 1'
>>                        'set cstyle 5' ; 'd lon'
>>                        'set cstyle 5' ; 'd lat'
>>
>>                       *  add title, x- and y-labels...
>>
>>                        'draw title \\ Track of Minimum Surface Pressure'
>>                        'draw xlab Longitude \\'
>>                        'draw ylab \\ Latitude'
>>
>>                       return
>>
>>                       _______________________________________________
>>                       gradsusr mailing list
>>                       gradsusr at gradsusr.org
>>         <mailto:gradsusr at gradsusr.org> <mailto:gradsusr at gradsusr.org
>>         <mailto:gradsusr at gradsusr.org>>
>>                    <mailto:gradsusr at gradsusr.org
>>         <mailto:gradsusr at gradsusr.org> <mailto:gradsusr at gradsusr.org
>>         <mailto:gradsusr at gradsusr.org>>>
>>
>>
>>                       http://gradsusr.org/mailman/listinfo/gradsusr
>>
>>
>>
>>
>>
>>
>>                           
>> ------------------------------------------------------------------------
>>
>>                    _______________________________________________
>>                    gradsusr mailing list
>>                    gradsusr at gradsusr.org <mailto:gradsusr at gradsusr.org>
>>         <mailto:gradsusr at gradsusr.org <mailto:gradsusr at gradsusr.org>>
>>                    http://gradsusr.org/mailman/listinfo/gradsusr
>>
>>
>>                --
>>                Please note that Charles.Seman at noaa.gov
>>         <mailto:Charles.Seman at noaa.gov>
>>                <mailto:Charles.Seman at noaa.gov
>>         <mailto:Charles.Seman at noaa.gov>> should be considered my NOAA
>>                email address, not cjs at gfdl.noaa.gov
>>         <mailto:cjs at gfdl.noaa.gov> <mailto:cjs at gfdl.noaa.gov
>>         <mailto:cjs at gfdl.noaa.gov>>.
>>
>>                       
>> ********************************************************************
>>                 Charles Seman                                      
>>         Charles.Seman at noaa.gov <mailto:Charles.Seman at noaa.gov>
>>         <mailto:Charles.Seman at noaa.gov <mailto:Charles.Seman at noaa.gov>>
>>                 U.S. Department of Commerce / NOAA / OAR
>>                 Geophysical Fluid Dynamics Laboratory         voice:
>>         (609) 452-6547
>>                 201 Forrestal Road                              fax:
>>         (609) 987-5063
>>                 Princeton, NJ  08540-6649                   
>> http://www.gfdl.noaa.gov/~cjs/
>>                       
>> ********************************************************************
>>
>>                "The contents of this message are mine personally and 
>> do not
>>                reflect any
>>                official or unofficial position of the United States 
>> Federal
>>                Government,
>>                the United States Department of Commerce, or NOAA."
>>
>>                *
>>                *
>>                * Subject: Re: Tracking Hurricanes
>>                * From: Kun-Hsuan Chou <cwujou at TYPHOON.AS.NTU.EDU.TW
>>         <mailto:cwujou at TYPHOON.AS.NTU.EDU.TW>
>>                <mailto:cwujou at TYPHOON.AS.NTU.EDU.TW
>>         <mailto:cwujou at TYPHOON.AS.NTU.EDU.TW>>>
>>
>>                * Date: Fri, 8 Oct 2004 08:03:20 +0800
>>                * To: GRADSUSR at LIST.CINECA.IT
>>         <mailto:GRADSUSR at LIST.CINECA.IT> <mailto:GRADSUSR at LIST.CINECA.IT
>>         <mailto:GRADSUSR at LIST.CINECA.IT>>
>>
>>                *
>>                * Hi,
>>                *
>>                * I write a sample to track the maxminum wind speed, it
>>         should
>>                be the script that you want.
>>
>>                *
>>                'd maxloc(max(mag(u,v),lon=120,lon=130),lat=15,lat=25)'
>>                 line=sublin(result,2)
>>                 ygrd=subwrd(line,4)
>>                'd maxloc(max(mag(u,v),lat=15,lat=25),lon=120,lon=130)'
>>                 line=sublin(result,2)
>>                 xgrd=subwrd(line,4)
>>                'set x 'xgrd
>>                lonval = subwrd(result,4)
>>                'set y 'ygrd
>>                latval = subwrd(result,4)
>>                'q w2xy 'lonval' 'latval
>>                xpos = subwrd(result,3)
>>                ypos = subwrd(result,6)
>>                'draw mark 1 'xpos' 'ypos' .2'
>>
>>                       
>> *============================================================================ 
>>
>>                *Kun-Hsuan Chou
>>                *Postdoctoral Researcher
>>                *Department of Atmospheric Sciences
>>                *National Taiwan University
>>                *No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan.
>>                *Phone:   886-2-23625896 ext. 243
>>                *Mobile:  0920079247
>>                *E-mail:   cwujou at typhoon.as.ntu.edu.tw
>>         <mailto:cwujou at typhoon.as.ntu.edu.tw>
>>                <mailto:cwujou at typhoon.as.ntu.edu.tw
>>         <mailto:cwujou at typhoon.as.ntu.edu.tw>>
>>
>>                *----- Original Message -----
>>                *From: Arturo Caracas Uribe
>>                *To: GRADSUSR at LIST.CINECA.IT
>>         <mailto:GRADSUSR at LIST.CINECA.IT> <mailto:GRADSUSR at LIST.CINECA.IT
>>         <mailto:GRADSUSR at LIST.CINECA.IT>>
>>
>>                *Sent: Thursday, October 07, 2004 11:48 PM
>>                *Subject: Tracking Hurricanes
>>                *
>>                *Does anyone know how to get the maximum values of
>>         vorticity of
>>                a domain? (the value, lat and lon).I need the positions
>>         in order
>>                to track a hurricane.
>>                *Thanks in advance
>>                *
>>                *Arturo Caracas
>>                *Atmospheric Sciences, México.
>>
>>
>>                       
>> *----------------------------------------------------------------------
>>                *
>>                *  Adapted from plot_hurricane_center2c.gs
>>         <http://plot_hurricane_center2c.gs>
>>                <http://plot_hurricane_center2c.gs>, which was adapted 
>> from:
>>                *
>>                *  (1) "plot_hurricane_center2[a][b].gs" (from
>>                "plot_hurricane_center.gs
>>         <http://plot_hurricane_center.gs>
>>         <http://plot_hurricane_center.gs>"),
>>
>>                *      locally modified versions derived from Joe
>>         Covert's script
>>                *      "plot_tc_shi.gs <http://plot_tc_shi.gs>
>>         <http://plot_tc_shi.gs>"
>>                (Joe.Covert at noaa.gov <mailto:Joe.Covert at noaa.gov>
>>         <mailto:Joe.Covert at noaa.gov <mailto:Joe.Covert at noaa.gov>>),
>>         which was
>>                posted to the
>>                *      GrADS Listserv on 9/13/2004 (his script was named
>>                plot_tc_shi.gs <http://plot_tc_shi.gs>
>>         <http://plot_tc_shi.gs>)
>>
>>                *      on 4/27/06, found via a Google search for
>>         "plot_tc_shi.gs <http://plot_tc_shi.gs>
>>                <http://plot_tc_shi.gs>":
>>                *      http://caos.iisc.ernet.in/gslib/plot_tc_shi.gs
>>                *
>>                *  (2) code in "hurricane_tracking.txt" (taken from an 
>> email
>>                exchange
>>                *      posted to the GrADS Listserv by Kun-Hsuan Chou and
>>                *      Arturo Caracas Uribe in Oct, 2004)
>>                *
>>                *
>>                *  To use: grads -l
>>                *
>>                       
>> *----------------------------------------------------------------------
>>
>>                function main()
>>
>>                 'reinit'
>>
>>                       
>> ************************************************************************
>>                *  Allow external GrADS functions
>>                       
>> ************************************************************************
>>
>>                 rc = gsfallow("on")
>>
>>                       
>> ************************************************************************
>>                *  Define dataset file information and plotting limits
>>         for base
>>                map...
>>                       
>> ************************************************************************
>>
>>                **  nc_file1 = ''
>>                **  nc_file2 = ''
>>                **  nc_file3 = ''
>>                **  nc_file = ''nc_file1' 'nc_file2' 'nc_file3''
>>                 nc_file = 'your_netCDF_file'
>>
>>                 lon1 = 298 ; lon2 = 308
>>                 lat1 =  20 ; lat2 =  25
>>
>>                       
>> ************************************************************************
>>                *  Legend captions, colors, and marks for the plots
>>                       
>> ************************************************************************
>>
>>                **  nmodels = 1
>>                **  model.1 = 'isabel_ras'
>>                **  model.2 = 'isabel_isotke'
>>                **  model.3 = 'isabel_my25'
>>
>>                **  titles.1 = model.1 ; colors.1 = 2 ; marks.1 = 2
>>                **  titles.2 = model.2 ; colors.2 = 3 ; marks.2 = 2
>>                **  titles.3 = model.3 ; colors.3 = 4 ; marks.3 = 2
>>                ***
>>                ***  Define the legend plotter input...
>>                ***
>>                **  titles = '-t' ; colors = '-c' ; marks = '-m' ; lines
>>         = '-l'
>>                **  n=1
>>                **  while ( n <= nmodels )
>>                **    titles = ''titles' "'titles.n'"'
>>                **    colors = ''colors' 'colors.n
>>                **    marks = ''marks' "'marks.n'"'
>>                **    lines = ''lines' 1'
>>                **    n=n+1
>>                **  endwhile
>>
>>                **  legend_info = ''colors' 'lines' 'marks' 'titles' -p'
>>
>>                 nmodels = 1
>>                 model.1 = 'title_name_for_your_netCDF_dataset'
>>
>>                 titles.1 = model.1 ; colors.1 = 2 ; marks.1 = 2
>>                *
>>                *  Define the legend plotter input...
>>                *
>>                 titles = '-t' ; colors = '-c' ; marks = '-m' ; lines = 
>> '-l'
>>                 n=1
>>                 while ( n <= nmodels )
>>                   titles = ''titles' "'titles.n'"'
>>                   colors = ''colors' 'colors.n
>>                   marks = ''marks' "'marks.n'"'
>>                   lines = ''lines' 1'
>>                   n=n+1
>>                 endwhile
>>
>>                 legend_info = ''colors' 'lines' 'marks' 'titles' -p'
>>
>>                *  ...other drawing primitives
>>
>>                 marksize = 0.1
>>
>>                 lstyle = 1 ; lthick = 5
>>
>>                       
>> ************************************************************************
>>                *  Use "cbar_line" or "cbar_line_box"?
>>                       
>> ************************************************************************
>>
>>                 legend_plotter = 'cbar_line'
>>                *  legend_plotter = 'cbar_line_box'
>>
>>                       
>> ************************************************************************
>>                *  Plot page limits
>>                       
>> ************************************************************************
>>
>>                 plot_vpage = '0 11 0 8.5'
>>                 plot_area  = '1 10 1 7.5'
>>
>>                 xl = subwrd(plot_area,1) ; xr = subwrd(plot_area,2)
>>                 yb = subwrd(plot_area,3) ; yt = subwrd(plot_area,4)
>>
>>                 xc = xl + (xr-xl)/2
>>
>>                       
>> ************************************************************************
>>                *  GrADS metafile output...
>>                       
>> ************************************************************************
>>
>>                 'enable print hurricane_track.gx'
>>
>>                       
>> *-----------------------------------------------------------------------
>>                *  Define and plot track of minimum surface pressure 
>> for each
>>                dataset...
>>                       
>> *-----------------------------------------------------------------------
>>
>>                 nf=1
>>                 while ( nf <= nmodels )
>>
>>                * Open dataset file and define parameters...
>>
>>                   fname = subwrd(nc_file,nf)
>>                   'sdfopen 'fname
>>                   'set dfile 'nf
>>                   'q file'
>>                   rec3 = sublin(result,3) ; binary_file = subwrd(rec3,2)
>>                   say
>>                   say
>>                   say '*** 'binary_file' ***'
>>                   say
>>                   rec5 = sublin(result,5)
>>                   nx = subwrd(rec5,3) ; ny = subwrd(rec5,6) ; nz =
>>                subwrd(rec5,9) ; nt = subwrd(rec5,12)
>>
>>                   if( nf = 1 )
>>
>>                * Plot base map...
>>
>>                     
>> plot_base_map(plot_vpage,plot_area,lon1,lon2,lat1,lat2)
>>
>>                   endif
>>
>>                * Define locations of "hurricane center" for plotting 
>> points,
>>                and write<
>>
>>     ...
>>
>>     [Message clipped]      function maxwind(args)
>>      'reinit'
>>      nc_file = subwrd(args,1)
>>      wind = subwrd(args,2)
>>      wind_units = subwrd(args,3)
>>      say
>>      say nc_file
>>      say wind' ('wind_units')'
>>      say
>>      'sdfopen 'nc_file
>>      'q file'
>>      say result
>>      say
>>      rec5 = sublin(result,5)
>>      nx = subwrd(rec5,3) ; ny = subwrd(rec5,6) ; nz = subwrd(rec5,9) ;
>>     nt = subwrd(rec5,12)
>>      say
>>      say '(nx,ny,nz,nt) = ('nx','ny','nz','nt')'
>>      say
>>      nxp = nx
>>      nyp = ny
>>      nzp = nz
>>     *
>>     * get the x- and y-limits for virtual page
>>     *
>>      'q gxinfo'
>>      rec3 = sublin(result,3) ; xpl = subwrd(rec3,4) ; xpu = 
>> subwrd(rec3,6)
>>      rec4 = sublin(result,4) ; ypl = subwrd(rec4,4) ; ypu = 
>> subwrd(rec4,6)
>>      tt = 1
>>      while ( tt <= nt )
>>        'set x 1'
>>        'set y 1'
>>        'set z 1'
>>        'set t 'tt
>>        say 'tt = 'tt
>>        'set gxout print'
>>        'd max(max(max('wind',x=1,x='nx'),y=1,y='ny'),z=1,z='nz')'
>>          rec = sublin(result,(nyp+1)*nzp+3)
>>          max_wind = subwrd(rec,1)
>>          say ' max 'wind' = 'max_wind
>>        'd maxloc(max(max('wind',y=1,y='ny'),z=1,z='nz'),x=1,x='nx')'
>>          rec = sublin(result,(nzp+1)*nxp+3)
>>          xc = subwrd(rec,1)
>>        'd maxloc(max(max('wind',x=1,x='nx'),z=1,z='nz'),y=1,y='ny')'
>>          rec = sublin(result,(nzp+1)*nyp+3)
>>          yc = subwrd(rec,1)
>>        'd maxloc(max(max('wind',x=1,x='nx'),y=1,y='ny'),z=1,z='nz')'
>>          rec = sublin(result,(nyp+1)*nzp+3)
>>          zc = subwrd(rec,1)
>>          say ' (xc,yc,zc) = ('xc','yc','zc')'
>>        'd 'wind'(x='xc',y='yc',z='zc')'
>>          rec = sublin(result,2)
>>          wind_xc_yc_zc = subwrd(rec,1)
>>          say ' 'wind'(x='xc',y='yc',z='zc') = 'wind_xc_yc_zc
>>     *
>>     * find "world" coordinates of (xc,yc) and convert "world" coordinates
>>     * to "xy" coordinates for plotting track of hurricane center...
>>     *
>>          'set x 'xc
>>          lonc = subwrd(result,4)
>>          'set y 'yc
>>          latc = subwrd(result,4)
>>          say ' (lonc,latc,zc) = ('lonc','latc','zc')'
>>        'd 'wind'(lon='lonc',lat='latc',z='zc')'
>>          rec = sublin(result,2)
>>          wind_lnc_ltc_zc = subwrd(rec,1)
>>          say ' 'wind'(lon='lonc',lat='latc',z='zc') = 'wind_lnc_ltc_zc
>>     *
>>     * plot the wind and place a mark at the max
>>     *
>>        'c'
>>        'set vpage 'xpl' 'xpu' 'ypl' 'ypu
>>        'set parea 'xpl+1' 'xpu-1' 'ypl+1' 'ypu-1
>>        'set x 1 'nx
>>        'set y 1 'ny
>>        'set z 'zc
>>        'set gxout shaded'
>>        'set grads off'
>>        'd 'wind
>>        'run cbar 0.7'
>>        'draw title \ Max 'wind' = 'wind_lnc_ltc_zc' ('wind_units')\at
>>     (lonc,latc,zc)=('lonc','latc','zc')'
>>        'q w2xy 'lonc' 'latc
>>          xpos = subwrd(result,3)
>>          ypos = subwrd(result,6)
>>          say ' (xpos,ypos) = ('xpos','ypos')'
>>        'set line 1 1 6'
>>        'draw mark 6 'xpos' 'ypos' 0.2'
>>        'c events'
>>        pause()
>>        tt=tt+1
>>      endwhile
>>      say '...finished.'
>>      'close 1'
>>     return
>>
>>     function pause()
>>     *
>>     * Pauses till ENTER key is pressed
>>     *
>>      say
>>      say '*********************************'
>>      say 'Press "ENTER" key to continue...'
>>      say '*********************************'
>>      pull answer
>>     *
>>     return
>>
>>
>>     _______________________________________________
>>     gradsusr mailing list
>>     gradsusr at gradsusr.org <mailto:gradsusr at gradsusr.org>
>>     http://gradsusr.org/mailman/listinfo/gradsusr
>>
>>
>>
>>
>>
>>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> gradsusr mailing list
>> gradsusr at gradsusr.org
>> http://gradsusr.org/mailman/listinfo/gradsusr
> 
> 
> ------------------------------------------------------------------------
> 
> _______________________________________________
> gradsusr mailing list
> gradsusr at gradsusr.org
> http://gradsusr.org/mailman/listinfo/gradsusr

-- 

Please note that Charles.Seman at noaa.gov should be considered my NOAA
email address, not cjs at gfdl.noaa.gov.

********************************************************************
  Charles Seman                                Charles.Seman at noaa.gov
  U.S. Department of Commerce / NOAA / OAR
  Geophysical Fluid Dynamics Laboratory         voice: (609) 452-6547
  201 Forrestal Road                              fax: (609) 987-5063
  Princeton, NJ  08540-6649            http://www.gfdl.noaa.gov/~cjs/
********************************************************************

"The contents of this message are mine personally and do not reflect any
official or unofficial position of the United States Federal Government,
the United States Department of Commerce, or NOAA."
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