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20010815: 20010814: GEMPAK Barnes upper-air analysis of CAPE?



Christian,

Let me clarify your question:

>Another related question, how can I have less-smooth contours with
>Barnes analysis (is it the gamma? If so, what can I use to still get a good
>analysis and get some more details?)


It is the display programs that draw "contours". Barnes analysis creates
a gridded data set from irregularly spaced observations.

There are several factors which affect drawing smooth contours.

1) In gridding your data, it is GAMMA that affects the convergence
   of dataand NPASS which create successive corrections of the data.
   SEARCH is the weighting factor which determines at what weight
   stations will not be included. Indirectly related to SEARCH is the 
   size of the grid spacing (DELTAN). Having a smaller grid point spacing
   allows more of the high frequency data signal to be resolved. You
   must have at least 3 points within the radius of influence of
   a point in order to produce a grid point value. OAGRID is a
   helpful program for automatically determining DELTAN, but it
   does have linmitations, such as always creating a CED grid.
   When you know more about your data and want to directly specify
   the grid point spacing, you can use gdcfil.

   Sucessive passes with NPASS interpolate the gridpoint back to the station
   locations and decrease the mean square difference, so additional passes
   restore some of the data noise that the original analysis smoothed out.

2) in contouring programs, the parameters CONTUR and CURVE affect the
   smoothness of the contours drawn though the gridded data. For smoother
   contours, increase the number of subboxes and smoothing passes in CONTUR.
   You can draw smooth contours through noisy data- which is different from
   your intemation about less-smooth analysis.

3) You can apply smoothers in your GFUNC such as SM5S and SM9S
   to smooth noisy data as well. These are useful with fields like OMEG
   which have lots of local noise in the data, as compared to HGHT fields
   which are generally smooth if the data is hydrostatic.

The tutorial covers the barnes scheme:
http://www.unidata.ucar.edu/packages/gempak/tutorial/barnes.html

Effects of GAMMA and SEARCH are shown in the excercises:
http://www.unidata.ucar.edu/packages/gempak/tutorial/barnes_exercises.html


Steve Chiswell
Unidata User Support



>From: Christian Page <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200108152103.f7FL3A118217

>
>Hi,
>
>Thanks, it works well now. The problem was that I didn't specify SNPARM when
>needed. Another related question, how can I have less-smooth contours with
>Barnes analysis (is it the gamma? If so, what can I use to still get a good
>analysis and get some more details?)
>
>Christian Page
>UQAM
>
>On Tue, 14 Aug 2001, Unidata Support wrote:
>
>>
>> Christian,
>>
>> If you are going to use OAGRID to create the grid file, you
>> need to specify a SNPARM (eg tmpc; dwpc; hght; uwnd or vwnd)
>> so that the program can determine the mean station spacing of reporting
>> locations (set the DELTA_ values to blank prior to running. Otherwise,
>> if you already know the DELTA values you want, you can use
>> GDCFIL to create the grid file. I think your FL -13 warning is OK- it
>> likely is emmited be checking for the alias first
>>
>> Then, in OABSND, you need at least one level parameter (SNPARM) in addition
>> to your STNDEX values you will grid.
>>
>> For example:
>>  GDFILE   = test.grd
>>  DELTAN   =
>>  DELTAX   =
>>  DELTAY   =
>>  GRDAREA  = us
>>  EXTEND   = 2;2;2;2
>>  DTAAREA  =
>>  SOURCE   = sn
>>  SNFILE   = uair
>>  SFFILE   =
>>  SNPARM   = tmpc;dwpc
>>  SFPARM   =
>>  DATTIM   = 1200
>>  LEVELS   = 500
>>  MAXGRD   = 1000
>>  GEMPAK-OAGRID>r
>>
>>                     OBJECTIVE ANALYSIS PARAMETERS
>>
>>  GRIDAREA           19.00   -119.00     46.90    -57.62  (us     47.00  -56.
> 00)
>>  DELTAN              3.730
>>  DELTAX              1.860
>>  DELTAY              1.860
>>
>>  GRID POINTS     X :  34  ( 2, 2 )        Y :  16  ( 2, 2 )
>>  EXTENDAREA           15.28   -122.72     50.62    -53.90
>>  DATAAREA             15.28   -122.72     50.62    -53.90
>>
>>
>>  CALCULATIONS:
>>    FILE      $GEMDATA/upperair/20010814_upa.gem
>>  SOURCE    SN               19.00   -119.00     47.00    -56.00       NSTN  
>  79
>>    PARM      TMPC        LEVEL    0.0        DATTIM       010814/1200
>>
>>      COMPUTED DATA SPACING           2.548
>>      UNIFORM  DATA SPACING           4.904
>>      RECOMMENDED   DELTAN =  3.726   DELTAX =  2.221   DELTAY =  1.863
>>
>> Enter <cr> to accept parameters or type EXIT:
>>  Parameters requested: GDFILE,DELTAN,DELTAX,DELTAY,GRDAREA,EXTEND,DTAAREA,
>>  SOURCE,SNFILE,SFFILE,SNPARM,SFPARM,DATTIM,LEVELS,MAXGRD.
>>  GEMPAK-OAGRID>
>>
>>
>>  SNFILE   = uair
>>  GDFILE   = test.grd
>>  SNPARM   = tmpc;dwpc
>>  STNDEX   = cape
>>  LEVELS   = 500
>>  VCOORD   = pres
>>  DATTIM   = 1200
>>  DTAAREA  =
>>  GUESS    =
>>  GAMMA    = 0.3
>>  SEARCH   = 50/EX
>>  NPASS    = 2
>>  QCNTL    =
>>  GEMPAK-OABSND>r
>>
>>  OABSND PARAMETERS:
>>
>>  Output grid file:        test.grd
>>  Number of x, y points:    34    16
>>  Grid bnds:     19.00  -119.00    46.90   -57.62 Grid xtnd:    2   2   2   2
>>  Station spacing:           3.73
>>  No first guess file is requested.
>>  Sounding file:           $GEMDATA/upperair/20010814_upa.gem
>>  Data area:               15.28;-122.72;50.62;-53.90
>>  Level parameters:        TMPC  DWPC
>>  QC threshold:             0.0   0.0
>>  Levels:                   500
>>  Vertical coordinate:     pres
>>  Station parameters:      CAPE
>>  Time:                   010814/1200
>>  GAMMA: 0.30   SEARCH:  50.00  NPASS:  2
>>  Data extrapolation may occur.
>> Enter <cr> to accept parameters or type EXIT:
>>
>>  Processing data at time 010814/1200
>>
>>  RMS values for pass  1
>>    PARAMETER:     TMPC    DWPC    CAPE
>>    LEVEL:          500     500       0
>>    RMS:           1.16    8.21  397.47
>>    #STN:            79      79      79
>>
>>  RMS values for pass  2
>>    PARAMETER:     TMPC    DWPC    CAPE
>>    LEVEL:          500     500       0
>>    RMS:           0.64    4.99  229.18
>>    #STN:            79      79      79
>>  Parameters requested: SNFILE,GDFILE,SNPARM,STNDEX,LEVELS,VCOORD,DATTIM,
>>  DTAAREA,GUESS,GAMMA,SEARCH,NPASS,QCNTL.
>>  GEMPAK-OABSND>
>>
>>
>> You should now be able to plot your cape grid using
>> GLEVEL = 0, GVCORD = NONE, GFUNC = CAPE.
>>
>> Steve Chiswell
>> Unidata User Support
>>
>>
>>
>>
>> >From: Christian Page <address@hidden>
>> >Organization: UCAR/Unidata
>> >Keywords: 200108141425.f7EEPK125035
>>
>> >
>> >Hi,
>> >
>> >I am trying to create a Barnes upper-air analysis of CAPE, but I am still
>> >struggling with OAGRID. I tried to do the same commands that I use for heig
> ht
>> >analysis, but it doesn't work.
>> >
>> >Here is what I get from OAGRID:
>> > GDFILE    Grid file
>> >/io/httpd/gempak/grids/europe_upa_cape.grid
>> > DELTAN    Station spacing                   3.50
>> > DELTAX    X spacing                         1.75
>> > DELTAY    Y spacing                         1.75
>> > GRDAREA   Area covered by grid              26;-20;62;40
>> > EXTEND    Points to extend grid             2;2;2;2
>> > DTAAREA   Data area for OA                  26;-20;62;40
>> > SOURCE    Data source (SN or SF)            SN
>> > SNFILE    Sounding data file                $GEMUPA/20010813_upa.gem
>> > SFFILE    Surface data file
>> > SNPARM    Sounding parameter list
>> > SFPARM    Surface parameter list
>> > DATTIM    Date/time                         010813/00
>> > LEVELS    Vertical levels                   500
>> > MAXGRD    Maximum number of grids           5000
>> >
>> >$GEMUPA/20010813_upa.gem is defined correctly and is a valid file.
>> >
>> >I then get: [FL -13]  No valid file for given type and cycle time.
>> >/io/httpd/gempak/grids/europe_upa_cape.grid is non-existent prior to runnin
> g
>> >oagrid, but it is create anyway even with the error.
>> >
>> >Then, oabsnd:
>> > SNFILE    Sounding data file                $GEMUPA/20010814_upa.gem
>> > GDFILE    Grid file
>> >/io/httpd/gempak/grids/europe_upa_cape.grid
>> > SNPARM    Sounding parameter list
>> > STNDEX    Stability indices                 cape
>> > LEVELS    Vertical levels                   500
>> > VCOORD    Vertical coordinate type          PRES
>> > DATTIM    Date/time                         010814/00
>> > DTAAREA   Data area for OA                  26;-20;62;40
>> > GUESS     Guess file*time
>> > GAMMA     Convergence parameter             0.3
>> > SEARCH    Search radius/Extrapolation       20/EX
>> > NPASS     Number of passes                  2
>> > QCNTL     Quality control threshold
>> >
>> >
>> >then gdcntr (failure):
>> > GDATTIM   Grid date/time                    010813/00
>> > GLEVEL    Grid level                        ALL
>> > GVCORD    Grid vertical coordinate          PRES
>> > GFUNC     Scalar grid                       cape
>> > GDFILE    Grid file
>> >/io/httpd/gempak/grids/europe_upa_cape.grid
>> > CINT      Contour interval/min/max          0
>> > LINE      Color/type/width/label/smth/fltr  15 / 3 / 2
>> > MAP       Map color/dash/width/filter flag  1
>> > TITLE     Title color/line/title
>> > DEVICE    Device|name|x size;y size|color   PS | eur_cape.ps | 11;8.5 | C
>> > SATFIL    Satellite image filename(s)
>> > RADFIL    Radar image filename(s)
>> > PROJ      Map projection/angles/margins|dr  nps
>> > GAREA     Graphics area                     #45;14;13;23
>> > CLEAR     Clear screen flag                 yes
>> > PANEL     Panel loc/color/dash/width/regn   0
>> > TEXT      Size/fnt/wdth/brdr/N-rot/just/hw  1
>> > SCALE     Scalar scale / vector scale       0
>> > LATLON    Line color/dash/width/label/inc   0
>> > HILO      Color/symbol/rng/rad/cnt/intp     2;4/H#;L#///yes
>> > HLSYM     HILO txt size/posn/font/wdth/hw   2;1/2/2/HW
>> > CLRBAR    Color/ornt/anch/x;y/ln;wd/freq
>> > CONTUR    Subbox/smooth                     0
>> > SKIP      Skip_cntr/skip_plt_x;skip_plt_y   0
>> > FINT      Fill interval/min/max             0
>> > FLINE     Fill colors                       10-20
>> > CTYPE     Contour type:  C/F                C
>> > LUTFIL    Enhancement lookup table filenam
>> > STNPLT    Txtc/txt attr|marker attr|stnfil
>> >
>> >[TG -4]  No times in input file.
>> > [TG -4]  No times in input file.
>> > [GR -20]  No times selected.
>> >
>> >Any idea what's wrong? I tried to do the same as my height objective analys
> is,
>> >but it doesn't work...
>> >
>> >Christian Page
>> >UQAM
>> >
>>
>> ****************************************************************************
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>