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SNLIST is the sounding (or upper air) listing program. It is analogous to the SFLIST program, with a few differences. As we work through this program, note how similar the user interface looks, and how it works in the same way as SFLIST. Let's start up the program:
prompt% snlist SNFILE Sounding data file GEMDATA:HRCBOB.SND AREA Data area roc DATTIM Date/time last SNPARM Sounding parameter list TMPC;DWPC STNDEX Stability indices SHOW LEVELS Vertical levels 500 VCOORD Vertical coordinate type PRES OUTPUT Output device (TPF) T MRGDAT Merge data file flag/part type YES Parameters requested: SNFILE,AREA,DATTIM,SNPARM,STNDEX,LEVELS,VCOORD,OUTPUT, MRGDAT.Remember, just like with SFLIST, we could learn about SNLIST by looking at the on-line help file. Type
phelp
snlist at any GEMPAK prompt. For now, lets proceed.OK, let's read in the defaults file:
GEMPAK-SNLIST>restore defaults/snlist.nts GEMPAK-SNLIST>dis SNFILE Sounding data file AREA Data area DATTIM Date/time SNPARM Sounding parameter list dset STNDEX Stability indices lift LEVELS Vertical levels all VCOORD Vertical coordinate type pres OUTPUT Output device (TPF) t MRGDAT Merge data file flag/part type yes GEMPAK-SNLIST>
Note: You can see the GEMPAK help files on each of these variables by typing
phelp name (where name is the name of the variable)
at any GEMPAK prompt. For convenience in the tutorial, we've added a link to
the help file for each variable below. ALSO, the variables are also described
in Chapter 5 of the GEMPAK users manual.
Analogous to SFFILE in SFLIST. Since we're using Hurricane Bob data:
GEMPAK-SNLIST>snfile = $GEMPAK/data/hrcbob.snd
Analogous to SFPARM in SFLIST. The
default value is DSET which returns all the recorded data.
GEMPAK-SNLIST>snparm = DSET
GEMPAK will calculate numerous stability indices based on the data available for a given station.
stndex = lift; kinx
Check phelp stndex for the list of stability indices available.
VCOORD is the vertical coordinate on which to list the data. GEMPAK can vertically interpolate sounding data between the various vertical coordinate systems.
The LEVELS variable determines for which levels the data are listed. There are a number of ways to specify the levels, including:
a. single value levels = 500
b. list of values(; separated) levels = 500;550;750
c. a range of values (-) levels = 500-750
d. Key words:
levels = MAN for mandatory levels
levels = VAS for mandatory VAS levels
levels = ALL for ALL levels
levels = SFC or levels = 0 surface
levels = TOP or levels = -1 top level
The units of the level are determined by the VCOORD variable:
For Example:
VCOORD=PRES VCOORD=THTA
LEVELS=300 VLEVELS=300
300mb 300K
When MRGDAT = NO sounding data is listed in its raw parts
form. When MRGDAT = YES all the available data is merged into a single
list ordered from the surface on up.
Un-merged data is ordered in the following parts: TTAA, TTBB, PPBB, TTCC, TTDD, PPDD. If you choose to display the data in its un-merged form, the format is fixed according to the standard WMO format. You have no control over which parameters, vertical coordinates or levels are displayed.
If you choose to merge the data, you may specify which parameters are listed on which levels in which vertical coordinate system. When necessary, data that are measured in alternate coordinate systems are interpolated to the requested vertical coordinate.
Regardless of how your upper air data are stored, both merged and un-merged listing formats are available. The difference between these forms will be more clear when we do some examples.
Practice EXERCISES!!
GEMPAK-SNLIST>area=eyw GEMPAK-SNLIST>dattim=list GEMPAK-SNLIST>dis SNFILE Sounding data file $GEMPAK/data/hrcbob.snd AREA Data area eyw DATTIM Date/time list SNPARM Sounding parameter list dset STNDEX Stability indices lift LEVELS Vertical levels all VCOORD Vertical coordinate type pres OUTPUT Output device (TPF) t MRGDAT Merge data file flag/part type yes GEMPAK-SNLIST>
Luckily, SNPARM is already set to dset by the defaults file!
GEMPAK-SNLIST>stndex=lift;kinx
Now run the program. The list should look like this:
Now the list should look like this:
Be sure to compare this un-merged part format to the merged format in the previous example!
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