7.4 MD files - Plotting and Contouring Point Data
RAOBCON, and RAOBPLOT
commands display surface and upper-air point data.
These commands are designed
to allow for shorter command entries by having commonly used defaults
for displaying their data types, and using positional parameters instead
of keywords for values that are always or often specified.
For example, the default for the DATASET keyword is to use the real-time
datasets. When looking at real-time data you will never have to
specify the DATASET keyword. However, in these examples, you will be
using the historical BLIZZARD dataset and will still have to specify the
These commands are easier
to use for plotting or contouring their specific data types than the
generic "toolbox" commands PTDISP and
PTCON. However, the "toolbox" commands are still
useful for calculating complicated mathematical equations and for
creating output that is completely controlled by the user instead of
by the command defaults.
In this exercise, you will plot and contour observed parameters, as well as
calculate the changes in these parameters over time and between different
levels in the atmosphere. You will also plot some derived parameters and
plot the results of your own mathematical equation.
Displaying Surface Data
- Erase both the images and graphics in frames 1 through 6.
- Type: ERASE F 1 6
- Display the two latest Meteosat-3 Vis images on frames 1 and 2
centered on Florence, South Carolina, with the resolution magnified
by a factor of 2. Show each frame and add a map in graphics color level 5.
- Type: IMGDISP BLIZZARD/M3-VIS.2 1 STA=KFLO MAG=2 REPEAT=2 SF=YES
REFRESH='MAP H 5'
- Show frame 1 and plot the snow depth at 18 UTC on 13 March 1993
on the satellite image using data from the BLIZZARD/SFCHOURLY dataset.
Use the alias you created in the previous lesson when specifying the
dataset. The X in the map positional parameter means
to use the default, which is to use the frame's current navigation.
- Type: AKA ADD SFC BLIZZARD/SFCHOURLYType: SF 1;SFCPLOT SNO X 18 1993/03/13 DATASET=SFC.1
- Contour the snow depth over the plot using the same data and
conditions as in the previous step.
- Type: SFCCON SNO X 18 13/MAR/93 DATA=SFC.1
- On frame 2, contour the pressure change from 00 UTC to 23 UTC.
- Type: SFCCON PRE X 23-00 93072 DAT=SFC GRA=2;SF 2
Displaying Upper-air Data
- Display a map of the United States in color level 8 (gray) on
frames 3 and 4.
- Type: SF 3;MAP USA 8 GRA=3-4
- Contour the 850-500 mb thickness on frame 3.
- Type: RAOBCON Z 500-850 X 12 93072 DAT=BLIZZARD/UPPERMAND.1
- Contour the 850 mb temperature over the United States at 12 UTC on
13 March 1993.
- Type: SF 4;RAOBCON T 850 X 12 93072 DAT=BLIZZARD/UPPERMAND.1 COL=9
- Plot the 850 mb streamlines over the temperature contours.
- Type: RAOBCON STREAML 850 X 12 93072 DAT=BLIZZARD/UPPERMAND.1
Displaying Calculated Parameters
In addition to plotting the observed parameters, these commands can also
calculate and plot some derived parameters, such as windchill, vorticity,
and temperature advection.
If you have a more complicated equation that you would like to use, you can
use the PTCON or PTDISP commands to plot the results of your equation.
- Contour the 850 mb temperature advection on frame 5, using a contour
interval of 5.
- Type: SF 5;RAOBCON TADV 850 USA 12 93072 DAT=BLIZZARD/UPPERMAND CINT=5
- Compare frames 4 and 5.
Notice that the areas of positive temperature advection
(warm air advection) calculated and plotted in frame 5 match the areas in frame 4
where streamlines are passing from warmer to colder air.
- Press: Alt B
- Press: Alt A
- Use the Hypsometric Equation to calculate the 1000-50 mb thickness in meters.
Only stations reporting both a 1000 mb and 500 mb temperature are included in the equation,
so stations that are above 1000 mb (e.g. Rocky Mountain stations) will not appear in the
- Type: PTDISP BLIZZARD/UPPERMAND 6 SEL='DAY 93072;TIME 12'
MAP=USA PARAM='THIK[M]=(287/9.8)*((P1+P2)/2)*LOG(1000/500)' P1=T[K] 'P 1000'
P2=T[K] 'P 500'; SF 6