Observations used to support RAMS
at Supercomputing'97
As part of the effort in developing forecasts, the results from the LAPS
pre-processing, assimilation step are analyzed as well as RAMS output.
Tools similar to those for RAMS were also developed for the study of LAPS
results. But since this step is critical to the application of RAMS as
well as other mesoscale models, the approach used for RAMS visualizations
has been applied to LAPS. These data were made available for interactive
three-dimensional visualization and analysis via a new Data Explorer-based
viewer application, similar to the RAMS application described earlier.
This includes all of computed variables from LAPS at hourly resolution.
Here is a some sample image for Wednesday, November 19 at 0900 UTC (1 AM
PST). An animation created with this application
that includes this time step is available, covering most of the Supercomputing
'97 period and LAPS runs used to support RAMS executions.
A surface variable (total precipitation) has been selected for display
as pseudo-color, which is overlaid on a topographic map. Rivers (blue)
and coastlines (black) are draped on the surface. An upper air variable
(relative humidity) has been selected for display via surface extraction.
The surface at 90% is requested in translucent white as a representation
of a cloud boundary. Another field (temperature) has been selected
to show as a vertical slice, which is pseudo-color contoured. Any
of the three-dimensional fields available from LAPS can be visualized with
either of these methods. The upper air wind data can be seen along
two vertical profiles, which are specified interactively. The direction
of the model wind field along these "virtual soundings" are shown via vector
arrows pseudo-colored by horizontal wind speed. The length of the
arrows also corresponds to the horizontal speed. The profile is realized
as a pseudo-colored tube, which is contoured by the variable selected for
isosurface realization (i.e., humidity).
With the LAPS viewer visualization and analysis application, you have
the ability to view and interact with the data in a latitude-longitude
(from the model's stereographic grid)-pressure coordinate system.
The coordinates are annotated with an axes box and base maps. The
focus of this application is the analysis (visualization and interrogation)
of the model output. There is a control panel, which gives
you the ability to select any of the surface and upper air variables to
visualize with pre-defined methods. Another control panel allows
you to select the LAPS output of interest. Additional information
about these options is available via the Help buttons in the control panels.
This is a screen dump of the application.
There are three other windows of interest. The primary one is
the Image window, within which you may view and directly interact with
the model output. There are several options available, including
changing viewing modes (Options pull-down, View-Control) and saving/printing
images/animations (File pull-down).
A third window is the Sequence Control. It is a graphical widget
with the appearance of a VCR. It gives you the ability to specify
a time step or frame within the model run you are currently examining.
You can move forward or backward in sequence, single step, pause, loop
continuously or loop back and forth. If you hit the button in the
upper right, you can manual control the time steps available as well as
the increment between steps to be examined.
The control panel in the viewer application allows you to select specific
visualization techniques and data. The visualization coordinate system
(latitude, longitude, pressure) is annotated with an axes box and base
coastlines, river and topographic maps. The vector/line maps are
draped over a topographic surface and displaced below the lower vertical
boundary. The surface may be pseudo-colored by any one of over two
dozen surface, scalar, two-dimensional variables produced by the model.
This may also include topographic height.
LAPS produces several upper air, three-dimensional fields. For
each of 14 upper air scalar fields, you may choose to realize the data
as an isosurface, vertical slice and horizontal (isobaric) slice.
For the isosurface, you may choose a specific threshold value. The
isosurface is colored according to a segmented colormap. When you
change the variable of interest, the default value for the isosurface is
the mean. You may indicate the desired value via a stepper widget.
For the vertical slice, you may select a grid position, and whether
the slice is meridional or zonal. The slice is color-filled, pseudo-colored
with a segmented colormap and line contoured. For the horizontal
slice, you may choose what pressure level is to be shown. The slice
is pseudo-colored with a continuous colormap.
You may probe the volume for specific values at selected locations within
the model output. If the probe button is pushed, the variable that
was selected for isosurface representation will be interrogated.
The results will be displayed in a dialog box that will pop up on the screen.
To change the location, go to Cursors Mode (Options pull-down in the Image
window, View-Control) and select probe_volume. You will see a little
probe point in the volume. With the left mouse button, you can drag
the point around, which will show coordinates in the upper left.
In execute-on-change mode, when you release the mouse button, the results
will be shown. An example of this feature is shown in the image.
The upper air three-dimensional wind velocity is visualized via interactive
marking of geographic locations of interest. You may define one or
more geographic locations for "virtual soundings" within the model
atmosphere. This is also done in Cursors Mode. You should select
profilers. You can either grab and move one of the locations already
set with the mouse or indicate a new location by double clicking with the
left mouse button at the desired place. You can also delete one of
the extant locations by pointing at it with the cursor and double-clicking
the left mouse button. At the locations that have been specified,
a vertical profile is extruded through the entire model atmosphere, which
is realized as a tube. The sounding location is used to derive information
about wind velocity. The wind velocity along the profile is shown
by a set of vector arrows that point in the direction of the wind.
Horizontal speed at these points are indicated by the color and length
of the arrows. Optionally, the locations on each "virtual wind profiler"
can be used for seed particles for particle advection, which is realized
as streamlines. These lines, which are also pseudo-colored by horizontal
speed, indicate the instantaneous direction of the modelled wind from these
locations. If a variable has been selected for realization as an
isosurface, then the values along each profile of that variable are also
shown as pseudo-colored, filled contour bands using the same segmented
colormap as is employed for the isosurface. These profiles are also shown
via a conventional pressure-profile plot as shown in a separate image window.
The previous images show LAPS output, derived from actual observations
at 1 AM PST on November 19 that were used for RAMS executions that day.
The image below is a prediction from RAMS for that period of cloud water
density not humidity as in the LAPS images. This simulation that
produced this result was initiated 10 hours earlier. Other results
from that simulation are visible on the previous page.
For comparison purposes, you can also look at satellite observations
from GOES-9 for this period in the infrared at 4 PM PST and the visible
10 AM PST on November. Animations of the available observations can
also be seen in the infrared and the visible.
Some of features visible in the RAMS predictions described earlier are
apparent.
For additional comparison, surface conditions for the entire United
States are shown below for 4 PM PST on November 18. Temperature,
wind velocity, radar results and pressure are depicted. An animation
of these data for the entire period is also available. Some of features
visible in the RAMS predictions described earlier are apparent.
lloydt@watson.ibm.com
