CASES-97 Short Description:
Operations Plan
Reports: 1
IOP 7 Summary
0900 - 2100 CDT Thursday, May 22, 1997
IOP 6 Summary
0900 - 2100 CDT Wednesday, May 21, 1997
IOP 5 Summary
0600 CDT Tuesday, May 20, 1997 - 0600 CDT Wednesday, May 21, 1997
IOP 4 Summary
0600 - 2100 CDT Friday, May 16, 1997
Special Weather Update
IOP 3 Summary
0600 CDT Saturday, May 10, 1997 - 0600 CDT Sunday, May 11, 1997
IOP 2 Summary
0600 CDT Sunday, May 4, 1997 - 0600 CDT Monday, May 5, 1997
IOP 1 Summary
1630 CDT Monday, April 28, 1997 - 1630 CDT Tuesday, April 29, 1997
Daily Summaries: 1
Week Five:
Tuesday, May 20, 1997
Week Four:
Monday, May 19, 1997
Sunday, May 18, 1997
Saturday, May 17, 1997
Thursday, May 15, 1997
Wednesday, May 14, 1997
Tuesday, May 13, 1997
Week Three:
Monday, May 12, 1997
Friday, May 9, 1997
Thursday, May 8, 1997
Wednesday, May 7, 1997
Tuesday, May 6, 1997
Week Two:
Saturday, May 3, 1997
Friday, May 2, 1997
Thursday, May 1, 1997
Wednesday, April 30, 1997
Week One:
Sunday, April 27, 1997
Saturday, April 26, 1997
Friday, April 25, 1997
Thursday, April 24, 1997
Wednesday, April 23, 1997
Tuesday, April 22, 1997
1 Peggy LeMone and
Julie Lundquist wrote the IOP reports and daily summaries.
IOP 7 Summary
0900 CDT - 2100 CDT Thursday, May 22, 1997
This brief overview was written by Bob
Grossman:
Just a quick summary of the last mission flown by the King Air on
the last day of CASES97. We landed with 5 minutes left on total
hours. There were actually two missions today. The first, during a
period of showery weather, was a traverse from Ponca to Augusta;
this gives us 7 ov these traverses to help characterize the gradient
structure south of the watershed. There were south easterly winds
today.
After the first mission the PIs gathered in Augusta for a concluding
science meeting (including NWS Science Officer from Wichita) to
outline our near future and on-going plans for analysis of what we
think is a very good data set.
The second mission was carried out as the showery weather (light
rain) dissipated and fair weather with high broken cloud and
scattered cumulus regained a hold on the watershed. The showery
weather produced patchy soil moisture distribution with the western
part of the watershed more moist than the eastern.
The second mission commenced from Augusta and a "V" pattern flown
(instead of the triangle) between the three profilers. Soundings
were taken at two of the three profilers. Following that a short
study was conducted to ascertain the influence of Butler Lake on its
surroundings.
Folliwng that a five level stack was performed at the southern edge
of the watershed. We then moved northward and performed another five
level stack finishing with a 60 nm alongwind run to obtain gradient
information south of the watershed. This mission profile will
produce budgets as well as a last check of the profilers. Since
there was no CLASS sounding support this mission will also be more
like future missions which will rely upon the remotely sensed
profiles rather than ballon profiles; a fitting end to CASES97.
Friday we will rerun the flux computations from all 7 IOPs as a first
quick look data set (currently only available to the PIs). Three IOPs
have been run, using the same software for the Twin Otter as well.
IOP 6 Summary
0600 CDT Tuesday, May 20, 1997 - 0600 CDT Wednesday, May 21, 1997
The full summary for this special IOP is not available yet.
The King Air did an evening transition flight during the evening.
Balloons where launched from Whitewater at 90-minute intervals
from 0900 to 2100 CDT.
IOP 5 Summary
0600 CDT Tuesday, May 20, 1997 - 0600 CDT Wednesday, May 21, 1997
Plan:
Aircraft:
Two aircraft, two missions.
- Morning transition: 2-aircraft Stack + Cat's Ears. KA
and TO switch roles, with KA doing Cat's Ears.
- Evening Transition: Cat's Ears + Stack.
Both aircraft land at Ponca City between flights.
Balloon launches:
Each 1.5 hours from 0600 May 20 to 0430 May 21, 1997.
Profilers:
Collect data on all three in full spectral mode;
Standard scans for all three profilers.
Radar:
Scan from 0600 May 20 through 0600 May 21. Alternate between
TREC and RHI scans.
General Impressions:
As in the previous IOPs, cumulus clouds failed to develop during the day.
We only observed some cirrus and very sparse middle clouds.
The unique aspects:
- Winds were light, and out of the east all day. This wind
direction could present a problem for the surface data, since the
flow past the sonic anemomenter is probably affected by the towers.
However, the light winds allow us to focus more on the effects of
surface properties on the boundary layer.
- Stratification strongly affected the boundary layer
development. A near-neutral layer near the surface allowed early
and rapid growth of the PBL. Above that, a stable layer (probably
due to subsidence).
- PBL mixing ratio significantly increased during the day.
- Despite the light winds, there may have been roll vortices
during the day. They were most well-developed in the early morning,
and could have been associated with a distinct jet within the
boundary layer in the early morning (Kuettner-type rolls).
Summary by Instrument Systems:
Aircraft:
The morning transition flights were flown as before, but
afternoon takeoffs were delayed until 4:30 CDT to focus on
the evening transition.
The morning flight legs were nearly parallel to the wind
direction. Unfortunately, radar reported structure parallel
to the wind, which may have caused sampling problems. In
response to this possibility, some special flight tracks
were flown perpendicular to the wind in the morning, and
afternoon flight legs were rotated to be more perpendicular
to the wind direction. (This rotation was not a trivial
exercise, since both aircraft were flying sets of flight
legs straddling a 60-km equilateral triangle). Aircraft
reported significant horiziontal gradients, light winds, and
significant changes in mixing ratio during the day.
Radar:
The radar was very helpful in updating the wind profiles.
In the morning, the growth of the boundary layer appeared
nicely, as did the evolution of the longitudinal structure
mentioned earlier. However, later in the day, the radar
produced spurious estimates of the PBL height. The apparent
1.8 km depth of the PBL (at 1830 LDT) seemed incorrect, when
compared with other instruments, and was probably due to an
elevated dry layer. It will be interesting to compare radar
structures to what was seen from the aircraft and
radiosondes.
Radiosones:
As before, the soundings were generally of high quality,
thanks to careful launch procedures.
Surface data:
Although we ran the experiment with an array partially
crippled by recent rains (3 fast humidity sensors no longer
functional after heavy rains), the stations affected were
the ones we would have sacrificed had we had the choice: one
station had redundent fast humidity, the second turned out
to be an 'extra' winter wheat site (the farmer had told us
it would be planted in milo), and the third has a complex
fetch in east winds. To account for the possible
deleterious effects of the suboptimal wind direction, we
will use conditional sampling to 'favor' data gathered when
the wind is not flowing to the instruments through the
tower. Also, the computers at the ASTER sites crashed in
the evening, so data from those periods (7:40 PM LDT -
11:20 AM LDT and 5:10 PM LDT- 12:20 PM LDT) has been lost.
Again, we are grateful to the many people who contributed to the success of
this IOP.
Tuesday, May 20, 1997
We are currently in an IOP, but are issuing a status report because
of a 'special' IOP tomorrow.
Instrumentation Status:
Aircraft:
Both aircraft flying today.
Profilers:
Radar:
Radiosondes:
Surface Stations:
PAM/ASTER: Up and running. No Krypton water-vapor fluxes
on Stations 4 and 5. CO2 on Station 7 intermittent.
Qualls: Up and running. Sonic is dismounted.
NOAA/MYERS: Up and running.
Smileyberg: Up and running except for the CO2 and H2O sensors.
Towanda (ARM): Unknown.
Julie Lundquist:
Up and stairmastering again. Also watching the grass grow
(final vegetative survey today).
JETEX:
Forecast:
Winds tomorrow will be out of the SE, slightly stronger than today.
No precip anticipated.
IOP:
The King Air will do an evening transition flight tomorrow evening.
Balloons will be launched from Whitewater at 90-minute intervals
from 0900 to 2100 CDT.
Monday, May 19, 1997
Instrumentation Status:
Aircraft:
Profilers:
Radar:
Radiosondes:
Surface Stations:
PAM/ASTER: Up and running. The computer at
station 7 has solved its problem. We suspect it was due
to hot weather, and because the next few days will be
cooler, we have decided to worry about other things.
Qualls: Up and running. Sonic is dismounted.
NOAA/MYERS: Up and running.
Smileyberg: Up and running except for the CO2 and H2O sensors.
Towanda (ARM): Unknown.
Julie Lundquist:
Up and stairmastering again.
JETEX:
Forecast:
Winds tomorrow will be light and variable, with directions varying
from slightly N of E to southerly. No precip is expected for the
next 36 hours.
IOP:
Despite the less-than optimal wind direction, we are commencing our
last IOP at 0600 Tuesday morning, hoping that the winds shift out of
the "danger zone" (67 degrees, +- 15 degrees) quickly. Because
precip is forecast for the rest of the week, we must seize the
day.
Sunday, May 18, 1997
Instrumentation Status:
Aircraft:
Profilers:
Radar:
Radiosondes:
Surface Stations:
PAM/ASTER: Up and running. The computer at station 7 is
overheating, leading to interruptions in the analog data,
which means loss of chemistry, pressure, Tsurface, and
radiation parameters except for solar and net. We will wait
and see if the cooler weather tomorrow will rectify the
situation. If it does not, we will switch that computer
with that at station 8.
Qualls: Up and running. Sonic is dismounted.
NOAA/MYERS: Up and running.
Smileyberg: Up and running except for the CO2 and H2O sensors.
Towanda (ARM): Unknown.
Julie Lundquist:
Up and stairmastering again.
JETEX:
Forecast:
Showers/thunderstorms anticipated tonight. Precip will continue
through most of the day tomorrow. Tuesday will likely have E to ENE
winds at dawn, shifting to SE, S, and SW throughout the day with no
precip.
IOP:
The precip on Monday will eliminate any chance for an IOP. We are
hoping for a 24 hour IOP starting at 0600 CDT Tuesday, but will
have to wait for the dictates of the weather.
Saturday, May 17, 1997
IOP 4 Summary
0600 - 2100 CDT Friday, May 16, 1997
Plan:
General Summary:
This IOP was conducted with full knowledge that a trough line with
the threat of severe weather was moving in from the northwest. We
shared soundings with the forecasters at the Wichita National
Weather Service throughout the day via email and fax. We concluded
the IOP with the 1930 CDT sounding because of a line of showers and
thunderstorms moving into the area.
This IOP afforded the opportunity to document boundary-layer growth
over patchy surface moisture. This patchiness arose from an uneven
distribution of precip through the night of May 13, not from an
uneven distribution of dry-down: the eastern stations received over
one inch of preceip, the western stations received much less, and
the southern station received no precip at all. Strong horizontal
advection by a low-level jet centered above the boundary layer
during the morning implied that
- the boundary layer was growing into warming air with
stable stratification.
- the boundary layer was growing into moister air (rather
than drier air, as is normally the case).
The result was an extended 'morning' (quotes appropriate for this
case) transition, with considerable variation of PBL height on the
mesoscale through 1630 CDT. This variation made it difficult to
determine the heights for aircraft flux profiles, though it
appeared, after the fact, that useful choices were made.
Highlights:
- The mixed layer heights derived from radiosondes, profilers, and
aircraft were consistent for corresponding locations and times.
However, interpretation of profiler and especially radar returns was
occasionally difficult because of turbulence in an elevated
near-neutral layer with high mixing ratios and moderate shear.
- This confusion also held when interpreting the rather complex
boundary-layer structure.
- Although the severe weather never materialized, it gave us
practice in making sure that sonde operators and aircraft crews
operated safely. We received nowcasting help from Vivekanadan at
the S-Pol radar, from a private forecasting firm under contract by
the Argonne Boundary Layer Experiments facility for the experiment,
and from the Wichita Weather Service, who not only responded to our
requests for information, but called us to let us know that the
convection was collapsing. We also monitored NOAA Weather Radio
receivers provided by ABLE at the ABLE/Cases Control Center and the
three sounding sites, and obtained radar data over the Internet.
Summary by Instrument Systems:
Aircraft:
The switch in aircraft roles went off smoothly, as did
rotation of the flux legs to be more normal to the wind.
Heights of flux legs and patterns appeared successful
despite the complexity of the situation. The aircraft took
off before 0900 CDT, refueled around 1400, and landed at
Ponca City by 1930.
Radar:
Performed fair-weather scans until 1915. Wind comparisons
with profilers indicate good data; differences between
apparent mixed layer height from radar and other platforms
probably related to unusual humidity profiles.
Unfortunately, convection collapsed before entering the
radar range, so little precip analysis took place.
Radiosones:
Most launches successful. Again, a great dataset. Recent
temperature and humidity comparisons at the sounding sites
by the NCAR SSSF surface crew along with Argonne data at
Oxford and Beaumont will complement careful launch
procedures and CLASS surface towers in removing biases.
Surface data:
Surface flux stations operated well during the IOP.
Again, we are grateful to the many people who contributed to the success of
this IOP.
Thursday, May 15, 1997
Instrumentation Status:
Aircraft:
Profilers:
Radar:
Radiosondes:
Up and running. Surface station intercomparisons at Beaumont
and Oxford yesterday.
Surface Stations:
PAM/ASTER: Up and ready.
Qualls: Up and ready. Sonic mounted and functional.
NOAA/MYERS: Up and running.
Smileyberg: Up and running except for the CO2 and H2O sensors.
Towanda (ARM): Unknown.
Julie Lundquist:
Down/standby. Will be up tomorrow or Saturday after checkout/repairs
last night and down today.
JETEX:
Forecast:
South winds tomorrow until passage of a wind-shift line around 8-10
p.m. tomorrow night. Possible showers and thunderstorms associated
with this feature.
IOP:
We will have an IOP tomorrow. Balloon launches at 90-min intervals
starting at 0600; last launch at 2100 CDT unless storms enter
watershed before that. Aircraft takeoffs as before for continuous
coverage through daylight hours, though stacks and cats ears will
exchange locations. Radar will do fair-weather scans unless
significant convection appears either in the watershed or within 60
km of the radar.
Wednesday, May 14, 1997
Instrumentation Status:
Aircraft:
Profilers:
Radar:
Radiosondes:
Surface Stations:
PAM/ASTER: Up and ready. All stations and all
equipment survived last night's unexpected
downpour. Rain gauges indicate patchy distribution
of precip.
Qualls: Up and ready. The sonic stopped
working during the night, but equipment has been
replaced and is now functional.
NOAA/MYERS: Up and running.
Smileyberg: Up and running except for the CO2 and H2O sensors.
Towanda (ARM): Unknown.
JETEX:
Forecast:
Although tomorrow will be clear, winds will be from the NE. Friday
looks partly cloudy with winds from the SW. We also predict that we
will be much more humble when calling for "no precip".
IOP:
Because our towers are all mounted so that NE winds will interfere
with the sonic's measurements, we will wait until Friday for an
IOP. (The official decision will be made Thursday afternoon.)
Special Weather Update
All personnel at the CASES Operations Center have been humbled by the
weather. Instead of a no-precip frontal passage, as we anticipated in
yesterday's status report, a strong squall line with some possible severe
weather passed through the Walnut watershed between 2100 and 2200, CDT on
May 13. The nine NCAR and NOAA sites came through the storm in good
shape. The CU site needed some minor repairs this morning. The Argonne
site continues to take data, so we are assuming it is still operational.
Preliminary rainfall totals are as follows:
(For more details later today, look at
ASTER
Data Report: CASES-97)
For the NE part of the profiler triangle:
Site 1 (8 miles W of Beaumont): 25-33 mm of rain.
Site 2 (5 miles W of Beaumont): 25-33 mm of rain.
For the central part of the profiler triangle:
Site 3 (3 miles SW of Douglas in the river valley): 10-13 mm.
Site 4 (6 miles NE of Douglas): 10-13 mm.
Site 5 (8 miles W of Douglas): 1.5 mm.
Site 7 (1 mile E of Rock): 8 mm.
Site 8 (5 miles SE of Rock): 10-13 mm.
NOAA site (12 miles E of Rock): 20 mm.
For the S part of the triangle:
Site 6: (2 miles N of Winfield): no rain.
Pea-sized hail was reported at the ABLE Office in Augusta (N part of
Watershed) where the CASES Control Center is located. There is an
unconfirmed report of softball-sized hail at Wilmot (8 miles SE of Rock).
Tuesday, May 13, 1997
Instrumentation Status:
Aircraft:
Profilers:
Radar:
Radiosondes:
Surface Stations:
PAM/ASTER: Up and ready.
Qualls: Up and ready. Sonic mounted and functional.
NOAA/MYERS: Up and running.
Smileyberg: Up and running except for the CO2 and H2O sensors.
Towanda (ARM): Unknown.
Internet Provider:
JETEX:
Forecast:
Two small fronts (with no accompanying precip) will roll through the
Watershed tomorrow. No precip is forecast through Sunday, so we
might catch a solid dry-down period.
IOP:
Because the frontal passages complicates the synoptic situation, we
will wait until at least Thursday for an IOP.
Monday, May 12, 1997
Instrumentation Status:
Aircraft:
Profilers:
Radar:
Radiosondes:
Surface Stations:
PAM/ASTER: Up and ready.
Qualls: Up and ready. Sonic mounted and functional.
NOAA/MYERS: Up and running.
Smileyberg: Up and running. CO2 and H2O sensors might not be
functional.
Towanda (ARM): Unknown.
JETEX:
Forecast:
We anticipate a frontal passage in the evening tomorrow. No
accompanying precip. is expected.
IOP:
Because the frontal passage complicates the synoptic situation, we
will wait until at least Wednesday for an IOP.
IOP 3 Summary
0600 CDT Saturday, May 10, 1997 - 0600 CDT Sunday, May 11, 1997
Overall Impression:
Excellent daytime light-wind case. Preliminary analysis indicates
that these conditions emphasize the effect of the surface on the BL;
aircraft, radar, and sondes all noticed extremely dry air above the BL.
Plan:
General Summary:
A high pressure system moving eastward from central Kansas
during the day provided light and variable winds in the
morning, followed by increasing south winds through the
afternoon and evening. With the exception of scattered
cirrus, skies were clear. This lack of cloudiness was
associated with extremely dry air: mixing ratios were NEAR
ZERO between 2.5 and 3 km msl. Strong subsidence and
strong heating led to a sharp inversion over much of the area,
with the exception of some horizontal variation in structure
on the convective- to meso-scale in the morning. Most
systems functioned normally.
With the air calm at sunrise, the surface inversion layer was
quite shallow and surmounted with a near-neutral layer. Once
the potential temperature of the surface layer matched that of
the near-neutral layer (around 11 a.m. CDT (10 a.m. CST)),
boundary-layer growth was explosive. This explosive growth
transpired around 11 a.m. CDT (10 a.m. CST). At this time,
the radar scientists noted considerable variation in their
measurements of the depth of the mixed layer from clear-air
echo; their estimates varied from ~500 m to ~1 km. This
explosive growth could explain why the aircraft scientists
were confused about boundary-layer depth at this time: one
aircraft reported a BL depth of 2500 ft msl (0.76 km msl) and
the other subsequently reported a depth of 6000 ft msl (1.83
km msl or 1.4 km agl, which is about the depth the BL
reached).
The radiosondes and profilers document divergent histories of
the PBL after 2-3 p.m. CDT (1-2 p.m. CST). The profilers
show the boundary layer depth decreasing at a rate of about 2
cm/sec, while the sondes show the depth of the PBL to be
roughly constant. This inconsistency could be related to our
ignorance of how to interpret profiler signals: when we think
they are seeing the top of the boundary layer, the profiler
might actually be seeing part of the stable inversion above the
boundary layer.
Nevertheless, we find ample evidence for subsidence of the
very dry air layer observed above the mixed layer from
- tracking of the height of the extreme humidity value, from the
sondes (and assuming no horizontal advection effects),
yielded a subsidence of 1.7 cm/sec.
- the boundary layer depth decrease, as revealed from signal-to-
noise ratio at the Beaumont and Whitewater profilers, was
about 2 cm/sec.
- the top of the 'fossil' boundary layer from the previous day,
as revealed by the signal-to-noise ratio, appeared to subside at a
rate of about 1.6 cm/sec.
Summary by Instrument Systems:
Concerns:
We do not yet know how well the instruments
responded to the extremely low mixing ratios observed.
A comparison of extreme humidity values and
surface humidity values suggests some systematic biases
between the stations. Careful comparisons to surface towers
(Argonne and NCAR/CLASS), plus intercomparison with a
standard, should mitigate these problems.
Friday, May 09, 1997
Instrumentation Status:
Aircraft:
Profilers:
Radar:
Radiosondes:
Surface Stations:
PAM/ASTER: Up and ready. Krypton sensors survived
rainfall. All instruments are functioning well, except for
surface temperature at Station 6, which will be checked.
Qualls: Up and ready. Sonic mounted and functional.
Pressure transducer wetted by rain replaced.
NOAA/MYERS: Up and running.
Smileyberg: Up and running.
Towanda (ARM): Unknown.
JETEX:
No IOP tonight; standby for tomorrow.
Forecast:
Winds will be southerly at 10-20 mph for most of tomorrow, with
clear skies and highs in the upper 70's. Southerlies will continue
through the night.
IOP:
IOP #3 will take place from 0600 CDT Saturday May 10 through 0600
CDT Sunday May 11. Balloons will be launched from the three
profiler sites at 0600, 0730, 0900, 1030, 1200, 1330, 1500, 1630,
1800, 1930, 2100, 2230, 2400, 0130, 0300, 0430CDT. The aircraft
will take off at 0930 CDT and about 1430 CDT for 2 4-4.5 hour
missions, following the same pattern as before (stacks and cat's
ears in morning; stacks + triangle in the afternoon). Radar will do
RHI and TREC scans 0600 May 10 through 0600 May 11. Argonne
profiler spectral data will be collected.
Thursday, May 08, 1997
Instrumentation Status:
Aircraft:
Up and ready. There will be a crew shift
on the Wyoming plane over Friday and Saturday.
Profilers:
Radar:
Their team is quite happy with the data from last night's storm.
Radiosondes:
The sonde data still look good. One operator has sprained his
back (not while sending up a sonde).
Surface Stations:
PAM/ASTER: Bringing up and checking krypton water-vapor
sensors after 10-20 mm of rain over watershed last night.
Krypton sensors seem to be in good shape today. They will
probably have to dry out from light rain this afternoon. The
malfunctioning Ophir sensor on Station 8 is now functional.
Qualls: Sonic remounted this morning. All other functions
operational as of this morning; we will re-examine it this
morning after unexpected rain this afternoon.
NOAA/MYERS: Functional - data looks good.
Smileyberg: Power problems have been resolved.
Towanda (ARM): We are assuming it is operational.
JETEX:
No IOP planned for tonight.
Forecast:
Northerly winds Friday, light and variable and changing to southerly
Saturday. Weather Service unofficially said that some rain might
fall overnight due to high-level instability.
IOP:
IOP #3 will possibly occur on Saturday. Friday, our original
choice, was canceled due to rain falling over the watershed during
this afternoon and possibility of rain tonight. Also, there was
some uncertainty about wind direction because of the movement of a
high pressure system through the region.
Wednesday, May 07, 1997
Instrumentation Status:
Aircraft:
Up and ready. The Wyoming Team will switch out pilots over
Friday and Saturday.
Profilers:
Up and working. The RASS at Oxford is
functioning erratically; Argonne is working on it.
Radar:
Team worked through last night and caught a nice LLJ.
Up and ready.
Radiosondes:
Excellent data from all three stations in the past two days.
Surface Stations:
PAM/ASTER: Up and ready. Krypton sensors are disabled
because of threat of precipitation.
Qualls: Up and ready. Sonic is disabled because of
threat of precipitation.
NOAA/MYERS: Up and ready. They have data going back to
right before IOP #2.
Smileyberg: Teams are working on the generator.
Towanda (ARM): Unknown.
JETEX:
They are all very happy about catching their LLJ last night.
No IOP tonight.
Forecast:
Although a storm is moving through the area now, we are not sure how
much precip it will produce. A front, moving through at 1900 LDT
tonight, will clear out all precip by midnight at the latest.
Tomorrow should be clear with northerly winds. Friday will be clear
with light and variable winds.
IOP:
Tomorrow would be a good day for an IOP if not for the logistics of
enabling the sensors that have been disabled because of impending
precip and the uncertain status of Oxford. Because the clear
weather will last through the weekend, and Friday will have light
and variable winds, we are tentatively planning an IOP for Friday.
This decision will be made Thursday afternoon.
Tuesday, May 06, 1997
Instrumentation Status:
JETEX:
Forecast:
Scattered thunderstorms should start tonight and continue
through Thursday. Some forecasts mention possibility of
MCS development. We are preparing for a possible IOP
Friday or Saturday.
IOP:
There is no IOP scheduled for tomorrow.
IOP 2 Summary
0600 CDT May 4, 1997 - 0600 CDT May 5, 1997
General Summary:
The second IOP, like the first, experienced southerly winds.
Otherwise, the two situations were quite different. During the
first IOP, we experienced very dry air above the boundary layer;
this moisture gradient allowed us easily to define the depth of the
boundary layer. Today, the boundary layer top was less distinct.
The boundary layer itself appeared to be quite complex: the air was
moister (but still too dry to produce cumulus clouds), with elevated
mixed layers and and some breakthroughs of the boundary layer into
the inversion. We also noticed that the rapid growth of the
boundary layer did not transpire simultaneously across the
watershed. Both radar and aircraft reported strong evidence of
rolls. Aircraft also sampled waves at the top of the BL. Judging
from the CLASS soundings, today's boundary layer was shallower than
that of IOP 1.
Operations overnight were successful. Just after the IOP concluded,
a squall line swept through the watershed. Because of the IOP,
radar crews were able to document the squall line. The storm did not
damage the krypton moisture-flux sensors on the surface stations
because the bulk of precip was to the south (max precip was 0.05
inches).
This IOP occurs two days after a heavy (one-inch) rain over the
watershed. The aircraft scientists noticed that the ground was
markedly greener. It will be interesting to see to what degree the
differences in the two IOPs is related to the differences in surface
properties (first IOP dry soil; 2nd IOP moist soil).
Intercomparisons: During this IOP, aircraft made a sounding near the
Oxford profiler at the time of a rawin launch. This coordination
will allow a three- way intercomparison between profiler, sonde, and
aircraft. Throughout the IOP, the CASES control center compared
radar to sondes and profilers for both wind and BL depth.
Summary by Instrument Systems:
Aircraft:
The aircraft flew two coordinated missions. Wind remained
southerly enough that we did not need to realign the pattern
to be normal to the wind.
- 0900-1345 LDT: Coordinated multilevel flux legs
(stacks) and vertical soundings through the top of the BL,
plus horizontal legs 200 ft below the inversion level and
~100 feet above the surface (cat's ears), with one triangle
connecting the three profilers at the end of the flight
pattern. King Air flew 3-level, four- level, and 5-level
stacks.
- 1445-1900 LDT: Coordinated stacks and triangles. King
Air flew stacks.
Profilers:
Collected data in full spectral mode for entire IOP.
Radar:
The S-Pol performed TREC and RHI scans during the entire
IOP. The RHI strategy changed during the day from one that
sampled every degree from 105 to 135 azimuth to one that
scanned every 3 degrees across the CASES triangle.
We did some comparisons of radar and sounding winds;
comparisons were very good. However, radar estimates of
inversion heights varied significantly from morning sonde
observations, possibly because of the elevated mixed layer
or large groups of migrating insects. After discussion, we
agreed to follow the afternoon scanning pattern for
nighttime, in order to isolate the effects of migrating
birds. We anticipate comparing the night-time winds from the
sondes, profilers, and radar.
Radiosondes:
Though it is too early to assess data quality, those
soundings we looked at during the day were consistent with
the aircraft scientists' view of complexity. There appeared
to be vertical shear of horizontal wind through the boundary
layer. Most if not all the soundings were successfully
completed. A final assessment awaits uploading data that
wasn't relayed to Boulder.
Surface Data:
The surface stations showed an interesting feature during
the daylight hours that bears investigation.
- ASTER/PAM: The CO2 sensor at the ASTER supersite is now
functional. Some data lost from ASTER #7 after 0400 local.
- ABLE: The Argonne site at Smileyberg is operational.
- NCAR: The NCAR sites are all operational.
- NOAA: The NOAA station was installed yesterday
At the close of the IOP, we again thank those who worked hard to
ensure this IOP's success: the NCAR surface, sounding, and radar
groups, the radiosonde operators, the Argonne profiler group, the
NOAA and University of Wyoming aircraft crews, the Weather Service,
and the FAA.
Saturday, May 03, 1997
Instrumentation Status:
Aircraft:
Profilers:
Radiosondes:
Surface Stations:
PAM/ASTER: All stations up and operational; krypton
sensors are unbagged.
Qualls: Sonic deployed, ready to go.
NOAA/MYERS: Being installed today
Smileyberg: Installing generator.
JETEX:
NO IOP tonioght, potential IOP Sunday night.
Forecast:
Today, skies clear, winds NW to N. Winds shift to southerly
tonight; increasing southerlies during day. Possible low-level
jet tomorrow night.
IOP:
YES. Balloon launches will take place every 90 minutes,
commencing at 0600 (CDT) Sunday morning, with the last launch
at 0430 CDT Monday morning. Radar will operate through the IOP.
Aircraft will have coordinated missions Sunday.
Friday, May 02, 1997
Instrumentation Status:
Aircraft:
Profilers:
Up and ready. No real-time data feed from Oxford.
Porto-potty tipped over at Whitewater during storm.
However, radar antenna has been realigned and
reguyed.
Radar:
The radar crews were up until 4 am last night for the squall
line and got interesting data.
Radiosondes:
Surface Stations:
NCAR PAM/ASTER: Krypton sensors are being debagged
today after last night's thunderstorm. All other
PAM/ASTER instruments are operational. Got 20-25 mm
of rain in the watershed last night; shows up
clearly in soil moisture data.
Quall: Sonic is being remounted tonight after last
night's thunderstorm.
NOAA Myers: The site should be installed this weekend.
Argonne: Smileyberg is up intermittently because of power
failures.
JETEX:
Forecast:
Rain should be out of the area by this afternoon. Saturday
will have northerly winds that will calm and then switch to
the south; no precip is forecast. Sunday will have winds
from the SSW and no precip.
IOP:
Quite probable for Sunday, weather permitting. Because
Saturday's winds should switch to the south through the
north-east, compromising surface measurements, we will wait
until Sunday. If it occurs, this IOP will most likely
commence at 6 AM.
Thursday, May 01, 1997
Instrumentation Status:
Aircraft:
Surface Stations:
PAM/ASTER: Krypton sensors bagged, CO2 pump
reinstalled (#7), data system crashes are still
happening.
Qualls: Sonic will be taken down tonight because of
rains tomorrow.
NOAA/Myers: Will be installed in a few days.
Argonne: Smileyberg is not operating. (Power problems.)
JETEX:
No IOP tonight, 90% unlikely tomorrow night.
Anticipating one Sunday night or Monday.
Forecast:
This morning we saw low to middle clouds and high southerly winds;
sprinkles fell around noon. Possible severe weather tonight and
Friday, clearing up Saturday. Sunday should be beautiful.
IOP:
No IOP Friday, but we are anticipating one for Saturday or Sunday.
Because the PAM/ASTER humidity sensors need to be unbagged before an
IOP, Sunday is more likely.
Wednesday, April 30, 1997
Instrument Status:
Aircraft:
Good condition after yesterday's IOP.
Profilers:
Still taking data reliably.
Radiosondes:
Over 75% of the data from the sondes has been
examined; at first glance, it looks very good.
Surface stations:
PAM/ASTER surface stations: They are operational.
The CO2 data is not available due to another pump
problem. Periodic data system crashes are still
happening but are being worked on. (The krypton
humidity sensors were unbagged for yesterday's IOP.)
Qualls site: Everything fine - the sonic anemometer
is up and running.
NOAA site: Being installed today and tomorrow.
Smileyburg: Still experiencing power outages, but
Argonne is working to rectify that situation.
Towanda (ARM): No information, but we are assuming the
Towanda site is functioning well.
JETEX:
The JETEX project: not planning an IOP for tonight -
they have used up 1/3 of their IOPs and are being
cautious with their time.
Forecast:
Forecasts for tomorrow vary. There are chances of rain
tomorrow afternoon and evening. Most forecasts agree that
the wind will be from the south tomorrow, which would
normally dictate an IOP if there were no chance of rain.
Rain and thunderstorms are predicted for Friday. Saturday
and Sunday should be clear with favorable winds. We will
consider having an IOP on one of those two days.
IOP:
Yesterday's IOP was deemed successful. Because of the
chance of rain tomorrow, we decided to wait until Saturday
or Sunday for an IOP.
IOP 1 Summary
1630 CDT April 28, 1997 - 1630 CDT April 29, 1997
Plan:
During this period, radiosondes will be launched from Beaumont,
Oxford, and Whitewater each hour and a half, meaning balloons will
be released at 1630, 1800, 1930, 2100, 2230, 2400 (April 28, 1997),
0130, 0300, 0430, 0600, 0730, 0900, 1030, 1200, 1330, and 1500.
The NOAA Twin Otter and the Wyoming King Air will have three missions:
- Commencing about 1500 CDT. Will fly 'Mixed Cat's Ears and
Stack' patterns with a Triangle at the beginning and end of the
mission. In the Mixed Cat's Ears and Stack pattern, one aircraft
will fly two legs just below the top of the boundary layer,
punctuated by pop-up soundings to locate the top of the boundary
layer, and one leg just above the surface, while the other
aircraft will fly multiple levels between the surface and
boundary layer top. The triangle pattern will be flown by both
aircraft (one aircraft will fly it before the major pattern and
one will fly it after) between the three profilers at Beaumont,
Oxford, and Whitewater.
- Commencing about 0800 CDT and ending between 1200 and
1230, Tuesday, April 29. Aircraft will fly Mixed Cat's Ears and
Stack.
- Commencing between 1300 and 1330 and ending around 1700
CDT, the two aircraft will fly Stacks and Triangles. In this
pattern, one aircraft will fly the triangles, while the other flies
the stack pattern. Both will be punctuated by pop-up soundings to
verify boundary-layer depth.
In all cases, the pop-up soundings will not only help dictate the
heights at which the aircraft will fly, but will be used for later
comparison with radiosondes and profilers.
We have requested support from the S-POL radar for at least the
daytime. The radar would do PPI scans to enable determination of
the wind field from tracking of eddies (TREC) and RHI scans for
still another look at the vertical structure of the boundary layer.
General Summary:
The first IOP studied a situation with increasing southerly winds
ahead of a developing low to the west and a slowly advancing cold
front to the north. The IOP was successful and should yield a good
data set. The JETEX group at Iowa State, under the leadership of
Ray Arritt and Moti Segal, joined us in the IOP.
The IOP commenced at 1500 LDT April 28 with the coordinated takeoffs
of the NOAA Twin Otter and the University of Wyoming King air, and
ended at 1900 LDT when the aircraft landed.
Summary by Instrument Systems:
Aircraft:
Three coordinated flight patterns were flown:
- ~1500-1930, April 28. One aircraft flew straight-and-level
crosswind legs at several levels in the boundary layer,
while the second alternated between low-level legs and legs
just below the top of the boundary layer. Triangle patterns
between the three ABLE profilers were flown at the beginning
and end of the pattern. The first will provide vertical
profiles of vertical fluxes; the latter pattern will yield
horizontal gradients over the experimental domain.
- 0900 - 1430. The NOAA Twin Otter (NOAA) and the Wyoming
King Air (WY) flew coordinated stacks to obtain flux
profiles. WY completed their pattern with a triangle. NOAA
landed at Augusta Airport between missions, while WY
returned to Ponca City to refuel.
- 1500 - 1700. NOAA continued flux stacks, while WY flew
triangles at the lower, middle, and upper parts of the
boundary layer. The triangles are particularly important
since the radiosonde launches are over. At the end of the
mission, the two aircraft flew triangles together.
During the patterns, the aircraft checked in to CASES Ops for
comparisons of boundary-layer depths to what we were seeing from
profiler and radar. The comparisons were fair, but it is clear we
need to learn to interpret both radar and profiler data better. The
flying scientists noted at the end of the mission that the
humidities were increasing rapidly through the day, and that a
low-level jet was observed upon landing at Ponca City. A great set
of missions.
Profilers:
Collected data in full spectral mode for entire IOP.
Radar:
The S-POL radar operated for the entire IOP. During the
day, TREC scans alternated with RHI scans. TREC scans track
reflectivity features to determine wind fields; it is assumed that
the features travel with the wind. The 360-degree scans also give
us an idea of the structure of the lower atmosphere -- in this case,
horizontal roll vortices parallel to the wind were observed. The
RHI (Range Height Indicator) scans are vertical cuts through the
atmosphere. They determine the depth of the boundary layer, and
provide a different view of boundary layer structure.
During the night, the radar operators noted several flocks of birds
migrating northward. The radar measured winds from the south at 16
m/s. However, the radiosondes only measured winds of 5-10 m/s, we
think the radar's high winds were actually migrating birds.
Boundary-layer depths in the earlier part of the day from the radar
seemed high; we speculated that measurement could also be flawed due
to migrating birds or insects. It was obvious that the Twin Otter
(which we saw) had flown through lots of insects.
The radar observed one unusual feature -- an unusual high, thin line
with no ZDR. It was at 5 km height, and stayed around for a long
time. It was located 60 km south of the radar, oriented zonally.
Radiosondes:
Were launched starting at 1630 CDT April 28.
The last launch was at 1500 April 29. Although there were some
problems, over 75% of the soundings launched successfully and have
reported good data.
Surface Data:
- NCAR: All eight NCAR stations were operating, all
systems operative except CO2 at the ASTER supersite (Site
7). There were short outages that caused loss of 13 minutes
of data at ASTER Site 8, and 1.5 h of data were lost at
ASTER Site 7. Soil moisture profiles were taken at both the
sites the morning of April 28.
- ABLE: The Smileyburg site weather data were
successfully collected. Flux data were more intermittent,
but problems should be resolved (this station was just
installed).
- NOAA: Station should be installed in the next few days
on pastureland.
The success of this IOP is due to some very hard work by a lot of
people out in the field through the night last night. Several
potentially major problems were turned into minor ones, thanks to
the dedication and professionalism of the CASES-97 team. We also
appreciate the help and cooperation of the Iowa State JETEX group
and the National Weather Service at Wichita.
Sunday April 27, 1997
Instrument Status:
Aircraft:
Aircraft are up and ready.
Profilers:
The profilers are all working fine, although
we will not have real-time data feed into the CASES Operations
Center until Tuesday at the earliest.
Radar:
The S-POL radar is working fine and ready to go.
Radiosondes:
The CLASS soundings are working fine.
Surface stations:
The PAM/ASTER surface stations are being debagged
today so that their humidity sensors will be
operational. Although the data feed between NCAR
and the ASTER base is down, no data is being lost.
The Qualls station sonic anemometer will be installed this
afternoon.
The NOAA Myers surface station is being shipped tomorrow.
The NOAA Smileyburg site is operational; we assume the
Towanda site is also.
JETEX:
The JETEX project is looking at a possible IOP
Monday or Tuesday.
Forecast:
Although the winds are from the ENE now, all models predict they
will turn around to the south by Monday afternoon at the latest.
Isolated showers are anticipated for Tuesday evening. Winds on
Tuesday morning will from the south.
IOP:
It appears as if Monday afternoon to Tuesday afternoon would be
the best time for an IOP, weather-wise. Depending on the pilots,
we might fly one coordinated flight Monday afternoon and two
flights Tuesday, and run the IOP from 1500/1630 Monday to
1500/1630 Tuesday. The other option is to start the IOP at
1800/1930 Monday night and fly only Tuesday. After consultation
with the pilots, we will decide which IOP to declare.
Saturday, April 26, 1997
Instrument Status:
Aircraft:
Aircraft are up and ready.
Profilers:
The Beaumont profiler is reporting data in
close-to-real time, but real-time data feeds for Oxford and
Beaumont will not be established until Tuesday at the earliest.
Radar:
The S-POL radar is operational.
Radiosondes:
The CLASS soundings are going up on schedule;
yesterday's sounding from Oxford looks very good, but the
Whitewater sounding reported no wind data (this problem has been
solved).
Surface stations:
The ASTER surface stations are
experiencing intermittent data-system crashes; staff are working
to rectify the situation.
The PAM stations are functional; the status of the crops
in Stations 3 and 5 are still unknown despite attempts to
contact the landowners. We are considering unbagging the
humidity sensors on Sunday afternoon.
The Qualls station is functioning well; the sonic anemometer
will be mounted when rain clears out.
JETEX:
The JETEX project does not plan an IOP for either
Sunday or Monday.
Forecast:
Light showers today and tomorrow morning, clearing by Sunday
afternoon. Northerly winds will dominate Sunday. On Monday
morning forecasters anticipate that the flow will begin
northeasterly and then switch through east to south by sometime
later in the day. Depending on the behavior of an influx of
moist air from the Gulf, isolated showers anticipated for Tuesday
afternoon might hold off until Wednesday.
IOP:
There is no IOP scheduled for Sunday. We are waiting for the
weather to see whether or not we will have an IOP Monday. Tuesday
looks more likely. (Flow from the ENE, which is expected Monday,
is the worst possible scenario, considering the orientation of
the surface stations.)
Friday, April 25, 1997
Instrument Status:
Aircraft:
The aircraft are both up and working properly. The
Wyoming King Air has used 2.5 of its approx. 60
hours. The NOAA Twin Otter has used 1.75 of its
approx. 50 hours. The total number of hours for
each aircraft is still subject to finalization.
Profiler:
The Whitewater power problem is being worked on today.
Radar:
The radar is tested and up.
Radiosondes:
The CLASS radiosondes for yesterday both went up,
but the Beaumont sounding could not make it past 700 mb.
Surface stations:
The ASTER team is having data system problems but
are working on them. The humidity sensors will remain bagged.
The Smileyburg site will bring smiles
to everyone's faces when it comes up tomorrow.
The NOAA surface
station is still waiting for installation.
Soil moisture probes (Cuenca/Kelly) are not in at Towanda, and
likely will not be installed until the latter parts of the CASES
experiment. The TRIME soil moisture equipment at ASTER
station 7 and 8 becomes much more important now.
Forecast:
The NWS is forecasting rain for tomorrow and Sunday,
but because we are on the north edge of the precipitation, rain
should be light, and we might escape the rain Sunday. Monday
looks clear and sunny.
IOP:
There is no IOP for tomorrow. There might be an IOP
Sunday, depending on the behavior of the system bringing in
slight rains. There is a strong chance of an IOP Monday.
Thursday, April 24, 1997
Wednesday, April 23, 1997
Tuesday, April 22, 1997
No rain is projected for Wednesday during the day, but there
may be some precip in the early morning Wind directions are
projected to change from NW during the morning to N and NE and
then E during the following 24 hours.
The NOAA Twin Otter flew today to check out the low-level flux
legs and radio communication. The UW King Air checked the
low-level legs yesterday. Both aircraft found the flux legs
acceptable. Aircraft communication was excellent.
NCAR surface and sounding systems are up. Argonne profilers
are up but not yet available at real time. NOAA station should
be installed later this week. Aircraft are operating.
There will be no IOP tomorrow. The weather situation is
marginal, since the surface stations are designed to measure
winds for winds from N through NW through W through S and wind
will be complex. Furthermore, the aircraft crews and pilots
are going through a planning exercise.
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