CASES-97 IOP Summaries

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
Wednesday, May 14, 1997
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

1Peggy 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:
  1. Two aircraft, two missions.
  2. Morning transition: 2-aircraft Stack + Cat's Ears. KA and TO switch roles, with KA doing Cat's Ears.
  3. 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:

  1. 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.
  2. 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).
  3. PBL mixing ratio significantly increased during the day.
  4. 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:

Up and running. See ABLE Homepage for an update.

Radar:

Up and running.

Radiosondes:

Up and running.

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:

No IOP tonight.

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:
Up and running.

Profilers:

Up and running. See ABLE Homepage for an update.

Radar:

Up and running.

Radiosondes:

Up and running.

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:

No IOP tonight.

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:
Up and running.

Profilers:

Up and running. See ABLE Homepage for an update.

Radar:

Up and running.

Radiosondes:

Up and running.

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:

No IOP tonight.

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

Instrumentation Status:

Aircraft:
Up and ready.

Profilers:

Up and running. See ABLE Homepage for an update.

Radar:

Up.

Radiosondes:

Up and running.

Surface Stations:

PAM/ASTER: Up and ready.

Qualls: Up and ready. Sonic will be dismounted this afternoon because of 30% chance of thunderstorms.

NOAA/MYERS: Up and running.

Smileyberg: Up and running except for the CO2 and H2O sensors.

Towanda (ARM): Unknown. Because the data is only downloaded in 2 week chunks, we will not be able to assess this station's operations until after the conclusion of CASES 97.

Julie Lundquist:

Sitting up. No running for a week.

JETEX:

No IOP tonight.

Forecast:

Sunday will see the passage of a trough in the early afternoon, followed by a frontal passage in the late afternoon. Showers/thunderstorms anticipated.

Monday will have N to NE winds throughout the day. Winds will change to easterly overnight, with a chance of scattered showers. Tuesday will see winds from E to SE to S (changing in the afternoon). Another chance of precip.

IOP:

Because the experiment is coming to a close, we exploring many possibilities for abbreviated IOPs. These possibilities include: a short IOP Monday morning, a full or short IOP Tuesday, and a short IOP Wednesday night. Standby for updates.

IOP 4 Summary

0600 - 2100 CDT Friday, May 16, 1997

Plan:

Aircraft:
Two aircraft, one mission.

Morning transition: 2-aircraft Stack + Cat's Ears. KA and TO switch roles, with KA doing Cat's Ears.2. Triangle + Stack. (King Air land at Augusta for lunch).

Balloon launches:

Each 1.5 hours from 0600 May 16 to 2100 May 16, 1997. Will be curtailed if severe weather threatens. Sonde operators should have adequate warning to get home in case of severe storms.

Profilers:

Collect data on all three in full spectral mode; Standard scans for all three profilers. Delayed power work at Whitewater.

Radar:

Scan from 0600 through 2100 May 16. During day, alternate between TREC and RHI scans.If storms enter the watershed, or if significant convection within 60 km of radar, storm scans will take higher priority.

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

  1. the boundary layer was growing into warming air with stable stratification.
  2. 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:

  1. 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.
  2. This confusion also held when interpreting the rather complex boundary-layer structure.
  3. 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:
Up and ready.

Profilers:

Up and running.

Radar:

Up.

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:

No IOP tonight.

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:
Up and ready.

Profilers:

Up and running.

Radar:

Up.

Radiosondes:

Up and running.

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:

No IOP tonight.

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

Wednesday, May 14, 1997

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:
Up and ready.

Profilers:

Up and running.

Radar:

Up.

Radiosondes:

Up and running.

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:

Intermittent crashing.

JETEX:

No IOP tonight.

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:
Up and ready.

Profilers:

Up and running.

Radar:

Up.

Radiosondes:

Up and running.

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:

No IOP tonight.

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:

Aircraft:
Two aircraft, one mission

Morning transition: 2-aircraft Stack + Cat's Ears. (Twin Otter land at Augusta for lunch). Triangle + Stack.

Balloon launches:

Each 1.5 hours from 0600 May 10 to 0430 May 11, 1997 (LDT).

Profilers:

Collect data at all three in full spectral mode; standard scans for all three profilers. Delay power work at Whitewater until after IOP.

Radar:

Scan from 0600 May 10 through 0600 May 11, LDT. During day, alternate between TREC and RHI scans.

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

  1. 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.
  2. the boundary layer depth decrease, as revealed from signal-to- noise ratio at the Beaumont and Whitewater profilers, was about 2 cm/sec.
  3. 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:

Observing systems worked perfectly, for the most part.

Aircraft:

Aircraft missions were conducted as planned, although the Twin Otter (NOAA) began the afternoon mission before the King Air (WY), allowing longer time coverage. Flight patterns were adjusted to accommodate for this change (WY mixed their stacks and triangles) and to accommodate a shift of the wind to SW (WY rotated their tracks to a more crosswind direction).

Radiosones:

After missing one launch at 0600, the radiosonde launches went well. We have started to include the sonde serial number in the datafile to help in post-experiment quality control.

Surface data:

NCAR stations seems to have worked well. The surface temperature at Station 6, reported as being questionable, seemed to work better yesterday. The Argonne Smileyberg site lost about 2 hours of eddy-correlation data, and the CO2 flux and humidity flux seems to be inoperative. The Qualls station worked well. The NOAA station status is unknown at this time.

Radar boundary-layer depth estimates seemed to correspond better with those from sondes and aircraft this time, as opposed to the earlier IOPs.

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:
Up and ready.

Profilers:

Up and running.

Radar:

Up.

Radiosondes:

Up and running.

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:

Operational.

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:

Aircraft:
Ready and waiting.

Profilers:

Operational.

Radar:

Ready and waiting.

Radiosondes:

Ready and waiting.

Surface Stations:

PAM/ASTER: With the exceptions of the krypton sensors (which have been disabled in preparation for storms tonight), all systems are up and operational.

Qualls: The sonic has been dismounted in preparation for storms. All other instrumentation is operational.

NOAA/MYERS: A team went out today to determine if it is functioning properly.

JETEX:

IOP tonight!

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:
  1. 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.
  2. 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.
  3. 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:

  1. The surface stations showed an interesting feature during the daylight hours that bears investigation.
  2. ASTER/PAM: The CO2 sensor at the ASTER supersite is now functional. Some data lost from ASTER #7 after 0400 local.
  3. ABLE: The Argonne site at Smileyberg is operational.
  4. NCAR: The NCAR sites are all operational.
  5. 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:
Ready to fly.

Profilers:

Operational.

Radiosondes:

Ready to go.

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:
Up and ready.

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:

Up and ready.

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:

No IOP tonight.

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:
Ready to fly.

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:

  1. 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.
  2. Commencing about 0800 CDT and ending between 1200 and 1230, Tuesday, April 29. Aircraft will fly Mixed Cat's Ears and Stack.
  3. 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:
  1. Three coordinated flight patterns were flown:
  2. ~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.
  3. 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.
  4. 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:

  1. 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.
  2. ABLE: The Smileyburg site weather data were successfully collected. Flux data were more intermittent, but problems should be resolved (this station was just installed).
  3. 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

Instrument Status:

Aircraft:
The aircraft are operational; the video on the NOAA Twin Otter has been fixed but not yet tested.

Radar:

The S-POL radar team sent out a chase vehicle with a disdrometer today to compare observed precipitation to that on the radar, and to 'shake down' procedures. They have had some minor transmitter problems.

Surface stations:

All the PAM/ASTER stations are up and taking data, although stations 3 and 5 require slight modifications. The krypton sensors are still bagged because of the precip.

The sonic anemometer at Qualls' site will not go up until at least Monday due to the rain. The NOAA tower will be installed tomorrow. Kelly is installing the rain gauges for the Cuenca/Kelly soil-moisture project.

Radiosondes:

CLASS soundings are going up as scheduled; data from those soundings is available at ftp://stout.atd.ucar.edu/pub/erik/cases/soundings.

IOP:

There will be no IOP until at least Monday, April 28 because of the rains expected in the area.

Schedule for radiosondes for April 25:

Whitewater: 1200 LDT
Oxford: 150 LDT

Forecast:

We are now experiencing a classic warm front. Precipitation will persist in the area through at least Sunday, with 70% chance of rain tomorrow and through the weekend. We hope for an IOP situation Monday or Tuesday.

Wednesday, April 23, 1997

Instrument Status:

The aircraft, radar, and the eight NCAR surface stations are all working fine. The Argonne surface station is being installed; completion is expected tomorrow. The CU surface station is complete except for the sonic anemometer, which will be installed when rain seems unlikely. The NOAA station is not yet in. The CLASS soundings are functional.

IOP:

No IOP is scheduled for Thursday, April 24 because of a forecast for rain that would interfere with the end of the IOP period. Also, winds are out of the easterly quadrant for part of the period.

Schedule for radiosondes for April 24:

Oxford: 1200 LDT
Beaumont: 1500 LDT

Forecast:

The weather looks complex and unsettled through Sunday; we may have to wait until Monday for an IOP. Thursday and Friday have strong chances of rain. Thunderstorms will move into the area Saturday and Sunday, certainly eliminating the possibility of an IOP those days.

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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