AUGSWAERO

Hypothesis: It is possible to obtain column closure on aerosol radiative properties measured at the surface, from vertical measurements with aircraft.

Our second objective was to provide aerosol data to the NASA BDRF campaign.

Who was involved: Pete Daum was the principal scientist.

Shortwave IOP The emphasis for this second Shortwave Radiation IOP (Warren Wiscombe, NASA-Goddard) will be on the clear sky since there will be no participating cloud physics aircraft and because the "atmospheric plankton" problem has not yet been remedied as of this writing. The main interest of the BDRF campaign also requires clear skies. Several uplooking spectrometers are planned for deployment at the central facility. These devices will cover the 0.4-1.0 and 0.4-2.5 micron widths. They tentatively include:

• Colorado State University SSP (solar spectral polarimeter; measures total flux and zenith radiance, and has polarization)
• SGP CART SWS (measures total flux)
• SGP CART RSS (measures total and diffuse flux separately)
• SUNY-Albany RSS-II (similar to RSS)
• SUNY-Albany UV Spectrometer

In addition, an enhanced level of broadband radiometry will be pursued for this IOP. This could include:

• NREL instruments, including windowed and unwindowed cavity radiometers
• SGP CART BORCAL (Broadband Outdoor Radiometer CALibration)
• SGP CART GRAMS
• SGP CART SIRS
• SGP CART RCF cavity radiometer

Also, use of the new SGP CART NFOV instrument and Raman Lidar retrievals of aerosol extinction coefficient is highly desired, along with use of the MMCR with some preliminary resolution of the atmospheric plankton problem and increased sonde launches during the middle of the day when the Gulfstream-1 is flying (mainly for humidity profiles). Aerosol IOP

The Aerosol IOP (Steve Schwartz and Pete Daum, BNL) will be featured by the Gulfstream-1 aircraft, which will begin clear-sky aerosol flights (similar to those made during fall 1997) on 11 August. The "G-1" has been contracted for 30 hours of flight time, which should allow for ten three-hour flights. Flight patterns will consist of a series of mid-day stepped legs over the central facility beginning at 500 feet AGL and ascending in increments to 17,000 feet AGL followed by a spiral back downward. In addition, some flights into stratus and ice clouds, and perhaps altocumulus from decaying convection, can be attempted as conditions warrant. The same measurement probes deployed during fall 1997 will be used again on the G-1, except for measurements of cloud condensation nuclei spectrum.

The operations of all three efforts will be coordinated to maximize the scientific potential of the experimental period.

We had 12 flights over a period of 11 (non totally overcast) days and typically obtained profiles to 18000 feet. We accumulated 25 flight hours.

Activity Summary

Wednesday, August 5, 1998: IOP Opening Activities: The IOP updates for the Shortwave/Aerosol/BDRF will be composed from notes taken during briefing sessions lead by Don Cahoon and company each night at the Marland Mansion in Ponca City. IOP Status as of 8/4/98 Weather forecasts indicate that cloudy conditions will prevail for the next few days. The Helicopter is on standby for clear sky conditions. Model output indicates clear sky's may move in later this week. BDRF Helicopter: Air space for the helicopter over the ARM site has been cleared by Vance AFB for the entire duration of the experiment. A tentative test flight for training and equipment testing may occur if marginally acceptable conditions occur today. Gulfstream-1: No information on the status of this aircraft as of yet.

Thursday, August 6, 1998: The IOP updates for the Shortwave/Aerosol/BDRF will be composed from notes taken during briefing sessions lead by Don Cahoon and company each night at the Marland Mansion in Ponca City. IOP Status as of 8/5/98: A training flight was made by the helicopter yesterday morning. An operational flight was made this morning during the clear sky conditions. This flight was made around 0750 local time. More information on the results from this flight will be received from tonight's meeting. Gulfstream-1: No information on the status of this aircraft as of yet.

Friday, August 7, 1998: The IOP updates for the Shortwave/Aerosol/BDRF will be composed from notes taken during briefing sessions lead by Don Cahoon and company each night at the Marland Mansion in Ponca City. IOP Status as of 8/6/98: Four operational flights where made yesterday 8/6/98 during the clear sky period in the morning. These flights were made at 0750, 0815, 0840, 1025 local time. The data collected during the 1025 flight was contaminated with cloud shadows and may be redone. These flights where made over a burnt wheat field on the Caughlin farm. Several flights were in progress this morning over a grass field. This is the location of the CERES surface station. Gulfstream-1: This aircraft will be on location on 8/10/98.

Tuesday, August 11, 1998: August 7: This was a great day! We were able to obtain seven bi-directional reflectance functions (BRDFs) over the grass field (our second highest priority). We made measurements for the 75, 70, 65, 50, 45, 40, and 35 degree solar zenith angles. Thus, over the grass field this leaves only two more solar zenith angles (SZA) to make measurements. Cumulus development began soon after the helicopter returned for fuel at the completion of the second flight. We used 4.5 hours of flight time today. The preliminary data looks good, but the variability of the grass is noticeable when compared to the soil BRDF's. For the first pattern in the morning, there were a few small patches of cirrostratus within 10 degrees of the solar disk. But the active cavity radiometer tracked smoothly in time indicating that there was no obscuration of the sun. These clouds burned off within a few minutes after the first measurement pattern began. The grass was very damp with morning dew for the first measurement, but quickly dried out by the third pattern (65 degree SZA). There was a very light haze this morning, and visibility was extremely good for at least 5 miles. There were no instrument malfunctions on either the aircraft or ground. We have had some difficulty with the fieldspec units occasionally locking up, and Bob Wheeler has begun to test the latest software from ASD. It will allow us to display calibrated radiances in real-time, unlike the current software that only displays counts. The MFRSRs still pose some alignment difficulties, but those may be completely resolved by tomorrow. Two balloon launches were made today prior to the helicopter arriving at the field site. The data is being analyzed and posted in notebooks everyday. Mark Wilson reports that he has written 10,000 lines of script since February in order to build the data system. I am not sure, but we may have some competition for Bruce Barkstrom! Tom Charlock has remarked about the high quality products that are being produced. Several of us agree that it would take several months for many other projects to reduce and present the data with comparable quality. Mark Wilson has done an excellent job developing this system. Now, we just need more clear sky!!!!! August 8-10: No flights were made because of the cloudy conditions. The helicopter and crew remain on standby. Gulfstream-1: This aircraft arrived yesterday afternoon and will be operational shortly. Tom Charlock has informed us that the Gulfstream flights will coincide with the satellite overpass times.

Wednesday, August 12: The information below records events from August 11, 1998. Once more we had broken multi-level cloud cover for the entire day, and once more we were on standby. In the afternoon, we did fly out to the grassland (Pawhuska) sites to make our final target selections. However, our selections are still not optimal by past standards due to the number of widely scattered watering holes in the area. We will have to examine any data acquired over the grasslands very closely. Alternatively, we could trade the grassland with small water pools on flat land for rolling grassland near the ARM extended facility that is located on the Tallgrass Prairie Preserve. We located this site during the flight and Tom is investigating the current operational status of this extended facility. This could possibly be a valuable validation site. The natural grasses on the prairie are less than a meter in height, but are very uniform. We met with the Battelle Northwest team this morning. We have defined the protocol for sharing airspace with them when we have to opportunity to fly simultaneously. This was largely worked out by the two pilots who were comfortable with the arrangements. The Battelle aircraft flew today and will try to fly each day during the CERES optimal overpass times. Thus, even with cloud cover, they will be making aerosol and possibly cloud microphysical property measurements on a daily basis. The Gulfstream made a flight over the ARM CF around 1900 GMT.

Thursday, August 13, 1998: The weather is not cooperating! Once more we had broken multi-level cloud cover for the entire day, and once more we were on standby. No flights were made by the helicopter because of the cloudy conditions. The Gulfstream did not make a flight today. Plans for 8/13: Two satellite overpasses will take place on 8/13. The Landsat will pass over the SGP area around 11 am local time and the CERES satellite will overpass around 3 pm local time. If mostly clear sky prevails the helicopter may fly to gather data in situ with both satellite passes. A discussion with the G1 team and Tom Charlock will take place on 8/13 at 9 am at the Ponca City airport to determine possible flight times for the G1 in conjunction with these activities.

Thursday, August 14, 1998: Well, today was slightly more entertaining than the previous n days (where n is too big of a number to appreciate). We did not have perfect sky conditions, but it was sufficient to make simultaneous measurements with Landsat. This activity was in cooperation with Gouyong Wen (GSFC, U. of Md.) and the PNL Gulfstream aircraft team. Gouyong used his fieldspec unit to measure surface reflectivity of the fallow wheat field. From the air we flew several lines across both the fallow wheat field and the grass field. During each pass we collected data from all of our nadir-oriented airborne instrumentation. Our nadir footprint, at 1000 feet, is about the same as a landsat pixel. Gouyong would like to compare our measurements to the Landsat imagery acquired today. As for the sky conditions, there was high cirrus to the southwest and cumulus creeping in from the northeast. Blue sky was above us at the time of the overpass, but the clouds began to creep overhead within minutes of the overpass time. Cloud shadows from the cumulus made the timing of the fallow wheat field fly-overs difficult. Some of our data is cloud shadow contaminated. The Gulfstream made 10 passes over our grass field site while making aerosol measurements. They began at 500 feet and increased their altitude on each subsequent pass to a maximum altitude of about 16000 feet. They reported haze up to about 6500 feet. All of their instruments worked nominally and quick-look data products will be available within a couple of days. Today during the Landsat overpass, we had three fieldspec units running simultaneously. One 5 degree field-of-view nadir pointing unit on the helicopter, one upward looking hemispherical unit on our trailer, and one 18 degree field-of-view unit with Gouyong in the fallow wheat field. All three units locked up during our measurement period, and in each case the problem occurred during optimization. However, each of the three units did recover after being rebooted. Despite the confidence that has been gained in the fieldspec calibration and measurements, this random problem is very frustrating. At the completion of the Landsat overpass measurements, we conducted two practice BRDF's for proficiency training. Bob Wheeler was the Mission Director onboard, Kevin Larmen operated the data acquisition system, and Eric Feldl ran the scanning pod. This was done under cirrostratus and broken cumulus. The data is not useable, but the training exercise was needed. Also, we completed the required flight hours to have the next maintenance cycle completed on the helicopter. We now have up to 14 flight hours before another inspection must be completed. Given the opportunities for clear sky the next few days, this was a strategic move on our part.

Saturday, August 15, 1998: Finally, we had a wonderful morning. The skies were clear enough to complete 5 wonderful looking BRDF's. For Milo, we completed BRDF's for the 75, 70, and 65 degree solar zenith angles. For fallow wheat, we completed measurements for the 50 and 45 degree solar zenith angles. Cumulus began to develop rapidly overhead with the mid-morning heating and the 40 degree measurement was aborted. All of the data looks good. We have now completed over half of our priority BRDF measurements. Currently, the weather looks favorable for a few more days. However, it will be difficult to get the mid-day solar zenith angles due to the persistent cumulus development. The helicopter fieldspec unit experienced a lock-up 3 times today, but the ground unit ran flawlessly. These instruments are essential to the work that we are doing and do perform very well overall. The latest fieldspec software that we have tested here is quite impressive. We can now view calibrated spectra in real-time. Surface activities continue to run smoothly. For each of our two flights, a radiosonde was launched. The ACR tracker computer problem was solved by substituting the old PC with a newer laptop. Ken Rutledge found that the faster computer can do a better job at running the sky scanning routines. The older computer is being tested to find the fault. Each day something new is learned about our instrumentation and we continue to explore a number of alternative operations at the request of the CERES science team. The gulfstream flew today in coordination with the CERES overpass. At 12,000 feet the atmosphere was dry and clear. Cumulus bases were around 6000 feet and had tops that reached 7000 to 8000 feet. The gulfstream entered many clouds in order to gather as much cloud statistics as possible. SEE BELOW FOR MORE DETAILS. Tom Charlock has been probing ARM about the status of the E-12 Pawhuska extended facility. This facility is located in the tallgrass prairie. The NIP and the PSP's were calibrated as recently as June. The E-12 tracker is having a problem, but by next week this problem should be corrected. This site could easily serve as the surface observation site for some limited BRDF measurements in the grasslands. This approach could be especially helpful if, due to weather, we begin to run out of time and cannot move our BSRN ground station to the grasslands. G-1 operations 8/14/98: The G-1 made an afternoon flight starting at 1330 local time. Objective of the flight was to characterize cloud and aerosol properties over the CART site in support of the CERES afternoon overflight. Aerosol loading was quite high in the boundary layer which extended up to about 5000 ft msl. Encountered scattered fair weather cumulus with bases at approximately 6000 ft. In some instances cloud top extended to 10,000 ft but most of the clouds topped out at below 8000. Worked the cloud layer at various altitudes for about 1 hr, then returned to Ponca City.

Sunday, August 16, 1998: Another good morning for the aircraft crew. We were graced with clear skies until 1100. This gave the us time to have two flights and complete 6 BRDF measurements. Today, we completed three BRDF's over the Soybeans (75, 70, and 65 degree solar zenith angle). It is worth noting that soybeans are the 4th priority crop type. We are working our way down the list! We also followed up on yesterday's Milo measurements with 3 more today at 50, 45, and 40 degree solar zenith angles. It is worth noting, that thanks to the many long hours of planning by Carl Purgold, the correct timing and flight planning to make all of these measurements runs extremely smoothly...like a Swiss watch! Given our current assessment of where we are toward mission completion, will make measurements over our fifth (and final) priority target tomorrow morning. While we wait for clear skies during the solar noon window, we will begin to conduct some of our secondary measurements. As TRMM overpasses occur earlier in the day, we can hope that in a week we will be finally able to make the ARM albedo flights. We have not made any albedo flights because of the cloud shadows from the cumulus. G-1 Flight Operations 8/15/98: The G-1 flew in support of the CERES overflight. Takeoff was at 1400 CDT, landing at 1600 CDT. Skies were partly cloudy with some fair weather cumulus. Temperatures were in the low 90's. Winds were calm at the surface. Aerosol concentrations were modest in the boundary layer with concentrations generally in the range of 700 - 900 cm-3. Boundary layer height was about 7,000 ft msl. Scattered fair weather cumulus with tops at about 7500' msl were found at the top of the boundary layer. Multiple transects were made through these clouds. Air was very clean above the boundary layer until about 13,000' where a layer of aerosol particles was encountered. The layer extended above our highest altitude which was 17,500 ft. Another flight in support of the CERES mission will be made at 1230 8/16.

Monday, August 17, 1998: This morning skies were completely clear, even for the first flight. Cumulus development did not begin until after noon. Since it appeared that the clear skies would linger a little longer today, we decided to attempt the reflectance mapping around the ARM site during the CERES overpass. Once again our efforts were foiled after we spent about 1.5 hours configuring the helicopter for spectral reflectance mapping. An additional 1.5 hours was required to reconfigure for spectral BRDF's which we will fly tomorrow morning. Not only was this configuration time significant, but temperatures are approaching 100 again and the hangar is a very uncomfortable place. Our measurement strategy will will be refined. We completed 3 more BRDF's today. For soybeans, the 50 and 45 degree solar zenith angles have been completed. For Milo, the 40 degree solar zenith angle has been completed. We had sustained winds of 20-30 mph on the ground during these BRDF flights. The quality of the data is amazing considering the difficulty of making the measurements under these windy conditions. Both our pilot, Bill Geloneck, and our scanning pod operator, Eric Feldl, did an outstanding job 'flying the line' and staying on target, receptively. Bob Wheeler was the mission director (MD or mad dog) on the flight, and Carl Purgold served as the instructor and the coordinator of the flight planning. Kevin Larman was the data system operator. We completely juggled our flight crew around and have demonstrated successful cross-training. It is worth noting that the on the solar cross plane pass over the soybeans, that this line was parallel to the winds at the surface. With the soybeans as much as a meter high, they were substantially blown over toward the north. We believe a change in reflectance is clearly discernible in the data. The blowing soybeans certainly created some noise in our data, but at least is very interesting noise. The helicopter has undergone another vibration test this afternoon and passed. We are now cleared for another 25 hours of flight time. As of today, we have flown 24 hours since we have been here. We had projected 60 hours of flight time, thus we are in no danger of exceeding our budget. It was another routine day for surface activities. We had two balloon launches timed to the BRDF flight and to the potential second flight. Each balloon launch had assistance from the Caughlin family, particularly the younger members. We had moved the fieldspec from the field site to the ARM central facility site in order to support the potential helicopter measurements. The instruments continue to function nominally and data was collected and brought in to the archive today. The data processing is completely caught up and running smoothly. In preparation for Mark Wilson's return to LaRC, Joanne Saunders is now running the data processing system. This system is designed to serve as the permanent archive for all of our data and to produce level 0 (voltages, counts,...) and level 1 (calibrated) plots. The level 1 plots are now available via our web page at http://sundog.larc.nasa.gov/~Ceres/okla98/. Other information about this activity can be found on our web page. We have decided to call this campaign CARE (CERES/ARM Radiation Experiment). After all, we are a NASA project and need to be referred to by an acronym. The gulfstream flew today during the CERES overpass despite the cumulus development, but they would also like clear skies during the overpass times. Pete Daum reported that they detected the boundary layer up to 9000 feet and that the cumulus development was on top of the boundary layer. Aerosol concentrations were still quite high above the boundary layer and by 16,000 feet, the air finally dries out. [This is consistent with our sounding and MPL data at the field site.] They will continue to time their flights to the CERES overpasses. SEE BELOW FORMORE INFORMATION. G-1 Flight Operations 8/16/98: G-1 flew in support of the CERES overflight at 1347 CDT. Takeoff was at 1230. Sky was mostly clear at takeoff, but shortly thereafter fair weather cumulus started to form in the area. Aerosol concentrations were moderate in the boundary layer. Accumulation mode number density was 800-900 cm-3 in the boundary layer which extended to about 8600 ft. Fair weather cumulus were found at the top of the boundary layer with some tops extending as high as 12,000 ft. Above the boundary layer aerosol number densities were significant (~200 cm-3) up to 16,000 ft. Above this altitude dewpoints decreased to -35 C and aerosol number densities decreased to about 10 cm-3.

Tuesday, August 18, 1998: This was a banner day! The clouds did not build up quick enough today to prevent us from completing our low solar zenith angles for our top 4 priority crops (fallow wheat, grass, milo, and soybeans). Some very small cumulus clouds began to develop during the flight, but never blocked the sun or casted significant shadows. The data looks very good. However, again we noticed some wind effects. The flight team, Carl Purgold, Bob Wheeler, Eric Feldl, Kevin Larman, and Mark Wilson, have all done an outstanding job of acquiring our BRDF data! And, I must also commend the skill and patience of our Army flight support team, Bill Geloneck and Manny Gutierrez! Without them this exercise would not be not possible. We also completed two mid-morning BRDF's for alfalfa and milo. Unfortunately, our early morning alfalfa BRDF's will have to be discarded due to a time synchronization problem with our aircraft computers. This time synchronization problem resulted from a GPS lock failure in the early morning hours. Otherwise, we have completed all of the cropland BRDF's that we had planned. Our ground crew reports that it was another routine day for them and everything is functioning nominally. Our surface team launched three balloons today. The third balloon was launched within 5 minutes of the cumulus development. Ken Rutledge and Fred Denn have done an exceptional job of providing high quality surface data. Their daily activities include cleaning the many instruments and windows to remove the ceaseless supply of dust, launching balloons, verifying the proper operation of all instrumentation, and downloading the data for transport to the archive (sneakernet). The gulfstream continues to dependably fly at the CERES overpass time. Today their profile was from 500 to 17,000 feet (I am uncomfortable using these atheist units, but the aero folks still cling to this...all of them...I guess I could convert these numbers to something rational like meters...naw). They found aerosol number densities to be similar to the past few days. The top of the boundary layer was found at 8500 feet and the cumulus development began at this level. They estimated that the cloud shadows only covered 10-20% of the surface during their flight. This is low compared to the past few days. It is with regret that I announce Tom Charlock's return to Langley Research Center. It was a pleasure for the entire team to have Tom around.

Wednesday, August 19, 1998: Since we have completed almost all of our BRDF measurements and the TRMM/CERES overpasses have slipped from late in the day (around August 8) to mid-day, we are now beginning to make our flux maps (we often refer to these as our albedo maps). Given the uncertainty of the weather and the necessity for mostly clear skies, for several solar zenith angles we will map out a 21x21 km box centered on the ARM central facility. Today we flew our patterns at 1000, 1100, and 1300 CDT. The 1300 flux flight was coincident with a gulfstream and TRMM/CERES overflight. The expectation is that the flux maps can be used for other satellite remote sensing investigations in addition to CERES. The aircraft instrument team reported that the fieldspec failed during one of our flights today. Fortunately, only a few seconds of spectra was lost. It is also worth noting the PSP and PIR data was uninterrupted. The surface instrumentation team moved the ground-based fieldspec to the ARM Central Facility to support the flux flights. There were three radiosondes launched today and the last one was launched with the assistance from the 4-H'ers (not to mention that it had some interest from the film crews). Today Ken Rutledge contacted our grassland ranch site and set up a surface team visit for tomorrow. As we transition to the grasslands, we will maintain our instrumentation at the ARM Central Facility and cannibalize our field site. We will carry a full BSRN suite of instrumentation with only the exception of the ACR. The ACR needs a computer controller which requires environmental controls. Since we are only expecting 3-4 days of flights over the grasslands, we want to move a minimum required set of instrumentation and not the trailer. Later this evening, our data processing system will be up-to-date with processing both the aircraft and surface data. Mark Wilson continues to amaze us with his magic. The data processing system is advanced and calibrated data is available for review within 24 hours after being recorded. Our web page is only 24 hours behind in posting our quick look data products. All is well, but we are in a continuous state of flux trying to balance the weather, CERES overpasses, gulfstream overflights, science, and most importantly, human limitations. This team is responding to our mission challenges in a very professional manner and we are trying to minimize the overall impact on the individuals. Saturday has been declared a day off! I would like to thank Carl Purgold for his daily flight mission planning. Give Carl the place and time that you want to be there and he will tell you when you are leaving, when you will get there, how long you will be there, and when you will land.

Thursday, August 20, 1998: Today the helicopter had another coincident flight with both the gulfstream aircraft and TRMM/CERES. We flew a 21x21 km pattern which is turned about 45 degrees on a corner. Thus, our flight legs are running in a southwest to northeast direction. This pattern was flown at 0900 and 1200 CDT. We had clear skies until the last few minutes of the 1200 CDT pattern and a few shadows were present. The onboard video recorder captured the cloud shadowing along the aircraft's path for later review. The fieldspec experienced considerable trouble during the second flight today. It is believed the entire unit may have experienced a heating problem after sitting in the helicopter on the tarmac for a couple of hours (keep in mind that this unit is bolted securely into the floor of the helicopter). After the helicopter reached 3000 feet on the second flight the unit began to behave appropriately (due to cooling?). The surface team visited the grassland site and has begun to disassemble our cropland field site for movement. Don Caughlin has been helping out by using a hydraulic lift, on one of his tractors, to pull our long grounding stacks out of the ground. He and his family have been extremely interested in our research and have been very helpful. It has been a real pleasure to work with them. They are willing to let us leave our power pole in their grass field in case we want to return to the site in the future. In support of today's helicopter and gulfstream flights, there were two balloon launches today. The gulfstream reliably flew again today coincidentally with the CERES overpass. Their flight altitude ranged from 500 to 17500 feet. The boundary layer was lower today when compared to the past few days. Dew point temperatures were swinging widely and the particulate concentrations followed the dew point. The mixed layer had half the particulate that were found in yesterday's mixed layer. There were a few sparsely distributed cumulus clouds. We are now doing our detailed planning one day at a time. We are constantly adjusting flight priorities to maximize our data collection and finish our cropland flights. This is quite an adjustment from the well prioritized BRDF flights. Despite the amount of time that we have been in the field, everyone is holding up rather well. G-1 Flight Operations 8/19/98: The G-1 flew in support of the CERES over flight @ 13:23 CDT. Take off was at 10:55. Sky was clear at takeoff with sparse cirrus to the south. A sparse layer of fair-weather cumulus formed during the flight. Aerosol concentrations were moderate in the boundary layer. Accumulation mode (PCASP) number density was 400 to 800 cm^-3 through the boundary layer at ~4500' (MSL). Above the boundary layer, there was considerable stratification corresponding with multiple visible layers. These layers stopped at ~13,000. Dew points varied from +15 to -25C above the boundary layer corresponding with visible layers and particulate levels. During the descent the fair-weather cumulus layer had increased with the boundary layer rising to 6500'. The G-1 landed at 12:45.

Timeline

Campaign Data Sets