The workhorse for the RACORO field campaign, the CIRPAS Twin Otter, comes in for a landing after completing a research flight.
The workhorse for the RACORO field campaign, the CIRPAS Twin Otter, comes in for a landing after completing a research flight.

“Wheels down.” That’s the term pilots use to log the end of their flight. After five months, the Routine AAF CLOWD Optical Radiative Observations, or RACORO, field campaign recorded its final wheels down. In the first long-term aircraft campaign of its kind, the RACORO team logged 59 flights and 259 research hours above the ARM Southern Great Plains site between January and June. Data gathered during this campaign will provide researchers with a statistically relevant data set of boundary-layer clouds and aerosols for future study.

"This long-term campaign enabled sampling of a sweeping variety of low-level cloud conditions from a single platform, which was precisely the goal of the program," said Andy Vogelmann from Brookhaven National Laboratory and the principal investigator for the campaign. "Over the months, we encountered stratus, cumulus, and finally cumulus towers as the summer months started to heat up, for which comprehensive aircraft measurements were made of their cloud microphysical properties, radiative fields, aerosol properties, and atmospheric state."

The prolonged campaign was an experiment in itself, as the team couldn’t predict the conditions from several months out. For instance, between January and March, the climatology for the area was unusually dry. It was several degrees warmer than average with 20-40% of average precipitation, and drought throughout much of the southern United States. The lack of moisture resulted in fewer cloudy days at the start of the campaign than expected.

These conditions associated with La Nina actually started in the fall and carried over through the winter. However, the conditions transitioned to more spring moisture and the flight hours ramped up significantly in April and May. In fact, the conditions in May resulted in some of the best cloud cases of the campaign.

“During the planning phases we tend to focus on acquiring statistics of the cloud fields," said John Hubbe, field operations leader for the ARM Aerial Facility. “The RACORO Science Team and the pilots did a great job of adapting the operational plans to the seasonal variability we experienced at the beginning of the campaign.”

Scientists on the RACORO steering committee rotated in two-week stints throughout the campaign. Working in pairs, they participated in weather briefings and, based on circumstances, set the flight priorities to cover the broad range of science objectives possible with this campaign.

Forecasters on Call

Because of the nature of flight operations, almost daily weather briefings took place throughout the campaign—sometimes even twice a day—to plan, confirm, change, or scrub the planned flight. The team also used the forecast to make tentative flight plans for the next day or two. This is because the pilots need to file them with the Federal Aviation Administration the day before a flight.

Throughout the lengthy campaign, forecasting duties rotated between Daniel Hartsock, the SGP site meteorologist, and Justin Monroe of the ARM Data Quality Office at the University of Oklahoma.

"The skill and dedication of our forecasters was outstanding," said Vogelmann. "They live in the area, so in addition to what the forecast models show, they provided local insight to the science team based on their personal experiences with the weather.”

Among the suite of tools they used to prepare for each weather briefing, they pulled the results of several different forecasting models into a single tool called "BUFKIT." Developed by the Buffalo Office of the National Weather Service, it enables displaying forecast views from different models that show a multitude of atmospheric state conditions—clouds, ice, temperature, pressure, mixing/boundary layer, wind speed and direction, potential energy, etc. From this information the team can see how deep the boundary layer will be, where and when convection is going to fire up, cloud boundaries and conditions at various altitudes, and the potential for rain.

"We relied on our forecasters to provide an integrated view from the different models, particularly in the tricky storm season when subsequent model runs could be very dissimilar and storms could potentially develop rapidly—conditions we certainly wanted to avoid putting our pilots into," explained Vogelmann.

Outreach Gets a Lift

Back in March we reported on some school visits in the Guthrie area by operations staff working on the RACORO campaign. Subsequent outreach activities in May and June resulted in several visitors to the hangar and SGP site, including a few prominent stakeholders.

 Dan Rusk (left) provides Anna Palmisano an informative and comprehensive guided tour of the SGP site.  Brad Orr (center), SGP site manager, hosted her visit along with Doug Sisterson, ARM operations manager. (Photo by Doug Sisterson)
Dan Rusk (left) provides Anna Palmisano an informative and comprehensive guided tour of the SGP site. Brad Orr (center), SGP site manager, hosted her visit along with Doug Sisterson, ARM operations manager. (Photo by Doug Sisterson)

In May, while still in Guthrie, ARM operations staff were invited to participate in a tour of the airport along with several Oklahoma dignitaries, including the Oklahoma Lieutenant Governor Jari Askins, and the Chief of Staff for Congressman Frank D. Lucas, Ms. Stacey Glasscock. After the tour, the group met in the airport boardroom where Debbie Ronfeld, AAF logistics specialist, described the field campaign and Dan Rusk, SGP site operations manager, described the ARM and specifically the SGP site. Everyone reacted with surprise upon hearing that Oklahoma had this type of facility and a few showed interested in touring the site.

After flight operations were moved to Ponca City in June, Ms. Glasscock and two of her colleagues drove up for a look at the Twin Otter and to tour the SGP site. Prior to their visit, Dr. Anna Palmasino, associate director for the Office of Biological and Environmental Research within the Department of Energy’s Office of Science, also visited the Twin Otter on her way out to tour the SGP site.

Later in June, a group of 13 students and their advisers from the Research Experiences for Undergraduates at the National Weather Center at the University of Oklahoma came by the hangar for a tour of both the Twin Otter and NASA's King Air. Many of the students commented that it was very different from their other field trips and that it was interesting to see what goes into a field experiment.

And finally, a connection with the Discovery Channel led to a blog about the campaign during its last month of flight operations in June. Available on the EarthLive website, the Skinny on Thin Clouds blog includes additional insights into daily life during an aircraft field campaign.