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April 2000

Plane talk: A Jeffco sampler

It sits on a windswept ridge more than 10 miles from NCAR's two main laboratories. It's a modest, aluminum-sided hangar that looks out over the mushrooming office parks, malls, and subdivisions of Broomfield. Though physically removed from the NCAR mainstream, ATD's Research Aviation Facility at the Jefferson County Airport is a center of activity. Scientists and technicians from across the institution meet at Jeffco to install equipment, shake it down on test flights, and embark on field programs.

Later this month RAF will open its doors to the public for the first time in more than five years to celebrate its flagship experiment of the new year: Tropospheric Ozone Production about the Spring Equinox (TOPSE). Watch This Week at UCAR for more details on the event. In this issue of Staff Notes Monthly, we provide a virtual open house with this sampling of recent RAF-related events, including a visit with the facility's new director (see below).

Next stop: Thule, Greenland

ACD scientist Lee Mauldin readies a probe for TOPSE on the side of the C-130. (Photos by Carlye Calvin.)

Some field projects are like mountaineering expeditions, with an exotic base camp from which forays depart. TOPSE is more like a bus route--if you can imagine a route over some of the most remote regions on earth.

The point of TOPSE is to understand why ozone levels in the Arctic's lower atmosphere peak in the springtime, says principal investigator Elliot Atlas of ACD. Ozone "leaks down" from the stratosphere into the troposphere, and it's also formed there by a variety of photochemical reactions involving sunlight, carbon compounds (from fossil fuel burning), nitrogen species, and water vapor. In the sunless polar winter, ozone production almost shuts down. Elliot calls this "dark side" chemistry: "There's not much happening--not much light, not much water. Then the sun comes up and photochemistry starts making ozone." Levels double, from 30-40 parts per billion to 50-60 ppb (still low compared to either the stratosphere or a heavily polluted city).

To capture the whole cycle from dark to light, the NSF/NCAR C-130 is making seven regular runs this spring from Jeffco, at 40°N latitude, to as far north as 85°N. The C-130 departs about every two weeks and is en route for about a week, staying at Churchill, Manitoba, and sometimes at Thule, Greenland. The first of these epic-length flights left on 5 February, and the last will return in mid-May. TOPSE's three-month span and long flight legs mean that the experiment will eventually record the winter-to-spring transition even in the farthest north.

This three-dimensional graphic shows the return trip of the thirteenth TOPSE flight on [DATE] March. The track from Churchill, Manitoba, to Jeffco appears as the broad, fuzzy-edged line. The aircraft shifted from less than 2,000 to more than 7,000 meters in altitude (6,600-23,000 feet) several times during the flight (back side of box). Ozone levels decreased from more than 400 Dobson units in Canada to about 200 units in Colorado. (Illustration courtesy Luca Cinquini, ACD.)

The mileage is only part of the story, though. On each deployment, the C-130 also zigzags from the boundary layer to the lower stratosphere and back. The legs from 5,000 to 20,000 feet give information on ozone and other trace gases in various levels of the atmosphere. The lowest-level flights may help to solve another mystery. Occasionally, surface air in some Arctic regions becomes completely depleted of ozone (see the UCAR Quarterly. The C-130 skims above Hudson and Baffin Bays to collect measurements related to these ozone depletion episodes. The low-altitude flights also gather data over leads (areas of open water, which are saltier than the Arctic ice).

For a guy with some very long flights ahead, TOPSE co-investigator Mike Coffee was all smiles just before the project began.

The ACD global and regional modeling groups are running chemical models driven by observed meteorology in near-real time to assist in the analysis of the TOPSE observations. Peter Hess and Andrzej Klonecki are running the regional model, while Xue-Xi Tie and Louisa Emmons are comparing results from the Model for Ozone and Related Chemical Tracers (MOZART) with chemical and meteorological data from the TOPSE flights. "It's the first time that we've been running the model at the same time that the measurements are being made and looking at them both, so it's pretty exciting," says Louisa. "For some species that we've compared so far, there seems to be pretty good agreement between the model and observations." She stresses that this finding is still very preliminary; the modelers haven't even received data from all instruments yet.

This is also the first time MOZART has been run using the observed winds that went along with observed chemistry, Louisa notes. "We've done quite a bit of comparisons of models and data, but always before we've been able to say, 'Well, the model was run using climatological winds, and the [real] meteorology was probably different.' Now we don't have that excuse." Additionally, they're looking at the results in much more detail than usual. A chemical model creates enormous quantities of data, so it's common to examine only monthly or even seasonal averages. "Now we're saving model results for every three hours," Louisa says. "We're seeing that [MOZART] generates quite a lot of variability, which is probably realistic."

Although the Arctic cold is part of what the TOPSE scientists are studying, it's also the enemy of their instruments. "It's a challenge, keeping complex equipment operating in a not particularly friendly environment," says Elliot. It can be especially hard at Churchill, where there's no hangar for the C-130. The plane was grounded there for a day by a blizzard with a wind chill of -90°C (-130°F). "The C-130 is heated, but in those conditions, everything that touches the floor freezes." RAF has used a number of heating systems to keep the instruments and aircraft warm while the aircraft is on the ground, including electrical block heaters for the engines and gas-powered heaters to keep the cabin warm. Principal investigator Chris Cantrell explains, "RAF staff must oversee these heaters 24 hours a day to ensure they continue to run. The RAF team has performed admirably in these difficult conditions."

"It's a tough experiment to do," Elliot sums up. "Each week seems like a month." However, he has nothing but kind words for the C-130 as an instrument platform. "It's quite a bus," he says.

Carol Rasmussen

The new manager settles in

Jeff Stith.

Jeff Stith started getting to know NCAR almost 25 years ago, during his days as a graduate student at the University of Washington. "Now I'm learning from a different perspective at a higher rate," Jeff says. After 19 years as a professor at the University of North Dakota, Jeff arrived at NCAR last summer and took over as RAF manager last August. He succeeded Paul Herzegh, interim RAF manager for nearly four years. (Paul is now back to full-time research, this time in RAP.)

One thing Jeff's getting used to is being surrounded by big planes. At North Dakota, Jeff worked with his university's Citation, a smaller, high-altitude aircraft that often probes thunderstorms. Today, NSF and NCAR maintain two sizable aircraft at Jeffco, the Electra and C-130. A large, high-altitude jet is in the works (HIAPER, see below). However, NCAR has flown smaller planes as well. A Sabreliner jet flew from 1969 to 1994. Also in the fleet for 16 years was a King Air, sold in 1997 to Flinders University in Australia. (The University of Wyoming has operated another King Air for NSF users for more than a decade.) Occasionally, NCAR scientists have used a sailplane that now sits in storage at Jeffco.

Big aircraft tend to support big science, and that's where things have been going in the past few years. "Usually these large programs are several years in the planning," notes Jeff. Each use of the aircraft must be approved by the Observing Facilities Advisory Panel (OFAP). This committee is managed by ATD and staffed by scientists from UCAR universities and NCAR. OFAP meets twice per year to consider requests submitted in the preceding months for ground-based systems and aircraft. Generally, more than half of the requests receive some funding.

Maximizing use of the aircraft within a given year's budget is "clearly one of the big issues that everyone struggles with," says Jeff. "If you want to study thunderstorms in the Midwest, you can't do it very effectively in January. If [OFAP] has two big projects for the same period, they'll assess the merits of the two projects--cost and other factors--and try to come up with a solution." Once a project is OK'd, "We start working with the scientists involved to make it a success--everything from trying to find a payload that's appropriate to the logistics side of mounting things on the airplane, developing flight plans, and trying to control costs."

One of Jeff's highest priorities is to coordinate with other institutions and build partnerships. NASA is a particular ally: "They also fly large airplanes, and a lot of times their objectives are similar to ours." Last year NSF helped RAF to secure a surplus C-130 from NASA. It's now at Jeffco, yielding parts that help to keep our first C-130 in flight.

Another acquisition made through teamwork is a cloud physics radar normally used aboard the Wyoming King Air. Under a new arrangement, the radar will be installed on the C-130 for specific projects, then returned to Wyoming. The radar spots small cloud droplets, helping to paint a better overall picture of microphysical activity. "This way we can share the radar and make it available to a wider set of users," says Jeff. "It's a good example of the kind of thing we'd like to do more of."

The biggest single upgrade now in the works for RAF is a high-altitude, long-range jet suitable for measurements near the troposphere-stratosphere interface. NCAR is now working on a requirements document for the proposed High-Altitude Integrated Airborne Platform for Environmental Research (see the November '98 issue of Staff Notes Monthly and the HIAPER web site). NCAR's plans to manage the HIAPER procurement were submitted in late 1998. Congress allocated $10 million in start-up money in fiscal year 2000, and NCAR hopes to receive the remaining project funds from NSF's Major Research Equipment account in FY01 or FY02. Under the current timeline, HIAPER would arrive at Jeffco for test flights in 2003 or 2004.

"We want to encourage more and better science throughout the community," says Jeff. "That means flying the best platforms, and it also means trying to get the best instruments and supporting the science in a variety of ways. I'm really happy with the direction we're taking."

Bob Henson

Surfing the Alps

A glider pilot who set world records for altitude in the 1950s, Joach Kuettner (see photo this issue in "Just One Look") now holds the UCAR Distinguished Chair for Atmospheric Sciences and International Research. He also heads the U.S. project office for the Mesoscale Alpine Project (see the October '99 issue of Staff Notes Monthly). MAP brought 120 Americans, including 60 UCAR staff (largely from ATD) to south-central Europe for its main field phase last fall. The project focused on two phenomena: mountain waves near the Alps (Dry-MAP) and heavy rains across northern Italy (Wet-MAP).

One of MAP's goals was to verify predictions of mountain waves "breaking" like ocean waves. Many airplane and glider pilots have experienced the sudden, dangerous turbulence of wave breaking. However, it's believed to occur on such small scales (less than 10 kilometers, or 6 miles) that only the highest-resolution mesoscale models of today have a shot at pinning down its location in advance.

The Canadian MC2 mesoscale model, with a resolution of 3 km, targeted areas of possible wave breaking on several days during MAP. NCAR's Scanning Aerosol Backscatter Lidar, mounted aboard the NSF/NCAR Electra, could not always verify these areas. However, according to Joach, a closer look at the SABL data may show that some breaking waves were in fact captured.

Among the MAP successes already documented are the first verification of potential vorticity (PV) banners predicted by mesoscale models. PV represents a blend of horizontal circulation and vertical stability. Since PV is conserved as it flows, PV banners that form near mountains can maintain their integrity far downstream. A PV feature "may travel for a thousand kilometers and help enhance a lee cyclone," notes Joach. On several days, the flight data hinted at PV banners to the north of the Alps (and off the Croatian coast during a bora wind event). The banners' existence was both predicted and confirmed by mesoscale models. NOAA's scanning lidar also provided unprecedented detail on "gap flow" as U.S. aircraft made numerous flights over Brenner Pass.

Not your usual European holiday

Ed Ringleman.

For Ed Ringleman, MAP provided a lot of piloting experience packed into a short amount of time. Still in his first year as an NCAR pilot, Ed accompanied first-in-command pilot Henry Boynton to Europe. Ed flew 13 of the Electra's 29 MAP missions, one of them with NCAR director Bob Serafin on board.

Ed says the MAP flights were "great for my confidence level, but also very trying." Takeoffs and landings on a relatively short runway added to the challenge of the mountain-wave flights themselves. The Electra was based at Innsbruck, Austria, where the airport lies within a valley only a few kilometers wide. Planes must descend at a steep 4-degree angle as opposed to the usual 2.5° or 3°.

Ed earned his private-pilot license right out of high school. He served as an aircraft mechanic at RAF for ten years and a flight engineer for five years after that. All the while, he flew on the side. Last May, Ed became the first NCAR pilot to be hired from within the RAF ranks. He is now working on his pilot rating for the C-130 and Electra. In the meantime, he alternates crew duties as pilot or copilot with the designated captain (Henry Boynton, Mike Heiting, or Lowell Genzlinger) as the second-in-command pilot.

"I've wanted to fly since I was a kid," says Ed. Thus far, he finds research flying an invigorating challenge. "The intensity level is high. It's an exhilarating experience. I don't think I'll ever get tired of this type of flying." •BH

Chills and thrills in the Arctic

A trek to the Arctic last summer gave RAF staff and collaborators some heated moments in their search for the coldest temperatures ever found aloft. The trip also marked the NSF/NCAR Electra's first trip to the North Pole.

That isn't just any patch of ice down there. Last summer the NSF/NCAR Electra made its first flight above the North Pole. (Photo courtesy Chet Gardner, University of Illinois.)

The Arctic Mesopause Temperature Study (AMTS) targeted the coldest part of the earth's atmosphere: the mesopause, about 85 kilometers (53 miles) above the North Pole in summer. The cold is caused by an upwelling of air over the polar caps, says principal investigator Chester Gardner (University of Illinois, UI).

Before AMTS, the highest altitude at which polar temperatures had been measured was about 30 km, using balloons. To sample the mesopause, Gardner collaborated with George Papen (UI), Jerry Gelbwachs (The Aerospace Corporation), and RAF to develop and deploy a new instrument, the Iron Boltzmann Lidar. It takes advantage of a layer of atomic iron in the mesosphere, the residue of meteors that burned up in this region. Iron absorbs light and re-emits it at certain wavelengths, giving a bright backscatter signal. The lasers in the lidar are tuned to two of those wavelengths. As the laser light passes through the iron layer, the resulting glow is detected by the lidar's two telescopes.

When Gardner and Papen left for Resolute Bay in Canada's Northwest Territories last June, "we were uncertain we'd be able to make the measurement. Our chemical models predicted very low iron densities." If the iron levels in the atmosphere were too low, the returning signal would be too weak for detection.

As the investigators flew north, the iron densities dropped even more drastically than expected. But on 21 June, on their first flight to the North Pole, Gardner and Papen noted a small iron layer developing around 100 km (60 mi) altitude. The iron densities increased steadily as the flight continued. Within a few hundred kilometers of the pole, the signal peaked at 250 times the levels observed on a flight to Sønde Strømfjord, Greenland. "We hadn't planned on observing an enormous sporadic layer [of iron]," Gardner says. "But that is why you do the experiment." Since the layer was also higher than expected, the team was able to infer temperatures up to 130 km.

On the return from the pole, the crew had to shut down one of the Electra's engines and use a fire extinguisher because of an alarm that later proved to be caused by a faulty sensor. RAF project manager Bruce Morley and Gardner both emphasize that the plane was not in danger: the Electra can easily fly on three engines. Still, it was hardly an everyday experience. In fact, before AMTS, Electra crews had only used the plane's fire extinguisher on an engine once. Oddly enough, Gardner and Papen were on board that time, too. "In a 1993 project to study Arctic noctilucent clouds, they actually had an engine fire," Morley says. "They were flying at night, and they could see flames coming out of the engine." The culprit was apparently an oil leak in the exhaust. Because of the fire's location in the exhaust, the extinguisher was not effective and the Electra was put into an intentional dive that blew out the fire.

By the end of last summer's experiment, the researchers had completed four flights to the North Pole as well as another flight to study noctilucent clouds. The final trip to the pole marked the Electra's first-ever flight into the stratosphere, just clearing the stratopause at around 29,000 feet near the pole. (In the tropics the stratosphere extends down only to around 45,000 to 50,000 feet.)

"The support was superb," says Gardner. "I've been flying with my colleagues in [RAF] for almost 15 years. Their concern about doing good science, their commitment to safety, and also their commitment to getting us back in the air when we had problems are outstanding."

In November, the lidar began a two-year stint at the South Pole, where it's measuring seasonal variations in temperature throughout the atmosphere, using scattering from the atmosphere to infer temperatures from about 25 to 100 km (15-60 miles) and the iron signal for higher altitudes. Already, the lidar has recorded temperatures over the Antarctic as low as -140°C (-220°F), and Gardner believes the values may go as low as -160°C in the summer polar mesopause--all in the presence of round-the-clock sunlight. The instrument also became the first lidar ever to document polar mesospheric clouds in the Southern Hemisphere.

"There are still a few very basic measurements that haven't been made, and this is one of them," Gardner says. "We're delighted that we have a crack at it. In some ways, it's still the golden age in atmospheric research." •CR

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Edited by Bob Henson, bhenson@ucar.edu
Prepared for the Web by Jacque Marshall