HIPPO Flight Lands Safely

After five missions and more than 50 flights, the HIPPO Project is finally back on the ground.

The atmospheric testing project wrapped up its final mission last week, and has already helped to paint a more complete picture of how greenhouse gases are distributed in the atmosphere.

HIPPO, which stands for HIAPER (High-Performance Instrumented Airborne Platform for Environmental Research) Pole-to-Pole Observations, “was intended to obtain a high resolution cross-section of the atmosphere” according to the Lead Principal Investigator, Harvard Professor Steven C. Wofsy.

Data regarding the distribution of greenhouse gases through the atmosphere has previously been collected from the ground and from satellites, Wofsy said. But this experiment was performed from a plane that continuously seesawed up and down from 500 feet to 30,000 feet, which provided an accurate picture of the stratigraphic layers of the atmosphere.

“You visit the surface of the planet every 25 minutes, and then you go into the stratosphere again,” Wofsy explained.

The first experiments of this type occurred in the late 1970s, according to Wofsy. However, that project was limited by the aviation technology of the time, namely a turboprop aircraft that did not have adequate range to carry scientists and measuring instruments up and down throughout the stratosphere.

Because of this, Wofsy had long been wanting to try the experiment again. When a suitable grant popped up in 2006, he jumped at the opportunity—this time planning to use a specially-equipped long-range Gulfstream V aircraft of the type usually reserved for moguls and CEOs.

After obtaining the grant and the use of the plane from the National Science Foundation, Wofsy planned five different three-week-long missions at different times of the year, each consisting of more than 10 eight-hour flights. Each mission hopscotched from the North Pole to the South Pole, and then back again.

Wofsy, along with his team and specialists in black carbon particles from the National Oceanic and Atmospheric Administration, has already found surprising results, and there are more to come as the information is processed.

In addition to creating the clearest cross-section of greenhouse gases at high altitudes, the project provided a tremendous amount of new information about black carbon particles—human-caused emissions resulting primarily from fires and diesel fuel—that are difficult to measure at the surface. It had previously been thought that these particles were distributed roughly evenly throughout the atmosphere, but they were instead found in dense clumps, Wofsy said.

In addition, Wofsy and his team found quantities of nitrous oxide, a greenhouse gas, high in the atmosphere, where it had not before been observed.

Wofsy emphasized that there is still more work to be done, and many of the findings remain unpublished. However, the study may prove important in the continual effort to understand the processes of global warming and greenhouse gas emission.

—Staff writer Joseph E. Glynias can be reached at jglynias@college.harvard.edu.