NASA - National Aeronautics and Space Administration

Slicing through the atmosphere from 28,000 feet, High Spectral Resolution Lidar (HSRL) from NASA’s Langley Research Center can see some of the smallest atmospheric particles, including natural and human-made components.

HSRL's perspective -- the 3-D view -- brought a new dimension to the recent Cumulus Humilis Aerosol Processing Study in Oklahoma. Researchers were scouting out the aerosol plumes from metropolitan areas like Oklahoma City.

Cumulus humilis is the scientific term used to describe the small, fair-weather clouds that dot the summer skies over Oklahoma. During June, the NASA team and other scientists sponsored by the U.S. Department of Energy’s Atmospheric Science Program used aircraft and ground-based instruments to obtain information about the physical and chemical properties of these clouds and the small airborne particles -- called aerosols -- within and around them. Aerosols, particularly those associated with human activity, are thought to be changing the brightness, the lifetime, the amount of precipitation and other properties of clouds.

Image right:The primary goal of the CHAPS campaign is to characterize and contrast freshly emitted aerosols above, within and below fields of cumulus humilis (or fair-weather cumulus). These observations will be used to examine the aerosol optical properties and cloud nucleating properties from both below-cloud and above-cloud, and how they differ downwind of a mid-size city relative to similar aerosols in air less affected by emissions. Click on the image to view a larger version. Credit: Pacific Northwest National Laboratory

During the campaign, the HSRL instrument flew on a NASA King Air B200 aircraft, based at Langley. This twin engine turboprop flew at altitudes of around 28,000 feet, conducting scouting missions to identify the Oklahoma City plume. The King Air also flew with the Department of Energy’s Gulfstream-1 aircraft to make simultaneous remote observations of fields of clouds and aerosols. These coordinated measurements are important for the CHAPS team to better understand the interaction of clouds and aerosols.

Despite an unusually rainy period, researchers were able to meet their science goals during the mission. "It was successful from the standpoint that our instrument and aircraft worked really well," said Mike Obland, NASA postdoctoral fellow working on the project. "We got a lot of data during the campaign."

Aerosols were somewhat elusive during most of the month-long campaign due to the inclement weather. "We were trying to locate plumes coming out of the city," Obland said. "Unfortunately, the plume had lower aerosol loading than expected. The rain was really cleaning out the atmosphere."

The HSRL technique provides a picture of a slice of the sky, highlighting atmospheric layers and components. The instrument is similar to radar. However, with lidar, radio waves are replaced with laser light. The advanced HSRL makes measurements that can even distinguish among different aerosol types and their sources.

Image left:A view from the inside of the King Air B200 showing Mike Obland, a postdoctoral fellow with the HSRL team, with the HSRL instrument. Pilots Rick Yasky and Les Kagey flew each day of the mission, and other crew members who made the flights possible were co-pilots Mike Wusk and Howard Lewis, and mechanics Dale Bowser and Scott Sims. Credit: HSRL team.

The King Air was specially equipped so that the researchers can transmit the laser out of a window in the bottom of the airplane and use a telescope to measure the amount of light that scatters back from aerosols and other atmospheric components like water droplets in clouds.

During the campaign, the HSRL team adopted some new capabilities, downlinking data in real time to the ground and to the Web.

"We felt that being able to broadcast our real-time data on the Web was a really important mechanism to incorporate, and it worked out well," said John Hair, co-principal investigator for HSRL. "People who weren't actually there in Oklahoma could be a part of what was going on and view data essentially real-time for the HSRL instrument."

With their new downlinking capabilities, members of instrument team were able to share data with their field campaign collaborators while making real-time flight track decisions. These real time flight track decisions were essential in tracking plumes and in choosing flights with the best observation opportunities.

This study was part of a larger campaign, the Cloud and Land Surface Interaction Campaign, or CLASIC, to investigate how changes in land use affect clouds through changes to surface heating. At the request of the CLASIC investigators, the NASA King Air also flew flight patterns coordinated with the other CLASIC aircraft so that HSRL data could be used to help understand how aerosols and clouds interact. The NASA King Air flew several flights to acquire data to validate measurements from the Cloud-Aerosol LIdar with Orthogonal Polarization instrument on board the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite.

These campaigns represent the culmination of nearly two years of preparation and coordination among the participating organizations, including NOAA, NASA, the U.S. Department of Agriculture and numerous national laboratories and universities.

Related Links:

+ High Spectral Resolution Lidar Web Site

+ CHAPS Web Site hosted by the Department of Energy's Atmospheric Science Program

Katie Lorentz
NASA Langley Research Center

Lynne Roeder
Pacific Northwest National Laboratory