Texas A&M University atmospheric sciences professor Don Collins has received grants from NASA and the National Science Foundation (NSF) to design instruments to measure the impacts of aerosol pollution on climate. Collins will use funds from the three-year NASA grant to develop an aircraft-mounted device to study the interaction of aerosols with light, while the five-year NSF grant money will go toward an instrument to determine exactly which particles will form droplets in clouds.
"Aerosols are man-made chemical particles that accumulate in our atmosphere," said Collins, who teaches and conducts research in the College of Geosciences' Department of Atmospheric Sciences. "Aerosols are the primary cause of the haze over a city on a polluted day. Certain aerosol particles can absorb sunlight, while others scatter or reflect light. Increased concentrations of particles can also modify clouds, which causes more energy to be reflected back into space."
Both scenarios can affect climate -- absorption of sunlight by aerosols causes warming, while enhanced scattering or increased cloud reflection causes a cooling effect.
"Under the NASA grant, we'll be developing an instrument to compare and validate results obtained by the PICASSO-CENA satellite, scheduled for launch in 2004," Collins said. "The NASA satellite will be equipped with Lidar, a pulsing laser pointed down on our atmosphere. The satellite emits intermittent laser pulses and measures how much of the laser energy is reflected from the atmosphere. The amount of reflection indicates the relative amount of aerosol loading or concentration at a particular point in our atmosphere.
"The aircraft on which our instrument is mounted will fly over the area directly under the satellite and make detailed measurements of the optical properties of the aerosol particles" he observed. "This will give us a direct measurement that will be coupled with the relative data from the satellite. The result is a measure of an important component of the Earth's radiation budget."
The instrument built with NSF funds will measure the activation of aerosol particles, a process by which water condenses on individual aerosol particles to form cloud droplets.
"This instrument will count and characterize the particles that are capable of forming cloud droplets," Collins said. "We can use this information to determine which types of aerosols lead to cloud formation and which do not.
Collins' work will be paired with research efforts of mechanical engineering faculty member Denis Phares, who is constructing a device to identify the composition of individual aerosol particles. The two instruments initially will be mounted together on the ground in a coastal area and a nearby forest area, but eventually they also will be placed on aircraft.
"As the atmosphere becomes more polluted by man's activities, more sunlight may be reflected back into space, leading to a cooling effect on Earth's climate," Collins said. "Although this cooling won't be enough to offset global warming over the entire Earth, it will compete with warming effects on a small scale."