NASA - National Aeronautics and Space Administration

By: Rachel C. Samples

Climate change is real and the main driver is human activity. Scientists know the "what" and "why" pieces to the global jigsaw puzzle. The largest and most enigmatic piece is "how".

For NASA Langley scientists working in Costa Rica this summer, there may be nothing more important and more complex than tropical cirrus clouds. Researchers hope the NASA-sponsored Tropical Composition Cloud and Climate Coupling (TC4) field campaign provides a better understanding of how cirrus cloud properties -- critical in the climate system -- are affected by aerosols in the region.

Image Left: Costa Rica has ideal qualities for studying atmospheric conditions such as tropical climate, proximity to the ocean and consistent storms. Credit: Terry Latham

TC4 is a NASA led, multi-institutional effort that includes scientists from numerous federal agencies, universities and private companies. It is also unlike any thus far, explains Charles Trepte, a member of the TC4 Satellite Mission Support Team and project scientist of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite.

"Over the ocean, cloud systems have a whole different configuration,” said Trepte. "The TC4 campaign is focused in Costa Rica because the tropical location is ideal to gather these measurements for a region we don't understand right now."

Just north of the equator, bordering both the Pacific Ocean and the Caribbean Sea, Costa Rica is located on the Central American isthmus and has the climate, proximity to the ocean and consistent storm activity important for the atmospheric study.

From the ground to outer space, TC4 scientists are using various instruments at different locations to record varying aspects of cloud formation, composition, position and eventually their dissipation. Combining and verifying ground and airborne atmospheric observations can provide a greater understanding of current environmental events, as well as the calibration and validation of satellite measurements. NASA is using a suite of Earth-observing satellites, three main aircraft, balloons and ground observations.

Image Right: The DC-8 plane being prepared in California for the TC4 campaign. Credit: Terry Latham

With satellite coverage being a key element to analyzing the tropics, the A-Train satellites and their numerous atmospheric observation instruments pass over the campaign location to make coordinated measurements. The NASA Langley led CALIPSO mission, launched in April 2006, is one of the A-Train satellites. While the high-altitude flying ER-2 and WB-57, and the low-to-mid-level DC-8 aircraft collect measurements closer to the Earth's surface with their own, unique set of instruments.

Experienced field campaigner, NASA Langley's Ed Browell is the principal investigator for two aircraft-based instruments: the differential absorption lidar for the study of ozone and airborne particles and the lidar atmospheric sensor experiment for the study of water vapor, particles and clouds. Both of these lidars are flown aboard the DC-8.

From the North Pole to the South Pole, Browell has been involved in more than 33 airborne field campaigns studying various aspects of atmospheric qualities with airborne lidar systems.

And each field campaign is unique.

"It's a concentrated period of time,” said Browell. "And often, you’re not really sure what you’re going to find because you’re making many of the first measurements."

Image Left: Terry Lathem, NASA Langley summer intern, studies data results during a test flight aboard the DC-8.

Browell’s group went to California on July 13 to equip the DC-8 plane with the two lidar instruments he directs. Two days later, they became part of a larger team of approximately 200 people who traveled to Costa Rica for TC4.

Also aboard the DC-8 is first-time field campaign participant, Terry Lathem, an intern at Langley working with Bruce Anderson. He explains that his team’s instrument is looking for aerosols -- small particles in the atmosphere. Aerosols can be natural elements like dust from the desert or human-made elements such as car exhaust traveling the Earth on air streams, much like ocean currents.

Lathem says that trying to precisely define any given aerosol is difficult because it can contain more than 1,000 complex compounds that can evolve quickly over time.

"My project with NASA looks at the cloud-forming potential of these particles in the atmosphere,” said Lathem. "Their ability to form cloud droplets -- and thus clouds -- is dependent on the variety of factors, including the size, chemical composition and atmospheric conditions present."

For Lathem and the participants, the hope is the TC4 experience of 2007 presents a unique opportunity to study and observe the atmospheric and oceanic conditions of the tropics.

In larger terms Trepte added, "We see it as yet another chance to evaluate our knowledge of climate."

The campaign will last through August 8.

For more information:
* The NASA Langley TC4 Satellite Support Site, http://www-angler.larc.nasa.gov/tc4/.

* The CALIPSO TC4 Site, http://www-calipso.larc.nasa.gov/field_missions/tc4/.

* "NASA Langley Scientists Meet Costa Rican President During TC4 Campaign," http://www.nasa.gov/centers/langley/news/researchernews/rn_tc4.html.

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