Tropical Pacific to be studied as major contributor of global climate change

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BOULDER, CO, Jan. 7, 2014 -- Next week, scientists at the National Center for Atmospheric Research (NCAR) will conduct a field project in the western tropical Pacific Ocean to study global climate change affected by high storm activity throughout the region.

The warm waters of the tropical Pacific fuel huge clusters of thunderstorms that act as a global chimney, lofting gases and particles into the stratosphere and affecting the planet. Although few people live in this area, these remote waters affect billions of people by shaping climate and air chemistry worldwide. During the project, scientists will aim to better understand its influence on the atmosphere, including its role in the future if storms over the Pacific become more powerful with rising global temperatures.

Called CONTRAST (Convective Transport of Active Species in the Tropics), the project is funded by the National Science Foundation (NSF), which sponsors NCAR. More than 40 scientists are taking part from NCAR, the University of Maryland, the University of Miami, other universities, and NASA. Likewise, CONTRAST, which will be based in Guam, is being coordinated with two other field projects in order to give researchers a detailed view of the air masses over the Pacific with a vertical range spanning tens of thousands of feet.

One of these projects, NASA's Airborne Tropical Tropopause Experiment (ATTREX), will use a Global Hawk, a robotic aerial vehicle, to study upper-atmospheric water vapor, which influences global climate. The other, CAST (Coordinated Airborne Studies in the Tropics) is funded by Britain's Natural Environment Research Council facility and will deploy a BAe146 research aircraft that will focus on air near the ocean surface. Together, the sensor-laden research flights will provide a comprehensive view of the atmosphere from the ocean surface, where gases produced by marine organisms enter the air to the stratosphere more than 60,000 feet above.

Gateway to the Stratosphere

As trade winds flow across the tropical Pacific, they push warm water to the west, where it piles up in and near the CONTRAST study region. The waters around Guam have the world's highest sea surface temperatures of open oceans. They provide heat and moisture to feed clusters of thunderstorms that lift air through the troposphere (the lowest level of the atmosphere) and the tropopause (a cold, shallow region atop the troposphere), and then up into the stratosphere.

Once in the stratosphere -- where the air tends to flow horizontally more than rising or sinking -- the gases and particles spread out around the world and linger for years or even decades. As atmospheric patterns evolve and sea surface temperatures warm further due to climate change, the storm clusters over the Pacific are likely to influence climate in ways that are now challenging to anticipate, NCAR's Pan noted.

Some of the gases, such as ozone and water vapor, affect the amount of energy from the Sun that reaches Earth's surface. The amount of these gases in the stratosphere is important for the planet's climate. Other chemicals, such as bromine compounds, have indirect effects by destroying ozone or otherwise altering the chemistry of the stratosphere. And the gases produced by ocean organisms create a signature of marine biology in the stratosphere.

Coordinated Flights

The CONTRAST team will deploy the NSF/NCAR HIAPER aircraft, a Gulfstream V jet modified for advanced research that will fly at altitudes between about 25,000 and 50,000 feet. Using spectrometers and other instruments on board, the researchers will measure various chemicals and take air samples across a wide region, both in storm clouds and far away from them. The measurements will be analyzed in conjunction with data from the ATTREX Global Hawk (covering altitudes up to 65,000 feet) and CAST BAe146 (with observations from the ocean surface to about 20,000 feet).

The researchers are planning as many as 16 flights, targeting both towering storms that loft fresh air into the stratosphere, as well as collapsed storms to examine the composition of the air that remains lower down, in the troposphere. While the scientists will have considerable follow-up research to conduct in their labs, some of the airborne instruments will provide real-time measurements to the team. State-of-the-art models of atmospheric chemistry will help guide the research flights in the field, as well as aid in subsequent analysis of the observations.

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