Mission

To study the massive plumes of dust and pollutants that are blown from Asia to North America and how these plumes may affect

• the formation of clouds and the development of precipitation
• the intensity of storms moving across the Pacific
• the amount of sunlight that reaches Earth
• the extent to which greenhouse gases will warm the Pacific basin as well as the entire globe in the next few decades

When

Starting soon after April 18 and lasting six weeks, until early June.

• Two missions lasting about 10 days each will be flown during the six-week project.
• The start date for each mission depends on weather conditions in Asia and how the winds are affecting dust and pollutants there.

Timing (Why Springtime?)

Spring is when prevailing winds blow the largest plumes of dust and pollutants across the Pacific.

Where

Related visual:
Hypothetical flight map

The NSF/NCAR Gulfstream-V will fly out of

• Boulder, Colorado;
• Anchorage, Alaska; and
• Yokota Air Base, near Akita, Japan.

Who

Two principal investigators

• Jeff Stith (NCAR)
• V. Ramanathan (Scripps Institution of Oceanography)

During each mission, one principal investigator will serve as mission scientist on the aircraft while the other directs a ground support team providing real-time information from computer models and satellite data to the mission scientist.

Also aboard the Gulfstream-V

• NCAR pilot and co-pilot
• Scientists and technicians operating research instruments and conducting measurements

On the ground

• Asian and North American scientists will use a suite of ground-based instruments to measure the extent of the plumes as they leave Asia and to study the plumes from below.
• The instruments will be based at sites in China, South Korea, Japan, and Alaska.

Participants and Costs

Total cost of the PACDEX field campaign is approximately $1 million. This does not include subsequent research by other organizations that will use the data collected during the campaign.

Dozens of scientists from North America and Asia will work on the field project.

North America
In addition to NCAR and Scripps, the main North American organizations are:

• NASA
• NOAA
• Arizona State University
• Colorado State University
• National Autonomous University of Mexico
• Naval Research Laboratory
• Oregon State University
• University of Alaska
• University of Colorado
• University of Iowa

Asia

• Japanese National Institute for Environmental Studies,
• Lanzhou University, China
• Peking University, China
• Seoul National University, Korea

Aircraft

Related visuals:
Readying the G-V;
The NSF/NCAR Gulfstream-V  

The NSF/NCAR Gulfstream-V is the nation's most advanced aircraft for environmental research. The G-V is owned by the National Science Foundation and operated by the National Center for Atmospheric Research.

Formerly known as the High-performance Instrumented Airborne Platform for Environmental Research, the G-V can fly nonstop as far as 6,000 miles, depending on its instrument load, and can achieve a top altitude of about 51,000 feet.

The G-V's capabilities will enable PACDEX researchers to trace plumes of dust and pollutants from Asia to North America, sampling air from just a few hundred feet above the Earth’s surface to as high as the lower stratosphere. The G-V joined the NCAR research aircraft fleet in March 2005; PACDEX is its first international mission.

Instruments on board

Related visual:
Readying the G-V

The NSF/NCAR Gulfstream-V will carry a large number of specialized instruments, some newly developed by NCAR or private companies. Some of the instruments will be mounted in pods under the wings or on the mainframe of the aircraft. Others will be inside the cabin. Examples include:

• A package of inlets to capture samples of air and transport them inside the cabin
• Aerosol particle counters that calculate size and concentration by measuring the light scattered by each particle
• Chambers that replicate conditions found in clouds, which will be used to determine the number of aerosol particles that form water droplets and ice particles, as they would in natural clouds
• Spectrometers that measure solar radiation at various wavelengths, so that changes in sunlight in and around the plume can be documented.

What will be measured

Onboard measurements will include:

• The levels of certain gases, such as carbon monoxide, that exist in very small amounts (measured in parts per billion). These trace gases indicate the presence of clean or polluted air.
• The size, concentration, and composition of water droplets and ice particles detected in clouds within and outside the plume.
• The size, concentration, and basic chemical composition of airborne particles, including dust, black carbon, and sulfates.
• The number of airborne particles that are able to form cloud droplets or ice crystals in clouds.
• The levels of various wavelengths of solar radiation in the plumes.

On the ground:

• Scientists will use laboratory equipment to conduct more sophisticated tests on the air samples collected by the aircraft.
• Mission data on clouds and solar radiation will be incorporated into computer models of the atmosphere to better understand weather conditions and long-term changes in climate.

Results

Scientists may start seeing preliminary results during the PACDEX field campaign.

In the months and years that follow, scientists around the world will have access to all the data gathered during the field campaign, which they can use to refine computer models and better understand the impacts of the plumes on cloud formation, storm systems, and global and regional climate.

What's unique about PACDEX?

In contrast to prior experiments, during PACDEX researchers will focus much of their efforts on understanding the interactions of Asian dust and pollution plumes with clouds. The research team will also try to follow a specific dust outbreak in its journey across the entire Pacific. PACDEX also marks the first international mission for the new NSF/NCAR Gulfstream-V research aircraft.

Prior studies have looked at other aspects of Asian dust and pollution. For example, international teams of researchers studied plumes over East Asia and nearby regions of the Pacific in 2001 in projects called the Aerosol Characterization Experiment–Asia (ACE-Asia) and Transport and Chemical Evolution over the Pacific (TRACE-P).

More recently, in 2006, a NASA-led campaign called the Intercontinental Chemical Transport Experiment (INTEX-B) included extensive chemical studies of Asian pollution plumes over the mid- and eastern Pacific.

Other sources of dust and pollutants

Understanding the downwind effects of dust and pollutants from all regions is an important problem for atmospheric scientists.

In 2004, for example, NCAR joined with other institutions in a large field campaign examining the effects of gases and particles lofted from North America across the Atlantic Ocean toward Europe. The campaign brought together several experiments under the umbrella of the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT), including the Intercontinental Chemical Transport Experiment–North America (INTEX-NA), and the New England Air Quality Study (NEAQS).