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Scientists Complete Trip to the Cape to Improve Climate Measurements
Cape Cod has lobsters, lighthouses and beaches, but NASA scientists who visited this summer were more interested in seeing the millions of small particles over the bay that are affecting Earth's climate.

TCAP flight path.

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A map of a typical flight path for the aircraft in the TCAP research campaign to study aerosols over Cape Cod, Mass. Credit: ARM Climate Research Facility


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NASA scientists participating in the TCAP mission used instruments that have been mounted inside the NASA King Air B200 aircraft to study natural and man-made particles generated from northeastern areas of the United States. Credit: NASA

These tiny, airborne particles, called "aerosols" are at the center of a 12-month research campaign supported by the U.S. Department of Energy's (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility. The campaign is called the Two-Column Aerosol Project, or TCAP, and the scientists are using planes and ground measurement sites to study these aerosols up close. These airborne and surface measurements provide more detailed information about the size and composition of the aerosols than can be obtained from satellites.

"We are studying how aerosols scatter and absorb sunlight and directly affect climate, and how they affect cloud properties formation, which indirectly affects the climate," explained Larry Berg, the lead scientist for TCAP, based out of DOE’s Pacific Northwest National Laboratory in Richland, Wash.

Some aerosols reflect sunlight back out into space, cooling the atmosphere, while other aerosols absorb sunlight, creating a warming affect. Scientists want to model this radiative forcing from aerosols, which is highly uncertain in the certain regions such as Cape Cod. This area is also a prime location for studying different types of aerosols.

"Cape Cod is located near the major metropolitan areas of the northeastern United States, which are the primary source of the large amounts of man-made particles found in the region, as well as large forested areas, which are the primary source of naturally occurring particles," explained Berg.

TCAP scientists hope to not only capture the characteristics of aerosols, but also try to understand how they change as they move and age. To help study these changes, a team of scientists from NASA’s Langley Research Center in Hampton, Va. deployed a plane over the coast and ocean, the NASA King Air B200 Aircraft, which was outfitted with special instruments.

One of those instruments is the HSRL-2 (High Spectral Resolution Lidar), which allows researchers to see the vertical distribution of aerosols within the atmosphere. HSRL-2 emits laser light out of the bottom of the plane, providing measurements that can help distinguish different aerosol types, such as urban pollution and wildfire smoke, as well as provide quantitative information on the spatial and vertical distributions of aerosols.

The second instrument on the B-200 was the Research Scanning Polarimeter (RSP), developed at NASA’s Goddard Institute of Space Studies in New York. RSP measures polarized light scattered at several angles to provide a fuller picture of the type, size, composition, and amount of airborne aerosols.

The B-200 plane flew at 28,000 feet in altitude, but it was not alone. Below the B-200, flying between the surface and about 10,000 feet, was the DOE's Gulfstream-1 (G-1) aircraft, which acquired coincident measurements of the same air and aerosols with an advanced suite of equipment. The coincident measurements from the B-200 and G-1 allow TCAP scientists to gain a more complete understanding of the optical and physical characteristics of these aerosols and their impact on sunlight and clouds.

In addition to the two planes, DOE's ARM Climate Research Facility deployed its ARM Mobile Facility (AMF) and Mobile Aerosol Observing System (MAOS) in North Truro, Massachusetts, within the National Park Service’s Cape Cod National Seashore. Flight paths included a pass over these ground measurements sites.

"The AMF includes state of the art scanning cloud radars, which provide a unique look at the three-dimensional structure of clouds, and other remote sensing instruments to measure the temperature, humidity and winds above the site," explains Berg.

The Department of Energy and NASA have been long-time partners in their efforts to study aerosols, participating jointly in several other field campaigns. Berg points to recent cooperative efforts including the Cumulus Humilis Aerosol Processing Study (CHAPS) mission in 2007 in Oklahoma, and the Megacity Initiative: Local and Global Research Observations (MILAGRO), which studied conditions around Mexico City.

"There has been a history of successful collaboration between DOE and NASA," says Berg.

NASA was with DOE during this year's summer intensive observation period, and DOE will continue taking measurements in Cape Cod through July 2013.

Jennifer LaPan, NASA Langley

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