New boreal forest biomass maps produced from radar satellite data

Paris, March 27 (ANI): A new processing algorithm has been developed using stacks of images from the Advanced Synthetic Aperture Radar (ASAR) on ESA’s (European Space Agency’s) Envisat satellite that allows for the retrieval of boreal forest biomass well beyond the levels that have been previously reported.

Forests play a crucial role in Earth’s carbon cycle by absorbing carbon from the atmosphere and storing it in biomass.

Undisturbed forests are carbon sinks as they absorb carbon, while forests that are logged or burnt down become carbon sources as they release carbon into the atmosphere.

Boreal forests and woodlands are estimated to cover approximately 14.5 percent of Earth’s land surface, comprising an area of nearly 16 million sq km (about the size of the contiguous 48 states of the US).

The boreal forest ecosystem, which spans Russia, northern Europe, Canada and Alaska, comprises interrelated habitats made up of forests, lakes, wetlands, rivers and tundra.

Boreal forests – including forest soil – store a third more carbon stocks per hectare as tropical forests, making them one of the most significant carbon sinks in the world.

These regions are considered global hotspots, that is, areas of increased warming, which represent possible important tipping points for abrupt climate change.

“Biomass, one of the most essential climate variables defining the functions of the Earth system, is the big unknown factor in the carbon cycle. Since no biomass maps exist with a high level of accuracy, we do not know how much is changing and cannot do calculations with any certainty,” said Professor Christiane Schmullius with the Friedrich Schiller University Jena.

“With this new algorithm, it is the first time that we have something in hand that may be a first step to a global biomass map,” she added.

The BIOMASAR project, sponsored by ESA’s Support to Science Element (STSE), has fully validated the algorithm using ASAR data, which is capable of acquiring images regardless of darkness and cloud cover, with existing in-situ information.

To validate the algorithm, several test sites were chosen in Scandinavia, Siberia and Canada, where both extensive datasets of ASAR images, acquired in ScanSAR mode at mid-resolution, and in-situ measurements were available.

The results show that the retrieval of forest growing stock volume (GSV) – the amount of wood expressed in cubic metres per hectare – is possible from Envisat ASAR data in boreal forests well beyond the levels that have been reported previously, that is, up to 500 cubic metres per hectare.

Using this method, Envisat archives can be exploited to generate global maps of GSV yearly over the entire boreal ecozone with a resolution of 10 km and accuracies of 20 percent. (ANI)

NASA Satellite Switches to Second Laser

HAMPTON, Va. — A space-borne lidar mission developed by NASA and the French space agency Centre National d’Etudes Spatiales (CNES) has successfully made the switch from its first laser to its back-up, guaranteeing a continued stream of data that is allowing scientists to better understand the complex roles clouds and aerosols play in Earth’s climate. The extended data set will help capture the pattern of year-to-year variations in cloudiness and the distribution of elevated dust layers that have been difficult to predict in climate models.

The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission is now operating on its redundant laser, which was designed as a contingency in case of a problem with the primary laser. A slow pressure leak in the canister that housed the primary laser, which the CALIPSO team had been aware of since launch, made the switch necessary. The backup laser, which stood ready for nearly three years, sent back its “first light” image on March 12. The instrument is now operational and undergoing a review of its calibration. The release of standard data products from CALIPSO should resume in late April. Eventually data from mid-March on will be processed and the total gap in data products will be limited to about 10 days in early March.

CALIPSO makes unique vertical profile measurements of clouds and aerosols. Aerosols are suspended particles from fires, industrial activities and natural processes that are one of the least understood weather and climate variables. CALIPSO’s lidar instrument measures the altitude and thickness of aerosol and cloud layers in the atmosphere. It also measures particles’ size, whether they are spherical or non-spherical and whether they are composed of water or ice. CALIPSO’s observations complement data recorded by four other satellites flying in formation called the A-Train, which provide an unprecedented comprehensive global view of atmospheric chemistry and composition within eight minutes of one another over the same ground track.

First operational in June 2006, CALIPSO’s primary laser generated more than 1.6 billion pulses of light and 20 terabytes of data that scientists from around the world are using to investigate our global integrated Earth system. More importantly, the CALIPSO data are giving scientists new insight into processes that control how aerosols are formed and dispersed, how clouds form and dissipate, and how aerosols and clouds interact.

The CALIPSO team became aware before launch that the pressure canister that housed the primary laser had a slow leak. The decision to launch was made because it was expected the primary laser could still complete the three-year prime mission. If it could not, the back-up instrument could take over. Early this year the laser showed unstable behavior consistent with low canister pressure. An investigation determined that turning on the backup laser now was the best solution.

“We designed the system with the ability to change to a back-up laser,” said Chip Trepte, CALIPSO’s project scientist at NASA’s Langley Research Center. Trepte compared building in the second laser to carrying an extra flashlight on a long camping trip. Very few lasers of the type used in CALIPSO had been flown in space before. It was unknown how it would perform in the hostile space environment. The back-up laser provided assurance that the mission would meet its objectives.

“The good news is we turned on the second laser that had been idle for three years, and it’s working as well as the primary laser did early in the mission,” Trepte said. “The pressure in the second laser canister is quite high, and it should be able to operate for many more years.”

Throughout the CALIPSO mission, NASA and CNES have worked closely, from developing the mission, building the satellite platform and integrating the payload to monitoring the instrument and processing its valuable measurements.

“Even though we are on each side of the Atlantic, we work as a single, integrated NASA-CNES team,” said Nadège Quéruel, mission operations manager with the CNES team.

CALIPSO is a joint effort between NASA and CNES. NASA and Ball Aerospace designed the lidar instrument; CNES and Thalès Alenia Space, previously Alcatel Space, built the Proteus satellite platform.

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