NASA Satellite Measurements Imply Texas Wind Farm Impact on Surface Temperature

A Texas region containing four of the world's largest wind farms showed an increase in land surface temperature over nine years that researchers have connected to local meteorological effects of the turbines.

The land surface temperature around the west-central Texas wind farms warmed at a rate of .72 degrees Celsius per decade during the study period relative to nearby regions without wind farms, an effect most likely caused by the turbulence in turbine wakes acting like fans to pull down warmer air from higher altitudes at night, said lead author Liming Zhou at the University of Albany, State University of New York.

The results were published in the April 29 issue of Nature Climate Change. Zhou and colleagues studied land surface temperature data ranging from 2003 to 2011, from the MODIS (Moderate-resolution Imaging Spectroradiometer) instruments on NASA's Aqua and Terra satellites.

Land surface temperature measures the temperature of the Earth’s surface itself, as opposed to the air temperature readings used in daily weather reports. Across a broad landscape, land surface temperature depends closely on the land cover type and nature of the surface. In specific locations, land surface temperature varies widely from day to night while air temperature varies within a smaller range.

The warming observed by MODIS mostly occurred at night. In the Texas region studied, the land surface temperature after sunset typically cools faster than the air temperature. But as the wind turbines continued to turn, the movement brought warmer air to the surface and thus created a warming effect compared to non-wind farm regions. The researchers expected to see the reverse during the day – a slight cooling effect – but the data instead showed a small warming or negligible effect in daytime.

The warming estimate applies specifically to this particular region, and covers a time when wind farms were expanding rapidly, Zhou said. The estimate should not be considered directly applicable for other regions and landscapes, nor should it be extrapolated over a longer period of time, as the warming would likely plateau rather than continue to increase if no new wind turbines are added. The warming is also considered a local effect, not one that would contribute to a larger global trend.

"This is a first step in exploring the potential of satellite data to quantify the possible impacts of big wind farms on weather and climate," said Chris Thorncroft, a coauthor of the study and chair of the Atmospheric and Environmental Sciences department at University at Albany, State University of New York. "We are now expanding this approach to other wind farms and building models to understand the physical processes and mechanisms driving the interactions of wind turbines and the atmospheric boundary layer near the surface."

The U.S. wind industry has installed a total of 46,919 megawatts of capacity through the end of 2011 – representing more than 20 percent of the world’s installed wind power and about 2.9 percent of all U.S. electric power – and has added more than 35 percent of all new U.S. generating capacity in the past four years, according to the American Wind Energy Association and the Department of Energy. This added capacity during that timeframe is second only to natural gas, and more than nuclear and coal combined.

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NASA Releases New WISE Mission Catalog of Entire Infrared Sky

NASA unveiled a new atlas and catalog of the entire infrared sky today showing more than a half billion stars, galaxies and other objects captured by the Wide-field Infrared Survey Explorer (WISE) mission.

"Today, WISE delivers the fruit of 14 years of effort to the astronomical community," said Edward Wright, WISE principal investigator at UCLA, who first began working on the mission with other team members in 1998.

WISE launched Dec. 14, 2009, and mapped the entire sky in 2010 with vastly better sensitivity than its predecessors. It collected more than 2.7 million images taken at four infrared wavelengths of light, capturing everything from nearby asteroids to distant galaxies. Since then, the team has been processing more than 15 trillion bytes of returned data. A preliminary release of WISE data, covering the first half of the sky surveyed, was made last April.

The WISE catalog of the entire sky meets the mission's fundamental objective. The individual WISE exposures have been combined into an atlas of more than 18,000 images covering the sky and a catalog listing the infrared properties of more than 560 million individual objects found in the images. Most of the objects are stars and galaxies, with roughly equal numbers of each. Many of them have never been seen before.

WISE observations have led to numerous discoveries, including the elusive, coolest class of stars. Astronomers hunted for these failed stars, called "Y-dwarfs," for more than a decade. Because they have been cooling since their formation, they don't shine in visible light and could not be spotted until WISE mapped the sky with its infrared vision.

WISE also took a poll of near-Earth asteroids, finding there are significantly fewer mid-size objects than previously thought. It also determined NASA has found more than 90 percent of the largest near-Earth asteroids.

Other discoveries were unexpected. WISE found the first known "Trojan" asteroid to share the same orbital path around the sun as Earth. One of the images released today shows a surprising view of an "echo" of infrared light surrounding an exploded star. The echo was etched in the clouds of gas and dust when the flash of light from the supernova explosion heated surrounding clouds. At least 100 papers on the results from the WISE survey already have been published. More discoveries are expected now that astronomers have access to the whole sky as seen by the spacecraft.

"With the release of the all-sky catalog and atlas, WISE joins the pantheon of great sky surveys that have led to many remarkable discoveries about the universe," said Roc Cutri, who leads the WISE data processing and archiving effort at the Infrared and Processing Analysis Center at the California Institute of Technology in Pasadena. "It will be exciting and rewarding to see the innovative ways the science and educational communities will use WISE in their studies now that they have the data at their fingertips."

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