Apart from producing clean, renewable energy, giant wind turbines are also changing local weather and land surface temperatures, finds a new study.
Researchers found that land bordering newly constructed wind farms warmed more than that of the adjacent areas.
Elevated temperatures may have a long-term impact on wildlife and regional weather patterns and could also change wind and rainfall patterns.
Liming Zhou, Research Associate Professor at the Department of Atmospheric and Environmental Sciences at the University of New York, who led the study stated, "Wind energy is among the world’s fastest growing sources of energy. The US wind industry has experienced a remarkably rapid expansion of capacity in recent years.
“While converting wind’s kinetic energy into electricity, wind turbines modify surface-atmosphere exchanges and transfer of energy, momentum, mass and moisture within the atmosphere. These changes, if spatially large enough, might have noticeable impacts on local to regional weather and climate.”
“The spatial pattern of the warming resembles the geographic distribution of wind turbines and the year-to-year land surface temperature over wind farms shows a persistent upward trend from 2003 to 2011, consistent with the increasing number of operational wind turbines with time,” -- Prof Zhou.
Satellite data examined
The scientists studied the area in western-central Texas which boasts of the world’s four largest wind farms. The region has witnessed a rapid growth of wind farms with numbers of wind turbines rising from 111 to 2358 in eight years.
The researchers used data obtained from the Modis instruments on NASA's Aqua and Terra satellites to measure ground temperatures near the wind farm sites from 2003-2011.
The analysis revealed a significant warming trend over the wind farms in the last decade. The scientists found an increase by up to 0.72 degree Celsius across the wind farms while in contrast, the Earth’s average temperatures had warmed by only 0.8 degree Celsius since 1900.
“The spatial pattern of the warming resembles the geographic distribution of wind turbines and the year-to-year land surface temperature over wind farms shows a persistent upward trend from 2003 to 2011, consistent with the increasing number of operational wind turbines with time,” said Prof Zhou.
Temperature change highest at night
At night, when the sun goes down and the Earth cools, the air closer to the ground becomes colder. However, the researchers believe the motion of turbines stir up the air bringing relatively warm air down to ground level, thereby pushing the overall temperature.
The researchers noted a weak warming effect during the day near the wind farms, but the temperatures were more elevated at night when the air is normally less turbulent.
Liming Zhou said, "Typically at night there's a stable atmosphere with a warm layer overlying a cool layer.
"Enhanced vertical mixing brings warm air down and cold air up, leading to a warming near the surface at night."
The University of Albany and the National Science Foundation in the US funded the Zhou study. The paper is published by 'Nature Climate Change.'