Birmingham, Alabama. (Credit: Andre Natta via Creative Commons 2.0)
While researchers have typically incorporated both daytime and nighttime temperatures into their estimates of surface temperature data, University of Alabama at Huntsville (UAH) scientists have found that nighttime temperatures can fluctuate so much that leaving them out may give a more accurate picture of surface temperature trends.
Fluctuations of nighttime surface temperatures were found to occur especially in highly populated places. Disturbances included turbulence caused by human activity, breezes blowing around buildings and heat absorbed during the day rising off roofs, parking lots and streets.
The study used surface temperature data from three inland Alabama cities that dated back to 1883: Huntsville, Birmingham and Montgomery. Researchers found they were able to create more stable and less noisy datasets when nighttime surface temperatures were removed.
In pristine conditions, a cool boundary layer is created at the Earth’s surface in the evening, but there is enough turbulence and heat rising off human-made surfaces in populated areas that the boundary layer is disturbed. The layer mixes with heat from higher in the atmosphere and raises surface temperatures, UAH scientists discovered.
Top image: Birmingham, Alabama. (Credit: Andre Natta via Creative Commons 2.0)