Daily Archives: May 20, 2019

Heat island effect on surface temperature measurements underestimated

R.D. Leeper, J. Kochendorfer, T. Henderson, M.A. Palecki. Impacts of Small-Scale Urban Encroachment on Air Temperature Observations. Journal of Applied Meteorology and Climatology. https://doi.org/10.1175/JAMC-D-19-0002.1

A field experiment was performed in Oak Ridge, TN, with four instrumented towers placed over grass at increasing distances (4, 30, 50, 124, and 300 m) from a built-up area. Stations were aligned in such a way to simulate the impact of small-scale encroachment on temperature observations. As expected, temperature observations were warmest for the site closest to the built environment with an average temperature difference of 0.31 and 0.24 °C for aspirated and unaspirated sensors respectively. Mean aspirated temperature differences were greater during the evening (0.47 °C) than day (0.16 °C). This was particularly true for evenings following greater daytime solar insolation (20+ MJDay−1) with surface winds from the direction of the built environment where mean differences exceeded 0.80 °C. The impact of the built environment on air temperature diminished with distance with a warm bias only detectable out to tower-B’ located 50 meters away.

The experimental findings were comparable to a known case of urban encroachment at a U. S. Climate Reference Network station in Kingston, RI. The experimental and operational results both lead to reductions in the diurnal temperature range of ~0.39 °C for fan aspirated sensors. Interestingly, the unaspirated sensor had a larger reduction in DTR of 0.48 °C. These results suggest that small-scale urban encroachment within 50 meters of a station can have important impacts on daily temperature extrema (maximum and minimum) with the magnitude of these differences dependent upon prevailing environmental conditions and sensing technology.

“…no dangerous warming in the past two decades,…even the past 200 years”

“It can, however, be declared with absolute certainty that there has been no dangerous warming in the past two decades, and even in the past 200 years. The post-Little Ice Age warming trend has been anything but dangerous, causing hardly any negative impact on the ecosystem or the life forms. Instead, it has brought lengthened growing seasons, more abundant vegetative growth, and more abundant food for people and everything else.” click here