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.
Betcha NOAA never tries to move those stations cooking like eggs on black tar parking lots. Why? Well, this:
30 year trends of temperature are shown to be lower, using well-sited high quality NOAA weather stations that do not require adjustments to the data.
NEW STUDY OF NOAA’S U.S. CLIMATE NETWORK SHOWS A LOWER 30-YEAR TEMPERATURE TREND WHEN HIGH QUALITY TEMPERATURE STATIONS UNPERTURBED BY URBANIZATION ARE CONSIDERED
We’re probably cooling, not warming.
(SteveF mentioned the same problem the other day – thanks!)
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