Accurate Temperature Measurements in a Naturally-Aspirated Radiation Shield

Abstract

Experiments and calculations were conducted with a 0.13 mm fine wire thermocouple within a naturally-aspirated Gill radiation shield to assess and improve the accuracy of air temperature measurements without the use of mechanical aspiration, wind speed or radiation measurements. It was found that this thermocouple measured the air temperature with root-mean-square errors of 0.35 K within the Gill shield without correction.A linear temperature correction was evaluated based on the difference between the interior plate and thermocouple temperatures. This correction was found to be relatively insensitive to shield design and yielded an error of 0.16 K for combined day and night observations.The correction was reliable in the daytime when the wind speed usually exceeds 1 m s -1 but occasionally performed poorly at night during very light winds. Inspection of the standard deviation in the thermocouple wire temperature identified these periods but did not unambiguously locate the most serious events. However, estimates of sensor accuracy during these periods is complicated by the much larger sampling volume of the mechanically-aspirated sensor compared with the naturally-aspirated sensor and the presence of significant near surface temperature gradients. The root-mean-square errors therefore are upper limits to the aspiration error since they include intrinsic sensor differences and intermittent volume sampling differences.

Inferior mirages: an improved model

“…Because of the logarithmic wind profile, these errors increase systematically toward the surface, leading to systematically incorrect estimates of Θ. Modern aspirated thermometers are not only shielded against radiation errors, but also provide artificial ventilation to ensure proper heat transfer, even at low wind speeds [39].…”

Air temperature measurements using autonomous self-recording dataloggers in mountainous and snow covered areas

“…These alternatives have usually been homemade, and generally have not been designed for snow covered and high-albedo environments, and as a result have produced measurements having substantial uncertainties (Hubbard et al, 2001). Although there have been studies of the performance of alternative radiation shields above grass ground or bare soil (Holden et al, 2013;Kurzeja, 2010;Richardson et al, 1999;Tarara and Hoheisel, 2007), few have been carried out above simulated high-albedo (Georges and Kaser, 2002;Hubbard et al, 2001) and snow covered surfaces (Huwald et al, 2009;Lundquist and Huggett, 2008). To avoid uncertainties associated with inappropriate uses of radiation shields, it is essential that shelter performance be analyzed.…”

“…The distribution of horizontal air temperature locally and regionally is mainly determined by elevation, orography, orientation, and land use (Lundquist and Cayan, 2007). However, other environmental factors can affect the air temperature, including sunshine, the presence of trees or buildings (Kurzeja, 2010), shrub height (Nakamura and Mahrt, 2005), the presence of water, and plant density. Consequently, it is extremely difficult to account for all the factors influencing temperature in designing a miniature temperature logger network, so device measurement differences in part result from interferences, and not just because of real horizontal differences in temperature.…”

A Temperature Error Correction Method for a Thermometer Screen

“…• C [22][23][24][25][26][27]. In conclusion, the screens may have difficulty to meet the present air temperature measurement accuracy requirements.…”