Radiation Shields for Air Temperature Thermometers

Fuchs, M; Tanner, C. B.

doi:10.1175/1520-0450(1965)004<0544:rsfatt>2.0.co;2

Cited by 50 publications

(25 citation statements)

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“…At each level, an unaspirated 36 a.w.g. copper-constantan thermocouple was positioned centrally within an open-ended radiation shield which consisted of fiberglass pipe insulation with a 2.5 cm wall thickness and an outer wrapping of highly reflective aluminized tape to protect against radiant heating (Fuchs and Tanner, 1965).…”

Section: Measurementsmentioning

confidence: 99%

A radiation and energy balance study of mature forest and clear-cut sites

McCaughey

1985

Boundary-Layer Meteorol

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Components of the radiation and energy balances were measured over a clear-cut area and a mature, mixed forest during the summer of 1981 at the Petawawa National Forestry Institute, Chalk River, Ontario. The work concentrated on the clear-cut site which supported a canopy layer composed primarily of bracken fern and logging remnants.Forty days ofradiation data were collected at the clear-cut site. After the first four weeks ofmeasurements (the 'green' season), most of the ferns quickly died, and their foliage changed appearance from a green to brownish colour (the 'brown' season). The daily mean reflection coefficient of solar radiation determined over the 'green' season was 0.20 and decreased to 0.13 for the 'brown' season. The corresponding value for the forest was 0.13, based on a limited amount of data. The clear-cut site received 11% and 21% less net radiation than the forest on a 24-hr and daylight-hours basis, respectively, as a consequence of the higher reflection coefficient and larger daytime longwave radiation emission.A reversing temperature difference measurement system (RTDMS), incorporating ten-junction thermopiles was employed at each site in order to determine Bowen ratios (/I) via differential psychrometry. Both systems performed well, especially the RTDMS over the forest which was capable of resolving very small differences of temperature, typically less than 0.2 "C over a height of 3 m. The mean hourly Bowen ratio, calculated from values from 0800 to 1600 hr, varied from 0.2 to 1.0 for the forest and from 0.4 to 0.8 for the clear-cut site in the 'green' season.A significant canopy heat storage component of the energy balance, Q,, was found at the clear-cut site. In the early morning, a portion of the available energy was used to heat the biomass materials and air within the canopy layer. The stored heat within the canopy was released later in the day, increasing the available energy total.The daily mean value of the Priestley-Taylor coefficient a (Priestley and Taylor, 1972) for the 'green' season at the clear-cut site was 1.14, and individual values tended to increase during wet surface conditions and decrease when the surface dried. The daylight mean a value during dry canopy conditions at the forest was 1.05, and much higher values occurred when the canopy was wet. The enhancement of a for the wet forest was a result of the evaporation of intercepted rain (which is not limited by stomata1 resistance) and the concomitant transfer of sensible heat to the forest.

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Section: Measurementsmentioning

confidence: 99%

A radiation and energy balance study of mature forest and clear-cut sites

McCaughey

1985

Boundary-Layer Meteorol

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“…In one of the housings, a linearized thermistor which measured T, was inserted The radiation shields were made of polyurethane tubing wrapped on the outside with aluminized tape. The tape has a very high reflectivity and forms an effective barrier to solar radiation (Fuchs and Tanner, 1965). The inner surface of the inner shield was painted with flat black paint, and the inner surface of the outer shield was covered in aluminized tape.…”

Section: Construction Of the Systemmentioning

confidence: 99%

A reversing temperature-difference measurement system for Bowen ratio determination

McCaughey

1981

Boundary-Layer Meteorol

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The design and performance of a reversing temperature difference measurement system are reported This system employs five-junction copper-constantan thermopiles for the measurement of AT and AT,, while a linearized thermistor is used to measure T,. Field performance has been checked against a precision lysimeter as well as against a second temperature difference measurement system in which diodes are used for temperature measurement. In both cases, the agreement between the systems is satisfactory for the measurement of hourly values of the Bowen ratio.

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“…The wind [13], radiation [14], and different coatings [15] displayed remarkable impacts on the energy balance of the screens, which might lead to 2-8 reflecting white to light beige. The temperature measured with the older screen was larger, and the maximum instantaneous difference was 1.63…”

Section: Introductionmentioning

confidence: 99%

A Temperature Error Correction Method for a Thermometer Screen

Yang¹,

Liu²

2017

Acta Phys. Pol. A

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Due to solar radiation exposure, air flowing inside a thermometer screen may produce a measurement error of 0.8• C or higher. To improve the air temperature observation accuracy, a temperature error correction method is proposed. The correction method is based on a computational fluid dynamics method and a genetic algorithm method. The computational fluid dynamics method is implemented to analyze and calculate the temperature errors of a screen under various environmental conditions. Then, a temperature error correction equation is obtained by fitting the computational fluid dynamics results using the genetic algorithm method. To verify the performance of the correction equation the screen and an aspirated temperature measurement platform are characterized in the same environment to conduct the intercomparison. The aspirated temperature measurement platform serves as an air temperature reference. The mean temperature error given by measurements is 0.77

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Radiation Shields for Air Temperature Thermometers

Cited by 50 publications

References 0 publications

A radiation and energy balance study of mature forest and clear-cut sites

A radiation and energy balance study of mature forest and clear-cut sites

A reversing temperature-difference measurement system for Bowen ratio determination

A Temperature Error Correction Method for a Thermometer Screen

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