Airflow Characteristics of Commonly Used Temperature Radiation Shields

X. Lin School of Natural Resource Sciences, University of Nebraska, Lincoln, Nebraska

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Kenneth G. Hubbard School of Natural Resource Sciences, University of Nebraska, Lincoln, Nebraska

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George E. Meyer Biological System Engineering Department, University of Nebraska, Lincoln, Nebraska

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Abstract

The air temperature radiation shield is a key component in air temperature measurement in weather station networks; however, it is widely recognized that significant errors in the measured air temperature exist due to insufficient airflow past the air temperature sensor housed inside the shield. During the last several decades, the U.S. National Weather Service has employed a number of different shields in air temperature measurements. This paper focuses on the airflow characteristics inside air temperature shields including the Maximum–Minimum Temperature System (MMTS), the Gill shields, and the Cotton Region Shelter (CRS).

Average airspeed profiles and airflow efficiency inside the shields are investigated in this study under both windtable and field conditions using an omnidirectional hot-wire sensor. Results from the windtable measurements indicate that the average airspeeds inside the shields oscillated along the center line of the Gill and MMTS shields as the “windtable air” speed was changed from 1.03 to 2.62 m s−1; the MMTS airflow efficiency demonstrated a nearly constant value, but the Gill’s airflow efficiency increased. A linear transfer equation between the airspeed measured at the normal operating position for the temperature sensor inside the shield and the ambient wind speed was found under field conditions for all three nonaspirated air temperature radiation shields (CRS, Gill, and MMTS). Results indicate that the naturally ventilated temperature radiation shields are unable to provide sufficient ventilation when the ambient wind speed is less than 5 m s −1 at the radiation shield height.

Corresponding author address: Dr. Kenneth G. Hubbard, School of Natural Resource Sciences, University of Nebraska, L. W. Chase Hall, P.O. Box 830728, Lincoln, NE 68583-0728.

Email: khubbard@unlnotes.unl.edu

Abstract

The air temperature radiation shield is a key component in air temperature measurement in weather station networks; however, it is widely recognized that significant errors in the measured air temperature exist due to insufficient airflow past the air temperature sensor housed inside the shield. During the last several decades, the U.S. National Weather Service has employed a number of different shields in air temperature measurements. This paper focuses on the airflow characteristics inside air temperature shields including the Maximum–Minimum Temperature System (MMTS), the Gill shields, and the Cotton Region Shelter (CRS).

Average airspeed profiles and airflow efficiency inside the shields are investigated in this study under both windtable and field conditions using an omnidirectional hot-wire sensor. Results from the windtable measurements indicate that the average airspeeds inside the shields oscillated along the center line of the Gill and MMTS shields as the “windtable air” speed was changed from 1.03 to 2.62 m s−1; the MMTS airflow efficiency demonstrated a nearly constant value, but the Gill’s airflow efficiency increased. A linear transfer equation between the airspeed measured at the normal operating position for the temperature sensor inside the shield and the ambient wind speed was found under field conditions for all three nonaspirated air temperature radiation shields (CRS, Gill, and MMTS). Results indicate that the naturally ventilated temperature radiation shields are unable to provide sufficient ventilation when the ambient wind speed is less than 5 m s −1 at the radiation shield height.

Corresponding author address: Dr. Kenneth G. Hubbard, School of Natural Resource Sciences, University of Nebraska, L. W. Chase Hall, P.O. Box 830728, Lincoln, NE 68583-0728.

Email: khubbard@unlnotes.unl.edu

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  • Albright, L. D., 1990: Environment Control for Animals and Plants. The American Society of Agricultural Engineers, 453 pp.

  • Brock, F. V., S. R. Semmer, and C. Jirak, 1995: Passive solar radiation shields: Wind tunnel testing. Preprints, Ninth Symp. on Meteorological Observations and Instrumentation, Charlotte, NC, Amer. Meteor. Soc., 329–334.

  • Bruun, H. H., 1995: Hot-Wire Anemometry, Principles and Signal Analysis. Oxford University Press, 507 pp.

    • Crossref
    • Export Citation
  • Busch, N. E., and L. Kristensen, 1976: Cup anemometer overspeeding. J. Appl. Meteor.,15, 1328–1332.

    • Crossref
    • Export Citation
  • Fritschen, L. J., and L. W. Gay, 1979: Environmental Instrumentation. Springer-Verlag, 216 pp.

    • Crossref
    • Export Citation
  • Global Energy Concepts, Inc., 1999: Nebraska wind energy site data study. Final report, 58 pp. [Available from Nebraska Power Association, 444 S. 16th St. Mall, 4E/EP1, Omaha, NE 68102.].

  • Izumi, Y., and M. L. Barad, 1970: Wind speeds as measured by cup and sonic anemometers and influenced by tower structure. J. Appl. Meteor.,9, 851–856.

    • Crossref
    • Export Citation
  • Lin, X., 1999: Microclimate inside air temperature radiation shields. Ph.D. thesis, University of Nebraska, 187 pp.

  • Perry, A. E., 1982: Hot-Wire Anemometry. Oxford University Press, 184 pp.

  • Richardson, S. J., 1995a: Passive solar radiation shields: Numerical simulation of flow dynamics. Preprints, Ninth Symp. on Meteorological Observations and Instrumentation, Charlotte, NC, Amer. Meteor. Soc., 253–258.

  • ——, 1995b: Multiplate radiation shields: Investigating radiational heating errors. Ph.D. thesis, University of Oklahoma, 133 pp. [Available online at http://www.oclc.org/firstsearch.].

  • Scheiman, J., C. Marple, and D. S. Vann, 1982: A calibration technique for a hot-wire-probe vector anemometer. NASA Tech. Memo. 83254, 48 pp.

  • TSI Inc., 1995: Model 8455/8465/8475 air velocity transducer. Service manual, 27 pp.

  • White, F. M., 1991: Viscous Fluid Flow. 2d ed. McGraw-Hill Series in Mechanical Engineering, McGraw-Hill, 614 pp.

  • WMO, 1983: Guide to meteorological instruments and methods of observation. WMO-8, 6th ed., WMO, Geneva, Switzerland, 248 pp.

  • Wyngaard, J. C., 1981: Cup, propeller, vane, and sonic anemometers in turbulence research. Annu. Rev. Fluid Mech.,13, 399–423.

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