The Eddy-Correlation Technique of Evaporation Measurement Using a Sensitized Quartz-Crystal Hygrometer

Hicks, B. B.; Goodman, Harris

doi:10.1175/1520-0450(1971)010<0221:tectoe>2.0.co;2

Cited by 5 publications

(1 citation statement)

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“…(Also see Perepelkina, 1959. ) These instruments use hot-wire anemometers and fine-wire dry and wet thermocouples and even more sensitive instruments are under study (Dyer, 1961;Goltz and others, 1970;Hicks and Goodman, 1971). The fact that enormous quantities of data have to be converted into required output over periods of 5 10 or more minutes and the resulting require-me~t fo; integrating circuits, analog computers, or digital microprocessor networks, makes this method very expensive.…”

Section: The Eddy-correlation Methodsmentioning

confidence: 99%

Weather and evapotranspiration studies in a saltcedar thicket, Arizona

Hylckama¹

1980

Professional Paper

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Water use by saltcedar, Tamarix chinensis, was studied from 1961 through 1967 near Buckeye, Ariz. The test site was located on the rim of the Gila River flood plain and was bordered on the north, east, and west sides by fetches of dense saltcedar thickets 1 or more kilometers wide. On the south side, however, the fetch was less than 100 meters.The climate of the area, typical of the Sonoran Desert, is characterized by low humidities, strong winds, and temperature extremes of <-lOoC in winter and >50°C in summer. Potential evaporation values are among the highest observed in the United States.Rates and quantities of evapotranspiration were observed in six plastic-lined evapotranspirometers (tanks) whose 81 square-meter surfaces were planted to saltcedar having heights and density equal to those of the surroundings.The test site was further equipped with instrumentation to measure the following data: solar short-wave radiation; long-and shortwave net radiation; albedo; humidity, temperature, and wind profiles in and over the vegetation; soil-temperature gradients and soil-heat flux; moisture content of the soil; and carbon dioxide content of the air. Detailed studies were made of the microclimate in and over a typical saltcedar thicket. Analyses showed that, above the vegetation, the wind profiles in more than 80 percent of the observations were logarithmic. Within the thickets considerable turbulence and irregular wind inversions (tunneling) occurred during daylight hours.It was concluded that transport constants for momentum, heat, and vapor are the same more than 80 percent of the time because plots of windspeed versus temperature at different heights and of windspeeds versus vapor pressure at those heights fall on straight lines. Fluxes of carbon dioxide and vapor are closely related. Vapor fluxes diminish, as do rates of photosynthesis, during hot afternoons when temperatures exceed 40°C, suggesting a variable stomatal resistance factor.Estimates of potential evapotranspiration rates using various models were plotted against measured values. For rough estimates of total yearly quantities of evapotranspiration, three independent methods gave values closest to those measured by evapotranspirometers with the shallowest (1.5 m) depth to water and with low salinity of soil moisture. (The effects of depth-to-water and of salinity have been discussed extensively in "Water use by saltcedar as measured by the water-budget method" (van Hylckama, 1974, U.S. Geological Survey Professional Paper 491-E).For short-term estimates (of the order of 1 hour) the 1966 combination method of C. H. M. van Bavel gave results that were too high during daytime hours. When appropriate corrections were made by taking stomatal and aerodynamic resistances into account, the calculated values fitted the measured ones very well. This shows that saltcedar reacts to extremely high windspeeds and temperatures by stomatal closure, thus diminishing evapotranspiration even though water is freely available (as it is in evapotranspirometers with favor...

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Section: The Eddy-correlation Methodsmentioning

confidence: 99%

Weather and evapotranspiration studies in a saltcedar thicket, Arizona

Hylckama¹

1980

Professional Paper

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Flux‐gradient relationships in the constant flux layer

Dyer

Hicks

1970

Quart J Royal Meteoro Soc

890

421

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SLMMARYAn analysis is made of the Monin-Obukhov function @.*I in the familiar wind profile equation, using data from two recent expeditions to Gurley (New South Wales) and Hay (New South Wales). In one, the friction velocity u1 is determined directly by the eddy correlation method, and in the other, conducted during mid-winter when small heat-fluxes were experienced, by the use of a friction coefficient applied to a low-!eve1 wind.By collating with a similar earlier analysis for heat and water vapour transfer, the variations of @.u, and @w with stability are presented in tabular torm in the z / L range --0.01 to -1.0. Within this range thc empirical relationships @JI = (1 -16 z/L)-i and @ H , IV -( 1 -16 z/L)-f, and the implied equality between Ri and z/L, are found to approximate the data to within a few per-cent. 1067 1% 1970 KEFERENCES ' Transfer of momentum and heat in the planetary boundary layer,' Proceedings of the Symposium on Arctic Heat Budget and Atmospheric Circulation (The Rand Chporation), pp. 305-332. ' Wind profiles and the shearing stressan anomaly resolved,' Quart. J. R. Met. Soc., 83, pp. 537-540. ' T h e turbulent transport of heat and water vapour in an unstable atmosphere,' Ibid., 93, pp. 501-5OX. The Fluxatron -A revised approach to the measurement of eddy fluxes in the lower atmosphere,' J. Appl. Met., 6, pp. 408-113.' The measurement of atmospheric fluxes near the surface :A generalized approach,' Ibid., (in press).' The eddy-correlation technique of evaporation measurement using a sensitized quartz-crystal hygrometer.'Submitted to J. Appl. Met. ' The structure of atmospheric turbulence,' Interscience Monographs and Texts in I'hysics and Astronomy, Vol.

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Measurement of Fluxes Over Land: Capabilities, Origins, and Remaining Challenges

Hicks

Baldocchi

2020

Boundary-Layer Meteorol

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The Eddy-Correlation Technique of Evaporation Measurement Using a Sensitized Quartz-Crystal Hygrometer

Cited by 5 publications

References 0 publications

Weather and evapotranspiration studies in a saltcedar thicket, Arizona

Weather and evapotranspiration studies in a saltcedar thicket, Arizona

Flux‐gradient relationships in the constant flux layer

Measurement of Fluxes Over Land: Capabilities, Origins, and Remaining Challenges

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