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This project was intended to design and produce a new version of an optical particle counter (OPC) that was well suited to the measurement of the dry deposition flux of small particles, i.e., those with diameters less than 1 μm. ...
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This project was intended to design and produce a new version of an optical particle counter (OPC) that was well suited to the measurement of the dry deposition flux of small particles, i.e., those with diameters less than 1 μm. The OPC employed a nonresonant cavity for particle detection, using an He-Cd laser as a light source, and a sample flow rate of 10 cm3/s or more. The system was designed to provide fast counting rates (50 kHz or more) that would improve the statistical accuracy of flux measurements over those possible with commercially available instruments. The electronics required for these counting rates have been tested successfully, but the minimum size detection limit of the apparatus is larger than is necessary for good flux measurements. Values ranging between 0.12 and 0.17 /μm have been achieved, depending on the noise levels of the light source. Limited field testing of the instrument has been carried out, although clean air generally made flux measurements impossible. Use of a more powerful laser would increase the signal-to-noise ratio to acceptable levels for field operation of the instrument.
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The report surveys the work undertaken in the field in Barbados from July 1, 1968 to December 31, 1969, and the resulting analyses. The conclusion is reached that energy budget and microclimatic conditions over Barbados represent ...
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The report surveys the work undertaken in the field in Barbados from July 1, 1968 to December 31, 1969, and the resulting analyses. The conclusion is reached that energy budget and microclimatic conditions over Barbados represent the interelationships between the prevailing wind field, the pattern of cloud and precipitation and topographic variations in net radiation. These express themselves by variations in surface moisture conditions, and water balance characteristics, rather than in large differences in temperature, or humidity. A key to understanding these features is though to lie in a better appreciative of the role of the steep east cost are of Barbados where moning heating results in mixed surface radiative temperature within three hours of sunrise during which time a maximum topographic variation in the radiation balances over the island results. (Author)
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Half-hourly averages of field measurements of flux rates of heat and evaporation are reported in 1963, 1964, 1965. Selected examples of momentum flux and the three corresponding profiles of airspeed, temperature, and moisture are ...
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Half-hourly averages of field measurements of flux rates of heat and evaporation are reported in 1963, 1964, 1965. Selected examples of momentum flux and the three corresponding profiles of airspeed, temperature, and moisture are included. Crop plantings around the flat, 5-hectare site are described in detail, and the meteorological conditions are thoroughly documented. The observations reveal a wide range in the ratios of eddy diffusivities and rather high magnitudes for the Karman constant (about 0.45 - 0.55). Various aerodynamic, energy balance and other evaporation equations were checked against evapotranspiration data from the 6.1 meter weighing lysimeter. Results show the need for very significant diabatic correction of the aerodynamic expressions at low wind speeds. Statistical treatment removing the cyclic variation from the record of the shear-stress meter show that this 50-ton float follows the varying drag of wind gusts well within one minute. The revised profile formula (log law and power law) has been found to fit observations of airspeed and temperature about 30 per cent better than the conventional Monin-Obukhov formula. The illogical averaging of friction-eddy forced convection with buoyant-parcel natural convection is discussed and a tentative lower airspeed limit of 2 m/sec at a 2-meter height is proposed for application of edd-transfer formulas. Several concepts are discussed of flow regimes near the ground and detailed descriptions of instrumentation and calibration are included. (Author)
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Micrometeorological and soil-moisture data were collected at two instrumented sites on Rainier Mesa at the Nevada Test Site, January 1, 2002 August 23, 2005. Data collected at each site include net radiation, air temperature, and ...
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Micrometeorological and soil-moisture data were collected at two instrumented sites on Rainier Mesa at the Nevada Test Site, January 1, 2002 August 23, 2005. Data collected at each site include net radiation, air temperature, and relative humidity at two heights; wind speed and direction; subsurface soil heat flux; subsurface soil temperature; volumetric soil water; and matric water potential. These data were used to estimate 20-minute average and daily average evapotranspiration values. The data presented in this report are collected and calculated evapotranspiration rates.
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The turbulent exchange of mass between a plant canopy and the atmosphere can bemodelled with either Eulerian or Lagrangian models. The application of Eulerian models for estimating turbulent transfer within and above plant canopie...
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The turbulent exchange of mass between a plant canopy and the atmosphere can bemodelled with either Eulerian or Lagrangian models. The application of Eulerian models for estimating turbulent transfer within and above plant canopies has been criticized because of an inability to treat the dispersion of material from nearby sources well. Lagrangian models do not suffer from this deficiency as they consider the diffusion of material from both nearby and far away sources explicitly. The authors developed three Lagrangian random walk models for computing the exchange of water vapor and water vapor mixing ratio profiles above and within a plant canopy. The movement of fluid parcels was computed using algorithms presented by Legg and Raupach (1982), Wilson et al. (1983) and Thomson (1984). The source strength of water vapor at discrete layers in the canopy was parameterized from estimates of net radiation flux density. The models were tested against measurement made within and above a soybean canopy.
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The manual describes a new Standard Reference Material (SRM 1965). The SRM consists of two single-layer groupings of contacting monosize 10-micrometer polystyrene spheres that have been permanently sealed in an air chamber on a mi...
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The manual describes a new Standard Reference Material (SRM 1965). The SRM consists of two single-layer groupings of contacting monosize 10-micrometer polystyrene spheres that have been permanently sealed in an air chamber on a microscope slide. One sphere grouping consists of hexagonally ordered arrays, while the other grouping is unordered. The diameter distribution of the sphere material (SRM 1960), which was made under microgravity conditions on a Space Shuttle, is accurately known. SRM 1965 has a dual function: supporting measurements involving microscopy and supporting teachings and experiments in micrometrology. The manual describes how to measure microscope magnification and image distortion at levels below 0.5% and describes micrometrology experiments at the 0.05 micrometer level.
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A platinium wire resistance temperature sensing unit capable of measuring temperature fluctuations with frequencies up to a few hundred Hz was developed. In micrometeorological research it enables the detection of small eddies wit...
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A platinium wire resistance temperature sensing unit capable of measuring temperature fluctuations with frequencies up to a few hundred Hz was developed. In micrometeorological research it enables the detection of small eddies with sizes down to the dissipation range. Thus, the device is particularly suitable for eddy correlation flux and temperature spectra measurements close to the Earth's surface.
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