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Abstract
Simultaneous measurements of humidity fluctuations over a crop made with a specially modified Lyman-alpha hygrometer and a fine-wire thermocouple psychrometer are compared. Standard deviations of the two sets of data are comparable except occasionally when wind speeds were low. The psychrometer appears to underestimate the vertical flux of water vapor due to its slow response. Analysis of humidity spectra and moisture flux cospectra shows that the Lyman-alpha hygrometer is superior to the psychrometer in response at high frequencies and low wind speeds.
Abstract
Simultaneous measurements of humidity fluctuations over a crop made with a specially modified Lyman-alpha hygrometer and a fine-wire thermocouple psychrometer are compared. Standard deviations of the two sets of data are comparable except occasionally when wind speeds were low. The psychrometer appears to underestimate the vertical flux of water vapor due to its slow response. Analysis of humidity spectra and moisture flux cospectra shows that the Lyman-alpha hygrometer is superior to the psychrometer in response at high frequencies and low wind speeds.
Abstract
Turbulent fluctuations of vertical wind and fluxes of momentum, sensible heat and latent heat measured with a drag anemometer are compared to like data measured with other instruments. Means of the measured parameters agreed well with energy balance computations of the heat fluxes and profile measurements of the momentum flux. Drag anemometer measurements of turbulent fluxes generally exceeded those obtained with a propeller anemometer, run concurrently. Spectral analysis indicates that the propeller anemometer did not respond well at high frequencies, causing an underestimation of the fluxes and vertical wind fluctuations. The drag anemometer appears to respond well up to 5 Hz.
Abstract
Turbulent fluctuations of vertical wind and fluxes of momentum, sensible heat and latent heat measured with a drag anemometer are compared to like data measured with other instruments. Means of the measured parameters agreed well with energy balance computations of the heat fluxes and profile measurements of the momentum flux. Drag anemometer measurements of turbulent fluxes generally exceeded those obtained with a propeller anemometer, run concurrently. Spectral analysis indicates that the propeller anemometer did not respond well at high frequencies, causing an underestimation of the fluxes and vertical wind fluctuations. The drag anemometer appears to respond well up to 5 Hz.
