Abstract

Authors

Yasuda, Y., Watanabe, T., Yamanoi, K., Ohtani, Y., Okano, M., Tani, M., Nakayama, K.

Year

1997

Title

Measurement of Scalar Flux from a Forest Using the Bandpass Covariance Method

Journal

Journal of agricultural meteorology

Volume

52(5)

Page

493-496

DOI

-

Keywords

Bandpass covariance method, Latent heat flux, Spectral similarity

URL

http://www.journalarchive.jst.go.jp/english/jnlabstract_en.

Abstract

The bandpass covariance method is proposed by Horst and Oncley (1995) for long term measurements of scalar flux. This method is similar to the direct measurement in principle, but can be achieved by an instrument with slow response and little maintenance on the assumption that there is spectral similarity among scalar fluxes. We measured the energy budget of a deciduous forest on July 25-27 in 1995, including an experiment for measuring turbulence. Instruments used for this experiment were a sonic anemometer, open-path infrared gas analyzer (fast response sensor) for eddy correlation, and an aspirated humidity sensor (slow response) for bandpass covariance. Using these results, we checked the applicability of the bandpass covariance method for latent heat flux by comparing it with the ordinary eddy correlation method. The spectral similarity in our experimental site was confirmed by the measurements taken by the fast response sensors which showed that normalized cospectra were almost identical between the latent heat and the sensible heat. Diurnal variation of the latent heat flux by the bandpass covariance method agreed well with that of the eddy correlation method. The daily mean value of the latent heat flux by bandpass covariance (July 27) was 108.9 Wm-2 and that by eddy correlation was 107.0 Wm-2. From these results, it can be concluded that the bandpass covariance method is applicable to a long term monitoring of the latent heat flux from a forest.

Site

KWG

Remarks

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