Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 399814
Title Analysis of the Systematic Errors Found in the Kipp & Zonen Large-Aperture Scintillometer
Author(s) Kesteren, A.J.H. van; Hartogensis, O.K.
Source Boundary-Layer Meteorology 138 (2011)3. - ISSN 0006-8314 - p. 493 - 509.
Department(s) Meteorology and Air Quality
Publication type Refereed Article in a scientific journal
Publication year 2011
Keyword(s) heterogeneous land-surface - sensible heat fluxes - optical scintillometer - refractive-index - c-n(2) - area
Abstract Studies have shown a systematic error in the Kipp & Zonen large-aperture scintillometer (K&ZLAS) measurements of the sensible heat flux, H. We improved on these studies and compared four K&ZLASs with a Wageningen large-aperture scintillometer at the Chilbolton Observatory. The scintillometers were installed such that their footprints were the same and independent flux measurements were made along the measurement path. This allowed us to compare H and the direct scintillometer output, the refractive index structure parameter, C2n. Furthermore, spectral analysis was performed on the raw scintillometer signal to investigate the characteristics of the error. Firstly, correlation coefficients =0.99 confirm the robustness of the scintillometer method, and secondly we discovered two systematic errors: the low-C2n error and the high-C2n error. The low-C2n error is a non-linear error that is caused by high-frequency noise, and we suspect the error to be caused by the calibration circuit in the receiver. It varies between each K&ZLAS, is significant for H = 50 W m-2, and we propose a solution to remove this error using the demodulated signal. The high-C2n error identified by us is the systematic error found in previous studies.We suspect this error to be caused by poor focal alignment of the receiver detector and the transmitter light-emitting diode that causes ineffective use of the Fresnel lens in the current Kipp & Zonen design. It varies between each K&ZLAS (35% up to 240%) and can only be removed by comparing with a reference scintillometer in the field.
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