Microwave transmission, a new tool in forest hydrological research

Bouten, W.; Swart, P.J.F. de; Water, E. De

doi:10.1016/0022-1694(91)90009-7

Cited by 53 publications

(29 citation statements)

References 20 publications

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“…From April to December, the system was operational for about 88% of the total time. A complete description of the design has been given by Bouten et al (1991b).…”

Section: Microwave Transmissionmentioning

confidence: 99%

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Monitoring and modelling canopy water storage amounts in support of atmospheric deposition studies

Bouten

Schaap

Aerts

et al. 1996

Journal of Hydrology

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Monitoring and modelling rainfall interception and canopy wetness in support of acidification research Bouten, W.; Schaap, M.; Aerts, J.C.J.H.; Vermetten, A. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. AbstractCanopy water storage amounts were measured with a newly developed measuring system based on the attenuation of a 10.26 GHz microwave signal. Every 5 min, vertical scans were made, over a period of 9 months. A physically based multi-layer interception model with empirical parameters was calibrated using a non-linear optimization technique. The calibrated model appeared to be capable of explaining up to 92% of the measured variance of water storage amounts for an independent validation period when using on-site measurements of meteorological variables. The performance decreased only slightly to 89% when other input sets were used for this period. These were necessary to extrapolate the results to longer time series required for evaluating canopy resistances in the study of deposition of airborne pollutants (Vermetten et al., Proc. 5th ZPSASEP Conf., Vol. 3, 1992). The resemblance between measured throughfall amounts and simulated results and the plausibility of the model parameters, although they were optimized without setting any limits, enhances confidence in the model results.

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“…From April to December, the system was operational for about 88% of the total time. A complete description of the design has been given by Bouten et al (1991b).…”

Section: Microwave Transmissionmentioning

confidence: 99%

“…Therefore, a new system based on the measurement of microwave attenuation was developed (Bouten et al, 1991b) and was used for a 9 month period.…”

Section: Introductionmentioning

confidence: 99%

Monitoring and modelling canopy water storage amounts in support of atmospheric deposition studies

Bouten

Schaap

Aerts

et al. 1996

Journal of Hydrology

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“…It was found that the high interception losses in Speulderbos at that time were due to a high leaf area index, resulting in high canopy storage capacity (2.5 mm) as measured by microwave transmission (Bouten et al, 1991). Evaporation during rainfall contributed minimally to the overall interception loss (Klaassen et al, 1998).…”

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confidence: 96%

“…Detailed measurements and modelling studies at the site included canopy growth and architecture (Evers et al, 1991b), soil 15 water dynamics (Tiktak and Bouten, 1994), modelling evaporation and transpiration (Bosveld and Bouten, 2001), spatial patterns of throughfall (Bouten et al, 1992), and measuring and modelling canopy water storage (Bouten et al, 1991;Bouten et al, 1996). It was found that the high interception losses in Speulderbos at that time were due to a high leaf area index, resulting in high canopy storage capacity (2.5 mm) as measured by microwave transmission (Bouten et al, 1991).…”

mentioning

confidence: 99%

The influence of long-term changes in canopy structure on rainfall interception loss: a case study in Speulderbos, the Netherlands

Vaca¹,

Tol²,

Ghimire³

2018

Preprint

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Abstract. The evaporation of intercepted water by forests is a significant contributor to both the water and energy budget of the Earth. In many studies, a discrepancy in the water and energy budget is found: the energy that is needed for evaporation is larger than the available energy supplied by net radiation. In this study, we analyse the water and energy budget of a mature 10 Douglas-fir stand in the Netherlands, for the two growing seasons of 2015 and 2016. Based on the wet-canopy water balance equation for these two growing seasons, derived interception losses were estimated to be 37% and 39% of gross rainfall, respectively.We further scrutinized eddy covariance energy balance data from these two consecutive growing seasons and found the average evaporation rate during wet canopy conditions was 0.20 mm h -1 . The source of energy for this wet-canopy evaporation was 15 net radiation (35 %), a negative sensible heat flux (45 %) and a negative energy storage change (15 %). This confirms that the energy for wet-canopy evaporation is extracted from the biomass as well as the atmosphere.Moreover, the measured interception loss at the forest was similar to that measured at the same site years before ( = 38 %), when the forest was younger (29 years old, vs 55 years old in 2015). At that time, the forest was denser and had a higher canopy storage capacity (2.4 mm then vs 1.90 mm in 2015), but the aerodynamic conductance was lower (0.065 m s -1 then vs 20 0.105 m s -1 in 2015), and therefore past evaporation rates were lower than evaporation rates found in the present study (0.077 mm h -1 vs 0.20 mm h -1 in 2015). Our findings emphasize the importance of quantifying downward sensible heat flux and heat release from canopy biomass in tall forest in order to improve the quantification of evaporative fluxes in wet canopies.

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“…An example of a microwave transmission technique was demonstrated by Bouten et al (1991) to quantify leaf wetness and to assess canopy water storage in forests. Microwave absorption was also investigated for assessing diurnal changes in water status of cucumber leaves (Ernst and Kuhn, 1989).…”

mentioning

confidence: 99%