Print Email Facebook Twitter A new method to measure bowen ratios using high resolution vertical dry and wet bulb temperature profiles Title A new method to measure bowen ratios using high resolution vertical dry and wet bulb temperature profiles Author Euser, T. Luxemburg, W. Everson, C. Mengistu, M. Clulow, A. Bastiaanssen, W. Faculty Civil Engineering and Geosciences Department Water Management Date 2013-06-05 Abstract The Bowen ratio surface energy balance method is a relatively simple method to determine the latent heat flux and the actual land surface evaporation. Despite its simplicity, the Bowen ratio method is generally considered to be unreliable due to the use of two-level sensors that are installed by default in operational Bowen ratio systems. In this paper we present the concept of a new measurement methodology to estimate the Bowen ratio from high resolution vertical dry and wet bulb temperature profiles. A short field experiment with Distributed Temperature Sensing (DTS) in a fibre optic cable having 13 levels was undertaken. A dry and a wetted section of a fibre optic cable were suspended on a 6 m high tower installed over a sugar beet trial near Pietermaritzburg (South Africa). Using the DTS cable as a psychrometer, a near continuous observation of vapour pressure and temperature at 0.20 m intervals was established. These data allows the computation of the Bowen ratio with a high precision. By linking the Bowen ratio to net radiation and soil heat flux, the daytime latent heat flux was estimated. The latent heat flux derived from DTS-based Bowen ratio (BR-DTS) showed consistent agreement (correlation coefficients between 0.97 and 0.98) with results derived from eddy covariance, surface layer scintillometer and surface renewal techniques. The latent heat from BR-DTS overestimated the latent heat derived with the eddy covariance by 4% and the latent heat derived with the surface layer scintillometer by 8%. Through this research, a new window is opened to engage on simplified, inexpensive and easy to interpret in situ measurement techniques for measuring evaporation. To reference this document use: http://resolver.tudelft.nl/uuid:f7d1d044-d3cc-431c-9385-e6951be2d937 DOI https://doi.org/10.5194/hessd-10-7161-2013 Publisher European Geosciences Union ISSN 1812-2108 Source Hydrology and Earth System Sciences Discussions, 10 (6), 2013 Part of collection Institutional Repository Document type journal article Rights © 2013 The Author(s)CC Attribution 3.0 License Files PDF Euser_2013.pdf 1006.26 KB Close viewer /islandora/object/uuid:f7d1d044-d3cc-431c-9385-e6951be2d937/datastream/OBJ/view