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dc.contributor.authorKuske, Tehani Janelleen_NZ
dc.date.accessioned2009-02-20T08:57:19Z
dc.date.available2009-07-30T09:33:27Z
dc.date.issued2009en_NZ
dc.identifier.citationKuske, T. J. (2009). Fluxes of Energy and Water Vapour from Grazed Pasture on a Mineral Soil in the Waikato (Thesis, Master of Science (MSc)). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/2772en
dc.identifier.urihttps://hdl.handle.net/10289/2772
dc.description.abstractThe eddy covariance (EC) technique was used to measure half hourly fluxes of energy and evaporation from 15 December 2007 to 30 November 2008 at the Scott Research Farm, located 7 km east of Hamilton. Many other supporting measurements of climate and soil variables were also made. The research addressed three objectives: 1. To examine the accuracy of the eddy covariance measurement technique. 2. Understand the surface partitioning of energy and water vapour on a diurnal to annual timescale. 3. Compare measurements of evaporation to methods of estimation. Average energy balance closure at Scott Farm was deficient by 24%, comparable to published studies of up to 30%. Three lysimeter studies were carried out to help verify eddy covariance data. These resulted in the conclusions that; 1) lysimeter pots needed to be deeper to allow for vegetation rooting depths to be encompassed adequately; 2) forcing energy balance closure was not supported by two of the studies (summer and winter); 3) latent heat flux (λE) gap filling of night time EC data during winter over estimated values by about 10 W m-2; and 4) the spring lysimeter study verified eddy covariance measurements including the closure forcing method. Some uncertainty still exists as to the accuracy of both lysimeter and EC methods of evaporation measurement because both methods still have potential biases, however for the purpose of this study, it would appear data are sufficiently accurate to have confidence in results. Energy and water vapour fluxes varied on both a diurnal and seasonal timescale. Diurnally, fluxes were small or negative at night and were highest during the day, usually at solar noon. Seasonally, spring and summer had the highest energy and evaporation fluxes and winter rates were small but tended to exceed available energy supply. Evaporation was constrained by soil moisture availability during summer and by energy availability during winter. Estimated annual evaporation at Scott Farm was 755 mm, 72% of precipitation. Two evaporation models were compared to eddy covariance evaporation (EEC) measurements; the FAO56 Penman-Monteith model (Eo) and the Priestley-Taylor model (EPT). Both models over estimated evaporation during dry conditions and slightly under estimated during winter. The α coefficient that is applied to EPT was not constant and a seasonally adjusted value would be most appropriate. A crop coefficient of 1.13 is needed for Eo measurements during moist conditions. Eo began over estimating evaporation when soil moisture contents dropped below ~44%. A water stress adjustment was applied to both models which improved evaporation estimates, however early onset of drying was not able to be adjusted for. The adjusted Eo model is the most accurate overall, when compared to EEC.en_NZ
dc.format.mimetypeapplication/pdf
dc.format.mimetypeapplication/zip
dc.language.isoen
dc.publisherThe University of Waikatoen_NZ
dc.rightsAll items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.
dc.subjecteddy covarianceen_NZ
dc.subjectenergyen_NZ
dc.subjectevaporationen_NZ
dc.subjectwater vapouren_NZ
dc.subjectevaporation modelsen_NZ
dc.subjectPriestley-Taylor modelen_NZ
dc.subjectEECen_NZ
dc.subjectEoen_NZ
dc.subjectEPTen_NZ
dc.titleFluxes of Energy and Water Vapour from Grazed Pasture on a Mineral Soil in the Waikatoen_NZ
dc.typeThesisen_NZ
thesis.degree.disciplineScience and Engineeringen_NZ
thesis.degree.grantorUniversity of Waikatoen_NZ
thesis.degree.levelMasters
thesis.degree.nameMaster of Science (MSc)en_NZ
uow.date.accession2009-02-20T08:57:19Zen_NZ
uow.date.available2009-07-30T09:33:27Zen_NZ
uow.identifier.adthttp://adt.waikato.ac.nz/public/adt-uow20090220.085719en_NZ
pubs.place-of-publicationHamilton, New Zealanden_NZ


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