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Title: Critical assessment of structure and parameterization of JULES land surface model at different spatial scales in a UK chalk catchment
Author: Bakopoulou, Christina
ISNI:       0000 0004 5367 5044
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2015
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The assessment of water resources and the prediction of future changes in water management are necessary due to global climate changes. The land surface model 'Joint UK Land Environment Simulator' (JULES), which lies in the borderline between hydrological and atmospheric modelling, was implemented in this study. The study focused on the Kennet catchment in the UK; a Chalk dominated catchment that includes a variety of different geological formations. The first spatial scale, where JULES was assessed, was the point scale; the scale at which equations central to JULES are regarded as applicable. The data used originated from the Warren Farm recharge site, located in the Lambourn catchment, a tributary of the Kennet. Due to the large number of model parameters that JULES includes, a Monte Carlo sensitivity analysis was implemented on a variety of different parameters at the point scale illustrating that that some soil parameters exhibit a bigger effect on the examined hydrological fluxes than others. For larger scale modelling, i.e. scales larger than 1 km2, soil data from the National Soil Resources Institute (NSRI) were used to parameterise JULES. NSRI database has a spatial resolution of 1 km x 1 km grid squares, where each square is attributed with the percentage of the various soil series included in it. Due to the lack of chalk soil hydraulic parameters in the NSRI dataset, Warren Farm observations were used to parameterise the Chalk sites. Moving to the Kennet catchment modelling, it was shown that a weather generator, which was representing the diurnal patterns of the climatic forcing data, led to more realistic hydrological outputs compared to the one available in the standard version of JULES (2.2). The issue of whether the effect of spatial variation in surface properties could be adequately represented in JULES was explored at 1 km and catchment scales. Thus, the extent of the heterogeneity present in the Kennet catchment was investigated, with and without a surface runoff production mechanism component, with the focus being on the various soil types included in the Kennet. The amount of heterogeneity in each of the 1 km grid cells of the NSRI database was also studied, showing that the dominant soil type in the majority of the grid squares of the catchment could sufficiently represent the annual average hydrological behaviour. Lastly, it was exhibited that the inclusion of the surface runoff component allowed the model to overcome the limitation of the unrealistic surface runoff values that were produced without the implementation of that component.
Supervisor: Butler, Adrian ; Le Vine, Nataliya ; Mcintyre, Neil Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available