Diagnosing hydrological limitations of a land surface model: application of JULES to a deep-groundwater chalk basin

摘要

Land surface models (LSMs) are prospective starting points to develop aglobal hyper-resolution model of the terrestrial water, energy, andbiogeochemical cycles. However, there are some fundamental limitations ofLSMs related to how meaningfully hydrological fluxes and stores arerepresented. A diagnostic approach to model evaluation and improvement is taken here thatexploits hydrological expert knowledge to detect LSM inadequacies throughconsideration of the major behavioural functions of a hydrological system:overall water balance, vertical water redistribution in the unsaturated zone,temporal water redistribution, and spatial water redistribution over thecatchment's groundwater and surface-water systems. Three types of informationare utilized to improve the model's hydrology: (a)?observations, (b)?informationabout expected response from regionalized data, and (c)?informationfrom an independent physics-based model. The study considers theJULES (Joint UK Land Environmental Simulator) LSM applied to adeep-groundwater chalk catchment in the UK. The diagnosed hydrologicallimitations and the proposed ways to address them are indicative of thechallenges faced while transitioning to a global high resolution model of thewater cycle.