1.2 Aim and objectives of this study
This study focuses on Ewc from forest canopies during large and extreme rainfall events. We use the Cumbrian Mountains, UK, as a focus for some of our analyses as large catchment-scale hydrological simulations of broad-scale tree planting are required. These simulations are designed to inform UK policy on the most effective methods of NFM. To inform these simulations, pertinent event-scale Ewc data from temperate sites around the world are collated and are contextualised using UK meteorological conditions via theoretical analyses. In the UK, large and extreme rainfall events primarily occur as long-duration autumn and winter storms when forest canopies can be continually wet, solar radiation is low and Ewc will dominate evaporative losses (Calder, 1990); these events are the focus of this study rather than extreme summer convective storms.
Our specific objectives are:
Objective 1 - to collate all available Ewc data from UK-relevant event-scale forest plot studies to quantify the magnitude and range of observed losses, particularly during large (> 50 mm d-1) and extreme (> 150 mm d-1) rainfall events;Objective 2 - to explore the meteorological conditions consistent with the magnitudes of Ewc losses from Objective 1 using the Penman-Monteith equation;Objective 3 - to examine meteorological data from Cumbria and other mountainous regions of the UK during large and extreme rainfall events and to compare with the findings of Objective 2;Objective 4 - to discuss the implications of the findings from objectives 1 to 3 for estimating Ewc across large catchments in complex terrain.