Abstract
ABSTRACTRepresentative precipitation data sets are very difficult to obtain due to the inherent spatial and temporal variability of rainfall. Gridded rainfall products exist at various scales, but temporal resolution is coarse (daily or, at best, a few hours). This study demonstrates the impact of low temporal resolution precipitation forcing data (PFD) on modelled energy fluxes, runoff and surface conditions, which could have implications for a range of applications including flood forecasting, irrigation scheduling and epidemiology. An evaporation‐interception model originally developed for forests is applied here within the framework of the Surface Urban Energy and Water balance Scheme (SUEWS). The model is forced with rainfall data representative of a range of temporal resolutions (from 5 min to 3 h). Taking the highest resolution case as a reference, differences in model output are found as the temporal resolution of PFD decreases, depending on the timing of rainfall occurrence, intensity and duration. Modelled evaporation, runoff and surface wetness deviate from the reference case, which affect other variables such as the turbulent sensible heat flux. The largest impacts are seen on days with greatest daily total rainfall and, even on days with no rain, differences in antecedent conditions (soil moisture or surface wetness) can cause deviations from the reference case. Errors can be reduced by applying a disaggregation scheme that provides a more realistic distribution of rainfall, importantly, one that allows for intermittent rainfall.
Highlights
Given the changing climate and predicted increase in frequency and severity of extreme weather (e.g. Meehl and Tebaldi, 2004; Lehtonen et al, 2014), knowledge of the earth-atmosphere system is becoming more and more important
Results demonstrate that as the temporal resolution decreases, rainfall intensity is reduced and rainfall duration is prolonged, leading to reduced runoff rates and lower runoff in total, increased infiltration resulting in moister soils, surfaces remaining wet for longer, and increased evaporation
Compared to the 5-min resolution case taken as a reference, annual evaporation may be overestimated and annual runoff underestimated by some tens of mm for resolutions of 60–180 min
Summary
Given the changing climate and predicted increase in frequency and severity of extreme weather (e.g. Meehl and Tebaldi, 2004; Lehtonen et al, 2014), knowledge of the earth-atmosphere system is becoming more and more important. Given the changing climate and predicted increase in frequency and severity of extreme weather The ability of weather and climate models to accurately predict or forecast depends on (1) how successfully physical processes are represented by model parameterisations and (2) the quality or suitability of the input data. Precipitation supplies moisture to the surface and is either intercepted and stored in the canopy, infiltrates into the soil, becomes runoff, or is evaporated. It plays an important role in both the water balance and the energy balance, as moisture availability affects the partitioning of energy between the turbulent sensible heat flux and turbulent latent heat flux (evaporation). High-evaporation rates from wet surfaces directly following precipitation events can be substantial
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