Experimental study on rainfall interception over an outdoor urban‐scale model

Abstract

[1] Rainfall interception (RI) over an outdoor urban-scale model was investigated from the perspectives of water and energy balance. On average, RI was 6% of the gross rainfall and smaller than typical values in forests. No correlation was found between RI and gross rainfall or rainfall duration unlike the correlations found in forests. Most RI occurred in the first several hours of rainfall, and then RI rapidly decreased with time during a rainfall event. RI was dependent on the saturation deficit at the beginning of the rainfall event. The latent heat for RI was approximately balanced by heat conduction from the concrete surfaces. Differences in the canopy structure are considered as possible reasons for the different behaviors of RI between the present site and forests. Accordingly, three aspects of the canopy structure, i.e., effective wet surface area, efficiency for scalar transfer, and canopy heat capacity, are discussed.Citation: Nakayoshi, M., R. Moriwaki, T. Kawai, and M. Kanda (2009), Experimental study on rainfall interception over an outdoor urban-scale model, Water Resour. Res., 45, W04415,

Particle Image Velocimetry Measurements of Turbulent Flow Within Outdoor and Indoor Urban Scale Models and Flushing Motions in Urban Canopy Layers

“…The experiments in COSMO have provided supplementary information to laboratory and field experiments under realistic conditions of sunshine and wind fluctuations [e.g. Kawai et al (2007) for the heat budget, Kanda et al (2007) and Kanda and Moriizumi (2009) for the urban land surface parameterization, Inagaki and Kanda (2008) for the turbulent flow similarity, for the turbulent structure, and Nakayoshi et al (2009) for the rainfall interception]. This scale model is an essential part of our study, since PIV experiments in real cities are difficult to realize as they involve the use of a high-power laser and a massive amount of tracer particles.…”

The impact of impervious water-storage parametrization on urban climate modelling

“…from Ramamurthy and Bou-Zeid, 2014;Rotach et al, 2005;Masson et al, 2008;Velasco et al, 2010) or for urban-scale models (e.g. Pearlmutter et al, 2009;Nakayoshi et al, 2009) are limited, especially during rainfall periods. Therefore, the investigation and evaluation of modelling the water balance for cities is limited as well (eg., Grimmond and Oke, 1991;Kanda et al, 2005;Nakayoshi et al, 2009;Demuzere et al, 2013).…”

“…Pearlmutter et al, 2009;Nakayoshi et al, 2009) are limited, especially during rainfall periods. Therefore, the investigation and evaluation of modelling the water balance for cities is limited as well (eg., Grimmond and Oke, 1991;Kanda et al, 2005;Nakayoshi et al, 2009;Demuzere et al, 2013). As a result, the representation of the urban water balance in existing urban land-surface parametrizations is very rudimentary: For instance, various urban models do not consider evaporation from the impervious surfaces as a first approximation to the reduction of ET in cities (Hénon et al, 2012;Martilli et al, 2002;Schubert et al, 2012).…”

Experimental study on canopy interception using artificial Christmas trees to evaluate evaporation during rainfall and the effects of tree height and thinning

“…This observation implies that turbulent mixing in the canopy, under the canopy, or vertical mixing through the canopy may boost I, and thus h is not necessarily a major parameter to determine I, though specific mechanisms are unknown. Nakayoshi et al (2009) conducted an experiment on I using an outdoor urban-scale model that consisted of cubic concrete blocks 1.5 m high and 1.5 m wide, but they could not find a correlation between P G and I. Their experiment was conducted under the extreme condition that no ventilation occurs under the canopy.…”