Development of the Surface Urban Energy and Water Balance Scheme (SUEWS) for cold climate cities

Abstract

Abstract. The Surface Urban Energy and Water Balance Scheme (SUEWS) is developed to include snow. The processes addressed include accumulation of snow on the different urban surface types: snow albedo and density aging, snow melting and re-freezing of meltwater. Individual model parameters are assessed and independently evaluated using long-term observations in the two cold climate cities of Helsinki and Montreal. Eddy covariance sensible and latent heat fluxes and snow depth observations are available for two sites in Montreal and one in Helsinki. Surface runoff from two catchments (24 and 45 ha) in Helsinki and snow properties (albedo and density) from two sites in Montreal are also analysed. As multiple observation sites with different land-cover characteristics are available in both cities, model development is conducted independent of evaluation.The developed model simulates snowmelt related runoff well (within 19 % and 3 % for the two catchments in Helsinki when there is snow on the ground), with the springtime peak estimated correctly. However, the observed runoff peaks tend to be smoother than the simulated ones, likely due to the water holding capacity of the catchments and the missing time lag between the catchment and the observation point in the model. For all three sites the model simulates the timing of the snow accumulation and melt events well, but underestimates the total snow depth by 18-20 % in Helsinki and 29-33 % in Montreal. The model is able to reproduce the diurnal pattern of net radiation and turbulent fluxes of sensible and latent heat during cold snow, melting snow and snowfree periods. The largest model uncertainties are related to the timing of the melting period and the parameterization of the snowmelt. The results show that the enhanced model can simulate correctly the exchange of energy and water in cold climate cities at sites with varying surface cover.

Impact of temporal resolution of precipitation forcing data on modelled urban‐atmosphere exchanges and surface conditions

“…Successful simulation of surface wetness state compared to observations was also obtained in Vancouver (Grimmond and Oke, 1991). No runoff observations were available for Swindon, however, previous evaluation in Helsinki showed good agreement with measured data (Järvi et al, 2014).…”

“…SUEWS has been evaluated using observations from North American cities (Järvi et al, 2011); Helsinki (Järvi et al, 2014;Karsisto et al, 2015); Montreal (Järvi et al, 2014); Dublin (Alexander et al, 2015;Alexander et al, 2016); Hamburg, Melbourne and Phoenix (Alexander et al, 2016); Singapore (Demuzere et al, 2017); and two UK sites: suburban Swindon and central London (Ward et al, 2016). In this study, SUEWS v2017a is run offline for a single grid point representative of the Swindon site (Section 2.2).…”

Linking urban climate classification with an urban energy and water budget model: Multi-site and multi-seasonal evaluation

“…To that end, we coupled the local climate zone (LCZ) scheme of Stewart and Oke (2012) with the surface energy and water balance scheme (SUEWS) v.2014b (Järvi et al, 2014). The approach was tested in four background climates and different urban configurations.…”

“…The SUEWS model (v.2014b) is outlined in detail in (Järvi et al, 2011) and (Järvi et al, 2014). In brief, the model calculates hourly radiative fluxes (Q* = K* + L*) using the net all-wave radiation parameterisation (NARP - Offerle et al, 2003) latent heat, Q E , using a modified Penman-Monteith equation heat storage, ΔQ S , using the Objective Hysteresis Model (OHM - Grimmond and Oke, 1999) and anthropogenic heat, Q F , using the Sailor and Vasireddy approach (Sailor and Vasireddy, 2006).…”

“…The model has already been evaluated in Helsinki, Los Angeles (Järvi et al, 2011;Järvi et al, 2014) and Dublin (Alexander et al, 2015) where the necessary inputs to force the model and evaluate its performance were available.…”