Meta-models for rapid appraisal of the benefits of urban greening in the European context

STUDY REGION: This study considers daily time series of 14 years of weather parameters (temperature, wind speed, rainfall, vapor pressure and radiation) for 671 functional urban areas (FUA) across Europe, from a latitude of 35° (Cyprus) to 65° (Finland). STUDY FOCUS: Quantification of urban greening effects usually requires relatively complex and integrated models. In this contribution, we apply well-established hydrological, biomass and energy balance equations to derive meta-models for the estimation of runoff reduction, urban surface heating and thermal protection of buildings, in order to quantify the effects of the greening of 1 m(2) of impervious surface (e.g. roofs, sealed ground surfaces and underground parking lots). NEW HYDROLOGICAL INSIGHTS FOR THE REGION: We propose empirical meta-models for the quick appraisal of urban greening benefits including: urban runoff reduction due to soil water retention and evapotranspiration, land surface temperature reduction, reduction of the indoor temperature beneath the greened surface, dry biomass growth. We show that the choice of vegetation growth parameters has a limited effect on the results, although the amount of produced bulk biomass obviously depends on vegetation type. The proposed meta-models can be applied for the assessment of urban greening benefits at the stage of policy evaluation, land planning and the programming of investments at regional or continental scale, before undertaking more detailed and site-specific calculations as required in the design phase.