Effects of increasing the surface reflectance over air quality levels using WRF-BEM/AEMM/CMAQ: application over the city of Madrid

Abstract

The effects of increasing the surface reflectance by albedo modifications have been evaluated using an air quality modelling system. We have evaluated the influence over pollutant concentrations of increasing from 0.20 to 0.55 the roof surface albedo (scenario called Albedo1) and increasing from 0.15 to 0.30 the ground surface albedo and from 0.20 to 0.55 the roof surface albedo for all urban categories (scenario called Albedo2). To obtain a better representation of the local processes we have considered very high resolution (333.33 m) and up to 10 different urban categories. Changes in albedo cause changes in different meteorological parameters (planetary boundary layer height, radiation and temperature), modifying the pollutant concentration in every single scenario. Results show that this mitigation measure is effective during summer periods, providing not high NO2 increments and O3 reduction on the urban areas of the city of Madrid. Whilst during winter periods the measure induces NO2 increments over polluted areas with high NOx emissions. In this way, the benefits of the measure, from the point of view of urban heat island effects, are greater than the detriments during summer periods, in comparison with air quality effects.