Assessment of Air Quality and Meteorological Changes Induced by Future Vegetation in Madrid

Abstract

Nature-based solutions and green urban infrastructures are becoming common measures in local air quality and climate strategies. However, there is a lack of analytical frameworks to anticipate the effect of such interventions on urban meteorology and air quality at a city scale. We present a modelling methodology that relies on the weather research and forecasting model (WRF) with the building effect parameterization (BEP) and the community multiscale air quality (CMAQ) model and apply it to assess envisaged plans involving vegetation in the Madrid (Spain) region. The study, developed within the VEGGAP Life project, includes the development of two detailed vegetation scenarios making use of Madrid’s municipality tree inventory (current situation) and future vegetation-related interventions. An annual simulation was performed for both scenarios (considering constant anthropogenic emissions) to identify (i) variations in surface temperature and the reasons for such changes, and (ii) implications on air-quality standards according to EU legislation for the main pollutants (PM10, PM2.5, NO2 and O3). Our results suggest that vegetation may have significant effects on urban meteorology due to changes induced in relevant surface properties such as albedo, roughness length or emissivity. We found a net-heating effect of around +0.18 °C when trees are introduced in dry, scarcely vegetated surfaces in the city outskirts. In turn, this enhances the planetary boundary layer height (PBLH), which brings about reductions in ambient concentrations of relevant pollutants such as NO2 (in the range of 0.5–0.8 µg m−3 for the annual mean, and 2–4 µg m−3 for the 19th highest 1 h value). Conversely, planting new trees in consolidated urban areas causes a cooling effect (up to −0.15 °C as an annual mean) that may slightly increase concentration levels due to less-effective vertical mixing and wind-speed reduction caused by increased roughness. This highlights the need to combine nature-based solutions with emission-reduction measures in Madrid.

The Role of Vegetation on Urban Atmosphere of Three European Cities—Part 1: Evaluation of Vegetation Impact on Meteorological Conditions

“…Ref. [36] estimated that Madrid trees have 13% of evergreen needleleaf trees and 2% of evergreen broadleaf trees, which can explain why the vegetation impact on humidity and latent heat flux remains more significant during the winter than in Bologna and Milano where deciduous species are largely dominant.…”

“…It is worth noting that, for both simulations, actual vegetation was used in non-strictly urban cells, that is, in cells where vegetation fraction prevails over urban fraction (hereafter named "vegetation cells"). Moreover, for NOVEG simulation over Madrid, urban vegetation was replaced by barren soil only in the urban cells located within municipality and containing urban trees and green spaces in the VEG simulation, leaving unchanged urban cells containing uncultivated areas, dryland cropland, or pastures, e.g., in peripheral or dismissed industrial areas (this treatment was suitable to model Madrid's peculiar land cover features; more details in Section 2.2 and in [36]). On the other hand, in the case of Bologna and Milano, each urban cell of the domains was affected.…”

“…The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/f14061235/s1, Figure S1: Domains used for simulations over Italy (Milano and Bologna, left) and Spain (Madrid, right); Table S1: Domain specifications; Table S2: WRF statistical scores over Bologna, Milano and Madrid [36] computed for temperature (T), relative humidity (RH) and wind speed (WS) against local networks surface observations; Figure S2: Average difference (VEG-NOVEG) for Latent Heat Flux (LHF, W/m 2 ), for January (top row) and July (bottom row), referred to Bologna (left column), Milano (middle column) and Madrid (right column); Figure S3: Same as in Figure S2 but referred to Sensible Heat Flux (SHF); Figure S4: Daily cycle of the median, 10th and 90th percentiles RH difference (VEG-NOVEG) within Bologna, Milano and Madrid municipalities (left, middle and right column, respectively). Top row is referred to quantities calculated over Urban cells where vegetation fraction was removed in NOVEG simulations, while bottom row shows quantities calculated over Vegetation cells where urban fraction is not prevalent and vegetation fraction was unchanged in both simulations.…”

The Role of Vegetation on Urban Atmosphere of Three European Cities. Part 2: Evaluation of Vegetation Impact on Air Pollutant Concentrations and Depositions

“…It also includes, for the first time, a detailed description of urban vegetation at a single tree level (Section 2) using urban tree inventories provided by municipalities and of urban morphology [11]. The robustness of the results is ensured by the application of two stateof-the-art air quality modelling systems: AMS-MINNI [12][13][14][15] for Bologna and Milan and WRF-CMAQ [16][17][18] for Madrid. The two AMS were extensively applied in air quality studies from continental to national and regional scales in Italy and Spain.…”

Advances on the Influence of Vegetation and Forest on Urban Air Quality and Thermal Comfort—Series II

“…Regarding the air quality effects, Yin et al [27] computed the effects of urban park green spaces in Beijing on PM2.5 retention at multiple scales. De la Paz et al [28] studied air quality and meteorological changes induced by future vegetation in Madrid at the city scale. This study highlights the need to combine nature-based solutions with emission-reduction measures.…”