Analysis of summer O<sub>3</sub> in the Madrid air basin with the LOTOS-EUROS chemical transport model

Abstract

<p><strong>Abstract.</strong> Tropospheric O<sub>3</sub> remains a major air-quality issue in the Mediterranean region. The combination of large anthropogenic emissions of precursors, transboundary contributions, a warm and dry aestival climate and topographical features results in severe cases of photochemical pollution. Chemical transport models (CTMs) are essential tools for studying O<sub>3</sub> dynamics and for assessing mitigation measures but they need to be evaluated specifically for each air basin. In this study, we present an optimisation of the LOTOS-EUROS CTM for the Madrid air basin. Five configurations using different meteorological datasets (from the European Centre for Medium Weather Forecast (ECMWF) and Weather Research and Forecasting (WRF)), horizontal resolution and number of vertical levels were compared for July 2016. LOTOS-EUROS responded satisfactorily in the five configurations reproducing observations of surface O<sub>3</sub> with notable correlation and reduced bias and errors. However, the best-fit simulations for surface O<sub>3</sub> were obtained by increasing spatial resolution and using a large number of vertical levels to reproduce vertical transport phenomena and the formation of reservoir layers. Using the optimal configuration obtained in the evaluation, three characteristic events have been described: recirculation (REC) episodes and northern and southern advection (NAD and SAD, respectively) events. REC events were found to produce the highest O<sub>3</sub> due to the reduced ventilation associated with low wind speeds and the contribution of reservoir layers formed by vertical transport of O<sub>3</sub> formed near the surface in the previous days of the event. NAD events, usually associated with higher wind speeds, present the lowest ground-level O<sub>3</sub> concentrations in the region. During SAD episodes, external contributions along with low wind speeds allow O<sub>3</sub> to increase considerably, but not as much as in REC events because steady southerly winds disperse local emissions and hinder the formation of reservoir layers.</p>

Impact on Air Quality of the COVID-19 Lockdown in the Urban Area of Palermo (Italy)

“…The temporal analysis of the O 3 level showed an opposite behavior during the block (63 µg·m −3 ) compared to the average values of NO 2 (21 µg·m − 3 ) at the same monitoring station. An increase in O 3 is usual during spring and summer due to the higher solar radiation (in terms of intensity and daily duration), which promotes the photolysis of NO 2 [ 34 , 35 ]. The increase in ozone concentrations registered in Palermo during the lockdown is linked to two factors: the decrease in NO 2 and the increased solar radiation [ 36 ].…”

A multi-meteorological comparison for episodes of PM10 concentrations in the Berlin agglomeration area in Germany with the LOTOS-EUROS CTM

“…A corresponding specification of the transformation of the available COSMO-CLM variables into the required fields within the LOTOS-EUROS CTM was performed like it was already implemented for the ECMWF model (Manders et al, 2017) and for the WRF model (Escudero et al, 2019). Both the horizontal and vertical grid configuration correspond to the model specification as provided by the DWD model family, avoiding interpolation of the data.…”

“…Due to deep reservoir layers overestimated mixing, particular during stable weather conditions with low MLHs, occurs. Therefore, recent model developments apply a much larger number of vertical layers in the LOTOS-EUROS CTM to reproduce the vertical structure of the planetary boundary layer (Escudero et al, 2019) and to provide a better understanding of the vertical distribution of pollutants, the multi-level version (MUL) negates the assumption of a well-mixed PBL and better accounts for the residual layer dynamics. The multilevel model version uses the vertical level information as provided by the meteorological input data.…”

Air quality change due to COVID-19 lockdown in India and its perception by public

“…Reduced PM in air results in increased photochemical activities and thus higher O 3 production by giving way for more sunlight to pass through the atmosphere (Dang and Liao 2017;Li et al 2018). This may also be due to the favorable conditions for ozone formation, such as high temperatures and solar radiation indices (Escudero et al 2019;Dantas et al 2020). The decrease in NOx concentration in the atmosphere (Monks et al 2015) and reduced utilization of O 3 by NO were also probably the reasons behind the increase in O 3 concentrations (Gorai et al 2017) during the control period.…”