Marc Guevara

Integrated assessment of air pollution using observations and modelling in Santa Cruz de Tenerife (Canary Islands)

The present study aims to analyse the atmospheric dynamics of the Santa Cruz de Tenerife region (Tenerife, Canary Islands). This area is defined by the presence of anthropogenic emissions (from a refinery, a port and road traffic) and by very specific meteorological and orographic conditions-it is a coastal area with a complex topography in which there is an interaction of regional atmospheric dynamics and a low thermal inversion layer. These factors lead to specific atmospheric pollution episodes, particularly in relation to SO2 and PM10. We applied a methodology to study these dynamics based on two complementary approaches: 1) the analysis of the observations from the air quality network stations and 2) simulation of atmospheric dynamics using the WRF-ARW/HERMESv2/CMAQ/BSC-DREAM8b and WRF-ARW/HYSPLIT modelling systems with a high spatial resolution (1×1 km(2)). The results of our study show that the refinery plume plays an important role in the maximum SO2 observed levels. The area of maximum impact of the refinery is confined to a radius of 3 km around this installation. A cluster analysis performed for the period: 1998-2011 identified six synoptic situations as predominant in the area. The episodes of air pollution by SO2 occur mainly in those with more limited dispersive conditions, such as the northeastern recirculation, the northwestern recirculation and the western advection, which represent 33.70%, 11.23% and 18.63% of the meteorological situations affecting the study area in the year 2011, respectively. In the case of particulate matter, Saharan dust intrusions result in episodes with high levels of PM10 that may exceed the daily limit value in all measurement station; these episodes occur when the synoptic situation is from the east (3.29% of the situations during the year 2011).

A novel approach to screen and compare emission inventories.

A methodology is proposed to support the evaluation and comparison of different types of emission inventories. The strengths and weaknesses of the methodology are presented and discussed based on an example. The approach results in a “diamond” diagram useful to flag out anomalous behaviors in the emission inventories and to get insight in possible explanations. In particular, the “diamond” diagram is shown to provide meaningful information in terms of: discrepancies between the total emissions reported by macro-sector and pollutant, contribution of each macro-sector to the total amount of emissions released by pollutant, and the identification and quantification of the different factors causing the discrepancies between total emissions. A practical example in Barcelona is used for testing and to provide relevant information for the analyzed emission datasets. The tests show the capability of the proposed methodology to flag inconsistencies in the existing inventories. The proposed methodology system may be useful for regional and urban inventory developers as an initial evaluation of the consistency of their inventories.

An emission processing system for air quality modelling in the Mexico City metropolitan area: Evaluation and comparison of the MOBILE6.2-Mexico and MOVES-Mexico traffic emissions

This article describes the High-Elective Resolution Modelling Emission System for Mexico (HERMES-Mex) model, an emission processing tool developed to transform the official Mexico City Metropolitan Area (MCMA) emission inventory into hourly, gridded (up to 1km2) and speciated emissions used to drive mesoscale air quality simulations with the Community Multi-scale Air Quality (CMAQ) model. The methods and ancillary information used for the spatial and temporal disaggregation and speciation of the emissions are presented and discussed. The resulting emission system is evaluated, and a case study on CO, NO2, O3, VOC and PM2.5 concentrations is conducted to demonstrate its applicability. Moreover, resulting traffic emissions from the Mobile Source Emission Factor Model for Mexico (MOBILE6.2-Mexico) and the MOtor Vehicle Emission Simulator for Mexico (MOVES-Mexico) models are integrated in the tool to assess and compare their performance. NOx and VOC total emissions modelled are reduced by 37% and 26% in the MCMA when replacing MOBILE6.2-Mexico for MOVES-Mexico traffic emissions. In terms of air quality, the system composed by the Weather Research and Forecasting model (WRF) coupled with the HERMES-Mex and CMAQ models properly reproduces the pollutant levels and patterns measured in the MCMA. The systems performance clearly improves in urban stations with a strong influence of traffic sources when applying MOVES-Mexico emissions. Despite reducing estimations of modelled precursor emissions, O3 peak averages are increased in the MCMA core urban area (up to 30ppb) when using MOVES-Mexico mobile emissions due to its VOC-limited regime, while concentrations in the surrounding suburban/rural areas decrease or increase depending on the meteorological conditions of the day. The results obtained suggest that the HERMES-Mex model can be used to provide model-ready emissions for air quality modelling in the MCMA.

A benchmarking tool to screen and compare bottom-up and top-down atmospheric emission inventories

This paper describes the Δ-Emis tool for emission inventories, recently developed in the framework of Forum for Air Quality Modelling in Europe (FAIRMODE). The Δ-Emis tool consists of a set of indicators and diagrams that support the comparison of bottom-up and top-down emission inventories. Four different comparison methods are proposed: (1) pollutant emission comparisons across sectors (bar plot), (2) quantification of the differences between inventories allocated in terms of activity data and emission factors (diamond diagram), (3) emission per capita comparisons (per-capita diagram) and (4) comparison of pollutant ratios (pollutant ratio diagram). The methodology has been tested for an urban emission inventory in Barcelona, and results show the capability of the system to flag inconsistencies in the existing inventories. The strengths and limitations of the tool are presented. The proposed methodology may be useful for regional and urban inventory developers as an initial evaluation of the consistency of their inventories.

Ozone source apportionment during peak summer events oversouthwestern Europe

It is well established that in Europe, high O3 concentrations are most pronounced in southern/Mediterranean countries due to the more favorable climatological conditions for its formation. However, the contribution of the different sources of precursors to O3 formation within each country relative to the imported (regional and hemispheric) O3 is poorly quantified. This lack of quantitative knowledge prevents local authorities from effectively designing plans that reduce the 15 exceedances of the O3 Target Value set by the European Air Quality Directive. O3 source attribution is a challenge because the concentration at each location and time results not only from local biogenic and anthropogenic precursors, but also from the transport of O3 and precursors from neighbouring regions, O3 regional and hemispheric transport and stratospheric O3 injections. The main goal of this study is to provide a first quantitative estimation of the contribution of the main anthropogenic activity sectors to peak O3 events in Spain relative to the contribution of imported (regional and hemispheric) O3. We also 20 assess the potential of our source apportionment method to improve O3 modelling. Our study applies and thoroughly evaluates a countrywide O3 source apportionment method implemented in the CALIOPE air quality forecast system for Spain at high resolution (4 x 4 km) over a 10-day period characterized by typical summer conditions in the Iberian Peninsula (IP). The method tags both O3 and its gas precursor emissions from source sectors within one simulation and each tagged species is subject to the typical physical processes (advection, vertical mixing, deposition, emission and chemistry) as the actual 25 conditions remain unperturbed. We quantify the individual contributions of the largest NOx local sources to high O3 concentrations compared to the contribution of imported O3. We show for the first time that imported O3 is the largest input to the ground-level O3 concentration in the IP, accounting for 46% to 68 % of the daily mean O3 concentration during exceedances of the European Target Value. The hourly imported O3 increases during typical northwestern advections (70-90%, 60-80 μg/m), and decreases during typical stagnant conditions (30-40%, 30-60 μg/m) due to the local NO titration. During stagnant 30 conditions, the local anthropogenic precursors control the O3 peaks in areas downwind of the main urban and industrial regions (up to 40% in hourly peaks). We also show that ground-level O3 concentrations are strongly affected by vertical mixing of O3rich layers present in the free troposphere, which result from local/regional layering and accumulation, and