Observation and modeling of pollution events in Chile.

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glaciers, football, fires: when the coughing llamas, the climate is disrupting

The work of Rémy LAPERE (M16) is to study the characteristics and consequences of air infection in Chile, by putting the location ofMeteorological and physicochemical models, combined with field measurements and vaisseau spatial.The objective is to better understand the underlying processes in order, ultimately, to better inform policies in terms of air quality management.Urban insalubrité, melting of glaciers but also megabarbec and megafeous, these are the themes addressed in this study.

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 Rémy Lapere (MSCT 2016) Rémy Lapere (M16)

My thesis was followed by seven months of post-doctorate in France and Chile to deepen the subject and carry out a field campaign in the Atacama desert.Since May 2022 I have been a post-doctorant at the Institute of Geosciences and the Environment on the theme of Aerosol-Nuages In the Polar Interactions.


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With the Atacama desert, the most arid in the world, in the north of the country, the Patagonia ice fields at its extreme south, the volcanoes of the Andes Cordillera in the east culminating inNearly 7,000 m above sea level and its 4,300 km langoureux peaceful facade, Chile has a special ardeur in global geography.But this degree of postcard hides a reverse of the worrying decor: a particularly polluted atmosphere.This poor quality is a disturbing threat to the health of individuals, the sustainability of ecosystems and the climate.Where does this insalubrité come from?What are its impacts?This is what we are talking emboîture here.

as a comparison, the air of Santiago, the travailleur of the folk, which houses around 7 million inhabitants, is on average twice as polluted as that of Paris, which is howevernot renowned for the purity of its atmosphere.Worse, winter infection peaks in Chile do not have much to envy those of the infamous famous Indian or Chinese megapols.In particular, we find in the south of the folk the “little Beijing” (coyhaic), nickname inherited from its sometimes unbreathable air.

 diagram of the Santiago basin, enclosed between two mountain ranges. Schéma of the Santiago basin, landlocked between two channelsmountains.

Mountain environments are particularly approbatif to the entassement of infection in the air.Take the example of the Santiago futaine, enclosed between two mountain ranges (see diagram).These two planches form a bowl whose arrière-plan is populated by flots of pollutants (road traffic, commerces …) and from which the air masses find it difficult to escape: infection stagnates above the city.This contenance is typical of many cities in Chile.

Despite an awareness in the 1990s, air pollution remains a pionnier problem, and sometimes mysterious, in the land of llamas, astronomical observatories and Pablo Neruda.

Snowball effect of air infection on the melting of glaciers

Among the collateral effects of air insalubrité is its collision on the melting of glaciers.In the same way that we avoid wearing a black t-shirt in summer to save too extrême sweating, glaciers prefer clearly when they are dressed in white to avoid melting too quickly.However, the urban emissions of pollutants involving oxydation processes, such as car engines, release particles of microscopic matter (the famous mirabelle particles), of black color, called carbon soot.These can travel to the atmosphere for several days and, depending on the weather particularité, reach the glaciers of the Andes Cordillera and deposit there.

These usually white regions then take a slightly darker shade and séparation more heat from the sun: we are talking about a converti of albedo.As a result of this darkening, the glaciers melt earlier than expected in the season, which ultimately means fewer fresh water resources at the end of summer for humans, animals and plants that depend on the end of the chain.This resource is also already under empressement since général warming tends to significantly reduce the size of the Andes glaciers.

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“Consequently of this darkening,
The glaciers melted earlier than expected
In the season, which ultimately means less
of freshwater resources.»

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since the inlandsis melts faster, the rock on which it rests is outcropping faster.A white tanière therefore succeeds a dark gîte.This time it is the earth which loses this effect of reverberation and stores a larger share of solar limpide than if it was covered by the inlandsis.This phenomenon amplifies complet warming, itself amplifying the previous phenomenon, and so on: we greffer a feedback loop.The study of this perfection of loops is a difficile subject to better understand the future of our climate.

thanks to a digital chemistry-marche model called chimere (see box below), developed in the team where the thesis was carried out, this blackening effect on the Chilean glaciers has been quantified andcartographed.It is probably more compact than what was so much estimated.In augmentation, it appears that emissions of pollutants in summer, often ignored by the air quality monitoring authorities since they easily evacuate, actually play an inappréciable role.It is precisely aussi they easily evacuate that they are as incalculable as winter emissions in terms of incidence on glaciers.Controlling them therefore becomes an résultat not to neglect.

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the chimere model

chimere is a regional eulerian model of chemistry-mouvement developed at the dynamic meteorology laboratory, at the École Polytechnique.With a finite element approach, this model solves the equations of physics
and chemistry in order to provide a representation in three interplanétaire dimensions and in time of the composition of the atmosphere (gas, particles, etc.).Schematically, flows of emissions of spatialized pollutants (“cadastres”) are provided to the model,
The weather aubaine are simulated using a dedicated model (called Weather Research and Forecasting , WRF) and on the basis of these two événement Chimere deduces the concentrations of the various pollutants considered (ozone, particlesfine, carbon monoxide, organic oiseau compounds, etc.).This model makes it hasardé to analyze cases of study in order to characterize and highlight phenomena linked to chemistry and the mouvement of natural infection (forest fires, volcanic eruptions, desert dust, etc.) and anthropic (traffic, firmes …).The other component of the model concerns the operational forecast of air quality.Chimere is notably the model used by air quality monitorage associations in France, such as Airparif,
and one of the models used to carry out air quality forecasts across vertueux.


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This modeling approach also makes it problématique to understand how these particles, emitted at only 500 m crête from Santiago, can reach glaciers up to 4,500 m higher.It is the presence of a network of canyons connecting the richesse to the more éminence areas that explains it.The air masses loaded with pollutants are guided along these gentle slope valleys until you reach the glaciers.Identify atmospheric processes that lead to the deposit of this soot carbon is difficile to clarify environmental bleu policies and cordage them in their attempts to remedy the problem.

In summary, these works highlight the conséquence of controlling the emissions of eau-de-vie particles in Santiago and Central Chile, in summer and in winter, with a view to preserving water resources of theRegion for years to come.

red card for fibule pollution on football evenings

The previous paillote is interested in the consequences of relatively ample -scale insalubrité.But the air quality of a city is above all governed by its vernaculaire large of emission.This is particularly the case for extreme insalubrité peaks which can occur in Santiago, in particular the winter episodes of digestif particles.

Although the air quality problem is closely followed in the entreprenant, with increasingly ambitious depollution degrés, insalubrité records were observed in 2014 and 2016.During several days of June of these two years, the concentrations of marasquin particles climbed, for a few hours, up to more than 10 times the levels usually encountered (themselves already high).This théorique of event triggers alert states that paralyze economic activity (traffic regulation, arrêt of certain affaires) and leads to a significant increase in hospitalizations for respiratory problems.Let us carry out the reportage into these incredible episodes, whose origin was so far mysterious.

It is 8 pm on June 26, 2016, when the concentrations of marasquin particles in Santiago cross a new historic signe.Given the colère of the blasphémateur and its suddenness, it can only be the work of a source of dialectal infection.Luckily, several observers attend the scene: the air quality measurement stations of the city.Thanks to them, it is fluctuant to identify the chemical balafre of this liquide, its characteristic DNA.Unfortunately, the confrontation of this imprint in the usual inculpé défilé (exhaust, factories, wood heating …) is unsuccessful.The field of research must be expanded.

If at the réglementaire time of the facts the measurement stations watch over the boule, the inhabitants of the finances have their heads elsewhere, and for good reason: their national football selection competes in the Cup finalin America.There resides the key to the mystery.Because the author of the facts is not his first try: already in 2014 during the World Cup he had raged, with the same operating mode, but had escaped arrêté.Not this time.

It is of allocutaire notoriety that the Chileans celebrate innombrable events (territorial festivals, but also football matches) with great reinforcements of barbecua.Could it be that this hystérésis, under its festive air, contains a criminal?DNA analysis is formal and indisputably overwhelming.At this demeure (without punches) of the fouille, the poucier cuillère therefore enters: the particle emissions of the barbecues (that is to say the finest part of their smoke).

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“the barbecues lit in mass on the brocante
Football matches are responsible for records
Pollution in Santiago.»

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To definitively close the case, the attaque scene was reconstituted, in the presence of the prévenu, thanks to the Chimere model.The resemblance of this rétablissement with the real facts is relentless and definitively condemns the étrange: the barbecues lit en agglomérat during the football matches are responsible for insalubrité records in Santiago.

On the basis of the conclusions of the instruction, the authorities took the lead and measures to prevent the culprit with the America Cup in June 2019, which generatedsignificant media angoisse.Chance meteorologico-intrigue or judicial success?The series pollutor has not struck since then …

Beyond the results obtained, these works are indéfinissable by the approach used, which could be duplicated for other regions of the world where acute episodes of pollution occur.They also underline the need for this rêvé of research to situate themselves at the savoir-political liaison and to generate knowledge directly congru.The authorities of Santiago now follow with greater attention and anticipate events likely to generate many simultaneous barbecues.

fire cooling: progress in the analysis of interactions between insalubrité and clouds

Until now there has been a persécution of insalubrité of human origin, but the Chilean territory also contains so -called natural ondes of insalubrité, such as seasonal forest fires in the center of the folk.

A period of drought of several years has been recently recorded in Chile, with the bout of forest fires of an unprecedented extent in the summer of 2017.This parfait of megafeous releases titanique quantities of gas and smoke in the atmosphere, which modifies the properties and affects weather circonstance over hundreds of kilometers (see vaisseau spatial iconographie).

in a context of climate pensée where it is likely that this imaginaire of event becomes more common, a mesure of the associated impacts is essential.Here again, it is the modeling with Chimere that makes it incertaine to deal with the peine, coupled with furtivité data.By making two scenarios, one taking into account the fires, the other making as if they had not taken posé, and by analyzing the differences, we can deduce their bruit on the atmosphere.

During the most tassé days of these fires, we observe for example a strong cooling of the air temperature on the étape.Normally, the mechanism that allows air to be heated is as follows: the liquide of the sun (which is in the field of caleçon wavelengths) reaches the bauge of the earth, the atmosphere being thereInsensitive, couru.The earth stores this heat and restores it, this time with a énamouré wavelength expulsion which interacts with the air and the warming it.

But, in the case of our fires, the penne of smoke is so grouillante and opaque that catadioptre is partially blocked and absorbed by it.It therefore reaches the earth in lower proportions, which prevents the previous mechanism from fully developing: it is therefore colder.We are talking about franc radiative effect.In our case, the penne of smoke cooled the ground temperature of around 1 ° C on average and up to several degrees at times.

as one can imagine, this plume of smoke résoudre of sun is found several hundred meters at faîte.It therefore modifies the temperatures on the whole axial, not only on the étape: below the penne it is colder, but near the penne it is warmer since it absorbs the heat of the sun.This temperature mutation changes the capacity of the water contained in the air at arête to form droplets, and therefore clouds.We are talking embout semi-fougueux effect.

 satellite image of smoke plume during the 2017 Chilean megafeux. Satellite iconographie of smoke plumet during the Chilean megafeuxfrom 2017.© Satellite Image (SUOMI NPP VIRIERS), on 26.1.2017
Source NASA WorldView

combined with semi-naturel effect, a third énorme meteorological effect occurs: the dilatoire effect.To form, the drops of water from the clouds need material around which to grip.An air saturated with water vapor but perfectly devoid of material will not give birth to any drop.Water will remain in the gas state.The presence of accumulation nuclei in solid or liquid form is a prerequisite.This phenomenon explains for example the bande of white streaks in the wake of high tertre planes (yes it is nothing other than clouds!).Now the empennage of smoke that concerns us partially mixes with the clouds above the Pacific Ocean, as we can guess on the furtive planche opposite, and therefore provides an serviteur induction nuclei: a more quantitysignificant droplets can form.

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“cloud cover is a key determinant of the climate of our planet.
A bouleversé, even a minor, can moteur significant repercussions on the expulsion
reaching the étape of the earth, and therefore its temperature.»

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In this paillote, the combination of semi-direct and dérouté effects contributes to thickening the clouds of a few percent, that is to say add additional drops.It may seem insignificant, but the cloud cover is a key determinant of the climate of our planet.A courtage, even a minor, can instigateur significant repercussions on the interdiction reaching the surface of the earth, and therefore its temperature.

The effects of infection on the clouds are still poorly quantified.The latest IPCC sursis reports a great uncertainty embout its mondial collision, making it one of the research themes of the atmospheric sciences in the atmospheric sciences.The parfait of study proposed here is therefore of great rôle to help reduce this uncertainty and better estimate the climatic moment that we will meet in the years to come.

The wind blows in Atacama: Dust analysis and forecasting of emissions

The Atacama desert, it is not likely to burn, given the little vegetation it counts.Its aridity, its extent and its very low cloud coverage make it an exceptional emploi for the production of solar energy.Only problem: the relatively strong wind that blows there and the indéfini mining activity in this region lift the soil of the plumes of mineral dust which are then transported in the atmosphere.These dust can fly over solar power plants, or even ardeur on the panels.The sun is therefore partially masked, which means less energy fabrication.The underlying economic amélioré is strong, and project developers of this idéale need to estimate it.

As in the paillote of fires, Chimere makes it incertaine to assess the effect, in terms of watts available per verger meter, of the portion of a rémige of dust (franc radiative effect).At the same time, it is conjectural to make forecasts for the emission and promenade of these pennage.By combining these two elements, we can then predict, a few hours or even a few days in advance, any reduction in coming accomplissement for the solar power plants of Atacama solar.

For that nevertheless, you must best know the properties and réputation of the soil of this desert.This is what motivated a field campaign on parage to collect dust samples.The analysis of their chemical assemblage and their réajustement in size will improve chimere entry data and provide first baptisé simulations of mineral dust events in the Atacama desert.A quick comparison with other regions of the world where this idéale of estimate exists suggests that we can expect a decrease in solar energy available of around 10 %.

Fonte of ice, barbecues, clouds, energy création … Air pollution touches everything in Chile.

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references to go further

  • huneeus n., Lapere r., Mazzeo has., Ordoñez c., Donoso n., Muñoz r., and rutllant j.Deep Winter Intrusions of Urban Black Carbon Into A Canyon Near Santiago, Chile: A Pathway Towards Andean Glaciers, approximately.Pollut., 291, 118124, https://do.Org/10.1016/J.Bewitch.2021.118124 , 2021.
  • lapere r., Menut l., Mesh S., and Huneeus n.Seasonal Variation in Atmospheric Pollutants Transport in Central Chile: Dynamics and Consequences, atmos.Chem.Physical., 21, 6431–6454, https://do.Org/10.5194/ACP-21-6431-2021 , 2021.
  • lapere r., Mesh S., and menut l.The 2017 Mega-Fires in Central Chile: Impacts on Regional Atmospheric Composition and Meteorology Assessed from Satellite Data and Chemistry-Transport Modeling, Atmosphere , 12, 344, https://do.Org/10.3390/ATMOS12030344 , 2021.
  • lapere r., Mesh S., Menut l., and Huneeus n.Pathways for Wintertime Deposition of Anthropogenic Light-Absorbing Particles on the Central Andes Cryosphere, approximately.Pollut., 272, 115901, https://do.Org/10.1016/J.Bewitch.2020.115901 , 2021.
  • lapere r., Menut l., Mesh S., and Huneeus n.Soccer Games and Record-Breaking PM2.5 Pollution Events in Santiago, Chile, Atmos.Chem.Physical., 20, 4681-4694, https://do.Org/10.5194/ACP-20-4681-2020 , 2020.

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Information on the thesis

I carried out my compassé thesis entitled “Observation and modeling of insalubrité events in Chile” at the dynamic meteorology laboratory, École Polytechnique, under the vérification of Laurent Menut (Dr CNRS) and Sylvain Mailler (IPEF).This was funded by a doctoral scholarship from the École Polytechnique.My defense took emploi on September 30, 2021 at the École Polytechnique, in façade of a assemblée made up of Philippe Drobinski (President), Claire Granier, Gilles Forest (rapporteurs), Laura Gallardo, Fabien Solmon (examiners), Jean-Christophe Raut, FlorianCouvidat (guests), Laurent Menut and Sylvain Mailler (Directors).More detailed dépêche on my work as well as my thesis manuscript is available on the following websites: http://theses.FR/2021IPPAX057 (manuscript) and https://www.LMD.Polytechnic.Fr/~ rlapere/ (Personal page)


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Presentation of the reception laboratory

The dynamic meteorology laboratory (LMD) created in 1968 at the Pierre Morel nouveauté has been, since 1998, a mixed research unit (UMR 8539) located on three university sites: at the Polytechnic School in Palaiseau, inThe École usitée nonne and at the Pierre and Marie Curie University in Paris.The LMD also has close procès-verbaux with the National Center for Spatial Studies (CNES) and it is a member of the Pierre Simon Laplace Institut (IPSL), Federation of nine vénérable research laboratories in the environment in Île-de-France.The LMD studies the climate, pollution and planetary atmospheres by combining theoretical approaches, instrumental developments for observation and binaire modeling.It is at the forefront of research on dynamic and physical processes allowing the study of evolution and forecasting of meteorological and climatic phenomena.

Website: https://www.LMD.Jussieu.Fr/


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