<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>0187-6236</journal-id>
<journal-title><![CDATA[Atmósfera]]></journal-title>
<abbrev-journal-title><![CDATA[Atmósfera]]></abbrev-journal-title>
<issn>0187-6236</issn>
<publisher>
<publisher-name><![CDATA[Universidad Nacional Autónoma de México, Instituto de Ciencias de la Atmósfera y Cambio Climático]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0187-62362023000300111</article-id>
<article-id pub-id-type="doi">10.20937/atm.53116</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[Satellite-based estimation of NO2 concentrations using a machine-learning model: A case study on Rio Grande do Sul, Brazil]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Becerra-Rondón]]></surname>
<given-names><![CDATA[Adriana]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Ducati]]></surname>
<given-names><![CDATA[Jorge]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Haag]]></surname>
<given-names><![CDATA[Rafael]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Universidade Federal do Rio Grande do Sul Centro Estadual de Pesquisas em Sensoriamento Remoto e Meteorologia ]]></institution>
<addr-line><![CDATA[Porto Alegre RS]]></addr-line>
<country>Brazil</country>
</aff>
<aff id="Af2">
<institution><![CDATA[,Universidade Estadual do Rio Grande do Sul  ]]></institution>
<addr-line><![CDATA[Porto Alegre RS]]></addr-line>
<country>Brazil</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>00</month>
<year>2023</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>00</month>
<year>2023</year>
</pub-date>
<volume>37</volume>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0187-62362023000300111&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0187-62362023000300111&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0187-62362023000300111&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[ABSTRACT Nitrogen dioxide (NO2) is one of the most important atmospheric pollutants, affecting human health (increasing susceptibility to respiratory infections) and the environment (soil and water acidification). In many regions of Brazil, NO2 measurements at ground level meet difficulties because monitoring stations are few and unevenly distributed. Satellite observations combined with machine learning models can mitigate this lack of data. This paper report results from an investigation on the ability of a machine learning approach (a non-linear statistical Random Forest algorithm, hereafter RF) to reconstruct the long-term spatiotemporal ground-level NO2 from 2006 to 2019 using as input parameters NO2 data retrieved from the Ozone Monitoring Instrument (OMI) sensor aboard Aura satellite, besides meteorological covariates and localized ground-level NO2 measurements. Results show that the RF model predicts NO2 with an accuracy expressed by an R2 = 0.68 correlation based on a 10-fold cross-validation. The model also predicted a mean NO2 concentration of 18.73 ± 3.86 &#956;g m-3. The total NO2 concentration over the entire region analyzed showed a decreasing trend (2.9 &#956;g m-3 yr-1), being 2006 the year with the higher concentrations and 2017 with the lowest. This study suggests that non-linear statistical algorithm reconstructions using RF can be complementary tools to in situ and satellite observations for NO2 mapping.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[RESUMEN El dióxido de nitrógeno (NO2) es uno de los contaminantes atmosféricos más importantes que afecta la salud humana (mayor propensión a infecciones respiratorias) y el medio ambiente (acidificación del suelo y agua). En muchas regiones de Brasil las mediciones de NO2 a nivel del suelo presentan dificultades debido a que la red de estaciones de monitoreo es escasa y está desigualmente espaciada. Las observaciones satelitales combinadas con modelos de aprendizaje automático pueden mitigar esta falta de datos. Este artículo es el resultado de una investigación sobre la capacidad de un enfoque de aprendizaje automático (un algoritmo estadístico no lineal de bosques aleatorios, en adelante RF) para ejecutar una reconstrucción espacio-temporal de NO2 a nivel del suelo, de 2006 a 2019, utilizando como parámetros de entrada datos de NO2 recuperados del sensor del Instrumento de Monitoreo de Ozono (OMI) a bordo del satélite Aura, además de covariables meteorológicas y mediciones localizadas de NO2 a nivel del suelo. Los resultados muestran que el modelo de RF predice el NO2 con una precisión expresada por una correlación R2 = 0.68 basada en una validación cruzada de 10 iteraciones. El modelo también predijo una concentración media de NO2 de 18.73 ± 3.86 &#956;g m-3. La concentración total de NO2 en toda la región analizada mostró una tendencia decreciente (2.9 &#956;g m-3 yr-1) entre 2006 y 2017. Este estudio demuestra que las estadísticas no lineales empleadas por el algoritmo de RF pueden ser herramientas complementarias a las observaciones in situ y por satélite para predecir NO2.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[nitrogen dioxide (NO2)]]></kwd>
<kwd lng="en"><![CDATA[Random Forest algorithm]]></kwd>
<kwd lng="en"><![CDATA[OMI sensor]]></kwd>
<kwd lng="en"><![CDATA[southern Brazil]]></kwd>
</kwd-group>
</article-meta>
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