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Measurements of Aerosol Vertical Distribution

By Andrea Baccarini, University of Trento, Italy

My name is Andrea, I’m a master’s student in physics from the University of Trento and I spent a couple of months in the Azores for my master’s thesis.

I’m studying the aerosol vertical structure from Pico, a remote island of the Azores, with a stratovolcano. An atmospheric observatory with meteorological observations is located at the top of the volcano. The position of that station is very particular, in fact thanks to its elevation it is situated in the so called “free troposphere”. And, for which reason should this matter? It matters, because it allows us to study air that comes from far away places, typically the North America. Within a certain approximation, we can say that the free tropospheric air is not influenced by the local emissions (I mean the emissions from the island itself) . This is motivated by the fact that the beginning of the free troposphere (called the boundary layer) is characterized by a thermal inversion (Figure 1). Thanks to the thermal inversion, the air masses do not easily exchange components at the boundary layer. The identification of the boundary layer is pretty easy if there are low clouds. In fact in that case the height at which the clouds disappear corresponds to the beginning of the free troposphere.


Figure1: The caldera of the Pico volcano with a visible thermal inversion as seen by the confined clouds.

However every time we speak of the atmosphere, we must keep in mind that the situation could be really dynamic, especially if you are on a remote island in the middle of nowhere, exposed to every kind of perturbation. For this reason, it is important to characterize the vertical structure of the atmosphere and to understand within which conditions measurements done at the observatory can be considered to be independent from local emissions.

How do I do this vertical characterization? 

In theory it is pretty simple; I put all my instruments in a backpack and hike (Figure 2), starting from an elevation of about 1200 meters above sea level to the Pico Mountain Observatory (2200 meters above sea level). In my backpack, I have an instrument that collects pressure, temperature and humidity,  although it is pretty small I usually put this instrument into a big case to protect it from direct exposure to solar radiation. I also have a nephelometer, this is the biggest instrument, and it measures the light scattered from the particles present in the atmosphere (i.e. Aerosol, dust, etc…). Moreover I carry a particle counter which allows me to measure the concentration of particles with diameters above 0.3 μm and 0.5 μm. This instrument is especially useful because it allows me to distinguish between the dust particles, generally bigger than 0.5 μm, and the combustion aerosols that are generally smaller. Finally I have a sunphotometer, an instrument that measures the intensity of the sunlight that reaches the detector. In this way, it is possible to have an idea of the quantity of haze present into the atmosphere above the observer. In addition to all these instruments, I also use a GPS in order to track my position and my elevation.


Figure 2: Andrea Baccani with his measurement backpack

A Strange Event

Recently, we noticed a very interesting event that I will describe briefly without much technical detail. On a clear day, with clouds well below the top of the mountain we noticed something unusual. Thin grey layers above the clouds are often visible and are an indication of the presence of some kind of particulate, like aerosol from anthropogenic emission or biomass burning, dust, etc… However on this specific day we noticed a particularity: the layer above the clouds was composed of three well-defined sub layers (Figure 3). This was the first time we observed an event like that and it would be very interesting to understand why that triple stratification happened and if the composition of the layers was different or not.


Figure 3: A photo of the aerosol layers above the clouds. High contrast was used to clarify the image (blue box).

The most interesting part is that these three layers were also present in my profiles measurement and this provides us with good informations about the height and the thickness of the layers.

To show this to you, I will use a couple of graphs. The first graph is the particle concentration profile (Figure 4). On the vertical axis there is the elevation while on the horizontal axis there are the particle concentrations. The particles with a size above 0.3 micron are shown in green and those above 0.5 micron are shown in blue. The first thing to notice is that both of the signals have a clear decrease around 1500 meters. This is likely associated with the passage into the free troposphere and is supported by the temperature profile that indicates an inversion at the same height (not reported here). Above the boundary layer there are evident variations in the signal of small particles concentration,while the signal for the bigger particles seems to be pretty stable (around 0.3 particles for cubic centimeter). Because most dust particles are bigger than 0.5 microns we may exclude the presence of dust in the layers. This is pretty important because dust is generally the most abundant type of remote atmospheric aerosols.


Figure 4: The particle concentration profile observed from the Pico Mountain profile measurements. 

Now we can notice that at the moment of the measurements, the first layer was approximately 450 meters thick, starting at a height of 1600 meters and ending at 2050. The second starts around 2100 meters and ends at 2250 meters and for the third later we can observed only the beginning at approximately 2300 meters above the sea level. Clearly the identification of the position of the layers is subjected to some uncertainties that we estimate to be approximately around 50 meters.

In order to confirm these observations we will look at the nephelometer data shown in the graphs below (Figure 5). The elevation is again on the vertical axis and the scattering coefficient is on the horizontal axis. The scattering coefficient, is a measure of the light scattered intensity (it corresponds to the size and the number of particles that scatter the light). In this data the three layers are somewhat less evident because the level of noise is higher, however their position corresponds quite well to those measured with the particle counter.


Figure 5: The aerosol scattering  profile observed from the Pico Mountain profile measurements. 

In summary, we measured the three aerosol layers above clouds with two different instruments. These measurements provide evidence to conclude that what we measured is effectively what we saw looking at the horizon and was not an artifact. However at this moment, this is only a preliminary analysis that requires further technical investigations in order to be confirmed. Moreover, it will be interesting to analyze additional data collected at the station in order to obtain more information about these layers and maybe understand their composition and origin. So, stay tuned because maybe some updates will come!!!

See also – Portuguese News about this study

Ilha Maior Artigo de Jornal – Portuguese Versão

Andrea Baccarini , Claudio Mazzoleni e Lynn Mazzoleni  foram entrevistados por David Borges, um repórter de um jornal local em Madalena, em julho de 2015. Aqui está a história jornal que resultou da nossa conversa.

Publican em 4 de setembro de 2015  (English Version Available)

‘Pico Nare’ é uma estação de referência para cientistas estudarem poluição atmosférica

Escrito por David Borges, Ilha Maior 

A estação ‘Pico Nare’ que está colocada na cratera da montanha continua a ser um observatório de excelência para estudar a poluição atmosférica que circula no Atlântico Norte.

Essa importância foi sublinhada em declarações a Ilha Maior por Claudio Mazzoleni. O cientista diz que a estação do Pico é única e está para a Europa como a do Hawai está para o continente americano: “São como sentinelas que intercetam a poluição que vem do oeste. No caso do Pico a estação é um ponto no meio do Atlântico, uma torre única que permite acesso à troposfera livre, possibilitando o estudo das propriedades dessas partículas.”

A cientista Lynn Mazzoleni, que nos últimos anos tem utilizado o observatório para desenvolver vários tipos de estudos, adianta que apesar das dificuldades sentidas para garantir o necessário financiamento o observatório não irá fechar. Segundo a cientista da Michigan Tech (universidade no michigan), além do interesse dos Estados Unidos em tudo o que se relaciona com o clima, Portugal também está atento ao observatório existindo inclusivamente um grande grupo ligado à investigação da atmosfera e da química que tem uma proposta para utilizar a estação como local privilegiado para desenvolver vários estudos atmosféricos.

“Há sempre coisas novas para descobrir e queremos saber mais e mais. Até já agora vimos a transformação de partículas de uma forma que nunca tinha sido observada antes porque a morfologia muda com o transporte e suspeitamos que isso é uma consequência das nuvens”, diz a cientista norte americana acrescentando que entre os vários estudos em curso na estação fundada em 2001 por Richard Honrath “os cientistas tentam identificar o segundo componente na atmosfera que contribui para o aquecimento e que pode constituir uma das grandes causas do aquecimento global resultante de incêndios ou de outros tipos de combustão”.

Além deste trabalho um dos estudos em curso atualmente na ‘Pico Nare’ está a ser desenvolvido por um aluno da universidade italiana de Trento.

O trabalho consiste em subir e descer a montanha com instrumentos de bolso para melhorar a precisão das medições, tentando caracterizar a composição vertical dos aerossóis na atmosfera

O estudo faz parte da tese final de Andrea Baccarini, tendo o aluno optado pelo Pico para, não trabalhar apenas em laboratório: “A estação do Pico é o local ideal para um estudo deste tipo por ser um local remoto fora das grandes cidades onde é possível fazer as medições na troposfera livre, o que permite ter a certeza que o que medimos não é de produção local da ilha, mas proveniente do norte dos Estados Unidos, Canadá e Alasca onde há muita falta de água e as partículas que vão para a atmosfera chegam a atingir esta ilha.”

O aluno da universidade italiana explica que seria possível realizar o trabalho mesmo que não houvesse a estação do Pico, porque os instrumentos podem ir no bolso. No entanto esclarece que a ‘Pico Nare’ contribui para de forma mais precisa comparar e confirmer as medições com as dos instrumentos de bolso.

Andrea Baccarini não sabe quando é que terá conclusões para apresentar, mas espera que até final do ano ter conseguido trabalhar todos os dados recolhidos e apresentar os resultados o mais rápido possível.

Composition of Long-Range Transported Aerosol

We recently published a technical paper in Atmospheric Chemistry and Physics about the composition of long-range transported aerosol observed at the Pico Mountain Observatory.  This work represents a novel perspective on the composition of free tropospheric aerosol. We believe this work is significant because it challenges the current understanding of aerosol aging. Although aerosol are oxidized with respect to time in the atmosphere, the long-lived aerosol observed here appear to represent the fraction of aerosol which is not easily removed.

To learn more please see: Dzepina et al., ACP, 2015.

Mountaineering for Science

Written by Lynn Mazzoleni

IMG_0414Sometimes our work at the Pico Mountain Observatory is both mentally and physically challenging, but it is always rewarding.  Since we arrived almost two weeks ago, the weather has been fairly uncooperative.  We had a few days of warm sunshine, kindly reminding us of why we are here, “to sample the air of the marine free troposphere far away from direct emission sources”.  From our previous work at this remote location, we recently published two technical papers about our observations of soot morphology and aerosol chemistry.  These technical observations  inform the scientific community about the effects of long-range transport on the aerosol mainly from North America.

This year’s fieldwork is now underway and just as we picked up some momentum, the weather became difficult to predict.  This means, that sometimes we will not be able to do our work upon reaching the Observatory and sometimes traversing up and down the mountain is dangerous and especially so with high winds and rain.  This year is particularly special, because we are hosting a guest scientist from Trento Italy, who’s planning to collect some very special mountain profile measurements by carrying several small instruments on his back.  Thus, sitting in the apartment and waiting for ideal conditions is absolutely out of the question.

Continue reading Mountaineering for Science

Research Personnel and Collaborators

Postdoctoral Researchers

Katja Dzepina, Postdoctoral Researcher in Chemistry at Michigan Tech, 2012- 2014

Dr. Dzepina worked at the Observatory in 2012 and 2013. She is the lead-author of “Molecular Characterization of Free Tropospheric Aerosol Collected at the Pico Mountain Observatory: A Case Study with a Long Range Transported Biomass Burning Plume” a technical paper published in Atmospheric Chemistry and Physics, 2015 (Learn more).

She is currently at the University of Rijeka (Curriculum Vitae).

Sumit Kumar, Postdoctoral Researcher in Physics at Michigan Tech 2012 – 2013

Dr. Kumar worked at the Observatory in 2012. He is finalizing a technical paper in collaboration with Dr. Paulo Fialho about the observed trends in black carbon over the years 2001 – 2014. He has also presented his work at the American Geophysical Union Fall Meeting in 2012.

He is currently at the National Center for Medium Range Weather Forecasting, Noida, India (Contact information).

Graduate Student Researchers

Kendra Wright, Ph. D. Student in Physics at Michigan Tech, 2012 – Current 

Kendra Wright was awarded a NASA graduate fellowship for her doctoral research related to novel measurements of black carbon to be done at the Pico Mountain Observatory.  She has worked at the Observatory in 2013 and 2014 and she is currently working with data collected over 2012-2014.  She presented some of the preliminary results of her research at the American Geophysical Union Fall Meeting in 2013 and 2014.

Simeon Schum, Ph. D. Student in Chemistry at Michigan Tech, 2013 – Current

Simeon Schum is working on the molecular characterization of aerosol samples collected at the Observatory.  He participated in fieldwork in 2014 and he is the lead chemist for the measurements of water-soluble ions.  He is also working on a new technical publication regarding the detailed composition of long-range transported biomass combustion plumes.

Bo Zhang, Ph. D. in Environmental Engineering, Michigan Tech, 2009 – 2015

Dr. Zhang worked with samples and data collected at the Pico Mountain Observatory.   He is the lead-author of a technical paper titled, “A Semi-Lagrangian View of Ozone Production Tendency in North American Outflow in the Summers of 2009 and 2010” published in Atmospheric Chemistry and Physics, 2014 (Learn more).  Currently, he is finalizing a publication about the age of long-range transported aerosol collected in 2013 using radioactive isotopic measurements.  Dr. Zhang also conducted FLEXPART trajectory analyses for a climatological analysis of the site over several years.

Bo is currently working as a postdoctoral researcher at the National Institute of Aerospace (Brief biography).

Lorentyna Harkness, M.S. in Applied Science Education, Michigan Tech, 2014

Lorentyna Harkness is a professional K-12 science teacher. She participated in fieldwork at the Pico Mountain Observatory in 2013 and developed a novel set of multimedia teaching materials for teachers of middle school science students.  The curriculum focuses on the science of the Pico Mountain Observatory research projects and the scientific process (Click here).

Swarup China, Ph. D. in Atmospheric Science, Michigan Tech, 2009 – 2015

Dr. China worked with our group on samples collected at the Observatory in 2012, 2013 and 2014.  He is the lead-author of a technical paper titled, “Morphology and Mixing State of Aged Soot Particles at a Remote Marine Free Troposphere Site: Implications for Optical Properties” published in Geophysical Research Letters, 2015 (Learn more). He is also a co-author of another technical paper titled,  “Perturbations of the Optical Properties of Mineral Dust Particles ” published in Atmospheric Chemistry and Physics, 2015 (Learn more).

Swarup is currently working as a postdoctoral researcher at the Pacific Northwest National Laboratory (Brief biography).

Andrea Baccarini, M.S. Student in Physics at the University of Trento, Italy

Andrea Baccarini is working at the Pico Mountain Observatory this summer (2015).  He is a masters student in Physics at the University of Trento, Italy.  He is collecting measurements to study the stratification of the atmosphere using backpack instrumentation while hiking from the Casa da Montanha (1225 m asl) to the top of the Pico volcano (2351 m asl) for his thesis research. Currently, he measures relative humidity, temperature, pressure, particle concentration, particle scattering and solar irradiance when the weather permits.


Noel Urban, Professor of Environmental Engineering at Michigan Tech (Professional page)

Judith Perlinger, Professor of Environmental Engineering at Michigan Tech (Professional page)

Robert Chris Owen, Scientist at the U.S. Environmental Protection Agency; Adjunct Professor of Geology at Michigan Tech (Linked IN profile)

Donald Wuebbles, Professor of Atmospheric Science at the University of Illinois (Professional page)

Sarah Green, Professor of Chemistry at Michigan Tech (Professional page)

K-12 Education Outreach

IMG_1407“I was out in the field on the island with the team for part of last summer,” Harkness says.

Lorentyna Harkness and Lynn Mazzoleni sat down with Michigan Tech reporter, Danny Messinger, to talk about our outreach activities for this project. Here’s an excerpt of the story.

Written by Danny Messinger

If you ask an eighth or ninth grader what a scientist really does, you’re likely to hear plenty about wearing lab goggles and white coats, watching bubbling beakers, and preparing microscope slides. But besides surface-level attributes, many students have trouble explaining what being a scientist actually entails.

That’s exactly the issue Lorentyna Harkness aims to tackle. Harkness is a high school science teacher earning a master’s in applied science education at Michigan Technological University. As part of her degree program, she is teaming up with Tech chemistry and physics faculty to break complex scientific principles into bite-sized chunks for teenage students and to clarify what scientists actually do. And that’s music to Lynn Mazzoleni’s ears.

Continue reading K-12 Education Outreach