Douglas Nilsson

About Douglas and his science...

WHY?

Although I have a broad interest in atmospheric environmental science, climate and earth-system science, my main focus is on sources of aerosol particles. You have probably heard that the current man-made climate changes are caused by green-house gases, certain gases that are able to absorb infrared radiation and trap that energy for a while in the atmosphere, resulting in a higher temperature. Mostly one talk about carbondioxide (CO2), which results from for example fossil fuel burning and biomass burning, and methane (CH4), which results from land use and cattle. But there are other things in the atmosphere that also influence the climate: aerosols and clouds.

An aerosol is particles suspended in air. These particles are responsible for the largest uncertainty in the radiative climate forcing due to man made pollutants, much larger than that of green house gases, potentially of the same magnitude,  but with oposite sign (cooling), see Figure from the IPCC 2013 report. High concentrations of aerosols are also related to increased health risks and mortality due to heart and lung deceases.

To predict climate change or air quality associated with aerosol particles, numerical atmospheric models of different type and scale are used. The quality of these predictions is dependent on how different processes are represented in the models, including the aerosol. Parameterisations of source, sink and transformation processes are needed. Among these, aerosol source parameterisations are probably the least well described. That motivates our foci.

Bar chart for Radiative Forcing RF (hatched) and Effective Radiative Forcing ERF (solid) for the period 1750–2011. Uncertainties (5 to 95% confidence range) are given for RF (dotted lines) and ERF (solid lines. From IPCC Climate Change 2013, The Physical Science Basis, chapter 8, Figure 8-15.

AEROSOLS V.S. GREENHOUSE GASES

It must be understood that the cooling effect of anthropogenic aerosols does not offer a hope to escape the man-made climate change. The current atmosphere is heavily loaded by man-made aerosols regionaly and has been so since the beginning of the industrial revolution. Hence, the observed global average warming so far (~1oC) is a net result of both aerosols and greenhouse gases and to minor degree some other (natural) processes. However, while the greenhouse gases have long life times, the aerosol life time range from minutes to a few weeks (depending on size). The day we stop using fossil fuels (if for no other reason because we run out of oil and coal), we will face the full consequences of the anthropogenic greenhouse gases, that are now partly masked by the anthropogenic aerosol. It is therefore important to be able to represent both anthropogenic and natural sources adequately in models, in order to model the present as well as pre-industrial conditions, and the conditions we will face once we stop burning the fossil fuels, leaving all its carbon in the atmosphere for centuries, but within weeks without the extra cooling aerosol.

Crater with a diameter of about 3 micrometer at the water surface caused by a bursting bubble with jet drop pillar and radial lines of film drops. Captured by camera in our Sea Spray Simulation tank. Photo: Douglas Nilsson

WHAT?

Currently my research focus on:

-The primary marine aerosol source (sea spray): sea salt, organic compounds, biological and toxic particles.

-Primary urban traffic aerosol emissions: combustion particles as well as mechanically produced particles from the road, tires or breaks.

-Representation of these processes in process models and climate models and what effect they have on climate change.

In the past I’ve also worked on:

-Secondary aerosol sources: nucleation of new particles and subsequent growth, in interaction with dynamic atmospheric processes, e.g. turbulence.

-Emissions of primary biogenic aerosol particles from the Amazonian rain forests.

-Arctic sulfur and sea spray aerosols, and everything that happens in the complex boyndary layer the atmosphere form over an ice covered ocean.

In the future I’d like to add some research fields to my work:

-Ship emissions are an important source of aerosols that get too little attention. I have good data from the Baltic sea, but would like to add measurements of NOx, SO2 and soot, and develop some good math and model tools to process the data. Then I think I’d like to move on to the Arctic sea where shipping will increase as the sea ice withdraw. Remember: 80% of our cargo is still moved on ships!

-Having studied one of the two big natural aerosol sources (sea spray) with eddy covariance flux measurements, I’d like to do the same with dust aerosols over desserts and semi arid land. There is a risk that these emissions will increase if climate change increase wind speed and decrease soil moisture.

However, so far I have not been able to take home the necessary grants to do this. But I haven’t given up…

Douglas instaling an Eddy Covariance aerosol flux system on a street in Stockholm. Photo: Billy Sjövall, SLB.

HOW?

The methods we use includes:

-In situ emission measurements with the eddy correlation method in e.g. the urban and marine environment, see photo above.

-Laboratory experiments of aerosol production from bubble bursting in real and artificial sea water, see photo below. I dare say that we have become word leading in this.

-Process models: numerical box models of aerosol dynamics, trajectory models, Monte-Carlo simulations.

-Global climate models: previously the Oslo-CAM model, now the Nor-ESM, in colaboration with colleagues in Osla, Norway .

-Analysis of measurements: aerosol number size distributions and supporting meteorological and chemical data from several measurements stations through international networks, campaigns and co-workers.

Sea spray simulation tank, temperature control, aerosol instrumentation etc. Matt Salter (left) and Douglas Nilsson (right). Photo: Douglas Nilsson.

OUTPUT

There are of course many aspects of our research results, but one I’d like to promote more than others are the most refined end-results, the source or process parameterisations. The intention is to provide a reasonable way to include complex processes in large models, where these of course have to be simplified, and where this has to be done as a fair compromise between accuracy and computational efficiency. Not all our parameterisations live up to this, but we are trying.

So far we have managed to parameterise, or express as emission factors:

Secondary aerosol formation (nucleation):

-The effect of air parcel mixing on binary nucleation (Nilsson and Kulmala, 1998)
-The effect of atmospheric waves on binary nucleation (Nilsson et al., 2000)
-The probability of nucleation as a function of vertical wind or temperature variance (Buzorius et al., 2003)
-The effect of spatial or temporal variability (e.g. turbulence) on binary nucleation (Lauros et al., 2006)
-The monthly probability of new aerosol formation (Nilsson et al., 2006)

The primary marine aerosol formation (sea spray):

-Primary marine total aerosol number emissions as a function of wind speed over open sea and partly ice covered sea, respectively (Nilsson et al., 2001)
-Primary marine sea salt aerosol number emissions as a function of wind speed and sea surface water temperature: 1st generation, Mårtensson et al. (2003); 2nd generation and much improved, Salter et al. (2015).
-Modal version of the Mårtensson et al. (2003) sea salt source parameterisation (Struthers et al., 2011).
-Aerosol optical thickness over the ocean as a function of wind speed (Glantz et al., 2006).

The primary aerosol source of road traffic:

-The aerosol number emission of particles from traffic as a function of traffic intensity, type and friction velocity (Mårtenssson et al., 2006).
-Size dependent emission factors for particles from 0.25 to 2.5 micrometer diameter (Vogt et al., 2011a).
-Size dependent emission velocities for particles from 0.25 to 2.5 micrometer diameter (Vogt et al., 2011b).
-Emission factors for particles of different volatility from 0.25 to 2.5 micrometer diameter (Vogt et al., 2011c).

Emissions of biogenic primary particles from the Amazonian rain forest:

-Number emissions as function of wind speed (Ahlm et al., 2011).

Comparison of the modeled Top of Atmosphere (TOA) aerosol direct radiative forcing and the first aerosol indirect effect for natural aerosols derived from simulations based on the difference between the climate (sea ice and water temperature) of 2000 compared to 2100. Figure 14 in Struthers et al. (2011).

Finally, we want these parameterisations to be used by modellers. That is necessary for our research to be useful for policymakers etc. After all, climate models are the primary tool to assess future climate and how it depends on different political and economical choices. The first time someone used our sea spray source parameterisation from Mårtensson et al. (2003) and published it was in 2004…and we celebrated! Over time, Mårtensson et al. (2003) became an accepted standard for sea spray source parameterisations, and the only one so far that took into account the surface water temperature. Now we have replaced it with the improved parameterisation of Salter et al. (2015).  With time we were also able to apply our parameterisations in models ourselfes, as in Mårtensson et al. (2010), Kirkevåg et al. (2013), Struthers et al. (2011, 2013) and Salter et al. (2015).

SMALL CONTRIBUTIONS TO IPCC

When IPCC in their 5th Assessment Report (2013) with a few lines cited our work in Struthers et al. (2011), on the feedback and aerosol radiative forcing caused by changes in sea spray aerosols following on changes in sea ice and water temperature due to climate change in the Arctic, it felt like a great victory after a decade of work, from experiment to GCM! In 2021, IPCC cited two more of our studies in their 6th Assessment Report: One of these was Struthers et al. (2013), where we use the sea spray source expressed by Mårtensson et al. (2003) and Struthers et al. (2011) to quantify the sea spray production over various parts of the world oceans from 1870 to 2100, following observed and modelled changes in sea surface temperature, wind speed and sea ice. The other was the laboratory study by Salter et al. (2014), where we in a much more advanced experimental sea spray simulation tank quantified how the sea spray production decrease with increasing temperature, and where we showed that this effect is caused by changes in the surface bubble spectra, possibly caused by the temperature sensitivity of bubble coalescence. While we realize that these three peer review papers are only small bricks in the large construction of the earth’s climate system, we take IPCC’s citations as a signal that our work have been found relevant by a wider part of the climate change research community.

WHO?

M.Sc. students/Internships I have supervised:

–Monica Mårtensson (2001), later took her Ph.D. for me.
–Anna Grönlund (2001), now at SMHI.
–Stefan van Ekeren (2002-2003), then took a Ph.D. degree at Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Switzerland, now Dozent at the Saxion University of Applied Sciences, Netherlands.
–Eva Brokhöj (2003), now at SMHI (I see her name now and then when the Swedish weather service issues a storm warning!).
-Xuan Liu (2009-2010).
–Karin Jonsson (2011), now operational forcast meteorologist at SMHI.
–Sarah Howald (2012-2013), now Ph.D. student at Alfred Wegener Institute, Helmholtz centre for Polar and Marine research, Bremen, Germany.

The team that installed equipment for ACES on R/S Celtic Explorer during the EU-project MAP. Standing from left: Kai Rosman, Radek Krejci, Göran Lidén, Kim Hultin, Lars Ahlm, Monica Mårtensson, and kneeling Douglas Nilsson. Photo: Douglas Nilsson

Ph.D. students I have supervised:

–Julika Zinke, started 2019, working on the CROISSANT-project (VR)
-Andrew Butcher (Ph.D. 2013, Copenhagen University), now at Infuser, Copenhagen, Denmark.
–Julia Zabori (Ph.D. 2012, Stockholm University), now works with climate data at SMHI.
–Matthias Vogt (Ph.D. 2011, Stockholm University). After a post doc in Helsinki, he now works as a researcher at NILU, Norway, focused on indoor aerosols.
–Camilla Fahlgren (Ph.D. 2011, Linnaeus University).
–Lars Ahlm (Ph.D. 2010, Stockholm University). Made a post-doc at Scripps Institute of Oceanography, San Diego, then returned to ACES. Now at ÅF consult, Stockholm, Sverige.
–Kim Hultin (Ph.D. 2010, Stockholm University), now wind power consultant at Pöyry, Sweden.
–Monica Mårtensson (Ph.D. 2007, Stockholm University), later worked for me as post-doc.
–Johanna Lauros (Fil. lic. 2005, Stockholm University; Ph.D. 2011, Helsinki University), now at University of Jyväskylä, Finland.
–Admir Targino (Ph.D. 2005, Stockholm University), after a post doc at University of Manchester, Centre for Atmospheric Science, U.K., now at Universidade Tecnológica Federal do Paraná, Brasil.
–Peter Tunved (Ph.D. 2004, Stockholm University), now researcher at ACES.

Post docs, Assistant Professors/Junior Researchers whom worked for/with me:

–Piotr Markuszewski, my post doc starting 2020-09-01, 2 years, working on sea spray including the CROISSANT project, see below.
–David Hadden, my post doc starting 2019-03-18, 2 years, working on the BREAD-project, see below.
–Matthew Salter, my post doc 2012-2017, now researcher at ACES.
–Hamish Struthers, my post doc 2010-2013, now at the National Supercomputer Centre, Linköping, Sweden.
–Monica Mårtensson, my post-doc 2007-2010, now Assistant Professor at Uppsala University, Department of Geoscience, Sweden.
–Paul Glantz, came to us with an Assistant Professor/Young researcher-position from FORMAS, now Associate Professor at ACES.
–Farahnaz Khosrawi, came to us for a M. Currie-post-doc 2004-2005, now at Karlsruhe Institute of Technology, Germany.
–Gintautaus Buzorius, my post-doc 2002-2003, then at Center for Interdisciplinary Remotely Piloted Aircraft Studies, Naval Postgraduate School, Monterey, California, USA. Now at Upwork, San Fransisco, USA.

Colaboration includes senior researchers and co-supervisors at ACES and numerous colleagues outside ACES, see specific projects below.

WHERE?

Since 2004 I am based in the Atmospheric Science Unit at the Department of Environmental Science and Analytical Chemistry (ACES) at Stockholm University. This is a great place to be in, where a lot of interesting research is performed; work that inspire us, complement or overlap our work. Most of my projects run with one or several of the other researchers here as partners, and did so already before moving here, which was one of the reasons to move. There is no sharp boarder between the research lead by different scientists here and different project link closely into each other, which helps form a creative environment. In 2004 ACES also transformed from an “institute” into a “department”, with the result that we are now building up our own master program in environmental science. It is a great opportunity to be able to influence the creation of a new education. Through ACES we also belong to several international networks/ centre of excellence and the Bolin Centre for Climate research.

VISION

I’m enrolled in this work for two main reasons. First of all, I can’t think of anything more fun and rewarding to do (except being parent) than to plan, lead and conduct scientific research. It is like being a detective when we are trying to lure the Nature to give up her secrets while building a better and better picture of how the Nature works. To try to understand those things I see around me like clouds or waves and how they are connected is a challenge, and much more fun (I think) than to study something more abstract. There is no lack of theoretically difficult aspects of our work (for one thing – we move around and within one of the big unsolved mysteries of science: turbulence), but on days when I’m up to my throat in administration, I can always go into the lab and grab a screwdriver or sit down and work with some data that originates from our measurements in the real atmosphere or ocean. Secondly, I find much of my motivation in the urgent need to understand the complexity of the planet Earth for reasons of the rapidly ongoing climate and environmental changes. It is obviously too late to stop, but we (as individuals and as society) can make choices that minimize the further damages, and we have no choice but to try to adapt to those changes that are now inescapable, and to do so we need to understand what is happening and to make the best possible guesses on the future.
All our work is only a few pieces of that puzzle, but no one is going to solve the whole problem alone, it can only be done with contributions from many, many research teams around the world. Somewhere on the road (it is unclear to me when) I decided to try to make a contribution to this puzzle. Running my own research projects, building up a team that work together, participating in international projects, collaborating with many other scientists, founding my own science, supervising students-about-to-become-researchers are all part of this work and an attempt to make a larger contribution than I could myself if I worked alone.
Supervising PhD-students are perhaps the most challenging part. Imaging that you are to teach someone something you don’t know yourself. To lead someone beyond what can be found in text books or specialist magazines, to enter areas where only Nature can be the teacher. To do this one have to transfer not only knowledge, but also how to find or build new knowledge. The direct translation of “supervisor” to Swedish have a negative sound to it. The word we use in Swedish is “handledare”, which indicates that we are more of a guide, someone who “lead you by the hand”. That is more close to my vision of what sort of supervisor I wish to be, but I am beginning to realize that there is not one correct way to supervise. For each new student I have to be a new supervisor.

SPONSORS

Our research is mainly supported by the European Commission, the Swedish Research Council (VR), and the Swedish Research Council for Environment, Agricultural Science and Spatial Planning (FORMAS). Up to know I have collected (cumulatively) ~6.8 millon Euros in grants.

CURRENT PROJECTS

–Brake particles and Road dust Emission factors based on in-situ Aerosol Direct micrometeorological fluxes (BREAD) /2017-2021 / FORMAS

–Characterising properties of Climate Relevant Organic and Inorganic Sea-Spray-aerosols, Sources and Air-seaexchange causing their Net-emission (CROISSANT) / 2019-2022 / VR

-Measurements of particulate mass over the Baltic Sea from sea spray and ship emissions / 2020-2022 / Carl Trygger Foundation

PAST PROJECTS

(data evaluation and publications may still be on its way)

–Long-range transport of pollutants associated with marine aerosols/2017-2020/ VR + FORMAS

–Climate Effects of Sea Spray Aerosols (CESSA) /2015-2019 / VR

–Influence of marine microbiology on sea spray aerosol, cloud and climate (MASC) / 2011-2013 / VR

–Seasonal variation in the primary marine aerosol source due to physical and bio/chemical processes/ 2008-2010 / FORMAS

–Green House Arctic Ocean and Climate Effects of Aerosols (GRACE)/ 2008-2010 / VR (Interdisciplinary Climate call together with FORMAS, jointly four departments at Stockholm University and Lineus University)

–Traffic Emissions of Aerosol Particles (TEA) / 2006-2008 / FORMAS

-Amazonian Biosphere-Atmosphere Aerosol Fluxes in view of their potential control of cloud properties and climate (AMAFLUX) / 2006-2009 / SIDA

–Primary Aerosol Emissions – Important sources of climate active aerosols / 2007-2008 / VR

–Land-atmosphere-biosphere facility (LAPBIAT) / 2006-2010 / EC 5th

–Ocean-atmosphere transfer of organic, biological and toxic aerosols / 2005-2007 / FORMAS

–Secondary Marine Aerosol Production from Natural Sources (MAP) / 2005-2009 / EC 6th

–The Primary Marine Aerosol Source (PMA) / 2004-2006 / VR

-Micrometeorological measurements of size-dependent particle and particle component emission above a city (CITYFLUX) / VINNOVA

–Particles in the upper troposphere and lower stratosphere and their role in the climate system (PARTS) / 2001-2004 / EC 5th

–Quantification of Aerosol Nucleation in the European Boundary Layer (QUEST) / 2001-2005 / EC 5th

-NorFA Network for Atmospheric Aerosol Dynamics (NAD) / 2001-2005 / NorFA

–Measurements of the primary marine aerosol source with the eddy correlation and relaxed eddy accumulation methods / 2004 / Medium expensive equipment / VR

–Physical Climatology / 2003-2008 / Rådsforskartjänst (Swedish Research Council Fellow) / VR

–Aerosol sources from a climate perspective / 2003 / VR

-Parameterisation of primary and secondary aerosol sources to help improve estimates of the aerosol climate forcing / 2001-2002 / VR

-Sub-grid scale aerosol dynamics for global models to improve aerosol climate effect estimations / 1999-2000 / VR

–Climate Effects of Aerosol Particles /1999-2003 / Forskarassistenttjänst (Position as Assistant Professor) / VR

-Aerosol deposition over Antarctic ice / 1999-2000 / Swedarp

–BIOFOR (Biological Aerosol Formation in the Boreal Forest) / 1997-1999 / EC 4th

-Atmospheric research on the Arctic-96 expedition – Sulphur and its climatic impact / 1995-1997 / VR

Students working on the Sea spray laboration as part of the Aerosol Physics course MI4004. They use a smaller simpler sea spray simulation tank than in the research studies.

TEACHING

Before 2004 I was student councelor at the Department of Meteorology (MISU), where I also teached in meteorology and chemical meteorology. From 2001-2005 I coordinated a NordForsk Network for Atmospheric Aerosol Dynamics, which arranged two international Ph.D. courses per year with 15-25 students each. In practise I functioned as an international graduate school headmaster. After that I served for several years in the board of the NordForsk graduate school C-BACCI.

At ACES I am the course coordinator of the course Aerosols, Clouds, and Climate (15 ECTS, MI7021). This is in many ways the most important course we have at the atmospheric lab at ACES, a must for students with the intention to make a master thesis or even a Ph.D. thesis with a climate focus. The corresponding 15 ECTS curse with a health ange is the course on Air Quality Out doors and In doors (15 ECTSm MI7007). On MI7007 I have only given some lectures on turbulence and micrometeorology in/over cities. But the Aerosol, Clouds, Climate course is a long term engagement. The course was first developed 10 years ago in an earlier version, with me as course coordinator, first as a stand alone master course, which also many of our Ph.D. students took. We have now updated the course with the same focus, but with new prerequisites, new litterature, 3 new laborations, and a climate role play game, and we have fit the course into the new master program at ACES: Master’s Programme Environmental Science: Atmosphere-Biogeochemistry-Climate (ES-ABC). The is given in its new form for the first time in spring term 2020. Within the same Master Programme, I also teach on Atmosphere, Biogeosphere and Climate (15 ECTS, MI7016). I’m specifically teaching the block of the course that covers the work by IPCC, how they work, and the results in their latest assesment report (AR15) and selected special reports (SRES, SR15, SROCC). I have to admit that I thought I knew these reports well. I had a lot of reading to do to be able to condence the content for the students, and now I know them quite well!

I’ve also been teaching minor parts in the courses Aerosol Physics (7.5 ECTS, MI4004), Environmental Physics (15 ETCS, MI4009), and Air Quality Outdoors and Indoors (15 ETCS, MI7007).

JOIN US, CONTAC US

If you find our research interesting, please don’t hesitate to contact us. Perhaps you are in need for a subject for your Master thesis, interested in graduate studies, or a place to spend your post doc? We are always in need for bright people. Maybe you just want a pdf of one of our papers, or help with implementing our parameterisations in your code (we typically have ready code in both matlab and Fortran). Give me a call!

OPEN POSITION

I have currently no open possitions as Ph.D. student or Post. Doc., but take a look at ACES web page, there might be possitions announced by my colleagues.

If you are in search of a project and super-visor for a master thesis/ex-job, me and my Post. Docs. have some ideas regarding projects that could suit for an exam in atmospheric science, earth sciences, environmental science, aerosol physics, meteorology, oceanography, or a civil engineering exam. Contact me if you are interested.