Douglas Nilsson

Associate professor
Room: X217
Phone: +46 8 674 7542

Research field

Although I have a broad interest in atmospheric environmental science, climate and earth-system science, my main focus is on sources of aerosol particles.

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, but with opposite sign and potentially of the same magnitude. High concentrations of ultra fine 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.

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 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 lifetime range from minutes to a few weeks (depending on size). The day we stop using fossil fuels (if for no other reasons 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 have spent the fossil fuels, leaving all its carbon in the atmosphere, soon without the extra aerosol.

Currently my research focus on:
-Secondary aerosol sources: nucleation of new particles and subsequent growth, in interaction with dynamic atmospheric processes, e.g. turbulence -The primary marine aerosol source: 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 -Emissions of primary biogenic aerosol particles from the Amazonian rain forests
-Representation of these processes in process models and climate models.

The methods we use includes:
-Laboratory experiments of aerosol production from bubble bursting in sea water. -Climate chamber experiments with tropical plants (barely started). -In situ emission measurements with the eddy correlation method in e.g. the urban and marine environment.
-Process models: numerical box models of aerosol dynamics, trajectory models, Monte-Carlo simulations.-Global models: currently the Oslo-CAM model, in the future probably also the EC-Earth model.
-Analysis of measurements: aerosol number size distributions and supporting meteorological and chemical data from several measurements stations through international networks, campaigns and collaborators.

There are of course many aspects of our research results, but one we wish 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 parameterised:

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 aerosol formation as a function of monthly frequency of Arctic air and the monhtly averaged normalised UV-B radiaiton in the morning hours (Nilsson et al., 2006)

The primary marine aerosol formation: -Primary marine total aerosol number emissions as a function of wind speed (Nilsson et al., 2001) -Primary marine sea salt aerosol number emissions from 20 nm to 3 um as a function of wind speed and sea surface water temperature (Mårtensson et al., 2003)
-Modal version of the sea salt source parameterisation (Struthers et al., 2011).
-Validation by an in situ independent data set of the same parameterisation from 100 nm to 1 um (Nilsson et al., 2007) -Aerosol optical thickness over the ocean as a function of wind speed (Glantz et al., 2006)
-Marine bacteria concentration as function of wind speed (Nilsson et al., 2011)

The primary urban aerosol source: -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)
M.SC. Students I supervise/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 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)

Ph.D. Students I supervise/have supervised
Andrew Butcher (started 2010 at Copenhagen University)
Julia Zabori (started 2009)
Matthias Vogt (dissertation scheduled for September 21 2011) Camilla Fahlgren (Ph.D. 2011 at the Linnaeus University)
Lars Ahlm (Ph.D. 2010), now at the Scripps Institute of Oceanography, San Diego Kim Hultin (Ph.D. 2010) Monica Mårtensson (Ph.D. 2007) Johanna Lauros (Fil. lic. 2005, Ph.D. 2011 at Helsinki University) Admir Targino (Ph.D. 2005), 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), now researcher at ITM, got himself a “fo-ass” from VR

Post docs, Assistant Professors/Junior Researchers I work(ed) with

Hamish Struthers
Monica Mårtensson, from 2011 also at Uppsala University, Department of Geoscience
Peter Tunved
Radovan Krejci
Paul Glantz
Farahnaz Khosrawi, now at the Department of Meteorology
Gintautaus Buzorius , now at Center for Interdisciplinary Remotely Piloted Aircraft Studies, Naval Postgraduate School, Monterey, California, U.S.A.

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

Since 2004 I am based in the Atmospheric Science Unit at the Department of Applied Environmental Science (ITM) 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 ITM 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 ITM we also belong to several international networks/ centre of excellence such as ACCENT, BACCI and CBACCI.

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 equations, 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 minimise 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, colaborating 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 beyound 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 realise that there is not one correct way to supervise. For each new student I have to be a new supervisor.

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) ~5.5 millon Euros in grants.


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

-Breaking waves clouds and climate/ Carlsbergsfondet

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

-Green House Arctic Ocean and Climate Effects of Aerosols (GRACE)/ VR

-Traffic Emissions of Aerosol Particles (TEA) / FORMAS

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

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

-The Primary Marine Aerosol Source (PMA) / VR

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

-Marine Aerosol Production by Natural Sources (MAP) / EC 6th

-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) / EC 5th

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

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

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

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

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

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

-Aerosol deposition over Antarctic ice (within Swedarp 1999/2000)

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

-Aerosol sources from a climate perspective / VR

-Aerosol cloud climate / VR


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. Give us a call!

Latest scientific papers

Calcium enrichment in sea spray aerosol particles

Salter, M.; Hamacher-Barth, E.; Leck, C.; Werner, J.; Johnson, C.; Riipinen, I.; Nilsson, D.; Zieger, P.
2016 | Geophys Res Lett

Seawater mesocosm experiments in the Arctic uncover differential transfer of marine bacteria to aerosols

Fahlgren, C.; Gomez-Consarnau, L.; Zabori, J.; Lindh, MV.; Krejci, R.; Martensson, EM.; Nilsson, D.; Pinhassi, J.
2015 | Environ. Microbiol. | 7 (3) (460-470)

On the seawater temperature dependence of the sea spray aerosol generated by a continuous plunging jet

Salter, ME; Nilsson, ED; Butcher, A; Bilde, M
2014 | J. Geophys. Res.-Atmos. | 119 (14) (9052-9072)

Heated submicron particle fluxes using an optical particle counter in urban environment.

Vogt, M.; Johansson, C.; Mårtensson, M.; Struthers, H.; Ahlm, L.; Nilsson, E. D.
2013 | Atmos. Chem. Phys. | 13 (3087-3096)

Comparison between summertime and wintertime Arctic Ocean primary marine aerosol properties

Zabori, J.; Krejci, R.; Ström, J.; Vaattovaara, P.; Ekman, A.M.L.; Salter, M.; Mårtensson, E.M.; Nilsson, E.D.
2013 | Atmos. Chem. Phys. | 13 (4783-4799)

All publications

Atmospheric Science

The life cycle and impact of tiny atmospheric particles known as aerosols – both indoors as well as outdoors.