ITM's Staff

Research field

WHY?

Although I have a broad interest in atmospheric environmental 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.

AEROSOLS V.S. GREENHOUSE GASES

It must be understood that the cooling effect of anthropogenic aerosols does not offer a hope to escape the climate change. The current atmosphere is heavily loaded by anthropogenic aerosols and has been so since the beginning of the industrial revolution. Hence, the observed global average warming so far (~1^oC) 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.

WHAT?

Currently my research group 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

HOW?

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

OUTPUT

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)
-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)

The primary urban aerosol source:
-The aerosol number emission of particles from traffic as a function of traffic intensity (and friction velocity) (Mårtenssson et al., 2006)

WHO?

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!)

Ph.D. Students I supervise/have supervised

Matthias Vogt (started 2007)
Lars Ahlm (started in 2006), our weatherman!
Kim Hultin (dissertation 2009)
Johanna Lauros (dissertation 2008), sharing her time between Stockholm and Helsinki
Monica Mårtensson (dissertated 2007)
Admir Targino (dissertated 2005), now post doc at University of Manchester, Centre for Atmospheric Science, U.K.
Peter Tunved (dissertated 2004), now researcher at ITM, back after post doc, got himself a "fo-ass" from VR

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

Monica Mårtensson (FORMAS+EU+SIDA)
Peter Tunved (VR, Junior Researcher 2007-2010)
Paul Glantz (FORMAS, Junior Researcher 2006-2009)
Farahnaz Khosrawi (PARTS+Marie Currie Grant 2004-2006)
Gintautaus Buzorius (Wenner Gren+BACCI+QUEST 2002-2003), 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.

WHERE?

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.

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 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.

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) ~3.5 millon Euros in grants.

CURRENT PROJECTS

Traffic Emissions of Aerosol Particles (TEA) / FORMAS

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

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

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

JOIN 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. Give us a call!

My portrait was taken by Johanna Lauros