MAX-DOAS and prospects for cooperations in
the framework of Nairobi air quality measurements
-
Visit to DOAS group Bremen
(research group of Prof. Burrows)
Jonas Lähnemann
8 August 2004
Sixten Fietkau is a PhD student in the research group of Prof. Burrows at
IUP-Bremen (Institute of Environmental Physics) and is working with the MAX-DOAS
(Multi-Axis Differential Optical Absorption Spectroscopy) system. In particular,
he is responsible for the Nairobi DOAS-system of BREDOM (Bremian DOAS Network
for Atmospheric Measurements). He kindly spend several hours to show and
explain their work to me. He and his colleague, Thomas Medeke, also took
great interest in the different aspects of my upcoming one-year study visit
to the University of Nairobi. They also told me about their experiences on
their own short term visits to Kenya.
A more detailed description of MAX-DOAS and factors that have to be included
in the calculations can be found, for example, in a recent paper of the Burrows
Group on measurements at Spitzbergen, which can be found at http://www.atmos-chem-phys.org/acp/4/955/)
The Bremian method, that is MAX-DOAS, is to use a mirror to observe the
light falling in not only from the zenith direction, but also from the “off-axis”
directions close to the horizon. In these directions the path through the
troposphere and boundary layers is longer than in the zenith direction. This
offers the possibility to get a kind of a vertical profile of the observed
substances (at least a distinction between tropospheric and stratospheric
substances) using model calculations. After introducing this new MAX system,
the work in Bremen seems to have been mainly the development of models evaluating
the data coming from BREDOM..
BREDOM with now five permanent automated stations is supposed to yield data
to validate the data retrieved from the satellite-based SCIAMCHY instrument
(also using the DOAS technique). Funding has been provided for this validation.
It is worth noting that the satellite system gives global coverage of different
pollutants, however, only the total vertical columns are observed without
any vertical profiling.
A part of BREDOM is also directed towards more global observations of the
distributions and movements of pollutants. Species that are measured are
mainly ozone and pollutants leading to the destruction of the ozone layer.
In this field, the measurements in Nairobi are pioneering because there is
not much data from lower latitudes which, however, is important for understanding
the global processes. This means that the DOAS-system in Nairobi is not suited
for classical air quality measurements, which are point measurements or determination
of pollutants very near the ground. Also, it cannot be used to pinpoint pollution
sources. However, seasonal variations and especially the development over
time of the air quality in the area can be extracted quite well. This offers
the possibility for long-term observations of how the emissions of pollutants
(for example NO2) are developing over the years. Thus, the DOAS-system in
Nairobi could in that particular way contribute to an air quality project
for Nairobi.
Sixten Fietkau reported that in the past, after setting up the DOAS-system
in Nairobi, they had tried to establish lasting contacts with local scientists.
It seemed to them quite hard to keep the contacts even though they have been
there on follow-up visits. They said that they were open to the possibility
a local scientist working, for example, on a thesis regarding the evaluation
of the data. However, no cooperation resulted. They would nevertheless still
be open to involve local scientists in their work. Unfortunately, they have
no current funding for such involvement, especially there is no funding for
trips of Kenyan researchers to Bremen. Their current status is that funding
will run out next year (February) and Sixten Fietkau will also finish his
doctoral thesis in the near future. The stations will, however, continue
to operate and to collect data for the next years. Discussions concerning
applications for follow-up projects are on the way, but prospects for funding
of such projects seem to be not yet clear. If the Berlin-Nairobi Exchange
can secure funding in the context of an air quality project for Nairobi,
the Bremen group would most probably be willing to offer their data and their
knowledge in evaluating it. This would allow maybe a local scientist of the
physics, or maybe more suitable of the meteorological department, to be integrated
in a project involving the DOAS data, which could lead to a graduate or doctoral
thesis.
Concerning a fourth year project at the University of Nairobi, Sixten Fietkau
will consult with the members of his group on what would be possible and
realistic for such a project. We agreed to stay in contact via email on this.
[Addition by Jurgen Theiss: Dr. Muthama, Chairman of the Department of Meterology
at the University of Nairobi, has offered to supervise Jonas Lähnemann
if he chooses a fourth year project involving the DOAS-system in Nairobi.]
This visit might not yet have resulted in any definite arrangements, but
I got quite a good overview of the MAX-DOAS system and its application. Furthermore,
I met Sixten Fietkau personally and both of us are now knowing whom we are
dealing with. The Borrows group definitely seemed interested in a cooperation
with Nairobi.
I want to thank the Burrows Group and especially Sixten Fietkau for their
hospitality and their interest in developing a cooperation with Nairobi.
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