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MAX-DOAS measurements in Nairobi
Introduction Instrument Data References Links Contact
Introduction:
In
July 2002, A new DOAS instrument was installed on the UNEP building in Nairobi
(1°S, 36.5°E), Kenya. Nairobi is a tropical high altitude (1798 m) site that
is strongly affected by local urban pollution (Nairobi has more than 2.5 million
inhabitants) and also by transport of air masses from biomass burning
regions.
Unlike the meteorological station at nearby Mount Kenya, this site is not ideal for stratospheric measurements, but rather has a focus on tropospheric pollution in tropical regions.
For
German students interested in spending a year at the University of Kenia, please
check
www.berlinnairobi.org/application/
for details.
Instrument:
The DOAS instrument in Nairobi is located in a temperature controlled office room inside the UNEP building. It consists of a temperature stabilized grating spectrometer equipped with a cooled CCD detector. The instrument is connected to a telescope which is located outside the building with a quartz fibre bundle and a number of electrical and control connections. The telescope has two viewing ports: One in zenith direction, the other one towards the horizon in the south (off-axis). In the off-axis direction, the horizon can be observed sequentially in the range of 0° to 30° elevation by means of a motorized mirror. Both line-lamp and white light calibration lamps are integrated in the telescope box and are used for daily calibration measurements. In January 2004, a second spectrometer covering the visible part of the spectrum was added to the instrument.
Due to hardware problems and frequent power outages, the Nairobi data set has many gaps.
The instrument is fully automated and controlled remotely over an internet connection to Bremen. More on the instrument and measurement principle can be found on our MAXDOAS page.
Data:
In the figure, an example of the measurements in Nairobi is shown. Daily averages of tropospheric NO2 columns, averaged over months have been computed for several years using the geometric approximation in combination with a criterion requiring similar results for the 30° and 15° directions. The results show a clear seasonality of the tropospheric NO2 columns with low values in winter and high values in summer. As can be seen from the error bars which give the standard deviation of all data within a month, NO2 variability is also much larger in summer.
If you have any requests, please contact Andreas Richter.
References:
- J. Lähnemann, Validation of Satellite Ozone Measurements Over Nairobi Using MAX-DOAS 2003-2004, A fourth year project at the Department of Physics, University of Nairobi, July 2005
- SCIAMACHY validation with ground-based DOAS observations final report (in German)
- Multi-axis DOAS observations of atmospheric trace gases in Nairobi and Bremen, S. Fietkau et al., IGAC meeting, September 2002
Links:
- Our local partner in Nairobi is the United Nations Environment Programme UNEP.
- Kenya Meteorological Department
- The instrument in Nairobi is used for the validation of SCIAMACHY.
Contact:
If you are interested in more information or would like to have access to our data, please contact Andreas Richter.