 |
| Titel |
Application of Relaxed Eddy Accumulation (REA) method to estimate CO2 and CH4 surface fluxes in the city of Krakow, southern Poland. |
| VerfasserIn |
Miroslaw Zimnoch, Zbigniew Gorczyca, Katarzyna Pieniazek, Alina Jasek, Lukasz Chmura, Kazimierz Różański |
| Konferenz |
EGU General Assembly 2013
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250079093
|
|
|
|
|
|
| Zusammenfassung |
| There is a growing interest in the recent years in studies aimed at quantifying carbon cycling
in urban centres. Worldwide migration of human population from rural to urban areas and
corresponding growth of extensive urban agglomerations and megacities leads to
intensification of anthropogenic emissions of carbon and strong disruption of natural carbon
cycle on these areas. Therefore, a deeper understanding of the carbon "metabolism" of such
regions is required. Apart of better quantification of surface carbon fluxes, also a thorough
understanding of the functioning of biosphere under strong anthropogenic influence is
needed.
Nowadays, covariance methods are widely applied for studying gas exchange between the
atmosphere and the Earth’s surface. Relaxed Eddy Accumulation method (REA), combined
with the CO2 and CH4 CRDS analyser allows simultaneous measurements of surface fluxes
of carbon dioxide and methane within the chosen footprint of the detection system, thus
making possible thorough characterisation of the overall exchange of those gases
between the atmosphere and the urban surface across diverse spatial and temporal
scales.
Here we present preliminary results of the study aimed at quantifying surface fluxes of
CO2 and CH4 in Krakow, southern Poland. The REA system for CO2 and CH4 flux
measurements has been installed on top of a 20m high tower mounted on the roof of the
faculty building, close to the city centre of Krakow. The sensors were installed ca 42 m
above the local ground. Gill Windmaster-Pro sonic anemometer was coupled with
self-made system, designed by the Poznan University of Life Sciences, Poland,
for collecting air samples in two pairs of 10-liter Tedlar bags, and with Picarro
G2101-i CRDS analyser. The air was collected in 30-min intervals. The CO2 and
CH4 mixing ratios in these cumulative downdraft and updraft air samples were
determined by the CRDS analyser after each sampling interval. Based on the measured
mixing ratios difference and the vertical wind component, the variability of the
mean surface fluxes of CO2 and CH4 was quantified. In case of CO2 flux, a typical
diurnal pattern with the maximum values of around 30 mmol m-2 h-1 occurring
during night hours and the minimum values, around -40 mmol m-2 h-1, occurring
early afternoon was observed during sunny days ("plus" and "minus" signs mark
upward and downward fluxes, respectively). In addition, some events with much
higher fluxes (up to 100 mmol m-2 h-1) were observed, mainly during rush hours.
Temporal variability of methane flux turned out to be much higher than that observed
for CO2. During summer, it varied from approximately -100 to +500 μmol m-2
h-1, with the mean value of around +100 μmol m-2 h-1 and maximum values
occurring predominantly during daytime. In addition to flux measurements, an
attempt was made to characterize also the isotopic signature of carbon in the CO2
flux components measured with the aid of REA method. The results showed that
the precision of δ13CO2 measurements performed with Picarro analyser was not
sufficient to differentiate the isotopic signatures of upward and downward CO2
fluxes.
Acknowledgement: This work is supported by the Ministry of Science and Higher
Education (project No. 817.N-COST/2010/0 and the statutory funds of the AGH University
of Science and Technology, project no. 11.11.220.01). |
|
|
|
|
|
|