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| Titel |
Comparison of ground-based remote sensing and in-situ observations of CO, CH4 and O3, accounting for representativeness uncertainty |
| VerfasserIn |
Stephan Henne, Martin Steinbacher, Emmanuel Mahieu, Whitney Bader, Thomas Blumenstock, Emilio Cuevas-Agulló, Dominik Brunner, Brigitte Buchmann |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250080328
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| Zusammenfassung |
| The EC project NORS (Demonstration Network Of ground-based Remote Sensing
Observations in support of the GMES Atmospheric Service) aims at demonstrating the value
of ground-based remote sensing data for quality assessment and improvement of the GMES
products. As part of NORS CO, CH4, O3 and NO2 tropospheric products as obtained by
ground-based remote sensing within the Network for the Detection of Atmospheric
Composition Change (NDACC) are compared to continuous surface in-situ measurements
that are reported on common international reference scales within the Global Atmospheric
Watch (GAW) Programme. However, a direct comparison between the different
methods is hindered by different sampling volumes, introducing uncertainties due to
representativeness.
Here we present a novel method that utilises high-resolution, backward Lagrangian
particle dispersion modelling to characterise the transport history of different sampling
volumes. Sampling volumes are defined as infinitesimally small point volumes for the in-situ
observations and as separate profile segments with horizontal and vertical extent for the
remote sensing observations. The characterisation is then used (a) to filter times for which a
direct comparison between in-situ and remote sensing data is unfavourable (large
representativeness uncertainty) and (b) to construct vertical profiles from the in-situ
observations, taking additional information from large scale atmospheric composition models
into account. These so called “in-situ” profiles are supposed to be more comparable to
the remote sensing profile as the surface value itself, while conserving the high
accuracy information of the latter and projecting it onto the profile. Therefore, these
profiles allow for a more direct comparison and validation of the remotely sensed
profiles.
The technique was first applied at two of the four NORS demonstration sites
(Jungfraujoch, Switzerland and Izana, Spain) and to the comparison of remote sensing
Fourier-transform infrared spectrometer (FTIR) measurements of CO, CH4, and O3 with the
responding in-situ observations. While previous studies generally showed good agreement
between the two kinds of observation, considerable amounts of scatter were evident.
Selecting only situations with relatively small representativeness uncertainty reduces
this scatter. Folding the “in-situ” profiles with the averaging kernels of the FTIR
retrieval gives a more realistic comparison result that is not influenced by any a-priori
assumptions. Results are also discussed with respect to season, time of day and weather
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