Analysing spatio-temporal patterns of the global NO2-distribution retrieved from GOME satellite observations using a generalized additive model 1Institut für Mathematik, University of Potsdam, Potsdam, Germany
2MPI for Chemistry, Mainz, Germany
3Interdisciplinary Center for Scientific Computing, University of Heidelberg, Heidelberg, Germany
4Institut für Umweltphysik, University of Heidelberg, Heidelberg, Germany
5Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge/MA, USA
Received: 20 Mar 2009 – Published in Atmos. Chem. Phys. Discuss.: 09 Apr 2009 Abstract. With the increasing availability of observational data from different sources at
a global level, joint analysis of these data is becoming especially attractive.
For such an analysis – oftentimes with little prior knowledge about local and
global interactions between the different observational variables at hand – an
exploratory, data-driven analysis of the data may be of particular relevance.
Revised: 22 Aug 2009 – Accepted: 25 Aug 2009 – Published: 08 Sep 2009
In the present work we used generalized additive models (GAM) in an exemplary
study of spatio-temporal patterns in the tropospheric NO2-distribution
derived from GOME satellite observations (1996 to 2001) at global scale. We
focused on identifying correlations between NO2 and local wind fields,
a quantity which is of particular interest in the analysis of spatio-temporal
interactions. Formulating general functional, parametric relationships between
the observed NO2 distribution and local wind fields, however, is difficult
– if not impossible. So, rather than following a model-based analysis testing
the data for predefined hypotheses (assuming, for example, sinusoidal seasonal
trends), we used a GAM with non-parametric model terms to learn this functional
relationship between NO2 and wind directly from the data.
The NO2 observations showed to be affected by wind-dominated processes over
large areas. We estimated the extent of areas affected by specific NO2
emission sources, and were able to highlight likely atmospheric transport
"pathways". General temporal trends which were also part of our model –
weekly, seasonal and linear changes – showed to be in good agreement with
previous studies and alternative ways of analysing the time series. Overall,
using a non-parametric model provided favorable means for a rapid inspection
of this large spatio-temporal NO2 data set, with less bias than parametric
approaches, and allowing to visualize dynamical processes of the NO2
distribution at a global scale.
Citation: Hayn, M., Beirle, S., Hamprecht, F. A., Platt, U., Menze, B. H., and Wagner, T.: Analysing spatio-temporal patterns of the global NO2-distribution retrieved from GOME satellite observations using a generalized additive model, Atmos. Chem. Phys., 9, 6459-6477, doi:10.5194/acp-9-6459-2009, 2009.