Open Session - SWISS GEOSCIENCE MEETINGs

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Digitization and homogenization of long-term climate series from
surface observation stations in Switzerland – DigiHom
Füllemann Christine*, Begert Michael*, Brönnimann Stefan**, Croci-Maspoli Mischa*
*Swiss Federal Office of Meteorology and Climatology MeteoSwiss, Krähbühlstrasse 58, CH-8044 Zurich (christine.fuellemann@meteoswiss.ch)
** Swiss Federal Institute of Technology, Institute for Atmospheric and Climate Science, Universitätstrasse 16, CH-8092 Zurich
The term DigiHom combines the intentions at MeteoSwiss i) to digitize long-term surface time-series from historical paper
data and ii) to homogenize the complete data series with respect to make accurate estimates of the dimension of climate
change and the corresponding effects. The goal of DigiHom is to make an important contribution to the national and international
climate observation system by means of long-term climate series of Switzerland.
DigiHom has a time-frame from 2008-2011 and is accomplished in close collaboration with ETH Zurich who has profound
experience in the digitization process (Brönnimann et al., 2006). The homogenization process will be carried out at
MeteoSwiss using a well established homogenization procedure (THOMAS, Tool for Homogenization of monthly data series,
cf. Begert et al. 2005).
The surface observation stations processed within DigiHom are the long–term climate series of the newly defined Swiss
National Basic Climatological Network (Swiss NBCN). This network defines the most valuable climatological stations in
Switzerland and accordingly guarantees a long-term perspective of their operation. The Swiss NBCN consists of 28 climatological
stations (different parameters), presented in Begert et al. (2007) and 46 precipitations stations (Begert, 2008) covering
respectively all climatological regions of Switzerland (Fig. 1). Representative climatological regions for the different surface
observation stations have been calculated using the complete-linkage cluster analysis.
After the successful completion of DigiHom in 2010 the following climatological variables will be available electronically and
in high-quality back to the year of their origin (most of them before 1900): temperature (mean, minimum, maximum), precipitation
and sunshine duration. Although the coverage of stations at different altitudes is quite good, stations with multivariate
time series are mainly located below 1000m asl (see Fig. 2). Higher elevated stations generally offer mean temperature
and precipitation series. 6 NBCN stations have all parameters starting before 1901.
In this study the technical background to accomplish DigiHom will be presented and first results of homogenized long-term
time-series will be introduced.
Figure 1. The 74 NBCN surface observation stations in Switzerland separated as 28 climatological stations (different parameters)
and 46 precipitation stations.
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Symposium 4: Meteorology and climatology