A network for regional atmospheric C02 observations had already been established in Germany by 1972, consisting of 5 stations with basically different characteristics: Westerland, a coastal station at the North Sea, 2 regional stations, Waldhof and Deuselbach, as well as 2 mountain stations, Brotjacklriegel at the eastern boarder of Germany and Schauinsland in the Black Forest. In addition to COz concentration observations, from 1977 onwards quasi-continuous 13 C02 and l4 C02 measurements were

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... erformed on samples from the Schauinsland site, and for the short period 1985-1988, 14 C02 measurements were also made on Westerland samples. C02 data selection based on wind velocity allows for an estimate of the representative continental COz level over Europe. The peak-to-peak amplitude of the seasonal cycles is between 12.1 ppmv (Schauinsland) and 17.6 ppmv (Waldhof). The phase of the seasonal cycles at the German sites is shifted if compared to maritime background sites with the concentration maxima occuring already between beginning of February and beginning of April, the minima in August. The longterm mean C02 increase rate in the last 20 years at Westerland and Schauinsland is 1.49 and 1.48 ppmv yr -1 , respectively. The mean d n C of the seasonal source C02 at Schauinsland is calculated from unselected d l3 C and C02 data to be -25.1 °/oo-From the 14 C observations in unselected C02, we derive yearly mean fossil fuel contributions at Westerland of 4 ppmv, and at Schauinsland of only 2.5 ppmv. Based on the seasonality of the fossil fuel C02 component at Schauinsland and on concurrently observed atmospheric 222 Radon activities, we derive a seasonal amplitude of the fossil fuel C02 source which is higher by a factor of 3 compared to emission estimates for Europe. * Corresponding author. the spatial and temporal variations of C02 in combination with atmospheric transport models. One shortcoming of the present global C02 network is, however, the lack of representative observations over the continents. The C02 climatology in the remote maritime atmosphere seems to be well documented today, which allows for budgeting the large-scale C02 fluxes between atmosphere and the surface reservoirs (oceans and terrestrial biosphere) to within ±20%. A better quantification of the uptake of anthropogenic C02 by different reservoirs, however, needs an improved knowledge of the sources and sinks on smaller scales, and particularly of the diverse terrestrial biosphere. One approach to gain this Tellus 47B (1995), 1/2