1. A brief analysis of the TransCom3 Continuous data Experiment at ECMWF Soumia SERRAR and Richard Engelen

2. TansCom3 Continuous Data Experiment Map of sampling locations used for the present analysis Locations sampling baseline air Continental stations at relatively low altitudes Mountainous stations Flux towers

3. 10 75 TansCom3 Continuous Data Experiment list of participating models From Law et al., in preparation GFDL, USA CSIRO, Australia ECMWF LSCE, France NIES, Japan GSFC, USA NOAA/ESRL USA

4. Trend and low frequency variations removedComplete time series Barrow – USA – 71.19N 156.36W (2003) South Pole – USA – 89.58S 24.48W (2003)

5. Performance of different models at some oceanic (or high altitude) background locations for CO 2 Correlation to observations (2002) STDV of the (Obs – Mod) (2002) Include all variations (synoptical + seasonal + trend) Trend and low frequency variations removed

6. Performance of different models at some continental locations for CO 2 Correlation to observations (2002) STDV of the (Obs – Mod) (2002) Correlation to observations (2002) STDV of the (Obs – Mod) (2002) High altitude stations(Relatively) Low altitude stations 48 m40 mCoastal stations

7. Comparison of biases for different models participating to the TRANCSOM-3 Continuous Data Experiment Background airLow altitude stationsMountains NH SH Biases show significant differences between the models - The vertical resolution (LMDZ) - Sub-grid parameterization (NIES05) - Mass conservation (IFS) - boundary layer scheme.. Continental Bias = (Model – Observation) annual mean

8. Comparison of biases for different models participating to the TRANCSOM-3 Continuous Data Experiment Sampling around 1:30 LT Sampling around 13:30 LT

9. Mean diurnal cycle at some continental locations for CO 2 when platforms heights are about 10 m above the surface Neuglobsow lat 53.15/long 13.03 (65m asl h~6m) Fraserdale lat 49.88/long -81.57 (210 asl h~40m) Waldhof (LGB) lat 47.05/long 12.95(74m asl h~10m?) Monte Cimone lat 44.18/long 10.7 (2165m asl h~10m?)

10. Mean diurnal cycle phase and vertical resolution Flux tower at Tapajos (62m, 29m 10m) Mean diurnal cycle for Tapajos (JJA)Diurnal variation at Tapajos 30Jul 2002 to 18 Aug 2002

11. Mean diurnal cycle phase and vertical resolution Flux tower at Boreas (30m) Mean diurnal cycle for Boreas (JJA) Diurnal variation at Boreas 30Jul 2002 to 18 Aug 2002

12. Conclusions  There are undoubtedly some CO 2 variability features reproduced by the different models at oceanic stations most of the reproduced variability is seasonal at continental stations this study needs to be extended to know which part of the simulated signal is seasonal, diurnal or synoptic  The vertical resolution is critical in order to simulate the amplitude of the diurnal cycle close to the surface the phase of the diurnal cycle at tall towers  There is a large spread of the mean annual biases shown by the different models over the continent possible causes are differences in the vertical resolution and/or in the boundary layer schemes  Differences in the simulated north-south gradients at oceanic stations are of the same the order of magnitude as the annual CO 2 growth rate this probably results from model differences over the continent, as models with thicker surface layer tend to have smaller gradients