During the first SWING workshop (see Workshops) a preliminary roadmap of future SWING activities was designed.
This phase will consist of setting up an initial website and database. Already available model output of present-day control simulations of the different isotope GCMs will be collected. In addition, a pool of the available forward proxy models (e.g. for coral records, foram records, lake carbonate, tree-ring cellulose) will be made distributable to all project members.
The first SWING simulations and analyses will focus on model-data-intercomparison for the present-day climate. Two new simulations with all available isotope GCMs will be performed using identical boundary conditions:
- A "climatological" control run with prescribed SST from the HadISST 1 data set, mean of period 1980-2000, all other boundary conditions (e.g. CO2) set to 1980's value
- A 100-years simulation with prescribed SST from the HadISST 1 data set, period 1880-2000, and "recommended" other common boundary conditions (still to be defined in detail)
The second SWING phase will -most likely- focus on model-data-intercomparison for selected paleo time
Several time slices of interest (LGM, YD, 8.2k) were already identified but the exact definition of boundary
conditions for such paleo-simulations was postponed to a next SWING meeting.
At present, three state-of-the-art isotope GCMs (GISS Model E, MUGCM, ECHAM4) are ready for common isotope simulations and present the initial core of the SWING model suite. Three more GCMs (CCSM3, HadCM3, CCSR) are most likely ready within the next 6-12 months and will join as soon as possible. Two older isotope GCMs (LMD, GISS II) are still used by other research groups, which might also be interested in joining the SWING project and thus will be invited to join.
In addition to performing isotope GCM intercomparison analyses, another key activity of this project is setting up a common database of observational isotope data sets to be used for in-depth model-data comparison. For the analyses of the Phase I simulation results, the following observational data was selected:
- Climatological monthly mean values of all GNIP stations with at least 3 continuous years of both 18O and D measurements.
- For the 100-yrs simulation, only: monthly mean values of all GNIP records with at least 20 years of continuous measurements.
- Isotope values of ocean surface waters will be derived from the 18O database maintained by Gavin Schmidt.
- The ATMOS satellite data of lower stratospheric (tropical) Deuterium minimum will be compared with January vertical profile minima of the different GCM simulations.
- The ADEOS satellite data provides dD values of the total water vapour column amount. These will be compared to GCM output by applying the weighting functions for both D and water vapour from the satellite retrieval algorithm to the GCM output data in an identical manner.
- Several available surface vapour measurement records (stations in Heidelberg, Saclay, Cape Grim, Vienna) will allow a model-data-comparison of short-term isotope variability.
- A selection of available Antarctic and Greenland snow measurements will be used to analyse the performance of the different isotope GCMs over Greenland and Antarctica.
- Detailed intercomparison of atmosphere land stable water isotope exchanges will be offered as an additional option based around one (or a few) locations where high quality observational data exist. These are likely to be selected from Heidelberg, Saclay, Cape Grim and Vienna but might alternatively be where the densest GNIP station continuous data exist.
All different GCM model output and available observational isotope data sets will be stored in a common NetCDF format and accessible to all project members and the public via this website.