BASE simulations within the Global Soil Wetness Project


Principal Investigator

Andrew Pitman

Earth Sciences,

Macquarie Universtiy

The Global Soil Wetness Project (GSWP) is a GEWEX/ISLSCP project which involves about
twenty international land surface modelling groups. It involves using 1o x 1o meteorological data for two years at 6 hourly time resolution to drive a land surface scheme. We have used this methodology to simulate the global fields of key quantities using a land surface scheme (BASE). The primary aim was to achieve a global simulation using BASE to enable us to participate in this project. We have also conducted a suite of experiments investigating the role of frozen soil moisture in controlling high latitude runoff. Finally, we have performed simulations investigating the role of leaf area index in explaining why different models in GSWP simulate different answers. We hope this will contribute to the overall explanation of results by the GSWP-core team.



Mei Zhao

Earth Sciences,

Macquarie University



g96 - VPP



What are the results to date and the future of this work?

The primary aim has been achieved and we have submitted results from our control climate to GSWP. These are integrated into their data base. The leaf area index runs are currently being written-up. We performed nine experiments examining different aspects of the sensitivity of BASE to the leaf area index. We find complex patterns of response both spatially and temporally. Overall, on the global average, we conclude that leaf area index is not a key mechanism for explaining the differences between results in GSWP, but regionally, and for transitional seasons (e.g. spring and autumn) the sensitivity of BASE to leaf area index is very significant.

There are three areas of "future work". First, the framework we have developed on the VPP allows us to conduct additional sensitivity experiments to aid in the understanding of the role of the land surface. Second, we have the opportunity to explore these results with different land surface structures to see which aspects control the model sensitivity. Finally, GSWP is about to move into Phase 2. Rather than a two year simulation at one degree resolution, the intension is to run at 0.5 degree resolution for ten years.

What computational techniques are used?

We are using FORTRAN vectorized for the VPP. We need the VPP because of memory and speed constraints on workstations.

- Appendix B