1. Reading e-Science Centre, Environmental Systems Science Centre, University of Reading, Reading RG6 6AL, UK
2. School of Engineering and Applied Science, Aston University, Birmingham B4 7ET, UK
3. Department of Geography, Universitat Autònoma de Barcelona, 08193 Bellaterra (Cerdanyola del Vallès), Spain
4. CREAF, Cerdanyola del Vallès 08193, Spain