1. FLOW, Engineering Mechanics, KTH Royal Institute of Technology 1 , SE-100 44 Stockholm, Sweden
2. Mines de Paris, Universite PSL 2 , 75005 Paris, France
3. IT Department, Norwegian Meteorological Institute 3 , Postboks 43, 0313 Oslo, Norway
4. Department of Mathematics, University of Oslo 4 , 0316 Oslo, Norway