[1] UNIV OXFORD,DEPT ATMOSPHER OCEAN & PLANETARY PHYS,OXFORD,ENGLAND
[2] UNIV ADELAIDE,DEPT PHYS,ADELAIDE,SA 5001,AUSTRALIA
[3] UNIV SASKATCHEWAN,INST SPACE & ATMOSPHER STUDIES,SASKATOON S7N 0W0,SASKATCHEWAN,CANADA
[4] UNIV NEW HAMPSHIRE,DEPT ELECT & COMP ENGN,DURHAM,NH 03824