[1] UNIV LEICESTER,DEPT PHYS,LEICESTER LE1 7RH,ENGLAND
[2] MAX PLANCK INST AERON,D-3411 KATLENBURG 3,FED REP GER
[3] UNIV LANCASTER,DEPT ENVIRONM SCI,LANCASTER LA1 4YW,ENGLAND
[4] UNIV SHEFFIELD,DEPT PHYS,SHEFFIELD S10 2TN,S YORKSHIRE,ENGLAND
[5] UNIV CAMBRIDGE,CAVENDISH LAB,CAMBRIDGE CB3 0HE,ENGLAND
[6] RUTHERFORD APPLETON LAB,DIDCOT OX11 0QX,OXON,ENGLAND
[7] BRITISH ANTARCTIC SURVEY,CAMBRIDGE CB3 0ET,ENGLAND