1. a Radar Systems and Remote Sensing Laboratory , University of Kansas Center for Research, Inc. , 2291 Irving Hill Road, Lawrence, Kansas, 66045-2969, U.S.A.
2. b U.S. Army Cold Regions Research and Engineering Laboratory , 72 Lyme Road, Hanover, New Hampshire, 03755-1290, U.S.A.
3. c Environmental Institute of Michigan , Radar Division , P.O. Box 8618, Ann Arbor, Michigan, 48107, U.S.A.