Polarization signatures of frozen and thawed forests of varying environmental state

During the two different overflights of t he Bonanza Creek Exper imenta l Fores t ( n e a r Fa i rbanks , Alaska) by t h e NASA/JPL r a d a r po la r ime te r in M a r c h 1988, t h e envi ronmental condi t ions over t he region changed significantly with tempe ra tu res ranging f r o m unseasonably w a r m (1 t o 9°C) d u r i n g one day t o well below freezing (-8 t o -15°C) d u r i n g the o the r . T h e mois ture conten t of t he snow a n d t r ees changed f r o m a liquid t o f rozen s ta te caus ing significant changes in the radiomet r ic a n d polar imetr ic responses of t he forest t o t he r a d a r wave. T h e L-band po la r ime t r i c observa t ions a r e s u m m a r i z e d in this pape r . U p t o a 6 d B c h a n g e in the backsca t t e r was obse rved in ce r t a in forest s t a n d s a t L b a n d . Fea tu res ex t r ac t ed f r o m the Stokes mat r ices of t h e s a m e s t ands f r o m the t h a w e d a n d frozen days suggest t h e changes in the relat ive con t r ibu t ion of t he different s ca t t e r ing mechanisms t o the r a d a r r e t u r n . Compar ison of t he polar imetr ic s igna tu res indicate relatively h igher con t r ibu t ion f r o m diffuse sca t t e re r s o n t h e t h a w e d d a y t h a n on the f rozen day. T h e sensitivity of t h e polar imetr ic signa tu res t o changing e n v i r o n m e n t a l condi t ions is clear ly d e m -