WE PROPOSE TO BE A TEAM MEMBER IN PLANNING AND PARTICIPATING IN THE RADAR AND RADIOMETER EXPERIMENTS FOR THE NEXT GENERATION COLD LAND PROCESSES EXPERIMENTS BASED ON OUR EXPERIENCES IN PHYSICAL MODELS RETRIEVAL ALGORITHMS SNOW AND BACKGROUND CHARACTERIZATION AND INTERNATIONAL COLLABORATIONS. RETRIEVAL OF SNOWPACK PARAMETERS REMOTELY USING MICROWAVES HAS BEEN STUDIED IN THE LAST DECADE. THE COLD LAND PROCESSES FIELD EXPERIMENTS (CLPX) (2002-2003) CLPX-II (2006-2008) AND THE ESA COLD REGIONS HYDROLOGY HIGH-RESOLUTION OBSERVATORY (COREH2O) MISSION CAMPAIGNS HAVE GATHERED DATASETS OF RADAR BACKSCATTER AND BRIGHTNESS TEMPERATURES OF SNOWPACK. OVER THE PAST YEARS WE HAVE WORKED ON THESE DATASET USING THE NEW PHYSICAL MODELS BASED ON NEW MEDIA CHARACTERIZATIONS AND NEW RETRIEVAL ALGORITHMS AND HAVE OBTAINED ENCOURAGING RESULTS. CORRELATIONS ARE FOUND BETWEEN THE MICROWAVE RESPONSE AND SNOWPACK PARAMETERS. IN THE COREH2O AND THE NASA SNOW AND COLD LAND PROCESSES MISSION (SCLP) THERE IS A SYNTHETIC APERTURE RADAR (SAR) SYSTEM WITH X- AND KU- BAND DUAL FREQUENCIES AND VV AND VH DUAL POLARIZATIONS. SCLP ALSO INCLUDES THE KU- AND KA- BAND RADIOMETER TO CONSTITUTE A COMBINED ACTIVE AND PASSIVE MICROWAVE REMOTE SENSING MISSION CONCEPT. TWO CHALLENGES IN PHYSICAL MODELLING OF SNOW MICROWAVE REMOTE SENSING ARE THE CORRELATION OF THE MICROWAVE SIGNAL (I) TO THE SNOW MICROSTRUCTURE AND LAYERING (II) AND TO THE BACKGROUND BACKSCATTERING FROM GROUND AND VEGETATION. THE NEXT GENERATION COLD LAND PROCESS EXPERIMENT (CLPX) SHOULD EMPHASIZE ON SYNERGETIC IN SITU GROUND MEASUREMENTS TOWER MEASUREMENTS AND AIRBORNE MEASUREMENTS AS REQUIRED BY THE PHYSICAL MODELS AND RETRIEVAL ALGORITHMS. THE NEW SNOW MICROSTRUCTURE SIZE CHARACTERIZATION REQUIRES TWO PARAMETERS. WE PROPOSE TO DERIVE THESE TWO PARAMETERS FROM IN SITU MEASUREMENTS OF VISUAL GRAIN SIZES AND SPECIFIC SURFACE AREAS (SSA). THE TWO PARAMETER APPROACH CAN REPRESENT GRAIN CLUSTERS IN THE SNOWPACK WHICH EXHIBIT NON-RAYLEIGH SCATTERING. IN ADDITION TO SNOW MICROSTRUCTURE AND LAYERING CHARACTERIZATION WE WILL ALSO PERFORM THE BACKGROUND CHARACTERIZATION IN RELATION TO SCATTERING BY THE GROUND SURFACE AND VEGETATION. IN THE NEW RADAR RETRIEVAL ALGORITHM THE BACKGROUND SCATTERING NEEDS TO BE SUBTRACTED FROM THE TOTAL SCATTERING. WE PROPOSE TO PLAN AND CONDUCT EXPERIMENTS TO MODEL THE BACKGROUND SCATTERING FROM IN SITU MEASUREMENTS OF SOIL PERMITTIVITY ROUGHNESS AND VEGETATION CHARACTERISTICS. THE RECENT PHYSICAL MODES FOR BOTH ACTIVE AND PASSIVE MICROWAVE REMOTE SENSING OF SNOW ARE BASED ON NUMERICAL SOLUTIONS OF MAXWELL S EQUATIONS IN 3D (NMM3D). THE SOLUTIONS ARE USED TO PREPARE LOOKUP TABLES OF BACKSCATTERING AND EMISSIVITIES. THE MAXWELL EQUATION BASED MODELS APPLY TO A WIDE RANGE OF PARAMETERS AND PROVIDE IMPROVED PHYSICALLY MODELLING OF FREQUENCY POLARIZATION AND ANGULAR DEPENDENCES. THE PARTIALLY COHERENT APPROACH OF DENSE MEDIA RADIATIVE TRANSFER (DMRT) AND THE FULLY COHERENT APPROACH THE LATTER OF WHICH COHERENTLY INCORPORATES THE THIN LAYER EFFECTS AND BACKSCATTERING ENHANCEMENT EFFECTS. THE SCATTERING FROM VEGETATED LAND SURFACE IS MODELED BY CONSIDERING THE DIRECT VEGETATION SCATTERING SURFACE SCATTERING AND VEGETATION/ SURFACE SCATTERING COUPLING. THE NEW RADAR RETRIEVAL ALGORITHM OF SWE IS BASED ON ABSORPTION LOSS WHICH IS DIRECTLY PROPORTIONAL TO SWE. THE ALGORITHM USES LOOKUP TABLES OF SNOW SCATTERING TO DERIVE THE CORRELATION OF SCATTERING ALBEDOS AND OPTICAL THICKNESSES AT MULTIPLE FREQUENCIES. THEN USING BACKSCATTERING AT TWO FREQUENCIES THE ABSORPTION AND SWE CAN BE RETRIEVED. WE PROPOSE TO PLAN AND PARTICIPATE IN THE EXPERIMENTS SO THAT WE CAN VALIDATE THE RETRIEVAL ALGORITHM USING SYNERGETIC IN SITU MEASUREMENTS AND MICROWAVE MEASUREMENTS IN THE NEXT GENERATION CLPX CAMPAIGN. OUR INTERNATIONAL COLLABORATORS INCLUDE JUHA LEMMETYINEN FROM THE FINNISH METEOROLOGICAL INSTITUTE FINLAND AND CHRIS DERKSEN FROM ENVIRONMENT CANADA.