1. GAMMA SWE • Snow Water Equivalent (SWE) over each MSA was measured using operational airborne gamma radiation measurements. • Water in the snow attenuates natural terrestrial gamma radiation emitted from soil, and is the basis for reliable airborne SWE measurements. • Principal source of SWE validation data over AMSR-footprint scale area NOAA AC690 over Rabbit Ears MSA (moderate topography) NOAA AC690 over North Park MSA (flat topography)

2. GAMMA SWE NORTH PARK MSA • 84 GAMMA Flight Lines, measuring 30% of the land surface of the MSA • Principal AMSR CalVal Site • Flat, unforested • Shallow, dry snow • “Best” conditions for AMSR algorithms to measure SWE Illinois River ISA Potter Creek ISA Michigan River ISA Mean SWE: 2.8 cm Std Dev: 1.3 cm Preliminary GAMMA SWE Analysis – IOP1

3. GAMMA SWE Rabbit Ears MSA Buffalo Pass ISA Spring Creek ISA • 22 GAMMA Flight Lines • Difficult test conditions for AMSR snow algorithm • Increased topographic complexity and forest cover • Increased snow depth increases scattering, reduces Tb; more difficult to differentiate from thin wet snow Walton Creek ISA Mean SWE: 26.7 cm Std Dev: 9.5 cm Preliminary GAMMA SWE Analysis – IOP1

4. GAMMA SWE FRASER MSA • 23 GAMMA Flight Lines • Difficult test conditions for AMSR snow algorithm • Greatly increased topographic complexity and forest cover St. Louis Creek ISA Fool Creek ISA Alpine ISA Mean SWE: 11.8 cm Std Dev: 3.0 cm Preliminary GAMMA SWE Analysis