Sensitivity of satellite observations to snow characteristics

The sensitivities of a large range of satellite observations to snow characteristics are evaluated and compared, for a winter season, for the Northern hemisphere. Satellite measurements include passive (SSM/I emissivities) and active (ERS scatterometer) microwaves, along with visible reflectances (AVHRR). The satellite responses are systematically compared with in situ snow measurements at 493 stations, in North America and Eurasia. Passive microwaves at high frequency (85 GHz) are very sensitive to the presence snow on the ground, even for very low snow depth. None of the tested satellite measurements is well correlated with the snow depth, at a global scale, making snow depth retrieval from these observations difficult. Active microwave observations show a high sensitivity to the onset of snow melting.