On the impact of ice emissivity on sea ice temperature retrieval using passive microwave radiance data

This letter examines the performance of two Advanced Microwave Scanning Radiometer-EOS (AMSR-E) ice temperature algorithms over first-year sea ice during the spring transition period where ice concentrations are close to 100%. The results showed, before snow melt, that the old AMSR-E algorithm overestimated the ice temperature by up to 18 K, which is relative to in situ and thermodynamically calculated snow/ice interface temperatures (T _si's). An adjustment of vertically polarized ice emissivity of 6.9 GHz [ε_I(6V)] to 0.98, which was identical to the constant value used in the latest version of the AMSR-E ice temperature algorithm (posted July 2007), demonstrated a significant improvement in ice temperature retrieval. However, after snow melt, the ice temperature retrieval with any constant ε_I(6V) failed to correctly estimate the ice temperatures due to large variability in the physical properties of snow and, in turn, penetration depth and ε_I(6V). The results suggest that a local adjustment of ε_I(6V), which is by incorporating a simple thermodynamic model into the AMSR-E ice temperature algorithm, would be useful in improving the performance of the algorithm.