Snow grain size retrieval SGSP from optical satellite data: Validation with ground measurements and detection of snow fall events

The size of snow grains plays an important role for modeling the snow albedo in polar regions. The Snow Grain Size and Pollution (SGSP) retrieval computes the snow grain size using spectral reflectances from the Moderate Imaging Spectrometer (MODIS): the channels at 0.47. μm, 0.86. μm, and 1.24. μm. The unique feature of the SGSP retrieval is that it does not require a-priori information on the snow grain shape.In this paper, the SGSP-retrieved snow grain size is validated with six data sets from ground measurement campaigns in the Arctic, the Antarctic, Greenland, and Japan. Almost half of the comparison cases have a difference below 15%; the correlation coefficient is 0.86. The application of the SGSP retrieval on the Antarctic Ross ice shelf demonstrates the potential to detect snow fall events by analyzing the snow grain size time series for sudden grain size decreases.