Abstract
Abstract. During spring and summer, melt ponds appear on the sea ice surface in the Arctic and play an important role in sea ice-albedo feedback effect. The melt pond fraction (MPF) can be retrieved using multi-band linear equations, but the calculation is complicated by the ill-conditioned reflectance matrix. In this paper, we calculated the condition numbers which represent the degree of the ill-conditioned reflectance matrix in the results of the MPF from a MODIS-based unmixing algorithm. The condition number is introduced here as a criterion for the sensitivity of the solution in the system to the error in the input value. By combining 3 bands among 5 visible and near-infrared bands of MODIS data, the results show that the three-band combination with the lowest sensitivity to the error of input is B245. To improve the algorithm, we introduce pre-processing to remove open water from the four surface types and then remove one reflectance equation from the original set. The best two-band combination algorithm is B15. Compared with the discrimination results from Landsat5-TM, the RMS is 0.14. This algorithm is applied in pan-Arctic scale, the MPF results are larger than that from University of Hamburg, especially in the Pacific sector.
Highlights
The albedo of melt ponds is between open water and sea ice
Observations have shown that the melt pond fraction can vary by more than 60% throughout the melt season and by up to 40% depending on years and locations (Polashenski et al, 2012; Landy et al, 2014; 2015)
Zege et al (2015) developed a melt pond fraction (MPF) algorithm using the analytical solution of optical thickness layer to describe the albedo of white ice to calculate the BRDF of white ice and melt ponds based on MEdium-Resolution Imaging Spectrometer (MERIS) data
Summary
The albedo of melt ponds is between open water and sea ice. Melt ponds occupy a large fraction of the Arctic sea ice surface during spring and summer. Zege et al (2015) developed a MPF algorithm using the analytical solution of optical thickness layer to describe the albedo of white ice to calculate the BRDF of white ice and melt ponds based on MEdium-Resolution Imaging Spectrometer (MERIS) data. This algorithm is more physically grounded than that of R12. MOD09A1 contains bands 1-7 at 500-meter resolution with quality control It provides the broad coverage of the whole Arctic data and has removed the strong effects of cloud, shadow, and aerosol compared with MOD09GA data, which is a grid track data. Landsat5-TM data archived by the United States Geological Survey (USGS) serves as the high-resolution data for validating MODIS products
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