Potential of Melt Pond Fraction Retrieval from High Spatial Resolution AMSR-E/2 Channels

Abstract

Estimation of melt pond fraction (MPF) using the Advanced Microwave Scanning Radiometer for the Earth Observing System (EOS)/2 (AMSR-E/2) brightness temperature ( $T_{\mathrm {B}}$ ) data is required for enhancing understanding of the role of melt ponds in the Arctic and in the earth's climate system. An original MPF retrieval is based on gradient ratio (GR), defined as the normalized difference between the 6.9 GHz horizontal (H) channel and the 89.0 GHz vertical channel GR(6/89) of AMSR-E. However, using the coarsest spatial resolution 6.9 GHz channel includes potential land contamination in $T_{\mathrm {B}}$ in regions of narrow waterways such as the Canadian Arctic Archipelago (CAA). This letter aims to provide a higher resolution MPF product, derived by using 10.7, 18.7, 23.8, 36.5, and 89.0 GHz $T_{\mathrm {B}}\text{s}$ at H-polarization instead of the 6.9 GHz $T_{\mathrm {B}}$ H-polarization in the GR calculation. For GR(10/89)- and GR(18/89)-based MPF retrievals, the difference standard deviations were 3.8%. This is lower than the 14.3% standard deviation of the GR(23/89)-, GR(36/89)-, and PR(89)-based MPF retrievals. Our results suggest that the GR(10/89) and (18/89) MPF retrievals are available at a product quality similar to the original GR(6/89)-based MPF retrieval. We recommend that the GR(18/89) MPF retrieval adopted is used in nearshore environments such as in the CAA.