Abstract
Abstract. Satellite records of microwave surface emission have been used to interpolate in-situ observations of Antarctic surface mass balance (SMB) and build continental-scale maps of accumulation. Using a carefully screened subset of SMB measurements in the 90°–180° E sector, we show a reasonable agreement with microwave-based accumulation map in the dry-snow regions, but large discrepancies in the coastal regions where melt occurs during summer. Using an emission microwave model, we explain the failure of microwave sensors to retrieve SMB by the presence of layers created by melt/refreeze cycles. We conclude that regions potentially affected by melting should be masked-out in microwave-based interpolation schemes.
Highlights
Arthern et al, 2006 have recently produced a new Antarctic Surface Mass Balance (SMB) map using both field measurements and microwave and thermal infrared remote sensing data
Using a carefully screened subset of surface mass balance (SMB) measurements in the 90◦–180◦ E sector, we show a reasonable agreement with microwave-based accumulation map in the dry-snow regions, but large discrepancies in the coastal regions where melt occurs during summer
We found that a snow pack composed of snow layers interleaved with 3-cm thick ice layers regularly spaced every 2 m has a polarisation ratio of Ln(P −Po)=–2.0, the upper bound of those observed in Fig. 4 for the pixels in the melt areas
Summary
Arthern et al, 2006 have recently produced a new Antarctic Surface Mass Balance (SMB) map (referred as A06) using both field measurements and microwave and thermal infrared remote sensing data. The interpolation relies on a spatial background model of the accumulation based on the annual-mean thermal infrared temperature and the polarisation ratio of microwave brightness temperature at 4.3 cm wavelength (6.9 GHz). Microwave brightness temperature has been shown to be a good proxy of SMB in Greenland (Winebrenner et al, 2001) and in Antarctica (Vaughan et al, 1999). These former studies used a shorter wavelength (0.8 cm, i.e. 37 GHz) which is more sensitive to snow grain scattering and is more dependent on grain size. The authors suggest the new SMB map may eliminate some of the discrepancies between climate models and earlier compilations or maps of SMB as observed by (Genthon and Krinner, 2001)
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