Abstract
ABSTRACTC band backscatter parameters contain information about the upper snowpack/firn in the dry snow zone. The wide incidence angle diversity of the Advanced Scatterometer (ASCAT) gives unprecedented characterisation of backscatter anisotropy, revealing the backscatter response to climatic forcing. TheA(isotropic component) andM2(bi-sinusoidal azimuth anisotropy) parameters are investigated here, in conjunction with data from atmospheric and snowpack models, to identify the backscatter response to surface forcing parameters (wind speed and persistence, precipitation, surface temperature, density and grain size). The long-term meanAparameter is successfully recreated with a regression using these drivers, indicating strong links between theAparameter and precipitation on long timescales. While the ASCAT time series is too short to determine which factors drive observed trends, factors influencing the seasonal and short timescale variability are revealed. On these timescales,Astrongly responds to the propagation of surface temperature cycles/anomalies downward through the firn, via direct modulation of the dielectric constant. The influence of precipitation onAis small at shorter timescales. TheM2parameter is controlled by wind speed and persistence, through modification of monodirectionally-aligned surface roughness. This variability indicates that throughout much of coastal Antarctica, a microwave ‘snapshot’ is generally not representative of longer-term conditions.
Highlights
Satellite-based microwave observations at C band (4 to 8 GHz) have been used for ice sheet near-surface parameter retrieval for several decades (e.g. Spiridonov and Ozerkina, 1984; Bingham and Drinkwater, 2000; Drinkwater and others, 2001; Winebrenner and others, 2001; Arthern and others, 2006; Fraser and others, 2014)
Assuming the atmosphere determines the physical state of the snow surface/upper snowpack, it should be possible to recreate the spatial distribution of Advanced Scatterometer (ASCAT) parameters using spatial time series of atmospheric parameters
This study has documented the variability in bulk backscatter and bi-sinusoidal azimuthal modulation strength on the dry snow zone of the Antarctic ice sheet (AIS)
Summary
Satellite-based microwave observations at C band (4 to 8 GHz) have been used for ice sheet near-surface parameter retrieval for several decades (e.g. Spiridonov and Ozerkina, 1984; Bingham and Drinkwater, 2000; Drinkwater and others, 2001; Winebrenner and others, 2001; Arthern and others, 2006; Fraser and others, 2014). There is no rough surface backscatter component in the model This model was applied to time series of Antarctic (Bingham and Drinkwater, 2000) and long-term mean Greenland (Drinkwater and others, 2001) scatterometer observations, in order to perform parameter retrieval. This study is conducted under the assumption that the observed ASCAT parameter variability is driven by changes in the physical properties of the snow surface and upper snowpack, including changes in density, layer roughness, grain size and temperature. While the Partington and Flach (2003) model may have been of some utility for this purpose, it does not include a rough surface scattering component, so is of limited use ( for studies of the M2 parameter, which is controlled primarily by surface roughness) Since it was developed primarily for use with the Greenland ice sheet, this model assumes a layered subsurface. Development of a replacement model (or modification of previous models) is outside the scope of this paper
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
