Coherent backscatter enhancement in bistatic Ku- and X-band radar observations of dry snow

• Published in: The Cryosphere
• Main Authors: M. Stefko, S. Leinss, O. Frey, I. Hajnsek
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2022
• Subjects: Environmental sciences; GE1-350; Geology; QE1-996.5; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-16-2859-2022; https://doaj.org/article/805bd9f821f04ae994283af7f8d99f85

The coherent backscatter opposition effect (CBOE) enhances the backscatter intensity of electromagnetic waves by up to a factor of 2 in a very narrow cone around the direct return direction when multiple scattering occurs in a weakly absorbing, disordered medium. So far, this effect has not been investigated in terrestrial snow in the microwave spectrum. It has also received little attention in scattering models. We present the first characterization of the CBOE in dry snow using ground-based and spaceborne bistatic radar systems. For a seasonal snowpack in the Ku-band (17.2 GHz), we found backscatter enhancement of 50 %–60 % ( +1.8 –2.0 dB) at a zero bistatic angle and a peak half-width at half-maximum (HWHM) of 0.25 ∘ . In the X-band (9.65 GHz), we found backscatter enhancement of at least 35 % ( +1.3 dB) and an estimated HWHM of 0.12 ∘ in the accumulation areas of glaciers in the Jungfrau–Aletsch region, Switzerland. Sampling of the peak shape at different bistatic angles allows estimating the scattering and absorption mean free paths, Λ T and Λ A . In the VV polarization, we obtained <math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi mathvariant="normal">Λ</mi><mi mathvariant="normal">T</mi></msub><mo>=</mo><mn mathvariant="normal">0.4</mn><mo>±</mo><mn mathvariant="normal">0.1</mn></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="70pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="12b3468f431a12d406d1166ba34a5406"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-16-2859-2022-ie00001.svg" width="70pt" height="12pt" src="tc-16-2859-2022-ie00001.png"/></svg:svg> m and <math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi mathvariant="normal">Λ</mi><mi ...