TY - JOUR
T1 - In situ measurements of polarization properties of snow surface under the brewster geometry in hokkaido, Japan, and northwest greenland ice sheet
AU - Tanikawa, Tomonori
AU - Hori, Masahiro
AU - Aoki, Teruo
AU - Hachikubo, Akihiro
AU - Kuchiki, Katsuyuki
AU - Niwano, Masashi
AU - Matoba, Sumito
AU - Yamaguchi, Satoru
AU - Stamnes, Knut
N1 - Funding Information:
All data for this paper are available. Requests for materials including the data should be addressed to T. Tanikawa (tanikawa.tomonori@jaxa.jp) or M. Hori (hori.masahiro@jaxa.jp). We thank the members of 2012 Summer Field Campaign in Greenland. Special thanks are due to Tetsuhide Yamasaki for his dedicated logistic support and to Yasuhiro Nakajima, Yukinori Nakajima, and Akira Deguchi for operating the laboratory equipment on an optical instrument calibration. We would like to thank Jouni Peltoniemi, Alexei Lyapustin, and anonymous reviewer for their many helpful comments. This work was conducted as part of (1) the Japan Society for the Promotion of Science (JSPS), Grants-in-Aid for Scientific Research, grant 23221004, (2) the Global Change Observation Mission?Climate (GCOM-C)/the Second-generation Global Imager (SGLI) Mission by Japan Aerospace Exploration Agency (JAXA), and (3) the Grant for Joint Research Program, the Institute of Low Temperature Science, Hokkaido University.
PY - 2014/12/27
Y1 - 2014/12/27
N2 - Ground-based measurements of spectral degree of linear polarization (DLP) of various snow types were made during intensive field campaigns in a snowfield in Hokkaido, Japan, and on the northwest Greenland ice sheet in 2012. Spectral measurements were conducted under the solar zenith angle of approximately the Brewster angle in order to quantify the polarization properties of light reflected from snow. We obtained spectral DLPs for five different snow types in both field campaigns including precipitation particles, needles, surface hoar, melt forms, and melt freeze crust covering the snow surface. The measurements showed that in the visible region the spectral dependence of the DLP was small while in the near infrared region it increased with increasing snow grain size with some distinct local peaks. The angular dependence indicated that the DLP exhibited small angular dependence in the visible region while in the near-infrared region it exhibited large and broad peaks in the forward direction. Especially for the melt-freeze crust, the DLP approached 1.0 at wavelengths close to λ = 1.5 and 2.0 μm. These features can be explained by (1) the relative contribution of surface versus volume scattering to the reflected light, (2) the incident angle (solar zenith angle) of approximately the Brewster angle, and (3) the ratio between direct and diffuse components of the solar radiation incident on the snow surface. The spectral DLP was found to be quiet sensitive to the incident solar radiation and solar elevation as well as snow optical properties. Comparison between the spectral DLP and snow grain size obtained by snow pit work shows that the DLP for λ > 1.5 μm was very sensitive to large snow grains close to the surface. This finding suggests that polarization measurements obtained from airborne/satellite polarimeters will be useful for surface snow grain size retrievals and help improve the accuracy of such retrievals based on the intensity-only measurements, especially for the large snow grain sizes.
AB - Ground-based measurements of spectral degree of linear polarization (DLP) of various snow types were made during intensive field campaigns in a snowfield in Hokkaido, Japan, and on the northwest Greenland ice sheet in 2012. Spectral measurements were conducted under the solar zenith angle of approximately the Brewster angle in order to quantify the polarization properties of light reflected from snow. We obtained spectral DLPs for five different snow types in both field campaigns including precipitation particles, needles, surface hoar, melt forms, and melt freeze crust covering the snow surface. The measurements showed that in the visible region the spectral dependence of the DLP was small while in the near infrared region it increased with increasing snow grain size with some distinct local peaks. The angular dependence indicated that the DLP exhibited small angular dependence in the visible region while in the near-infrared region it exhibited large and broad peaks in the forward direction. Especially for the melt-freeze crust, the DLP approached 1.0 at wavelengths close to λ = 1.5 and 2.0 μm. These features can be explained by (1) the relative contribution of surface versus volume scattering to the reflected light, (2) the incident angle (solar zenith angle) of approximately the Brewster angle, and (3) the ratio between direct and diffuse components of the solar radiation incident on the snow surface. The spectral DLP was found to be quiet sensitive to the incident solar radiation and solar elevation as well as snow optical properties. Comparison between the spectral DLP and snow grain size obtained by snow pit work shows that the DLP for λ > 1.5 μm was very sensitive to large snow grains close to the surface. This finding suggests that polarization measurements obtained from airborne/satellite polarimeters will be useful for surface snow grain size retrievals and help improve the accuracy of such retrievals based on the intensity-only measurements, especially for the large snow grain sizes.
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U2 - 10.1002/2014JD022325
DO - 10.1002/2014JD022325
M3 - Article
AN - SCOPUS:84921435940
SN - 0148-0227
VL - 119
SP - 13,946-13,964
JO - Journal of Geophysical Research Atmospheres
JF - Journal of Geophysical Research Atmospheres
IS - 24
ER -