Dependence of thermal infrared emissive behaviors of snow cover on the surface snow type（雪面の熱赤外射出特性の雪質依存性）

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概要

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• The potential of the thermal infrared (TIR) remote sensing for discriminating surface snow types was examined by analyzing TIR radiances acquired from space over the Greenland ice sheet.　The brightness temperature difference (BTD) between TIR wavelengths of 11 and 12μm was found to increase in accordance with in situ observed evolutions of surface snow type.　Spatial and temporal distributions of BTD over the entire ice sheet indicated that BTD has a sensitivity of about 1.2 K for variations of the possible snow types.　The observed behaviors of BTD were coincident with those predicted by a radiative transfer calculation using previous in situ measured snow emissivities, although some biases on the order of 0.1-0.3 K remain.　The dependence of BTD on the surface snow type was also consistent with the behaviors of snow reflectance at the shortwave infrared (SWIR) wavelength 1.6μm, which is a measure of snow grain size, except for the case of melting wet snow.　The inconsistency in the wet snow case was considered to be due to the different optical responses of the TIR and SWIR signals to wet snow, which suggested the possibility of using TIR signals to discriminate wet/dry conditions of snow cover in an old stage.　As a result, it is determined that TIR remote sensing has potential not only as an approach supplementary to the SWIR method for assessing surface snow types in daytime but also as the only method for simultaneous retrieval of snow type and surface temperature in nighttime.

• 公益社団法人 日本雪氷学会の論文

著者

• MATOBA Sumito（的場澄人）

  Institute of Low Temperature Science, Hokkaido University

• HORI Masahiro（堀雅裕）

  Earth Observation Research Center, Japan Aerospace Exploration Agency

• AOKI Teruo（青木輝夫）

  Meteorological Research Institute

• TANIKAWA Tomonori（谷川朋範）

  Earth Observation Research Center, Japan Aerospace Exploration Agency

• KUCHIKI Katsuyuki（朽木勝幸）

  Meteorological Research Institute

• NIWANO Masashi（庭野匡思）

  Meteorological Research Institute

• YAMAGUCHI Satoru（山口悟）

  Snow and Ice Research Center, National Research Institute for Earth Science and Disaster Prevention

関連論文

• Field activities of the "Snow Impurity and Glacial Microbe effects on abrupt warming in the Arctic" (SIGMA) Project in Greenland in 2011-2013（2011-2013年グリーンランドにおけるSIGMAプロジェクトの野外活動報告）
• Light-absorbing snow impurity concentrations measured on Northwest Greenland ice sheet in 2011 and 2012（2011年及び2012年に北西グリーンランド氷床上で観測された光吸収性積雪不純物濃度）
• Application of snow specific surface area measurement using an optical method based on near-infrared reflectance around 900-nm wavelength to wet snow zones in Japan（近赤外領域の反射率を用いた日本の濡れ雪地域の積雪比表面積の測定）
• Effects of temperature and grain type on time variation of snow specific surface area（積雪比表面積の時間変化に及ぼす温度および雪質の影響）
• Dependence of thermal infrared emissive behaviors of snow cover on the surface snow type（雪面の熱赤外射出特性の雪質依存性）
• Glaciological observations in 2012 and 2013 at SIGMA-A site, Northwest Greenland（北西グリーンランド , SIGMA-Aサイトにおける 2012年, 2013年の雪氷調査）
• Evaluation of updated physical snowpack model SMAP（アップデートした積雪変質モデルSMAPの精度評価）

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