Measurements and Modeling of Optical-Equivalent Snow Grain Sizes under Arctic Low-Sun Conditions
Measurements and Modeling of Optical-Equivalent Snow Grain Sizes under Arctic Low-Sun Conditions
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北极低日照条件下光学等效雪粒尺寸的测量和建模
DOI：
10.3390/rs13234904
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Anika Rohde
中科院分区：
文献类型：
--
作者：
E. Jäkel;T. Carlsen;A. Ehrlich;M. Wendisch;M. Schäfer;Sophie Rosenburg;K. Nakoudi;M. Zanatta;G. Birnbaum;V. Helm;A. Herber;L. Istomina;L. Mei;Anika Rohde
雪粒的大小和形状直接影响积雪的反射。本文比较了利用卫星、机载和地面观测数据获取光学等效雪粒度（ropt）或比表面积（SSA）的不同方法，并将其用于评估ICON-ART （ICOsahedral non - hydrostatic - aerosol and Reactive痕量气体）模拟。反演方法以光学测量为基础，依赖于雪中对太阳辐射的依赖吸收。测量数据是在2018年3月/ 4月在格陵兰北部进行的为期三周的活动中获取的，因此在这些低太阳条件下，检索方法和辐射测量受到增强的不确定性的影响。利用1700nm波段的反照率，结合大气和雪的辐射传输模式，提出了一种调整后的机载反演方法，以计算太阳辐射直接到全球的分量。与之前的方法相比，这种方法显著提高了不确定度（<25%），减少了大气掩蔽的影响。地面现场测量表明，在降雪事件发生后的5天内，ropt增加了15 μ m，这与以前在类似温度条件下的观测结果相比较小。ICON-ART捕获了降雪期间观测到的ropt变化，但系统地高估了随后的雪粒生长约100%。将生长速率因子调整为0.012µm2 s−1，使模型与观测值之间的差异最小化。基于卫星和机载的反演方法显示，海冰（<300µm）的坡度高于陆地表面（<100µm），这是通过表面粗糙度特征的数据过滤而降低的。中分辨率成像光谱仪（MODIS）反演结果显示，在随后的一系列单独立交桥中存在较大的分布，表明其在观测早春低太阳条件下积雪粒度演变的局限性。
The size and shape of snow grains directly impacts the reflection by a snowpack. In this article, different approaches to retrieve the optical-equivalent snow grain size (ropt) or, alternatively, the specific surface area (SSA) using satellite, airborne, and ground-based observations are compared and used to evaluate ICON-ART (ICOsahedral Nonhydrostatic—Aerosols and Reactive Trace gases) simulations. The retrieval methods are based on optical measurements and rely on the ropt-dependent absorption of solar radiation in snow. The measurement data were taken during a three-week campaign that was conducted in the North of Greenland in March/April 2018, such that the retrieval methods and radiation measurements are affected by enhanced uncertainties under these low-Sun conditions. An adjusted airborne retrieval method is applied which uses the albedo at 1700 nm wavelength and combines an atmospheric and snow radiative transfer model to account for the direct-to-global fraction of the solar radiation incident on the snow. From this approach, we achieved a significantly improved uncertainty (<25%) and a reduced effect of atmospheric masking compared to the previous method. Ground-based in situ measurements indicated an increase of ropt of 15 µm within a five-day period after a snowfall event which is small compared to previous observations under similar temperature regimes. ICON-ART captured the observed change of ropt during snowfall events, but systematically overestimated the subsequent snow grain growth by about 100%. Adjusting the growth rate factor to 0.012 µm2 s−1 minimized the difference between model and observations. Satellite-based and airborne retrieval methods showed higher ropt over sea ice (<300 µm) than over land surfaces (<100 µm) which was reduced by data filtering of surface roughness features. Moderate-Resolution Imaging Spectroradiometer (MODIS) retrievals revealed a large spread within a series of subsequent individual overpasses, indicating their limitations in observing the snow grain size evolution in early spring conditions with low Sun.
南极洲中部光学当量雪粒尺寸不同方法反演比较
DOI：
10.5194/tc-11-2727-2017
发表时间：
2017
期刊：
The Cryosphere
影响因子：
--
作者：
Carlsen;Birnbaum;Ehrlich;Freitag;Heygster;Istomina;Kipfstuhl;Schäfer;M. Wendisch
通讯作者：
M. Wendisch
影响因子：
5.2
作者：
Hartmann, M.;Adachi, K.;Stratmann, F.
通讯作者：
Stratmann, F.