Relationships between summertime surface albedo and melt pond fraction in the central Arctic Ocean: The aggregate scale of albedo obtained on the MOSAiC floe
Relationships between summertime surface albedo and melt pond fraction in the central Arctic Ocean: The aggregate scale of albedo obtained on the MOSAiC floe
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DOI：
10.1525/elementa.2023.00001
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发表时间：
2023
期刊：
影响因子：
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通讯作者：
R. Calmer;G. de Boer;Jonathan Hamilton;Dale A. Lawrence;M. Webster;N. Wright;M. Shupe;C. Cox;J. Cassano
中科院分区：
文献类型：
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作者：
R. Calmer;G. de Boer;Jonathan Hamilton;Dale A. Lawrence;M. Webster;N. Wright;M. Shupe;C. Cox;J. Cassano
作为北极气候研究多学科漂流观测站（MOSAiC）的一部分，HELiX无人驾驶飞机系统（UAS）于2020年夏季部署在北冰洋中部的海冰上。反照率测量是用稳定的热辐射计获得的，熔池分数是用表面成像多光谱相机的正射影计算的。本研究分析了HELiX飞行数据，以了解MOSAiC浮冰在融化季节向南漂移通过Fram海峡时的反照率和融化池分数的时空演变。随着季节的推进，地表反照率的峰值由高反照率（0.55 ~ 0.6）向低反照率（0.3）转变。受卫星数据提取方法的启发，建立了一种从正射影图像中提取熔池分数的算法。研究表明，熔池分数的近地表观测高度依赖于样本面积，从而揭示了卫星观测中亚网格尺度特征和空间异质性的影响。利用HELiX进行的垂直观测，量化了融化池尺度对观测到的地表反照率的影响，并将其作为传感器足迹的函数。这些标度结果用于将MOSAiC期间收集的基于地表的测量数据与更大尺度的卫星数据联系起来，以研究地表特征对观测到的反照率的影响。反照率值混合了传感器足迹内的潜在特征，由融化池的大小和浓度决定。本研究提出了与不同空间尺度的地面反照率的航空（地面）观测相关的降尺度（升尺度）问题。
As part of the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC), the HELiX uncrewed aircraft system (UAS) was deployed over the sea ice in the central Arctic Ocean during summer 2020. Albedo measurements were obtained with stabilized pyranometers, and melt pond fraction was calculated from orthomosaic imagery from a surface-imaging multispectral camera. This study analyzed HELiX flight data to provide insights on the temporal and spatial evolution of albedo and melt pond fraction of the MOSAiC floe during the melt season as it drifted south through Fram Strait. The surface albedo distributions showed peak values changing from high albedo (0.55–0.6) to lower values (0.3) as the season advanced. Inspired by methods developed for satellite data, an algorithm was established to retrieve melt pond fraction from the orthomosaic images. We demonstrate that the near-surface observations of melt pond fraction were highly dependent on sample area, offering insight into the influence of subgrid scale features and spatial heterogeneity in satellite observations. Vertical observations conducted with the HELiX were used to quantify the influence of melt pond scales on observed surface albedo as a function of sensor footprint. These scaling results were used to link surface-based measurements collected during MOSAiC to broader-scale satellite data to investigate the influence of surface features on observed albedo. Albedo values blend underlying features within the sensor footprint, as determined by the melt pond size and concentration. This study framed the downscaling (upscaling) problem related to the airborne (surface) observations of surface albedo across a variety of spatial scales.