Implications and Applications of Emerging Polarimetric Synthetic Aperture Radar for the Retrieval of Freshwater Ice Properties

地球上超过四分之一的湖泊位于北方地区，经历着季节性的冰的发展和衰变。北极景观的物理组成部分在面对放大变暖的情况下发生变化的速度对于栖息地，可持续社区发展和基础设施考虑至关重要。特别是，季节性冰的生长，物候（冻结和解体的时间）和冰的厚度提供了监测气候的代理，是全球气候观测系统中的基本气候变量。利用微波频率进行遥感对恢复冰的特性特别有用。最近的研究已经确定了湖冰后向散射的来源是冰底的粗糙度，从而有可能推导出冰的厚度并绘制出冰水界面的轮廓。绘制冰底图的一个必要条件是保持相干性，相干性描述了两幅图像之间目标的雷达反射和入射角的相似性。利用两个新的传感器：雷达卫星星座使命（RCM）和NISAR，现在可能保持冰的相干性。RCM（C波段5.5厘米）允许每4天重复一次，提高了时间分辨率，减少了采集之间的冰增长量。NISAR是一个计划中的极化干涉合成孔径雷达使命，计划于2022年发射，具有L-（24厘米）和S-波段（12厘米）和12天重复通过。NISAR观测到的长波长可能会超过两次采集之间的冰增长，从而保持相干性。RCM的推出提出了一种新的光束模式：紧凑偏振（CP）。CP发送圆极化波形并接收垂直和水平极化。很少有研究涉及淡水冰的CP观测，仅使用Radarsat-2场景的CP模拟。从模拟CP数据的初步结果表明，冰参数可以检索（冰的范围和破碎），但测试没有使用实际的RCM收购。 我的研究计划的总体目标是改善新的传感器和光束模式与淡水冰相互作用的应用，以检索和交流冰参数投资的利益相关者。此外，这项研究将提供一个基线的检索作为蓝图，以适用于不断增长的数据库的RCM CP和NISAR收购。这项研究计划是独特的定位，以开发初步CP冰算法作为加拿大的旗舰卫星过渡到收集主要在CP模式，并将奠定基础的冰检索算法在泛加拿大的规模，并在全球范围内当NISAR的收购开始。这项工作对于了解加拿大亚北极和北极地区的水文过程至关重要，检索到的冰参数直接有利于社区获得生态系统服务（如冰上运输、越冬鱼类栖息地和可用水资源）。

Over one-quarter of Earth's lakes are located in northern regions and experience seasonal ice development and decay. The rate at which physical components of the Arctic landscape are changing in the face of amplified warming is of importance for habitat, sustainable community development, and infrastructure considerations. In particular, seasonal ice growth, phenology (timing of freeze-up and break-up), and ice thickness provide a proxy for monitoring climate, and are Essential Climate Variables in the Global Climate Observing System. Remote sensing utilizing microwave frequencies have been particularly useful for retrieving ice properties. Recent studies have identified the source of backscatter in lake ice is roughness at the ice bottom, allowing for the potential to derive ice thickness and map the contour of the ice-water interface. A necessity in mapping the ice bottom is to retain coherence, which describes the similarity of radar reflection of a target and incidence angle between two images. Retaining coherence for ice may now be a possibility using two new sensors: Radarsat Constellation Mission (RCM), and NISAR. RCM (C-band 5.5 cm) allows for repeat passes every 4 days, improving temporal resolution and reducing the amount of ice growth between acquisitions. NISAR is a planned polarimetric interferometric Synthetic Aperture Radar mission scheduled to launch in 2022 with L- (24 cm) and S-band (12 cm) and 12 day repeat pass. The long wavelengths observed by NISAR could exceed ice growth between acquisitions, allowing for retained coherence. RCM's launch presents a new beam mode: compact polarimetry (CP). CP sends circularly polarized waveforms and receives vertical and horizontal polarizations. There have been few studies that have addressed CP observations of freshwater ice, having only used CP simulations from Radarsat-2 scenes. Preliminary results from simulated CP data indicate that ice parameters can be retrieved (ice extent and break-up), but tests have not used actual RCM acquisitions. The overarching goal of my research program is to improve the application of new sensors and beam modes interacting with freshwater ice to retrieve and communicate ice parameters to invested stakeholders. Additionally, this research will provide a baseline of retrievals as a blueprint to be applied to the growing database of RCM CP and NISAR acquisitions. This research program is uniquely positioned to develop preliminary CP ice algorithms as Canada's flagship satellite transitions to collect predominantly in CP mode, and will lay the foundation of ice retrieval algorithms at a Pan-Canadian scale, and globally when NISAR's acquisitions begin. The work is of critical importance for the understanding of hydrological processes in Canada's sub-Arctic and Arctic regions, with retrieved ice parameters directly benefitting communities' access to ecosystem services (e.g. transportation over ice, overwintering fish habitat, and available water resources).