Data assimilation of satellite snow thickness products in the Arctic Ocean

准确监测和模拟北极海冰厚度对于了解该地区对区域和全球气候、航运路线以及生活在冰上和冰下的野生动物的影响至关重要。卫星雷达高度计为估计海冰厚度提供了一个宝贵的工具，测量雷达脉冲到达海冰表面和返回的旅行时间，以获得雷达干舷，这是冰高于周围海水的高度的代理。将雷达干舷估计值转换为海冰厚度的方法需要假设雷达波穿透积雪的部分深度（a），然后返回到仪器。目前所有的冬季海冰厚度反演方法都假设雷达完全穿透积雪（a = 1）。越来越多的研究表明，实际情况并非如此，雪和天气特性会影响雷达波穿透积雪的能力。在雷达干舷和假设的雷达穿透的整体误差计算的海冰厚度，造成高估海冰厚度的高估，没有竞争的偏见。本论文旨在提高我们的理解CryoSat-2雪渗透北极海冰和它的代表性建模框架。

Accurate monitoring and modeling of Arctic sea ice thickness is vital to understanding the region's effects on regional and global climates, shipping routes, and wildlife living on and under the ice. Satellite radar altimeters offer a valuable tool for estimating sea ice thickness, where the travel time of a radar pulse to the sea ice surface and back is measured to obtain the radar freeboard, a proxy for the height of the ice above the surrounding sea water. The method for converting radar freeboard estimates to sea ice thickness requires an assumption regarding the fractional depth of the snowpack penetrated by radar waves (a), which then return to the instrument. All current winter sea ice thickness retrieval methods assume full radar penetration through the snowpack (a = 1). A growing body of research has shown this not to be the case in reality, with snow and weather properties affecting the ability of radar waves to penetrate the snowpack. Uncertainties in the radar freeboard and assumed radar penetration contribute to the overall error in calculated sea ice thickness, with an overestimation of a causing an overestimation in sea ice thickness, without competing biases. This thesis aims to improve our understanding of CryoSat-2 snow penetration over Arctic sea ice and its representation in modelling frameworks.