Data assimilation of satellite snow thickness products in the Arctic Ocean

对北极海冰厚度的准确监测和建模对于了解该地区对区域和全球气候、航道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有价值的工具，通过测量雷达脉冲到海冰表面和返回海冰的旅行时间来获得雷达干板，这是周围海水上方冰层高度的替代指标。将雷达干舷估算转换为海冰厚度的方法需要假设被雷达波(A)穿透的积雪的部分深度，然后将其返回仪器。目前所有的冬季海冰厚度反演方法都假定雷达完全穿透积雪(a=1)。越来越多的研究表明，事实并非如此，雪和天气特性会影响雷达波穿透积雪的能力。雷达干舷和假定雷达穿透的不确定性造成了计算海冰厚度的总体误差，高估了海冰厚度，导致了海冰厚度的高估，而不存在相互竞争的偏差。本论文旨在加深我们对CryoSat-2积雪在北极海冰上的穿透及其在模式框架中的表现的理解。

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.