Modeled microwave properties of snow over sea ice at 17 and 37 gigahertz (GHz)

The goals of this project are to model the microwave properties of snow over sea ice through High Performance Computing (HPC) three dimensional (3D) simulations of solutions of Maxwell equations and 3D simulations of snow microstructure. To apply the 3D simulation results to the analysis of active and passive microwave remote sensing data of snow over sea ice; and to design future microwave remote sensing measurements including signals of opportunities. During the project period, we have developed techniques for 3D full wave numerical solutions of Maxwell equations (NMM3D) for snow over sea ice. We have applied the 3D simulation results to the analysis of active and passive microwave remote sensing data of snow and sea ice. We have generated Lookup Tables (LUTs) that relate different properties of snow and sea ice to brightness temperature (Tb) and backscatter responses with NMM3D. For passive remote sensing, we have generated LUTs of Tb at Ku (17 gigahertz) and Ka (37 gigahertz) band for retrieval of Snow Depth (SD) over sea ice with Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E/2) observations. For active remote sensing, LUTs of snow over sea ice at Ku and Ka band have been built. We also have built backscatter LUT for sea ice at L (1-2 gigahertz), C (4-8 gigahertz) and X (8-12 gigahertz) bands. In the 3D full wave simulations, the scattering matrix of the snowpack is directly obtained including both amplitude and phase. Both bistatic scattering coefficients and brightness temperatures (Tbs) of the snowpack are computed. Simulation results demonstrate backscattering enhancement effects and coherent layer effects which are missed in radiative transfer theory that only describes the incoherent wave interactions. We also found that the roughness of the snow/ice interface weakens the coherent layer effects. Our simulations also demonstrated that both Tb and backscattering are highly related to roughness of the snow/ice interface and the ice/water interface. The snow/ice interface roughness increases Tbs and backscatter more at high frequency and for thick ice, while the ice/water interface roughness increases Tbs and backscatter more at low frequency and for thin ice. Results from the numerical simulations were used to characterize signatures of microwave signals at different bands. This dataset contains full model results in the included zip directory. A readme file explaining the directory structure is available in the top level of the zip file.

本项目的目标为：通过求解麦克斯韦方程组（Maxwell equations）的高性能计算（High Performance Computing, HPC）三维（3D）模拟与雪微结构的三维模拟，对海冰上方积雪的微波特性开展建模；将三维模拟结果应用于海冰上方积雪的主动与被动微波遥感数据分析；并设计未来的微波遥感探测方案，包括机会信号。项目执行期间，本团队开发了针对海冰上方积雪的麦克斯韦方程组三维全波数值求解技术（NMM3D）。我们将三维模拟结果应用于积雪与海冰的主动、被动微波遥感数据分析。我们构建了查找表（Lookup Tables, LUTs），通过NMM3D将积雪与海冰的各类属性与亮度温度（brightness temperature, Tb）及后向散射响应建立关联。针对被动遥感场景，我们基于先进微波扫描辐射计-地球观测系统（Advanced Microwave Scanning Radiometer - Earth Observing System, AMSR-E/2）的观测数据，生成了适用于海冰上方积雪深度（Snow Depth, SD）反演的Ku波段（17吉赫兹）与Ka波段（37吉赫兹）亮度温度查找表。针对主动遥感场景，我们构建了海冰上方积雪的Ku、Ka波段后向散射查找表。此外，我们还搭建了海冰在L波段（1-2吉赫兹）、C波段（4-8吉赫兹）与X波段（8-12吉赫兹）的后向散射查找表。在三维全波模拟中，我们可直接获取积雪层的散射矩阵，其中包含幅度与相位信息。我们同时计算了积雪层的双站散射系数与亮度温度（Tbs）。模拟结果揭示了后向散射增强效应与相干层效应，而仅描述非相干波相互作用的辐射传输理论无法捕捉此类效应。我们还发现，雪/冰界面的粗糙度会削弱相干层效应。本团队的模拟结果还证实，亮度温度与后向散射均与雪/冰界面及冰/水界面的粗糙度密切相关。雪/冰界面粗糙度在高频波段与厚冰场景下，对亮度温度与后向散射的增强作用更为显著；而冰/水界面粗糙度则在低频波段与薄冰场景下，对二者的增强效果更为明显。数值模拟结果被用于表征不同波段的微波信号特征。本数据集包含压缩包目录中的全部模型结果。压缩包的顶层目录中附有说明文档，详细解释了目录结构。