In order to estimate the spatially varying bottom friction coefficients (BFCs) in the Bohai, Yellow and East China Seas (BYECS), multi-mission satellite observations from TOPEX/Poseidon, Jason-1 and Jason-2 are assimilated into a two-dimensional tidal model with an adjoint method. This work aims to: (1) study the characteristics of spatially varying BFCs in BYECS; and (2) find out the possible sources and mechanisms of spatially varying BFCs. In the numerical experiment, the $M_2$ tide is simulated and the spatially varying BFCs in BYECS are estimated by assimilating observations from tidal gauge stations and multi-mission altimeters. The simulated $M_2$ tide matches well with the tide gauge data, indicating the reasonability of present methodology of spatially varying BFCs. The characteristics and possible mechanisms of the spatially varying BFCs in BYECS are concluded and discussed, and the main conclusions include: (1) the values of BFCs in shallow water are usually larger than those in deep water, which can reach the order of 10⁻² in shallow areas; (2) the values of BFCs generally decrease with the strengthened depth-averaged tidal current velocity in BYECS; (3) the high-value BFC areas near the coasts always appear in the downstream sides of headlands or peninsulas, which are possibly caused by the propagation of tidal waves; (4) the high-value BFC area along Jiangsu coast is affected by the bottom morphology of radially distributed tidal sand ridges, which might enhance the form drag; (5) the high-value BFC areas in the middle of the South Yellow Sea and Fujian coast correspond to the muddy areas, where the mixture of different sediment types changes the bottom roughness.

为了估算渤海，黄海和东海（BYECS）在空间上变化的底部摩擦系数（BFC），将来自TOPEX / Poseidon，Jason-1和Jason-2的多任务卫星观测值同化为二维伴随方法的潮汐模型。这项工作旨在：（1）研究BYECS中空间变化的BFC的特征；（2）找出空间变化的BFC的可能来源和机制。在数值实验中，${\mathrm{中号}}_{\mathrm{2个}}$模拟潮汐，并通过吸收潮汐站和多任务高度计的观测值，估算BYECS中空间变化的BFC。模拟的${\mathrm{中号}}_{\mathrm{2个}}$潮汐与潮汐仪数据非常吻合，表明了目前空间变化的BFC方法学的合理性。总结并讨论了BYECS中空间变化的BFC的特征和可能的机理，主要结论包括：（1）浅水中的BFC值通常大于深水中的BFC，其值可达到10的数量级^{- 2个}在浅水区 （2）随着BYECS的深度平均潮汐速度的增加，BFCs的值通常会降低；（3）海岸附近的高价值BFC区域总是出现在岬角或半岛的下游，这可能是由潮汐波的传播引起的；（4）江苏沿岸的高价值BFC区受到径向分布的潮汐沙脊底部形态的影响，可能会增加形态阻力。（5）南黄海中部和福建沿海的高价值BFC区域对应于泥泞区，其中不同沉积物类型的混合物改变了底部的粗糙度。