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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >The quality of sea ice velocity estimates
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The quality of sea ice velocity estimates

机译：海冰速度估算的质量

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Several aspects of observed and estimated velocities for Arctic sea ice are explored. The long-term mean ice motion field and associated variance are derived using 15 years (over 85,000 observations) of daily buoy motions. The mean field is separated into the part due to long-term currents and internal ice stress and the part due to mean winds. The velocity variance is partitioned into "linear" and "nonlinear" parts. The linear response has no trend over the 15 years examined. For a 5-year subset of the buoy data, an ice-ocean model with constant air-drag parameters is used to estimate daily ice velocities at the buoy locations, and then the linear relationship between the modeled velocities and the geostrophic winds is examined. Compared with buoy velocities, the modeled velocities have a larger variance and larger linear response to the winds. In a parameter study, the effects of seasonally varying air-drag coefficients, increased ice strength, and different ocean currents are examined. Seasonally varying air drag, with smaller average magnitude than the standard value, significantly improves the match of total, linear, and nonlinear variances between observed and modeled velocities. The model simulations with varying air drag also have a smaller rootmean-square daily velocity error. Comparison of daily large-scale deformations shows that the day-to-day deformations are not modeled well but generally have means and standard deviations within +-50% of the observed values. No one version of the model is consistently better than the others at matching the means and standard deviations of the observed daily divergence, vorticity, and shear. Ice thickness is sensitive to the model parameters varied, with 5-year average thicknesses ranging from 2.2 to 3.4 m for the various simulations.
机译：探索了北极海冰观测速度和估计速度的几个方面。长期平均冰运动场和相关的方差是使用15年的每日浮标运动（超过85,000个观测值）得出的。由于长期的电流和内部的冰应力，平均场被分为一部分，而由于平均风，该场被分为一部分。速度方差分为“线性”和“非线性”两部分。在检查的15年中，线性响应没有趋势。对于浮标数据的5年子集，使用具有恒定风阻参数的冰海模型来估计浮标位置的每日冰速，然后检查模型速度与地转风之间的线性关系。与浮标速度相比，建模速度具有较大的方差和对风的线性响应。在参数研究中，研究了季节性变化的风阻系数，增加的冰强度和不同洋流的影响。季节性变化的空气阻力的平均幅度小于标准值，可显着改善观测速度和模型速度之间的总，线性和非线性方差的匹配度。空气阻力变化的模型模拟也具有较小的均方根日速度误差。日常大范围变形的比较表明，日常变形不能很好地建模，但通常具有均值和标准偏差在观测值的+ -50％之内。该模型的任何一个版本在匹配所观察到的每日散度，涡度和切变的均值和标准偏差方面均始终优于其他版本。冰厚度对变化的模型参数敏感，各种模拟的5年平均厚度范围从2.2到3.4 m。

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