Snow Property Controls on Modeled Ku-Band Altimeter Estimates of First-Year Sea Ice Thickness: Case Studies From the Canadian and Norwegian Arctic
Snow Property Controls on Modeled Ku-Band Altimeter Estimates of First-Year Sea Ice Thickness: Case Studies From the Canadian and Norwegian Arctic
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对第一年海冰厚度的模拟 Ku 波段高度计估计的雪属性控制：来自加拿大和挪威北极的案例研究
DOI：
10.1109/jstars.2020.2966432
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发表时间：
2020
影响因子：
5.5
通讯作者：
Nandan V
中科院分区：
文献类型：
--
作者：
Nandan V
雪特性的不确定性影响了雷达测高估算北极海冰厚度的准确性。在第一年海冰(FYI)上，雪性质的时空变化会导致Ku波段主雷达散射视界出现在雪/海冰界面上方。这可能会使估计的海冰干板增加几厘米，导致FYI厚度被高估。这篇文章考察了Ku波段主散射层的预期变化及其对FYI厚度估计的影响，来自10个自然发生的北极FYI案例的积雪温度、盐度和密度的变化，包括覆盖在FYI(48-170 cm)上的盐分/非盐分、暖/冷、简单/复杂的分层雪(4-45厘米)。利用半经验建模方法，利用这些情况下的积雪特性，得到层状卤水体积和介电常数的估计，模拟Ku波段的主散射视界和雷达传播速度的延迟。计算模拟的FYI厚度和观测的FYI厚度之间的差异以评估误差来源。在寒冷和温暖条件下，盐分积雪使主散射面从雪/海冰界面上移位，从而造成厚度反演误差。高达65%的FYI厚度被发现是由于温暖的盐分积雪覆盖着薄薄的海冰。我们的模拟显示，当雪层密度大于440公斤/立方米时，特别是在较温暖的积雪条件下，主散射视界发生了明显的移动。我们的模拟表明，降雪的平均Ku波段传播延迟为39%，高于先前研究提出的25%。
Uncertainty in snow properties impacts the accuracy of Arctic sea ice thickness estimates from radar altimetry. On first-year sea ice (FYI), spatiotemporal variations in snow properties can cause the Ku-band main radar scattering horizon to appear above the snow/sea ice interface. This can increase the estimated sea ice freeboard by several centimeters, leading to FYI thickness overestimations. This article examines the expected changes in Ku-band main scattering horizon and its impact on FYI thickness estimates, with variations in snow temperature, salinity, and density derived from ten naturally occurring Arctic FYI Cases encompassing saline/nonsaline, warm/cold, simple/complexly layered snow (4-45 cm) overlying FYI (48-170 cm). Using a semi-empirical modeling approach, snow properties from these Cases are used to derive layer-wise brine volume and dielectric constant estimates, to simulate the Ku-band main scattering horizon and delays in radar propagation speed. Differences between modeled and observed FYI thickness are calculated to assess sources of error. Under both cold and warm conditions, saline snow covers are shown to shift the main scattering horizon above from the snow/sea ice interface, causing thickness retrieval errors. Overestimates in FYI thicknesses of up to 65% are found for warm, saline snow overlaying thin sea ice. Our simulations exhibited a distinct shift in the main scattering horizon when the snow layer densities became greater than 440 kg/m3, especially under warmer snow conditions. Our simulations suggest a mean Ku-band propagation delay for snow of 39%, which is higher than 25%, suggested in previous studies.
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