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首页> 外文期刊>Remote Sensing of Environment: An Interdisciplinary Journal >Simulating seasonally and spatially varying snow cover brightness temperature using HUT snow emission model and retrieval of a microwave effective grain size
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Simulating seasonally and spatially varying snow cover brightness temperature using HUT snow emission model and retrieval of a microwave effective grain size

机译：使用HUT雪发射模型模拟季节性和空间变化的积雪亮度温度并检索微波有效粒径

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The Helsinki University of Technology (HUT) snow emission model forms the basis of the European Space Agency's GlobSnow snow water equivalent (SWE) product (Takala et al., 2011). The model applies a semi-empirical radiative transfer calculation to account for the interaction of the snow medium with microwaves; separate components are applied to account for vegetation, the atmosphere, and emission from the ground surface. For the retrieval of SWE, an innovative method is used to account for spatial and temporal variability in snow conditions by retrieving an effective parameter describing the scattering behavior of microwaves in the snow (a proxy indicator of the microwave effective snow grain size). In this study, the influence of differing snow conditions, as well as varying land cover, on the retrieved microwave effective snow grain size was analyzed. Passive microwave measurements were acquired using tower-based, mobile sled-based and airborne radiometers in a mixed forest environment near Sodankyla, Finland. Forward simulations at the tower site over an entire winter period showed that the use of an empirical relation to modify the classical in situ measured grain size produced HUT model bias errors less than 6 K on average at 19 and 37 GHz from a similar to 20-80 cm deep boreal snowpack. Model simulations for airborne and sled-based observations showed that using a simplified 2-layer representation of the snowpack improves simulation biases and RMSE, although modification of the measured grain size was again necessary to achieve these results, regardless of the layering configuration. The microwave effective grain size retrieved from HUT predictions was closely related to a simple average grain size measured in situ, both in terms of magnitude and temporal trend. This is an important finding as the retrieval scheme of Takala et al. (2011) relies on the microwave effective grain size to retain a degree of physical basis for values to be generally applicable over larger areas, which is challenging because this free parameter also accounts for errors unrelated to the effective snow grain size (i.e. vegetation, soil conditions, scene heterogeneity, etc.). (C) 2014 Elsevier Inc. All rights reserved.
机译：赫尔辛基工业大学（HUT）的积雪排放模型构成了欧洲航天局GlobSnow积雪当量（SWE）产品的基础（Takala等人，2011年）。该模型采用半经验辐射传递计算来解释雪介质与微波的相互作用。单独的组件用于说明植被，大气和地面排放。对于SWE的检索，一种创新方法用于通过获取描述微波在雪中的散射行为的有效参数（微波有效雪粒大小的替代指标）来解决雪况中的时空变化。在这项研究中，分析了不同的雪况以及不同的土地覆盖对回收的微波有效雪粒大小的影响。在芬兰Sodankyla附近的混合森林环境中，使用基于塔的，基于移动橇的和机载辐射计获取了无源微波测量值。在整个冬季的塔楼现场进行的前向模拟表明，使用经验关系来修改经典的原位测量晶粒尺寸，在19 GHz和37 GHz时平均产生的HUT模型偏差误差小于20 K，而在20 GHz时， 80厘米深的北方积雪。针对机载和基于雪橇的观测的模型仿真表明，使用简化的两层积雪表示可以改善仿真偏差和RMSE，尽管无论分层结构如何，都必须修改测量的晶粒尺寸才能获得这些结果。从HUT预测中获得的微波有效晶粒尺寸与就地测量的简单平均晶粒尺寸和时间趋势都密切相关。作为Takala等人的检索方案，这是一个重要发现。 （2011年）依靠微波有效粒度来保持一定程度的物理基础，使其值普遍适用于较大的区域，这具有挑战性，因为该自由参数还考虑了与有效雪粒度无关的误差（即植被，土壤条件，场景异质性等）。 （C）2014 Elsevier Inc.保留所有权利。

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