Evaluating seasonal loading models and their impact on global and regional reference frame alignment
Evaluating seasonal loading models and their impact on global and regional reference frame alignment
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DOI：
10.1002/2013jb010186
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发表时间：
2014-02
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影响因子：
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通讯作者：
Rong Zou;J. Freymueller;K. Ding;Shaomin Yang;Qi Wang
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文献类型：
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作者：
Rong Zou;J. Freymueller;K. Ding;Shaomin Yang;Qi Wang
在全球定位系统时间序列中观察到季节性变化，但没有包括在国际地球参考框架（ITRF）模型中。用于参考坐标系对齐的站点处的未建模季节性变化被混叠到参考坐标系参数中，并使变换后的解决方案中的所有坐标发生偏差。我们增加ITRF 2008的季节性负荷模型的基础上重力恢复和气候实验（GRACE）测量或一套模型的大气压力，大陆水文，和非潮汐海洋负荷。我们使用年度和半年期或非参数方法对季节性成分进行建模。当我们包括季节变化模型时，相对于使用ITRF 2008的基线情况，根据所使用的网络和季节模型，七参数转换后的加权均方根失配在70-90%的每日GPS解中减少。当参考框架解决方案中包含季节变化时，在80-85%的GPS站点（未用于框架对齐），观察到的季节变化与基于GRACE的模型更加一致。这套正演模型在北美的表现几乎与基于GRACE的模型一样好，但在世界其他地区则要差得多。我们解释这些发现意味着，使用ITRF 2008没有季节性条款的坐标时间序列的季节性变化的幅度被阻尼下来相对于真实的加载变形，所观察到的GPS时间序列是更一致的TRF模型，包括季节性变化。目前，一个季节性模型来自GRACE更忠实地捕捉季节变化比一个基于水文模型。
Seasonal variations are observed in GPS time series, but are not included in the International Terrestrial Reference Frame (ITRF) models. Unmodeled seasonal variations at sites used for reference frame alignment are aliased into the reference frame parameters and bias all coordinates in the transformed solution. We augment ITRF2008 with seasonal loading models based either on Gravity Recovery and Climate Experiment (GRACE) measurements or a suite of models for atmospheric pressure, continental hydrology, and nontidal ocean loading. We model the seasonal components using either annual and semiannual terms or a nonparametric approach. When we include a seasonal variation model, the weighted root‐mean‐square misfit after seven‐parameter transformation decreases for 70–90% of the daily GPS solutions depending on the network and seasonal model used, relative to a baseline case using ITRF2008. When seasonal variations are included in the reference frame solution, the observed seasonal variations are more consistent with the GRACE‐based model at 80–85% of the GPS sites that were not used in the frame alignment. The suite of forward models performs nearly as well as the GRACE‐based model for North America, but substantially worse for other parts of the world. We interpret these findings to mean that the use of ITRF2008 without seasonal terms causes the amplitude of seasonal variations in the coordinate time series to be damped down relative to the true loading deformation and that the observed GPS time series are more consistent with a TRF model that includes seasonal variations. At present, a seasonal model derived from GRACE captures seasonal variations more faithfully than one based on hydrologic models.