Abstract Water vapor is the most variable constituent in the atmosphere and plays an important role in climate studies, mesoscale meteorology modeling and numerical weather forecasting. Being able to penetrate clouds, interferometric synthetic aperture radar (InSAR) shows great potential in atmospheric water vapor mapping. But InSAR can only measure differential water vapor between two acquisitions. In this paper, we formulate a general framework by constructing the Gauss-Markov model and developing the estimation method to retrieve the non-differential water vapor from Small BAseline Subset InSAR (SBAS-InSAR). To address the rank-deficiency in the Gauss-Markov model, we propose a new constraint, i.e., the temporal mean of water vapor being invariant. Simulated and real data experiments are conducted to validate the effectiveness of the framework and the advantages of the proposed constraint. The results show that the new constraint can offer an estimation more robust than the two traditional ones, i.e., the temporal mean of water vapor being zero and single or multiple epoch water vapor referencing. In addition, we found that there exists a constant bias, which equals to the temporal mean of water vapors, between the solutions under the new constraint and that under the constraint of the temporal mean of water vapor being zero. Finally, the possible methods to evaluate the temporal mean of water vapor are discussed.

中文翻译：

---

来自 SBAS-InSAR 的非差分水汽估计

摘要 水汽是大气中变化最大的成分，在气候研究、中尺度气象建模和数值天气预报中发挥着重要作用。干涉合成孔径雷达（InSAR）能够穿透云层，在大气水汽测绘中显示出巨大的潜力。但 InSAR 只能测量两次采集之间的差异水汽。在本文中，我们通过构建高斯-马尔可夫模型并开发估计方法来从小基线子集 InSAR (SBAS-InSAR) 中检索非差分水汽，从而制定了一个通用框架。为了解决高斯-马尔可夫模型中的秩亏问题，我们提出了一个新的约束条件，即水蒸气的时间平均值是不变的。进行了模拟和真实数据实验，以验证框架的有效性和所提出约束的优势。结果表明，新约束可以提供比两个传统约束更稳健的估计，即水汽的时间平均值为零和单或多历元水汽参考。此外，我们发现新约束条件下的解与水蒸气时间平均值为零的约束条件下的解之间存在恒定偏差，该偏差等于水蒸气的时间平均值。最后，讨论了评估水蒸气时间平均值的可能方法。水汽的时间平均值为零和单个或多个时期的水汽参考。此外，我们发现新约束条件下的解与水蒸气时间平均值为零的约束条件下的解之间存在恒定偏差，该偏差等于水蒸气的时间平均值。最后，讨论了评估水蒸气时间平均值的可能方法。水汽的时间平均值为零和单个或多个时期的水汽参考。此外，我们发现新约束条件下的解与水蒸气时间平均值为零的约束条件下的解之间存在恒定偏差，该偏差等于水蒸气的时间平均值。最后，讨论了评估水蒸气时间平均值的可能方法。