融合InSAR、GNSS观测和WRF模式反演高空间分辨率大气可降水量

星载InSAR地表形变监测中被视为无价值的对流层延迟“噪声”在气象学上却是很有价值的“信号”，可反演大气可降水量。然而，InSAR作为水汽反演工具，尚存在如下问题：获得的仅是两景影像的水汽差分相对值、失相干区信息缺失。本项目综合利用SBAS-InSAR和地基GNSS技术并基于附加约束条件的加权最小二乘方法反演SAR影像时刻的大气水汽绝对量，然后基于修正秩克里金插值方法将WRF模拟的水汽与InSAR反演的水汽进行融合，填补失相干区缺失的水汽信息。项目的实施可以为气象研究提供高精度、高空间分辨率且分布连续的大气可降水量产品，空间分辨率可与SAR影像相当（几米到几十米），反映了大气水汽的精细化分布特征。这有助于揭示中小尺度灾害性天气发生和发展的机理，对于提高数值天气预报能力有重要价值。反过来，气象预报精度的提高可以更好地用以改正GNSS、InSAR、VLBI等空间大地测量技术的大气延迟。

When use spaceborne-InSAR for monitoring earth surface deformation, the tropospheric delay is one of the main error sources. From the meteorology point of view, however, the tropospheric delay is a valuable signal reflecting the spatial-temporal variation of water vapour. Therefore, InSAR can be used for mapping the spatial distribution of precipitable water vapour (PWV). However, there are some problems when using InSAR as a tool for water vapor mapping: InSAR produces PWV difference maps at two SAR acquisitions, discontinuous information in areas due to decorrelation. .This project comprehensively exploits data from SBAS-InSAR and Global Navigation Satellite Systems (GNSS), and applies the weighted least square method to derive maps of the absolute PWV maps at each SAR acquisition time. Continuous grids of PWV are then produced by applying the fixed rank kriging technique to combine the PWV observations from InSAR and WRF based on their spatial correlations. This project can provide atmospheric water vapor products with high precision, high spatial resolution and continuous distribution for meteorological research, and the spatial resolution can be equivalent to SAR images (several meters to tens of meters). The fine distribution of atmospheric water vapor information is helpful to reveal the occurrence, development process and mechanism of small and medium scale disastrous weathers, and has an important value on improving the ability of numerical weather prediction. On the other hand, the improvement of the numerical weather prediction can be better used to correct the atmospheric delays in space geodetic techniques such as GNSS, InSAR, VLBI, etc.