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Correction of tropospheric water vapour effect on ASAR interferogram using synchronous MERIS data

The water vapour in troposphere has been identified as one of the major errors in SAR interferograms, which can cause a spatial delay during two non-simultaneous acquisitions. The microwave-signal propagation path delay due to water vapour may reduce the reliability of deformation measurements. In this paper, it aims to assess the water vapour effect on interferograms, and apply synchronous MERIS data to reduce the effect on ASAR interferograms. Due to the co-existence of MERIS and ASAR on board of ENVISAT satellite, they can acquire data co-located in the same time and space. So it has a unique advantage to combine MERIS and ASAR data to reduce the tropospheric water vapour effect on ASAR interferograms. However, the method is not so well operational, and still existing some problems need to be further discussed, such as: how to deal with the cloud coverage over MERIS water vapour image; and how to register MERIS to ASAR from different reference systems, and so on. These will be discussed in this paper, and novel ideas are proposed to deal with them. The discussions are based on the application of the test site in the middle and lower reaches of Yangze River, southwest Hubei province, China.