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W. Preimesberger:
"Homogenisation of structural breaks in the global ESA CCI Soil Moisture (multi-satellite) climate data record";
Supervisor: W. Dorigo; Department für Geodäsie und Geoinformation, 2019; final examination: 2019-12-19.

The ESA CCI Soil Moisture COMBINED product is a more than 40 year long data record on global soil moisture for climate studies and applications. It merges soil moisture observations derived from multiple active and passive satellite remote sensing instruments in the microwave domain. Differences in sensor characteristics (such as frequency or polarisation) can cause structural breaks in the product, which are not completely removed during the merging process. These artificially caused discontinuities can adversely affect studies using the long-term data set as they make changes in the observations unrepresentative of long-term changes in reality. Here we compare three adjustment methods in terms of reducing the number of detected breaks in the soil moisture record. We investigate their impact on the data with multiple validation metrics. Their potential (negative) influence is examined by comparing trends in the data before and after homogenisation. We find that all three presented methods can reduce the number of detected breaks in ESA CCI SM. Differences between the methods mainly concern their ability to handle inhomogeneities in variance. Evaluation of the corrected data shows limited impact of homogenisation in terms of quantitative validation metrics. Changes in soil moisture trends due to removing breaks are found in some areas. We find that break correction overall improves the already rather homogeneous data set while preserving its climate describing characteristics. Quantile Category Matching is identified as the preferred method in terms of correcting breaks in ESA CCI SM.

https://repositum.tuwien.ac.at/urn:nbn:at:at-ubtuw:1-131916