Global Automated Quality Control of In Situ Soil Moisture Data from the International Soil Moisture Network

Abstract

The International Soil Moisture Network (ISMN) was initiated in 2009 to support calibration and validation of remote sensing products and land surface models, and to facilitate studying the behavior of our climate over space and time. The ISMN does this by collecting and harmonizing soil moisture data sets from a large variety of individually operating networks and making them available through a centralized data portal. Due to the diversity of climatological conditions covered by the stations and differences in measurement devices and setup, the quality of the measurements is highly variable. Therefore, appropriate quality characterization is desirable for a correct use of the data sets. This study presents a new, automated quality control system for soil moisture measurements contained in the ISMN. Two types of quality control procedures are presented. The first category is based on the geophysical dynamic range and consistency of the measurements. It includes flagging values exceeding a certain threshold and checking the validity of soil moisture variations in relation to changes in soil temperature and precipitation. In particular, the usability of global model‐ or remote sensing–based temperature and precipitation data sets were tested for this purpose as an alternative to in situ measurements, which are often not recorded at the soil moisture sites themselves. The second category of procedures analyzes the shape of the soil moisture time series to detect outliers (spikes), positive and negative breaks, saturation of the signal, and unresponsive sensors. All methods were first validated and then applied to all the data sets currently contained in the ISMN. A validation example of an AMSR‐E satellite and a GLDAS‐Noah model product showed a small but positive impact of the flagging. On the basis of the positive results of this study we will add the flags as a standard attribute to all soil moisture measurements contained in the ISMN.

Multi-decadal analysis of root-zone soil moisture applying the exponential filter across CONUS

“…Before calculation of SWI values for all four satellite products at each in situ station, a series of filters were applied to remove any spurious results following the quality control guidelines articulated by Dorigo et al (2013). Surface temperature and precipitation data from co-located PRISM grid cells flagged problematic dates within the time series of each dataset.…”

“…Satellite soil moisture retrievals were particularly fraught with difficulty under freezing conditions (Dorigo et al, 2011). Likewise, precipitation can be problematic and days with greater than 1 mm day −1 were excised following the guidance of Dorigo et al (2013). Three additional flags related to the quality of the in situ data were applied.…”

JASMIN: A prototype high resolution soil moisture analysis system for Australia

“…In this study, the OzFlux observations are quality controlled (QC) using an automated system based on Dorigo et al (2013). The automated QC scheme rejects about 2% of the observations.…”

Intercomparison of Soil Moisture Retrievals From In Situ, ASAR, and ECV SM Data Sets Over Different European Sites

“…The predominant land cover type is forest. (Dorigo et al, 2011;Dorigo et al, 2013) at https://ismn.geo.tuwien.ac.at/. At all sites, soil moisture values have been evaluated on a daily basis, by averaging the measurements recorded at 30 minute intervals from 00:00 to 23:30 of the same day as the ASAR and ECV SM acquisition.…”