SPM71 | In situ soil moisture: What are the errors sources, and how can we derive a traceable uncertainty budget?
In situ soil moisture: What are the errors sources, and how can we derive a traceable uncertainty budget?
Convener: Irene HimmelbauerECSECS | Co-conveners: François GibonECSECS, raffaele crapolicchio, Miroslav Zboril, Matthias Zink
Thu, 18 Apr, 14:00–15:45 (CEST)
Room 2.83
Thu, 14:00
The correct measurement and availability of soil moisture data is crucial for the assessment of plant available water and the separation of energy and water fluxes on the land surface. Furthermore, in situ soil moisture data is used as “ground truth” to improve soil moisture model or satellite data products in many disciplines and communities, like climate and environmental sciences, hydrology, meteorology, agricultural engineering, decision making, disaster risk assessment and management. Although, in situ measurement error sources are well understood, there are still many unknowns concerning the uncertainties and their magnitudes that need to be considered when using in situ soil moisture data as a reference.

The collection, harmonization and quality control of freely available in situ soil moisture is the main mission of the International Soil Moisture Network (ISMN). In the last decade data from more than 77 networks (~3000 stations, ~12000 time series) covering the time period from 1952 until near real time were collected by the ISMN. This extensive database enables us to take the next important steps towards reliable model and satellite soil moisture product validation: identifying error sources of in situ soil moisture measurements, and calculating the uncertainty budgets of individual soil moisture sensors. For this purpose, ESA`s “Fiducial Reference Measurement for Soil Moisture” (FRM4SM) project and EURAMET`s “Soil Moisture Metrology” (SoMMet) Green Deal project were initiated in 2021 and 2022, respectively. All three initiatives—ISMN, FRM4SM, and SoMMet—are interdisciplinary collaborations that bring together a number of scientific communities to tackle data availabil ity and the deeper understanding of the soil moisture measurement, e.g., remote sensing, metrology, soil science, hydrology, and sensor production.

Within this splinter meeting, we want to take the opportunity to facilitate a lively discussion between soil moisture enthusiasts, users, data providers, and sensor manufacturers that are interested in the assessment of in situ soil moisture and their uncertainties. Our goal is to get a better understanding of:

· data availability, usage, and quality control · influences and error sources that drive the in situ soil moisture component, · challenges currently faced (e.g., missing standards to derive reliable data, etc.) · what we are still missing (e.g., stations at certain locations, etc.) in order to answer the questions: (1) what are the error sources; and (2) how can we derive a traceable uncertainty budget.

If you are working with in situ soil moisture probes, calibration, installation, or data, you are very welcome to join this open discussion round, organized by the FRM4SM, SoMMet, and ISMN project teams.