The aim of this work package is to provide and develop a metrological framework for on-site measurements of soil moisture on lateral scales ranging from 10^-1 m to 10² m. This includes setting up calibration facilities (under metrological laboratory conditions) for point-scale soil moisture measuring devices and for neutron probes used for CRNS, as well as the development of transfer standards for on-site calibration of point-scale soil moisture measuring devices. The improved methodologies will then be used in WP2 for the validation of the on-site instrumentation to ensure the traceability of the field measurements.

WP1 consists of the following tasks:

• Task 1.1: Definition of the needed metrological framework
• Task 1.2: Calibration facilities for point-scale sensors and transfer standards
• Task 1.3: Calibration procedures for neutron-measuring devices of CRNS methodology

The aim of this work package is to develop SI-traceable validation practices for CRNS methodology in outdoor conditions. Three high-level test field sites will be selected and further enhanced, to enable the comparison and research of the different soil moisture assessment methods in subsequent tasks and work packages. The existing neutron transport models, used to interpret CRNS neutron signals specific to the soil moisture measurand, will be benchmarked on the test field sites, and validated. Finally, the approaches for the soil moisture assessment from the neutron count rates measured in the CRNS neutron probes will be reviewed, compared and a good practice guide developed.

WP2 consists of the following tasks:

• Task 2.1: Selection and further enhancement of high-level test field sites
• Task 2.2: Validation of existing neutron transport models used to interpret CRNS signals specific to the soil moisture measurand
• Task 2.3: Standardisation of the CRNS on-field calibration procedure for soil moisture assessment

The aim of this work package is to compare and harmonise soil moisture observation methods on multiple spatial and temporal scales. Point-scale, intermediate scale and remote sensing methods will be systematically reviewed and compared in terms of their measurand and its uncertainty, sensing volume, and the systematic effects affecting the process of soil moisture assessment within each method. A harmonisation method will be developed to enable a better comparison of the detected signals and to merge the specific strengths of each soil moisture assessment method.

WP3 consists of the following tasks:

• Task 3.1: Comparison of methods, their constraints and different spatial and temporal characteristics
• Task 3.2: Development of the harmonisation approach

This work package aims at integrating the multi-scale soil moisture measurements to provide new schemes and recommendations to facilitate the generation of high-quality, temporally and spatially consistent soil moisture information useful for land surface sciences and applications, such as climate observations, weather forecasting, hydrology, and agriculture. Strategies for fusion of the soil moisture data on multiple spatial and temporal scales will be reviewed and compared, and the most suited method will be selected and implemented.

WP4 consists of the following tasks:

• Task 4.1: Definition of data fusion methods for soil moisture measurements on multiple scales
• Task 4.2: Implementation of data fusion of soil moisture measurements on multiple scales

This work package ensures that the work carried out in the project is correctly communicated to the relevant user communities and the knowledge gained during the project duration is available to interested parties. The WP5 consists of various activities related to the knowledge transfer, dissemination via trainings and workshops, exploitation and uptake.

Within this work package the project is coordinated, and project meetings and reporting documents are organized.