Project Ambition, objectives and Work Packages
WG1
Enhancing upper-air radiosonde and lidar measurements for climate study
Radio sondes and Water vapor Raman lidars are used for observations of the Essential Climate Variable “Upper Air Water Vapor”. The WG focuses on improving upper-air climate measurements specifically targeting the optimization and standardisation of radiosoundings (from manual and automatic launchers) and temperature and water vapour lidar measurements. In particular, the focus will be on establishing a common metrological framework to ensure measurement traceability to the International System of Units (SI), enhancing the comparability and quality assurance of observational data. This will lead to more robust scientific analyses and improved reliability of climate assessments. WG1 will promote the transparent quantification of uncertainties in upper-air climate measurements through standardised methodologies, enhancing the credibility of climate studies. New solutions from academia and industry for reference measurements in critical climatic regions or extreme conditions will be assessed.
Task 1.1: Traceability and quality of upper-air radiosonde and lidar measurements
:::: Support the development of end-to-end guidelines and standardised protocols for upper-air radiosonde and lidar measurements and their processing, ensuring traceability to SI or community standard
:::: Analyse the impact of calibration methodologies on data accuracy and consistency
:::: Provide a quality assurance framework for those measurements
:::: Short term scientfic missions will be organised in the first year, aimed at
- implementation of a common Water Vapour Raman lidar data processing platform
- sharing of operational procedures for executing GRUAN radio soundings and lidar observations in various locations
- Uncertainty analysis for the lower part of the sounding range.
Task 1.2: Upper-air measurement uncertainty quantification and communication Main Activities:
:::: Improve methods for estimating uncertainty in GRUAN data products, with specific reference to the identification of all known sources of uncertainties and classification of their nature at different time scales.
:::: Provide tools and guidance on uncertainty reporting practices for transparent communication of uncertainties, ensuring that the data are easily interpretable and usable by end-users and enhancing the reliability and credibility of climate studies and assessments.
Task 1.3: Radiosonde Network Optimization and Best Practices Dissemination
Task 1.3: Radiosonde Network Optimization and Best Practices Dissemination:
:::: Provide a scientific sound justification for the temporal and spatial sampling requested to GRUAN.
:::: Ensure the best practices from GRUAN sites are properly shared and adopted with a special attention paid to the remote sites and sites in regions with contingent issues in the instrument maintenance.
:::: Promote the dissemination of best practices for improving data quality in other global measurement networks and global initiatives.
D1: Report on the end-to-end guidelines and standardised protocols for upper-air radiosonde and lidar measurements
D2: Recommendation for the quality assurance framework to adopt for upper-air radiosonde and lidar measurements
D3: Report on the improved methodologies for uncertainty quantification in GRUAN data products
D4: Guidance on uncertainty reporting practices for transparent communication of uncertainties
D5: Tools on uncertainty reporting practices for transparent communication of uncertainties
WG1 Leader: Arnoud Apituley – arnoud.apituley@knmi.nl
WG1 Vice Chair: Ruud Dirksen – ruud.dirksen@dwd.de
WG2
Metrology for near-surface climate reference sites
WG2 focuses on advancing metrology for near-surface climate reference sites. Our mission is to strengthen standardisation, traceability to SI units, and uncertainty evaluation in near-surface climate measurements. The WG2 brings together researchers, meteorological services, and institutions to assess and improve existing guidelines and protocols for reference observations. It also develops practical approaches for reducing measurement uncertainty.
WG2 activities will focus on review and improve existing guidelines and standardised protocols for near-surface climate measurements. Particular attention will be given to practices currently used at climate reference stations. The group will assess these prescriptions in the context of GSRN and WMO measurement quality requirements. Existing knowledge from operational services, research networks, and the scientific literature will be brought together in this assessment. Participants will discuss how effective current approaches are for evaluating uncertainty in essential climate variables measurements. They will also examine how feasible these approaches are in practical station operation. This work will support a clearer and more consistent basis for uncertainty evaluation at climatological reference stations. An additional activity will be the initiation of a users’ forum linking research and services. The forum will support discussion on the adoption of standardised measurement best practices and metrological principles.
- D6: Report on the assessment and practical adoption of existing guidelines and standardized protocols for climate reference stations performing near-surface measurements
- D7: Report on methods and procedures for the reduction of uncertainty in measurements from climate reference stations
- D8: Web tools for the inclusion of uncertainty in data products from climatological reference stations
• WG2 Leader: Branislava Lalic – branislava.lalic@polj.edu.rs
• WG Vice Chair: Andrea Merlone –a.merlone@inrim.it
• Task 2.1 Lead: Mareile Astrid Wolff & Mesut Demircan – mareile.astrid.wolff@nmbu.no & demircanm@gmail.com
• Task 2.2 Lead: Athanassios Argiriou & Graziano Coppa – apascha@fmenr.duth.gr & g. coppa@inrim.it
• Task 2.3 Lead: Sibylle von Löwis & Claire Gallacher – sibylle@vedur.is & claire.gallacher@mailbox.tu-dresden.de
WG3
Metrology for GNSS water vapour measurements and retrievals
Working Group 3 (WG3) is refining the way we estimate GNSS-precipitable water vapor (GNSS-PWV) to better serve the scientific community, bridging the gap between technical data processing and the practical needs of weather and climate analysts. The team is benchmarking different GNSS processing methods to deliver high-quality values that meet end-users’ stringent uncertainty requirements. This involves distinguishing between errors inherent to GNSS technology and those caused by natural water vapor variations.
Beyond the technical calculations, WG3 connects collaborators within the field. It establishes effective processing strategies and communicates the capabilities and limitations of these observations, ensuring users understand the data. This culminates in comprehensive guidance on obtaining high-quality measurements and an active forum for dialogue between providers and users.
The activities of WG3 are planned in line with the objectives defined in Task 3.1, Task 3.2, and Task 3.3:
Task 3.1.: Towards a better quality of GNSS-PWV:
WG3 will start with benchmarking the GNSS sites/GNSS processing types to determine high-quality GNSS-PWV values. We are going to conduct a benchmark study with following drafted methodology for Task 3.1. (towards a better quality of GNSS-PWV).
- Select GNSS sites (IGS or GRUAN, etc.) with various collocated GNSS and RS.
- Decide GNSS processing software packages (GAMIT, Bernese, etc.).
- Apply various processing options and compare processing results with different parametrization in processing (tropospheric model, cutoff angle, etc.) and different software packages.
- Assess results with reference products (GRUAN).
Task 3.2.: GNSS uncertainty quantification and communication
- Uncertainty quantification by considering instrumental errors and atmospheric variability.
- Development of standardized methodologies for uncertainty evaluations for weather and climate applications separately.
- Prepare consistent guidelines for GNSS-PWV uncertainty to different user communities.
Task 3.3.: GNSS Best Practices
- Collection and analysis of best practices from existing GNSS-PWV sites.
- Ensure the adaptation of best practices across global GNSS networks.
D9: Report on current types of processing of GNSS observations and its impact on current GNSS-PWV values. (Year 1)
D10: Guidance on processing GNSS observations for achieving the best quality of GNSS- PWV for weather and climate applications.(Year 2)
D11: Report on the improved methodologies tor uncertainty quantification in GNSS-PWV. (Year 2)
D12: Guidance on uncertainty reporting practices tor transparent communication of GNSS- PWV (Year 3)
D13: at least 5 scientific papers on calibration and sampling requirements, benchmarking on the three main subjects of the GOST Action: GRUAN, GSRN, GNSS (Year 4)
WG3 Leader: Emine Tanır Kayıkçı – etanir@ktu.edu.tr
WG3 Vice Chair: Anna Klos – anna.klos@wat.edu.pl
WG3 Vice Chair: Karin Kollo – karinkollo@gmail.com
WG4
Dissemination and Knowledge Transfer
WG4 aims to coordinate the dissemination activities and promote the knowledge transfer among the COST action participants and outside, with a particular attention to the intersectoral target audience. The open access tools will be also encouraged. Another challenge is to foster the exchange of knowledge and the improvement of the expertise, by contributing to the professional development of early-career researchers and climate scientists and to valorise the interdisciplinary research.
Main activities will be carried out according to the MoU and the Science Communication Plan, approved in March 2026 (link to the SC Plan)
Task 4.1: Dissemination activities
The activities will be focused to promote CRIM COST Action results and updates to the general public, the scientific communities and potential interested stakeholders. To foster the dialogue between the different communities and promote the guidelines and the best practice, workshop and meetings will be organized. They will be organised in continuity to the Management Committee meeting, in order to save time and resources. CRIM LinkedIn social page will be constantly updated.
Task 4.2: Knowledge transfer
Short-term mobility among the consortium institution will be promoted and the outputs and the experiences by each applicant will be valorised among the CRIM network as well as on the communication channels. Structured training programs and workshops, with sessions devoted to project results and tools will be organized as well as three Summer Schools addressed to young researchers to introduce them both to the reference climate data uses and to the handling data and tools. A user forum will be set up to facilitate the exchange of information among participants, collect the requirements from the users and share common strategies and approaches.
Next event:
1st Stakeholder Workshop, Rome, CNR, 18 and 19 May 2026 [link to the event page]
- D13: at least 5 scientific papers on calibration and sampling requirements, benchmarking on the three main subjects of the COST Action: GRUAN, GSRN, GNSS
- D14: creation of a forum for dialogue between academic, research, users, industrial institutions and service providers
- D15: Training material of summer schools publicly available
- D16: Report on the exchange visits
- D17: Recommendation from the User’s Forum
- WG4 Leader: Monica Proto – monica.proto@cnr.it
- WG4 Vice Chair: Peter Pavlasek – pavlasek@smu.gov.sk
CRIM: Expected results
The CRIM action is expected to deliver significant scientific, technological and social results, improving confidence in climate trend detection and severe event prediction. From a scientific perspective, it will establish a standardised framework for quantifying uncertainties in climate measurements, thereby enhancing the accuracy of weather models, atmospheric reanalysis and long-term trend evaluations. This framework is designed to be adaptable across diverse sectors, including agriculture, energy, and transport. The project will develop new tools for quantifying uncertainty and establish reference-grade measurement protocols that will set global standards for data quality. These advancements will facilitate the development of specific climate resilience applications. The expected results include increased effectiveness of early warning systems for extreme events such as floods and droughts, thanks to improved forecasting accuracy. By providing robust, traceable and high-quality climate data, CRIM will enable policymakers to make informed decisions on mitigation and adaptation, thereby aiming to reduce political controversy and foster public trust in climate science. Ultimately, the project aims to establish a cohesive European global climate reference network to ensure integrated monitoring and data sharing across the continent.
ACTION DETAILS
• MoU – 064/25
• CSO Approval date – 19/05/2025
• START DATE – 19/09/2025
• END DATE – 18/09/2029
Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or name of the granting autority. Neither the European Union nor the granting authority can be held responsible for them.
Project Ambition, objectives and Work Packages
WG1
Enhancing upper-air radiosonde and lidar measurements for climate study
Radio sondes and Water vapor Raman lidars are used for observations of the Essential Climate Variable “Upper Air Water Vapor”. The WG focuses on improving upper-air climate measurements specifically targeting the optimization and standardisation of radiosoundings (from manual and automatic launchers) and temperature and water vapour lidar measurements. In particular, the focus will be on establishing a common metrological framework to ensure measurement traceability to the International System of Units (SI), enhancing the comparability and quality assurance of observational data. This will lead to more robust scientific analyses and improved reliability of climate assessments. WG1 will promote the transparent quantification of uncertainties in upper-air climate measurements through standardised methodologies, enhancing the credibility of climate studies. New solutions from academia and industry for reference measurements in critical climatic regions or extreme conditions will be assessed.
Task 1.1: Traceability and quality of upper-air radiosonde and lidar measurements
:::: Support the development of end-to-end guidelines and standardised protocols for upper-air radiosonde and lidar measurements and their processing, ensuring traceability to SI or community standard
:::: Analyse the impact of calibration methodologies on data accuracy and consistency
:::: Provide a quality assurance framework for those measurements
:::: Short term scientfic missions will be organised in the first year, aimed at
- implementation of a common Water Vapour Raman lidar data processing platform
- sharing of operational procedures for executing GRUAN radio soundings and lidar observations in various locations
- Uncertainty analysis for the lower part of the sounding range.
Task 1.2: Upper-air measurement uncertainty quantification and communication Main Activities:
:::: Improve methods for estimating uncertainty in GRUAN data products, with specific reference to the identification of all known sources of uncertainties and classification of their nature at different time scales.
:::: Provide tools and guidance on uncertainty reporting practices for transparent communication of uncertainties, ensuring that the data are easily interpretable and usable by end-users and enhancing the reliability and credibility of climate studies and assessments.
Task 1.3: Radiosonde Network Optimization and Best Practices Dissemination
Task 1.3: Radiosonde Network Optimization and Best Practices Dissemination:
:::: Provide a scientific sound justification for the temporal and spatial sampling requested to GRUAN.
:::: Ensure the best practices from GRUAN sites are properly shared and adopted with a special attention paid to the remote sites and sites in regions with contingent issues in the instrument maintenance.
:::: Promote the dissemination of best practices for improving data quality in other global measurement networks and global initiatives.
D1: Report on the end-to-end guidelines and standardised protocols for upper-air radiosonde and lidar measurements
D2: Recommendation for the quality assurance framework to adopt for upper-air radiosonde and lidar measurements
D3: Report on the improved methodologies for uncertainty quantification in GRUAN data products
D4: Guidance on uncertainty reporting practices for transparent communication of uncertainties
D5: Tools on uncertainty reporting practices for transparent communication of uncertainties
WG1 Leader: Arnoud Apituley – arnoud.apituley@knmi.nl
WG1 Vice Chair: Ruud Dirksen – ruud.dirksen@dwd.de
WG2
Metrology for near-surface climate reference sites
WG2 focuses on advancing metrology for near-surface climate reference sites. Our mission is to strengthen standardisation, traceability to SI units, and uncertainty evaluation in near-surface climate measurements. The WG2 brings together researchers, meteorological services, and institutions to assess and improve existing guidelines and protocols for reference observations. It also develops practical approaches for reducing measurement uncertainty.
WG2 activities will focus on review and improve existing guidelines and standardised protocols for near-surface climate measurements. Particular attention will be given to practices currently used at climate reference stations. The group will assess these prescriptions in the context of GSRN and WMO measurement quality requirements. Existing knowledge from operational services, research networks, and the scientific literature will be brought together in this assessment. Participants will discuss how effective current approaches are for evaluating uncertainty in essential climate variables measurements. They will also examine how feasible these approaches are in practical station operation. This work will support a clearer and more consistent basis for uncertainty evaluation at climatological reference stations. An additional activity will be the initiation of a users’ forum linking research and services. The forum will support discussion on the adoption of standardised measurement best practices and metrological principles.
- D6: Report on the assessment and practical adoption of existing guidelines and standardized protocols for climate reference stations performing near-surface measurements
- D7: Report on methods and procedures for the reduction of uncertainty in measurements from climate reference stations
- D8: Web tools for the inclusion of uncertainty in data products from climatological reference stations
• WG2 Leader: Branislava Lalic – branislava.lalic@polj.edu.rs
• WG Vice Chair: Andrea Merlone –a.merlone@inrim.it
• Task 2.1 Lead: Mareile Astrid Wolff & Mesut Demircan – mareile.astrid.wolff@nmbu.no & demircanm@gmail.com
• Task 2.2 Lead: Athanassios Argiriou & Graziano Coppa – apascha@fmenr.duth.gr & g. coppa@inrim.it
• Task 2.3 Lead: Sibylle von Löwis & Claire Gallacher – sibylle@vedur.is & claire.gallacher@mailbox.tu-dresden.de
WG4
Dissemination and Knowledge Transfer
WG4 aims to coordinate the dissemination activities and promote the knowledge transfer among the COST action participants and outside, with a particular attention to the intersectoral target audience. The open access tools will be also encouraged. Another challenge is to foster the exchange of knowledge and the improvement of the expertise, by contributing to the professional development of early-career researchers and climate scientists and to valorise the interdisciplinary research.
The activities of WG3 are planned in line with the objectives defined in Task 3.1, Task 3.2, and Task 3.3:
Task 3.1.: Towards a better quality of GNSS-PWV:
WG3 will start with benchmarking the GNSS sites/GNSS processing types to determine high-quality GNSS-PWV values. We are going to conduct a benchmark study with following drafted methodology for Task 3.1. (towards a better quality of GNSS-PWV).
- Select GNSS sites (IGS or GRUAN, etc.) with various collocated GNSS and RS.
- Decide GNSS processing software packages (GAMIT, Bernese, etc.).
- Apply various processing options and compare processing results with different parametrization in processing (tropospheric model, cutoff angle, etc.) and different software packages.
- Assess results with reference products (GRUAN).
Task 3.2.: GNSS uncertainty quantification and communication
- Uncertainty quantification by considering instrumental errors and atmospheric variability.
- Development of standardized methodologies for uncertainty evaluations for weather and climate applications separately.
- Prepare consistent guidelines for GNSS-PWV uncertainty to different user communities.
Task 3.3.: GNSS Best Practices
- Collection and analysis of best practices from existing GNSS-PWV sites.
- Ensure the adaptation of best practices across global GNSS networks.
D9: Report on current types of processing of GNSS observations and its impact on current GNSS-PWV values. (Year 1)
D10: Guidance on processing GNSS observations for achieving the best quality of GNSS- PWV for weather and climate applications.(Year 2)
D11: Report on the improved methodologies tor uncertainty quantification in GNSS-PWV. (Year 2)
D12: Guidance on uncertainty reporting practices tor transparent communication of GNSS- PWV (Year 3)
D13: at least 5 scientific papers on calibration and sampling requirements, benchmarking on the three main subjects of the GOST Action: GRUAN, GSRN, GNSS (Year 4)
WG3 Leader: Emine Tanır Kayıkçı – etanir@ktu.edu.tr
WG3 Vice Chair: Anna Klos – anna.klos@wat.edu.pl
WG3 Vice Chair: Karin Kollo – karinkollo@gmail.com
WG3
Metrology for GNSS water vapour measurements and retrievals
Working Group 3 (WG3) is refining the way we estimate GNSS-precipitable water vapor (GNSS-PWV) to better serve the scientific community, bridging the gap between technical data processing and the practical needs of weather and climate analysts. The team is benchmarking different GNSS processing methods to deliver high-quality values that meet end-users’ stringent uncertainty requirements. This involves distinguishing between errors inherent to GNSS technology and those caused by natural water vapor variations.
Beyond the technical calculations, WG3 connects collaborators within the field. It establishes effective processing strategies and communicates the capabilities and limitations of these observations, ensuring users understand the data. This culminates in comprehensive guidance on obtaining high-quality measurements and an active forum for dialogue between providers and users.
Main activities will be carried out according to the MoU and the Science Communication Plan, approved in March 2026 (link to the SC Plan)
Task 4.1: Dissemination activities
The activities will be focused to promote CRIM COST Action results and updates to the general public, the scientific communities and potential interested stakeholders. To foster the dialogue between the different communities and promote the guidelines and the best practice, workshop and meetings will be organized. They will be organised in continuity to the Management Committee meeting, in order to save time and resources. CRIM LinkedIn social page will be constantly updated.
Task 4.2: Knowledge transfer
Short-term mobility among the consortium institution will be promoted and the outputs and the experiences by each applicant will be valorised among the CRIM network as well as on the communication channels. Structured training programs and workshops, with sessions devoted to project results and tools will be organized as well as three Summer Schools addressed to young researchers to introduce them both to the reference climate data uses and to the handling data and tools. A user forum will be set up to facilitate the exchange of information among participants, collect the requirements from the users and share common strategies and approaches.
Next event:
1st Stakeholder Workshop, Rome, CNR, 18 and 19 May 2026 [link to the event page]
- D13: at least 5 scientific papers on calibration and sampling requirements, benchmarking on the three main subjects of the COST Action: GRUAN, GSRN, GNSS
- D14: creation of a forum for dialogue between academic, research, users, industrial institutions and service providers
- D15: Training material of summer schools publicly available
- D16: Report on the exchange visits
- D17: Recommendation from the User’s Forum
- WG4 Leader: Monica Proto – monica.proto@cnr.it
- WG4 Vice Chair: Peter Pavlasek – pavlasek@smu.gov.sk
CRIM: Expected results
The CRIM action is expected to deliver significant scientific, technological and social results, improving confidence in climate trend detection and severe event prediction. From a scientific perspective, it will establish a standardised framework for quantifying uncertainties in climate measurements, thereby enhancing the accuracy of weather models, atmospheric reanalysis and long-term trend evaluations. This framework is designed to be adaptable across diverse sectors, including agriculture, energy, and transport. The project will develop new tools for quantifying uncertainty and establish reference-grade measurement protocols that will set global standards for data quality. These advancements will facilitate the development of specific climate resilience applications. The expected results include increased effectiveness of early warning systems for extreme events such as floods and droughts, thanks to improved forecasting accuracy. By providing robust, traceable and high-quality climate data, CRIM will enable policymakers to make informed decisions on mitigation and adaptation, thereby aiming to reduce political controversy and foster public trust in climate science. Ultimately, the project aims to establish a cohesive European global climate reference network to ensure integrated monitoring and data sharing across the continent.
ACTION DETAILS
• MoU – 064/25
• CSO Approval date – 19/05/2025
• START DATE – 19/09/2025
• END DATE – 18/09/2029
Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or name of the granting autority. Neither the European Union nor the granting authority can be held responsible for them.
