who we are, what we do
The Reanalysis Working Group (RWG) is a self-organised initiative supported by WEMC, bringing together wind, power grid, and marine engineers and scientists. It facilitates collaboration between reanalysis centres and end-users to maximise the value of reanalysis data for the energy sector.
The RWG has four main goals:
- Collection of user input and feedback
- Reanalysis validation using sector-specific in-situ measurements, and incorporation of electric sector meteorological data into reanalysis products.
- Fair and proper use of reanalysis for Wind Energy and Power System Modelling
- Advocacy for reanalysis
The RWG is a spin-off from the International Energy Agency Wind Technology Collaboration Program (IEA Wind TCP) Topical Expert Meeting 111, held in April 2024.
The RWG is a mixed group of engineers and scientists, check our profiles below.
“The wind energy practitioners have shown great interest in co-developing the next-generation global reanalysis ERA6 from the European Union Copernicus Climate Change Service (C3S). Being a user driven programme we were delighted by such an interest and openly engaged with them. As a consequence of this interaction, specific new products will be added, such as height-level data. The wind energy community has also provided us with key feedback on the test products we made publicly available for that purpose. We look forward to continued fruitful exchanges and welcome their support, as we are now in the last preparation stages for launching ERA6 production. Carlo Buontempo, Director of C3S.
Maximising reanalysis data value for energy sector use
The RWG is involved in the following projects:
Collection of user inputs: The RWG facilitates the collection of user inputs and feedback by reanalysis groups. This includes:
- Keeping a list of up-to-date reanalysis in the making, including “hearing periods”, user input surveys and contact details. This list is regularly shared with end-users in the “Resources” section.
- Support during collection of user input, via online meetings/workshops and polls.
- Follow-ups and facilitation of user input intake.
Validation: The RWG facilitates the validation of reanalysis datasets using high quality, publicly available in-situ measurements. This includes:
- Keeping a list of measurement datasets available for such validations, see the “Resources” section.
- Support during validation exercises, via online meetings/workshops and polls.
- Follow-ups and facilitation of user input intake.
Fair and proper use: The expert group issues a guideline providing minimum requirements for critical applications which require certification, or with large scale implications for infrastructure planning, regarding documentation, traceability, validation, data processing and usage.
Advocacy: The RWG participates to high-level user consultations regarding reanalysis applications, conferences, public event where advocacy work is required
Reanalysis Working Group
- RWG’s charter
- RWG’s roadmap (will be released in Q1-25)
Existing Reanalysis datasets
The go-to website for accessing exhaustive information on reanalyses and their applications is reanalyses.org.
upcoming reanalysis datasets
The RWG is actively monitoring the development of reanalysis datasets and is currently facilitating user input collection for the following reanalyses:
The ECMWF have released test batches (2 x 3 months) of ERA6 experiments, freely available under DOI for testing purposes. Feedback should be provided to the ECMWF on a private forum. Fore more information about how the RWG is involved in this testing initiative, please contact Rémi Gandoin rga@c2wind.com.
CATALOG of high quality in-situ measurements for validation
Publicly available measurement datasets from the Wind Energy Assessment Group: a list of high quality, publicly available measurement datasets is provided on the WRAG’s wiki page under “Datasets“.
upcoming conferences
RWG members will contribute to the below conferences and workshops.
past conferences
RWG members participated to the below conferences and workshops.
The RWG led a session focused on Reanalysis datasets at the 8th International Conference on Energy & Meteorology (ICEM 2025) organised by WEMC. Slides below:
- Introduction and keynote by Justin Sharp
- Presentation from Laurent Dubus (RTE, France)
- Presentation from Matti Koivisto (DTU, Denmark)
Rémi Gandoin and Jacob Tornfeldt Sørensen attended the 6th WCRP International Conference on Reanalysis (ICR6) and presented the outcome the IEA Wind TEM#111 Reanalyses for Wind Energy, see the slides.
Rémi Gandoin attended NOAA’s Subseasonal and Seasonal Applications Workshop in September 2024 and presented the outcome the IEA Wind TEM#111 Reanalyses for Wind Energy, see the slides here.
Justin Sharp and Julia Gottschall presented the outcome of the TEM#111 was presented and discussed at the NAWEA WindTech 2024 side event: IEA Wind Task 51 Workshop on Extremes in the Power Systems.
The IEA Wind Topical Expert Meeting #111 “Reanalyses for Wind Energy” was held in Denmark in April 2024. Proceedings are available on the IEA Wind Task 11 website.
Get in touch!
Write to us, our contact person is:
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Frequently Asked Questions
Below is a log of the FAQ sent to the RWG. If you have better answers, please let us know and we’ll update the page.
Do you know any studies analyzing the consistency of reanalysis bias over time? I imagine the accuracy of products like ERA5 will get better as more high quality measurements are included in the assimilation. So perhaps data from the last 5 years is more accurate than 10-15 years ago?
Yes, we do. A good place to start is the ERA5: uncertainty estimation wiki page, the CoreClimax project and the UERRA project documentation, see uerra.eu. See below selected publications:
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- “Uncertainties in Regional Reanalyses – Final Report from the Met Office” (2017)
- “Impact of satellite data on reanalysis uncertainty” (ICR5 20217)
- “Observation Feedback Information of the ECMWF Coupled Climate Reanalysis” (ICR5, 2017)
- “Why should we bother about exchanging reanalysis observation feedback and blacklists?” (ECMWF, 2014)
These reports show the effect of the change in data assimilation on the ensemble spread and on the difference with in-situ measurements for the analysis runs. From a practical user perspective, it is best to perform an analysis for every site, and 1) look at the ensemble spread time series (available for ex in ERA5), and 2) carry out a change point analysis including several reanalyses. See below an example using the criteria discussed in (Buishand, 1991), where clearly the JRA-3Q differs much more from measurements (a long-term time series from SHMI) compared with ERA5 and MERRA-2 for this location. This type of “gross” change points can be detected. The remaining small difference between ERA5 and MERRA-2 are much harder to trace, but the question has been raised again to reanalysis centers and we will keep all posted if/when new data/method are available.
Of course, there are studies looking at comparing reanalyses with measurements at the global scale, see below, but again only gross differences can be derived from such analyses, not the type of percent-wise changes typically worrisome for Wind Energy applications (for example).
Also, have a look at technical publications from consultancies:
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- “Tackling the uncertainty of the reanalysis surface winds for a climate variability assessment, demystifying the Y2k-bug” (Ocean Winds, 2024)
- “Bias and uncertainty in reanalysis and climate projections for wind conditions” (Climate Scale, 2024)
- “A review of MERRA-2 data in Scandinavia” (2017)
- “A review of the performance of MERRA-2: the next era of global long-term reference data” (DNV, 2017) — WindEurope Technology Workshop 2017 – not publicly available
- “A study of MERRA as a source of long-term reference wind data in the United Kingdom and Ireland” (DNV, 2015) — not publicly available, concluding MERRA consistency from 1996 onwards
On the idea of obtaining information on “which measurements are assimilated, and when”, see:
Lastly, the following papers may be relevant when analysis changes in assimilated observations systems which may have an impact on reanalysis products:
Reanalysis Appreciation Week 2025 (RAW25)
Nov 3rd – 7th
Join us online for an entire week celebrating reanalyses!
- Follow the RAW25 LinkedIn account.
- Share your experience, questions and reflections about Reanalyses using the hashtag #ReanalysisMatters.
- Check the list of in-person and online events in the table below.
- Set up your own in-person or online event!
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Mon 3/11 |
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Tue 4/11 |
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Wed 5/11 |
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Thu 6/11 |
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Fri 7/11 |
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