ERA6 reanalysis
What is a reanalysis?
The next generation of ECMWF atmospheric reanalysis of the global climate is being prepared. Reanalysis integrates model data with observations worldwide to create a globally comprehensive and consistent dataset through the application of physical laws. This process, known as data assimilation, mirrors the methodology employed by numerical weather prediction centers. At regular intervals (e.g., every 12 hours at ECMWF), a previous forecast is merged with newly available observations using an optimal approach to generate a refined estimate of the atmospheric state, known as analysis. This analysis serves as the foundation for producing updated and enhanced forecasts.
A scheme of the reanalysis process. Credit: Copernicus Climate Change Service/ECMWF
Observations have historically been unevenly distributed and prone to errors. Even with advancements in satellite technology, relying solely on observations cannot offer a comprehensive and precise depiction of the Earth's system worldwide at any given moment. Reanalyses play a crucial role in bridging the gaps in the observational record. They provide consistent temporal coverage, thereby reducing the likelihood of spurious signals of change
ERA5 reanalysis
ERA5, the fifth-generation reanalysis from ECMWF, offers comprehensive climate and weather data spanning the past eight decades, with records available from 1940 onward. Introduced in 2018, ERA5 supersedes the ERA-Interim reanalysis.ERA5 provides hourly estimates for numerous atmospheric, ocean-wave, and land-surface variables. Updated daily with a latency of approximately five days, ERA5 ensures timely access to critical data. It's worth noting that an initial release, referred to as ERA5T, precedes the final version by 2 to 3 months. Any significant discrepancies identified in ERA5T may be rectified in subsequent releases.
To facilitate analysis, the data has been regridded to a regular latitudinal and longitudinal grid with a resolution of 0.25 degrees
Transition towards ERA6
The groundwork for ERA6, the successor to ERA5, is already in progress, aiming to leverage cutting-edge advancements in Earth system modeling. ERA6 will be a coupled reanalysis, incorporating both atmospheric and ocean observations. This integrated approach acknowledges the intricate interactions between the atmosphere and the ocean, offering the potential for a more comprehensive and harmonized reconstruction of the Earth's climate system.
ECMWF hosted an online workshop in October 2023, bringing together lead ERA scientists and key users of reanalysis products. The workshop aimed to represent the diverse ERA user community and foster a dialogue on the development plans for ERA6, along with user needs and priorities. Presentations highlighted the development plans and added value of ERA6, followed by discussions on concrete product developments and the necessity for scientific advancements to ensure alignment with user needs and expectations.
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