ERA5 reanalysis

ERA5 reanalysis
Name	ERA5 reanalysis
Occupation	Reanalysis dataset

ERA5 reanalysis is a global atmospheric reanalysis dataset produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) as part of the Copernicus Programme. It provides hourly estimates of a wide range of atmospheric, land-surface and sea-state parameters spanning multiple decades, designed to support climate change research, meteorology operations and hydrology studies. ERA5 replaces earlier ECMWF products and is widely cited in assessments by organizations such as the Intergovernmental Panel on Climate Change (IPCC), the World Meteorological Organization (WMO), and national agencies like the United States National Oceanic and Atmospheric Administration (NOAA).

Overview

ERA5 offers a comprehensive, consistent retrospective estimate of the state of the atmosphere, land and oceans based on a fixed assimilation system developed at ECMWF and implemented under the Copernicus Climate Change Service. The dataset is produced using the ECMWF Integrated Forecasting System and archived by the European Space Agency (ESA) and ECMWF data servers, supporting work by institutions such as the Met Office, NASA, National Aeronautics and Space Administration, NOAA, and research centres including the Max Planck Institute for Meteorology and the Scripps Institution of Oceanography. ERA5 has been integrated into analyses by the IPCC, cited in reports alongside datasets like HadCRUT and NOAA GHCN records, and is used by operational services in regions served by organizations such as EUMETSAT and the African Centre of Meteorological Applications for Development.

Data and Variables

ERA5 provides hourly fields of three-dimensional atmospheric variables (temperature, wind, humidity), two-dimensional surface variables (skin temperature, soil moisture, snow depth), and ocean-wave parameters (significant wave height) produced at multiple model levels and pressure surfaces. Users can extract variables relevant to atmospheric chemistry studies undertaken at institutions like Institut Pierre-Simon Laplace, extreme-weather analyses used by European Commission services, or renewable energy assessments referenced by companies such as Ørsted and Vestas. The dataset includes derived diagnostics used in hydrological modelling by groups like International Centre for Water Resources and Global Change and cryosphere research by teams at the National Snow and Ice Data Center and Alfred Wegener Institute.

Methodology and Data Assimilation

ERA5 is generated by assimilating a vast array of observations into the ECMWF Integrated Forecasting System using four-dimensional variational data assimilation and ensemble-based methods. Observational inputs originate from satellite missions such as ERS-1, ERS-2, Envisat, MetOp, Sentinel-3, and Jason (satellite), from radiosonde networks coordinated by the World Meteorological Organization, and from surface networks including stations maintained by Météo-France and the Deutscher Wetterdienst. The assimilation strategy is informed by techniques developed in collaborations with academic groups at University of Reading, ETH Zurich, and University of Oxford and benefits from supercomputing facilities like the Centre for Environmental Data Analysis and national high-performance centres such as the Swiss National Supercomputing Centre.

Validation and Uncertainty

ERA5 validation involves comparison against independent observations, reanalyses such as NCEP/NCAR Reanalysis and JRA-55, and targeted field campaigns conducted by agencies like NOAA and research programmes including the Global Energy and Water Exchanges (GEWEX) project. Uncertainties arise from model formulation within the ECMWF system, observation errors, and representativeness issues highlighted in assessments by the IPCC and studies published by research groups at Columbia University and Princeton University. Ensemble-based products such as the ERA5 reanalysis ensemble provide probabilistic estimates that are used by risk analysts at institutions like Lloyd's of London and research teams investigating attribution of extreme events in affiliation with the World Weather Attribution network.

Applications and Impact

ERA5 underpins a wide range of applications: climate monitoring for public bodies like the European Environment Agency, extreme-event analysis for insurers and emergency services in collaboration with European Civil Protection and Humanitarian Aid Operations, renewable energy resource assessment for firms including Iberdrola and Siemens Gamesa, and agricultural modelling used by Food and Agriculture Organization (FAO) programmes. It supports climate services used by cities in networks such as C40 Cities and national adaptation planning referenced in United Nations Framework Convention on Climate Change submissions. ERA5-derived datasets have informed peer-reviewed studies in journals produced by societies like the American Meteorological Society and the Royal Meteorological Society.

Access and Tools

ERA5 data are distributed via ECMWF and the Copernicus Climate Data Store, accessible to researchers and practitioners through APIs, web portals and cloud platforms supported by providers like Amazon Web Services and Google Cloud Platform. Analysis tools and libraries for ERA5 include software developed by communities at European Space Agency labs, open-source packages maintained by contributors associated with University of Oxford and Technical University of Denmark, and visualization platforms used by operational services such as the Met Office web services. Training materials and user support are provided through workshops organised by ECMWF, the Copernicus Programme Office, and regional training centres including the WMO Regional Training Centre network.

Category:Reanalysis datasets