The ERA5 Atmospheric Reanalysis.

This presentation provides an overview and status on the forthcoming ECMWF atmospheric reanalysis ERA5.After many years of research and a great deal of technical preparation, the production of this climate reanalysis to replace ERA-Interim was started in 2016. ERA5 is the fifth generation of ECMWF atmospheric reanalyses of the global climate, which was pioneered with the FGGE reanalyses produced in the 1980s, followed by ERA-15, ERA-40 and most recently ERA-Interim. Reanalyses provide a numerical description of the recent climate by combining models with observations and are invaluable to numerous users around the world. Reanalysis is now a key ECMWF contribution to the implementation of the EU-funded Copernicus Climate Change Service (C3S). Once complete (end 2017 - begin 2018), the new ERA5 reanalysis will span the modern observing period from 1979 onward, with daily updates continuing forward in time. ERA5 will eventually replace ERA-Interim, which is increasingly difficult to maintain. ERA5 data will be at a much higher resolution than ERA-Interim: hourly analysis fields will be available at a horizontal resolution of 31 km on 139 levels, from the surface up to 0.01 hPa (around 80 km). ERA5 data products will also include information about uncertainties, which will be provided at 3-hourly intervals and at a horizontal resolution of 62 km. In addtion, a dedicated ERA5 land component will deliver a land-surface reanalysis product at an enhanced resolution. A number of new parameters, such as 100-metre windspeed and direction, will be available as part of the output. A database containing all ingested observations, together with detailed information about how they are used, will be available and accessible to users. Altogether, the entire ERA5 production will generate over 5 petabytes of data.