ERA5 Reanalysis (Monthly Mean 0.25 Degree Latitude-Longitude Grid)

For RDA ERA5 monthly mean data prior to 1979, please see ds633.5: ERA5 monthly mean back extension 1950-1978 (Preliminary version) [https://rda.ucar.edu/datasets/ds633.5/]After many years of research and technical preparation, the production of a new ECMWF climate reanalysis to replace ERA-Interim is in progress. ERA5 is the fifth generation of ECMWF atmospheric reanalyses of the global climate, which started with the FGGE reanalyses produced in the 1980s, followed by ERA-15, ERA-40 and most recently ERA-Interim. ERA5 will cover the period January 1950 to near real time.ERA5 is produced using high-resolution forecasts (HRES) at 31 kilometer resolution (one fourth the spatial resolution of the operational model) and a 62 kilometer resolution ten member 4D-Var ensemble of data assimilation (EDA) in CY41r2 of ECMWF's Integrated Forecast System (IFS) with 137 hybrid sigma-pressure (model) levels in the vertical, up to a top level of 0.01 hPa. Atmospheric data on these levels are interpolated to 37 pressure levels (the same levels as in ERA-Interim). Surface or single level data are also available, containing 2D parameters such as precipitation, 2 meter temperature, top of atmosphere radiation and vertical integrals over the entire atmosphere. The IFS is coupled to a soil model, the parameters of which are also designated as surface parameters, and an ocean wave model. Generally, the data is available at an hourly frequency and consists of analyses and short (12 hour) forecasts, initialized twice daily from analyses at 06 and 18 UTC. Most analyses parameters are also available from the forecasts. There are a number of forecast parameters, e.g. mean rates and accumulations, that are not available from the analyses.Improvements to ERA5, compared to ERA-Interim, include use of HadISST.2, reprocessed ECMWF climate data records (CDR), and implementation of RTTOV11 radiative transfer. Variational bias corrections have not only been applied to satellite radiances, but also ozone retrievals, aircraft observations, surface pressure, and radiosonde profiles.

如需获取1979年之前的RDA ERA5逐月平均数据，请查阅ds633.5：《ERA5逐月平均回溯扩展数据集1950-1978（预览版）》[https://rda.ucar.edu/datasets/ds633.5/]
经过多年研究与技术筹备，旨在替代ERA-Interim的新一代欧洲中期天气预报中心（ECMWF）气候再分析产品研发工作已正式启动。ERA5是ECMWF第五代全球大气气候再分析数据集，其发展历程可追溯至20世纪80年代推出的全球大气研究计划第一次全球试验（FGGE）再分析数据，后续依次推出了ERA-15、ERA-40以及最新的ERA-Interim。ERA5的覆盖时段为1950年1月至近实时。
ERA5的制作基于ECMWF集成预报系统（IFS）CY41r2版本中的两项核心方案：一是分辨率达31公里的高分辨率预报（HRES，其空间分辨率为业务模式的四分之一）；二是分辨率62公里、包含10个成员的四维变分（4D-Var）数据同化集合（EDA）。该系统垂直方向设有137个混合西格玛-气压（模式）层级，顶层气压可达0.01百帕。
上述垂直层级的大气数据会被插值至37个气压层级（与ERA-Interim所用层级一致）。此外还提供地表或单层级数据，涵盖降水、2米气温、大气顶辐射以及整层大气垂直积分等二维参数。
IFS还耦合了土壤模式与海浪模式，其中土壤模式的参数也被归类为地表参数。通常来说，该数据集以小时为时间分辨率，包含分析场与短期（12小时）预报场两类数据，每日从协调世界时（UTC）06时与18时的分析场启动两次预报。多数分析场参数可从预报场中获取，但部分预报参数（如平均速率与累积量）则无法从分析场中获得。
相较于ERA-Interim，ERA5的改进之处包括：采用HadISST.2数据集、重新处理的ECMWF气候数据记录（CDR），以及搭载RTTOV11辐射传输模型。变分偏差校正不仅应用于卫星辐射观测，还覆盖了臭氧反演、飞机观测、地表气压以及无线电探空廓线数据。