ERA5 Reanalysis

Please note: Please use ds633.0 to access RDA maintained ERA-5 data, see ERA5 Reanalysis (0.25 Degree Latitude-Longitude Grid) [https://rda.ucar.edu/datasets/ds633.0], RDA dataset ds633.0. This dataset is no longer being updated, and web access has been removed.After many years of research and technical preparation, the production of a new ECMWF climate reanalysis to replace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, though the first segment of data to be released will span the period 2010-2016.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 (18 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.NCAR's Data Support Section (DSS) is performing and supplying a grid transformed version of ERA5, in which variables originally represented as spectral coefficients or archived on a reduced Gaussian grid are transformed to a regular 1280 longitude by 640 latitude N320 Gaussian grid. In addition, DSS is also computing horizontal winds (u-component, v-component) from spectral vorticity and divergence where these are available. Finally, the data is reprocessed into single parameter time series.Please note: As of November 2017, DSS is also producing a CF 1.6 compliant netCDF-4/HDF5 version of ERA5 for CISL RDA at NCAR. The netCDF-4/HDF5 version is the de facto RDA ERA5 online data format. The GRIB1 data format is only available via NCAR's High Performance Storage System (HPSS). We encourage users to evaluate the netCDF-4/HDF5 version for their work, and to use the currently existing GRIB1 files as a reference and basis of comparison. To ease this transition, there is a one-to-one correspondence between the netCDF-4/HDF5 and GRIB1 files, with as much GRIB1 metadata as possible incorporated into the attributes of the netCDF-4/HDF5 counterpart.

请注意：请使用ds633.0访问研究数据档案（Research Data Archive, RDA）维护的ERA5数据，详见ERA5再分析数据（0.25度经纬网格）[https://rda.ucar.edu/datasets/ds633.0]，即RDA数据集ds633.0。该数据集已停止更新，且网页访问通道已关闭。
历经多年研究与技术筹备，用于替代ERA-Interim的全新欧洲中期天气预报中心（European Centre for Medium-Range Weather Forecasts, ECMWF）气候再分析产品的制作工作已启动。ERA5是ECMWF第五代全球大气气候再分析数据集，其溯源可至20世纪80年代产出的全球大气研究计划第一次全球试验（First GARP Global Experiment, 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，但首批发布的数据时段为2010-2016年。
ERA5的生产依托ECMWF集成预报系统（Integrated Forecast System, IFS）CY41r2版本中的高分辨率预报（High-Resolution Forecast, HRES，空间分辨率为31公里，约为业务模式的1/4），以及分辨率为62公里的10成员四维变分（4-dimensional Variational, 4D-Var）集合数据同化（Ensemble Data Assimilation, EDA）方案。该模式垂直方向共设137层混合西格玛-气压模式层级，顶层气压达0.01百帕（hPa）。
各垂直层级的大气数据会被插值至37个气压层（与ERA-Interim采用的层级一致）。此外还提供地表或单层数据，包含降水、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模式耦合了陆面模式与海浪模式，其中陆面模式的参数也被归类为地表参数。
通常而言，该数据以每小时为频次发布，包含分析场与短期（18小时）预报场两类数据，每日从协调世界时（Coordinated Universal Time, UTC）06时与18时的分析场启动两次预报。多数分析场参数也可从预报场中获取，但部分预报参数（如平均速率与累积量）无法从分析场获得。
相较于ERA-Interim，ERA5的改进之处包括：采用HadISST.2海表温度数据集、重新处理的ECMWF气候数据记录（Climate Data Record, CDR），以及搭载RTTOV11辐射传输模块。变分偏差校正不仅应用于卫星辐射观测，还覆盖臭氧反演、飞机观测、地表气压与无线电探空廓线数据。
美国国家大气研究中心（National Center for Atmospheric Research, NCAR）的数据支持部门（Data Support Section, DSS）正在制作并提供ERA5的网格转换版本：将原本以谱系数形式表示或存储于缩减高斯网格的变量，转换为规则的1280经度×640纬度的N320高斯网格。此外，DSS还会在谱涡度与散度数据可用时，通过其计算水平风场的纬向分量（u-component）与经向分量（v-component）。最终，数据会被重新处理为单参数时间序列。
请注意：自2017年11月起，DSS还为NCAR的计算与信息系统实验室（Computational and Information Systems Laboratory, CISL）RDA平台制作了符合CF 1.6标准的netCDF-4/HDF5格式ERA5数据。netCDF-4/HDF5格式已成为RDA平台上ERA5的事实上的在线数据格式。GRIB1格式数据仅可通过NCAR的高性能存储系统（High Performance Storage System, HPSS）获取。我们建议用户在研究工作中优先使用netCDF-4/HDF5格式数据，并以现有的GRIB1文件作为参考与对比基准。为简化格式转换过渡，netCDF-4/HDF5与GRIB1文件之间存在一一对应关系，且尽可能将GRIB1的元数据整合至netCDF-4/HDF5格式文件的属性中。

搜集汇总

背景与挑战

背景概述

ERA5 Reanalysis是ECMWF提供的高分辨率全球气候再分析数据集，覆盖2002年至2019年，包含多种气象变量，适用于气候研究和气象分析。数据集采用先进的同化技术和多种数据格式，适合科研和业务使用。