JRA-55: Japanese 55-year Reanalysis, Monthly Means and Variances

The Japan Meteorological Agency (JMA) conducted JRA-55, the second Japanese global atmospheric reanalysis project. It covers 55 years, extending back to 1958, coinciding with the establishment of the global radiosonde observing system. Compared to its predecessor, JRA-25, JRA-55 is based on a new data assimilation and prediction system (DA) that improves many deficiencies found in the first Japanese reanalysis. These improvements have come about by implementing higher spatial resolution (TL319L60), a new radiation scheme, four-dimensional variational data assimilation (4D-Var) with Variational Bias Correction (VarBC) for satellite radiances, and introduction of greenhouse gases with time varying concentrations. The entire JRA-55 production was completed in 2013, and thereafter will be continued on a real time basis.Specific early results of quality assessment of JRA-55 indicate that a large temperature bias in the lower stratosphere has been significantly reduced compared to JRA-25 through a combination of the new radiation scheme and application of VarBC (which also reduces unrealistic temperature variations). In addition, a dry land surface anomaly in the Amazon basin has been mitigated, and overall forecast scores are much improved over JRA-25.Most of the observational data employed in JRA-55 are those used in JRA-25. Additionally, newly reprocessed METEOSAT and GMS data were supplied by EUMETSAT and MSC/JMA respectively. Snow depth data over the United States, Russia and Mongolia were supplied by UCAR, RIHMI and IMH respectively.The Data Support Section (DSS) at NCAR has processed the 1.25 degree version of JRA-55 with the RDA (Research Data Archive) archiving and metadata system. The model resolution data has also been acquired, archived and processed as well, including transformation of the TL319L60 grid to a regular latitude-longitude Gaussian grid (320 latitudes by 640 longitudes, nominally 0.5625 degree). All RDA JRA-55 data is available for internet download, including complete subsetting and data format conversion services.

日本气象厅（Japan Meteorological Agency, JMA）牵头实施了JRA-55项目，这是日本第二项全球大气再分析项目。该项目的时间跨度达55年，回溯至1958年，恰逢全球无线电探空观测系统建立之时。相较于其初代项目JRA-25，JRA-55采用了全新的数据同化与预报系统（DA），弥补了日本首套再分析产品存在的多项不足。此类改进通过多项技术升级得以实现：更高的空间分辨率（TL319L60）、全新的辐射方案、针对卫星辐射率处理的四维变分数据同化（four-dimensional variational data assimilation, 4D-Var）技术（搭载变分偏差校正（Variational Bias Correction, VarBC）），以及引入浓度随时间变化的温室气体。JRA-55的全部生产工作于2013年完成，此后将持续开展实时业务化更新。JRA-55的多项早期质量评估结果显示，通过结合全新辐射方案与VarBC技术的应用，平流层低层的显著温度偏差相较JRA-25已得到大幅改善——该技术同时还可抑制不合理的温度波动。此外，亚马逊流域的陆面干异常现象已得到缓解，整体预报评分相较JRA-25也有显著提升。JRA-55所使用的大部分观测数据与JRA-25一致。此外，欧洲气象卫星应用组织（EUMETSAT）与日本气象厅卫星中心（MSC/JMA）分别提供了经过重新处理的METEOSAT与GMS数据。美国、俄罗斯与蒙古国的雪深数据则分别由美国大学大气研究联合会（UCAR）、俄罗斯水文气象研究所（RIHMI）与蒙古气象水文研究所（IMH）提供。美国国家大气研究中心（NCAR）的数据支持部门（DSS）已将1.25°分辨率版本的JRA-55数据交由研究数据档案库（RDA, Research Data Archive）进行归档与元数据管理。该中心同时还完成了模型分辨率数据的获取、归档与处理工作，包括将TL319L60网格转换为规则经纬高斯基网格（共320个纬度格点×640个经度格点，名义分辨率为0.5625°）。所有研究数据档案库中的JRA-55数据均可通过互联网下载，并提供完整的数据子集提取与格式转换服务。

搜集汇总

背景与挑战

背景概述

JRA-55是日本气象厅（JMA）发布的全球大气再分析数据集，覆盖1958年至2024年共55年，提供月均值和方差数据。该数据集相比前代JRA-25有显著改进，包括更高空间分辨率（TL319L60）、四维变分数据同化（4D-Var）和变分偏差校正等技术，涵盖气温、降水、湿度等多种气象变量，空间覆盖全球并支持多种分辨率（如1.25度、2.5度），数据格式为WMO GRIB1，适用于气候研究和预测。