The Japan Meteorological Agency (JMA) conducted the second Japanese global atmospheric reanalysis, known as the Japanese 55-year Reanalysis (JRA-55), covering the period from 1958 when regular radiosonde observations began globally. JRA-55 is the first comprehensive reanalysis to cover the last half-century since the European Centre for Medium-Range Weather Forecasts 45-year Reanalysis (ERA-40) and the first to apply four-dimensional variational analysis (4D-Var) to this period. The main objectives were to address issues found in previous reanalyses and to produce a comprehensive atmospheric dataset suitable for studying multidecadal variability and climate change.
JRA-55 was produced using the TL319 version of JMA's operational data assimilation system, which was extensively improved since the Japanese 25-year Reanalysis (JRA-25). It also utilized several newly available and improved past observations. The resulting reanalysis products are significantly better than those of JRA-25, with improvements in the cold bias in the lower stratosphere and the dry bias in the Amazon basin. The temporal consistency of temperature analysis has also been improved compared to previous reanalysis products.
The paper outlines the general specifications and basic characteristics of JRA-55, including data sources, quality control (QC), and data selection for observations. It describes the data assimilation system and the forecast model used, and provides details on the computational environment and production streams. The paper also examines the basic performance of the data assimilation system and assesses the impacts of model biases and changes in the observing system. Finally, it reviews the basic characteristics of the products and presents conclusions.The Japan Meteorological Agency (JMA) conducted the second Japanese global atmospheric reanalysis, known as the Japanese 55-year Reanalysis (JRA-55), covering the period from 1958 when regular radiosonde observations began globally. JRA-55 is the first comprehensive reanalysis to cover the last half-century since the European Centre for Medium-Range Weather Forecasts 45-year Reanalysis (ERA-40) and the first to apply four-dimensional variational analysis (4D-Var) to this period. The main objectives were to address issues found in previous reanalyses and to produce a comprehensive atmospheric dataset suitable for studying multidecadal variability and climate change.
JRA-55 was produced using the TL319 version of JMA's operational data assimilation system, which was extensively improved since the Japanese 25-year Reanalysis (JRA-25). It also utilized several newly available and improved past observations. The resulting reanalysis products are significantly better than those of JRA-25, with improvements in the cold bias in the lower stratosphere and the dry bias in the Amazon basin. The temporal consistency of temperature analysis has also been improved compared to previous reanalysis products.
The paper outlines the general specifications and basic characteristics of JRA-55, including data sources, quality control (QC), and data selection for observations. It describes the data assimilation system and the forecast model used, and provides details on the computational environment and production streams. The paper also examines the basic performance of the data assimilation system and assesses the impacts of model biases and changes in the observing system. Finally, it reviews the basic characteristics of the products and presents conclusions.