Japanese 55-year Reanalysis (JRA-55)

The Japan Meteorological Agency (JMA) conducted the second Japanese global atmospheric reanalysis, called the Japanese 55-year Reanalysis or JRA-55, to produce a comprehensive atmospheric dataset suitable for studying multidecadal variability and climate change. The data cover the period from 1958, when regular radiosonde observations began on a global basis. JRA-55 is the first comprehensive reanalysis to apply four-dimensional variational analysis to the last half-century. JRA-55 has been produced with the TL319 version of JMA’s operational data assimilation system as of December 2009, which was extensively improved since the Japanese 25-year Reanalysis (JRA-25). It also uses several newly available and improved past observations. The resulting reanalysis products are considerably better than the JRA-25 product. Two major problems of JRA-25 were a cold bias in the lower stratosphere, which has been diminished, and a dry bias in the Amazon basin, which has been mitigated. The temporal consistency of temperature analysis has also been considerably improved compared to previous reanalysis products. JMA continues the production of JRA-55 dataset on a near-real-time basis with the data assimilation system used for this dataset. The dataset is provided in GRIB