The Japanese 55-year Reanalysis "JRA-55": An Interim Report

TLDR

The Japan Meteorological Agency launched the Japanese 55‑year Reanalysis (JRA‑55), covering 1958‑2013 and addressing many shortcomings of the earlier JRA‑25. This paper introduces JRA‑55, a comprehensive, time‑consistent atmospheric dataset designed for climate change and multi‑decadal variability studies. JRA‑55 was produced from 2010 to early 2013 using a data‑assimilation and prediction system that improves upon JRA‑25 and will continue as a real‑time JCDAS. Early results demonstrate general improvements over JRA‑25.

Abstract

The Japan Meteorological Agency (JMA) started the second Japanese global atmospheric reanalysis project named the Japanese 55-year Reanalysis (JRA-55). It covers 55 years, extending back to 1958, when the global radiosonde observing system was established. Many of the deficiencies found in the first Japanese reanalysis, the Japanese 25-year Reanalysis (JRA-25), have been improved. It aims at providing a comprehensive atmospheric dataset that is suitable for studies of climate change or multi-decadal variability, by producing a more time-consistent dataset for a longer period than JRA-25.Production of JRA-55 started in 2010, and computations for more than 16 years have been completed as of August 2011. The entire JRA-55 production will be completed in early 2013 and thereafter JRA-55 will be continued as a new JCDAS on real time basis. This paper is a brief report to introduce the JRA-55 reanalysis project. The data assimilation and prediction (DA) system used in JRA-55 is introduced and compared to that used in JRA-25. Early results of JRA-55 are presented and discussed, showing general improvements.