著者
Shinya KOBAYASHI Yukinari OTA Yayoi HARADA Ayataka EBITA Masami MORIYA Hirokatsu ONODA Kazutoshi ONOGI Hirotaka KAMAHORI Chiaki KOBAYASHI Hirokazu ENDO Kengo MIYAOKA Kiyotoshi TAKAHASHI
出版者
(公社)日本気象学会
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
vol.93, no.1, pp.5-48, 2015 (Released:2015-03-18)
参考文献数
128
被引用文献数
213 1458

The Japan Meteorological Agency (JMA) conducted the second Japanese global atmospheric reanalysis, called the Japanese 55-year Reanalysis or JRA-55. It covers the period from 1958, when regular radiosonde observations began on a global basis. JRA-55 is the first comprehensive reanalysis that has covered the last half-century since the European Centre for Medium-Range Weather Forecasts 45-year Reanalysis (ERA-40), and is the first one to apply four-dimensional variational analysis to this period. The main objectives of JRA-55 were to address issues found in previous reanalyses and to produce a comprehensive atmospheric dataset suitable for studying multidecadal variability and climate change. This paper describes the observations, data assimilation system, and forecast model used to produce JRA-55 as well as the basic characteristics of the JRA-55 product. 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. Our initial quality evaluation revealed problems such as a warm bias in the upper troposphere, large upward imbalance in the global mean net energy fluxes at the top of the atmosphere and at the surface, excessive precipitation over the tropics, and unrealistic trends in analyzed tropical cyclone strength. This paper also assesses the impacts of model biases and changes in the observing system, and mentions efforts to further investigate the representation of low-frequency variability and trends in JRA-55.
著者
Ayataka Ebita Shinya Kobayashi Yukinari Ota Masami Moriya Ryoji Kumabe Kazutoshi Onogi Yayoi Harada Soichiro Yasui Kengo Miyaoka Kiyotoshi Takahashi Hirotaka Kamahori Chiaki Kobayashi Hirokazu Endo Motomu Soma Yoshinori Oikawa Takahisa Ishimizu
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.7, pp.149-152, 2011 (Released:2011-10-06)
参考文献数
24
被引用文献数
289 302

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.