The JRA-55 Reanalysis: General Specifications and Basic Characteristics
The JRA-55 Reanalysis: General Specifications and Basic Characteristics
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DOI：
10.2151/jmsj.2015-001
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发表时间：
2015-01-01
影响因子：
3.1
通讯作者：
Takahashi, Kiyotoshi
中科院分区：
文献类型：
--
作者：
Kobayashi, Shinya;Ota, Yukinari;Takahashi, Kiyotoshi
日本气象厅（JMA）进行了第二次日本全球大气再分析，称为日本55年再分析或JRA-55。它涵盖了从1958年开始在全球范围内进行定期无线电探空仪观测的时期。JRA-55是自欧洲中期天气预报中心45年再分析（ERA-40）以来第一个覆盖过去半个世纪的综合再分析，也是第一个将四维变分分析应用于这一时期的再分析。JRA-55的主要目标是解决以前再分析中发现的问题，并制作适合于研究多年变率和气候变化的综合大气数据集。本文介绍了JRA-55的观测资料、同化系统和预报模式，以及JRA-55产品的基本特征。JRA-55是在日本25年再分析（JRA-25）之后经过大规模改进的日本气象厅业务同化系统TL 319版本（2009年12月）上制作的。它还使用了几个新的和改进的过去的观察。所得的再分析产品比JRA-25产品好得多。JRA-25的两个主要问题是平流层下部的冷偏差，这已经减少，亚马逊盆地的干燥偏差，这已经减轻。与以前的再分析产品相比，温度分析的时间一致性也得到了很大的改善。我们的初步质量评估发现的问题，如在对流层上部的温暖偏差，在大气层顶部和地面的全球平均净能量通量大向上的不平衡，热带地区的降水过多，分析热带气旋强度和不切实际的趋势。本文还评估了观测系统中模型偏差和变化的影响，并提到了进一步研究JRA-55中低频变化和趋势的代表性的努力。
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.