JMSJ Highlights

Editor's Highlight : Kosaka et al. (2024)

Kosaka Y., S. Kobayashi, Y. Harada, C. Kobayashi, H. Naoe, K. Yoshimoto, M. Harada, N. Goto, J. Chiba, K. Miyaoka, R. Sekiguchi, M. Deushi, H. Kamahori, T. Nakaegawa; T. Y.Tanaka, T. Tokuhiro, Y. Sato, Y. Matsushita, K. Onogi, 2024: The JRA-3Q Reanalysis. J. Meteor. Soc. Japan, 102.
https://doi.org/10.2151/jmsj.2024-004.
Graphical Abstract

Editor in charge: Dr. Ryo Mizuta

I highlight this paper which describes a new global atmospheric reanalysis JRA-3Q developed by Japan Meteorological Agency, focusing on the improvements from the previous reanalysis.
• The large upward imbalance in the global mean net energy flux at the top of the atmosphere and at the surface, one of the major problems of JRA-55, has been significantly reduced.
• The artificial decrease in the detection of tropical cyclones seen in JRA-55 has been resolved by the use of a tropical cyclone bogus generation method based on the JMA operational system.
• For the pre-1957 period, which is first included in Japanese reanalyses, major typhoons, such as Typhoon Kathleen and Typhoon Marie, are clearly represented in the mean sea level pressure field of JRA-3Q, and the pressure fields are generally consistent with the original weather map analyzed at that time.

Abstract
The Japan Meteorological Agency (JMA) has developed the third Japanese global atmospheric reanalysis, the Japanese Reanalysis for Three Quarters of a Century (JRA-3Q). The objective of JRA-3Q is to improve quality in terms of issues identified in the previous Japanese 55-year Reanalysis (JRA-55) and to extend the reanalysis period further into the past. JRA-3Q is based on the TL479 version of the JMA global Numerical Weather Prediction (NWP) system as of December 2018 and uses results of developments in the operational NWP system, boundary conditions, and forcing fields achieved at JMA since JRA-55. It covers the period from September 1947, when Typhoon Kathleen brought severe flood damage to Japan, and uses rescued historical observations to extend its analyses backwards in time about 10 years earlier than JRA-55. This paper describes the data assimilation system, forecast model, observations, boundary conditions, and forcing fields used to produce JRA-3Q as well as the basic characteristics of the JRA-3Q product. The initial quality evaluation revealed major improvements from JRA-55 in the global energy budget and representation of tropical cyclones (TCs). One of the major problems in JRA-55—global energy imbalance with excess upward net energy flux at the top of the atmosphere and at the surface—has been significantly reduced in JRA-3Q. Another problem—a trend of artificial weakening of TCs—has been resolved through the use of a method that generates TC bogus based on the JMA operational system. There remain several problems such that volcanic-induced stratospheric warming is smaller than expected. This paper discusses the causes of such problems and possible solutions in future reanalyses.