著者

Akira Yamazaki Takeshi Enomoto Takemasa Miyoshi Akira Kuwano-Yoshida Nobumasa Komori

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.13, pp.41-46, 2017 (Released:2017-03-25)

参考文献数

26

被引用文献数

7

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The observation operators in the local ensemble transform Kalman filter (LETKF) were improved to enable use of observations in the vicinity of the poles in the data assimilation system composed of the atmospheric general circulation model for the Earth Simulator (AFES) and the LETKF. The improved observation operators allow to assimilate the observations located south (north) of southernmost (northernmost) Gaussian grid latitudes. An algorithm for searching the nearest observations from an analyzed grid for error covariance localization was also modified to efficiently assimilate observations near the poles.The new algorithms were incorporated into the LETKF, and the impacts of routine radiosonde observations at the South Pole during the periods of July 2012 and January 2013 were assessed. The radiosonde observations suppressed an artificial expansion of the analysis ensemble spread which occasionally caused numerical instability in the upper troposphere and the lower stratosphere over the Antarctic regions. The analysis was also improved in the Antarctic regions.