Articles | Volume 10, issue 6
Geosci. Model Dev., 10, 2201–2219, 2017
https://doi.org/10.5194/gmd-10-2201-2017
Geosci. Model Dev., 10, 2201–2219, 2017
https://doi.org/10.5194/gmd-10-2201-2017

Development and technical paper 15 Jun 2017

Development and technical paper | 15 Jun 2017

A 4D-Var inversion system based on the icosahedral grid model (NICAM-TM 4D-Var v1.0) – Part 2: Optimization scheme and identical twin experiment of atmospheric CO2 inversion

Yosuke Niwa et al.

Model code and software

NICAM-TM 4D-Var 1. H. Tomita and M. Satoh; 2. M. Sato, T. Matsuno, H. Tomita, H. Miura, T. Nasuno and S. Iga; 3. M. Satoh, H. Tomita, H. Yashiro, H. Miura, C. Kodama, T. Seiki, A. T. Noda, Y. Yamada, D. Goto, M. Sawada, T. Miyoshi, Y. Niwa, M. Hara, T. Ohno, S. Iga, T. Arakawa, T. Inoue, and H. Kubokawa http://nicam.jp/hiki/?Research+Collaborations

POpULar Y.~Fujii http://www.mri-jma.go.jp/Member/oc/kefujiiyosukefu_en.html

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Short summary
A new 4D-Var inversion system based on the icosahedral grid model, NICAM, is introduced and tested. Adding to the offline forward and adjoint models, this study has introduced the optimization method of POpULar; it does not require difficult decomposition of a matrix that establishes the correlation among the prior flux errors. In identical twin experiments of atmospheric CO2 inversion, the system successfully reproduces the spatiotemporal variations of the surface fluxes.