[6] Multi-scale & multi-component treatments 1

[6-3] February 28, 10:30-10:50

Development of a Coupled Atmosphere-Ocean Data Assimilation System in JMA/MRI and a Reanalysis Experiment

Y. Fujii, T. Ishibashi, T. Iriguchi, N. Saito, Y. Takaya, Y. Takeuchi (Meteorological Research Institute), T. Yausda (Japan Meteorological Agency)


JMA/MRI have developed a weakly-coupled Data Assimilation (DA) system, MRI-CDA1, based on JMA's operational systems. MRI-CDA1 is composed of the global atmosphere DA system for numerical weather predictions, NAPEX, the global ocean DA system for seasonal predictions, MOVE-G2, and the coupled atmosphere-ocean model for seasonal predictions, JMA/MRI-CGCM2. A reanalysis experiment is performed with MRI-CDA1 for the period from November 2013 to December 2015. Comparison of the result with Japanese 55-year Reanalysis (JRA-55) indicates that the overestimation of the sea surface latent heat flux found in JRA-55 are disappeared in the reanalysis of MRI-CDA1. MRI-CDA1 also effectively suppresses the excess rainfall in the tropics in JRA-55, particularly in the Intertropcal Convergence Zone (ITCZ) in the Pacific. Anomaly correlation coefficients of precipitation in MRI-CDA1 with observation-based datasets (CMAP and GPCP) have quite similar distributions with JRA-55, but decreases in a few areas. Although the sea surface temperature field is well reproduced by MRI-CDA1, the equatorial Pacific thermocline is shallower and the Pacific Equatorial Undercurrent is weaker than those in an uncoupled ocean reanalysis with MOVE-G2. These differences stem from difference of the bulk formula for estimating the wind stress fields.

  Presentation file: 06_3_Y.Fujii.pdf