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Masutomi, Y., T. Iizumi, K. Oyoshi, N. Kayaba, W. Kim, T. Takimoto and Y. Masaki, 2023: Systematic global evaluation of seasonal climate forecast skill for monthly precipitation of JMA/MRI-CPS2 comparedwith a statistical forecast system using climate indices. J. Meteor. Soc. Japan, 101.
https://doi.org/10.2151/jmsj.2023-014
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Plain Language Summary: This study aimed to systematically and globally evaluate the monthly precipitation forecasts of JMA/MRI-CPS2, a dynamical seasonal climate forecast (Dyn-SCF) system operated by the Japan Meteorological Agency, by comparing its forecasts with those of a statistical SCF (St-SCF) system using climate indices. Consequently, the skill of JMA/MRI-CPS2 was determined to be globally higher than that of the St-SCF for zero-month lead forecasts. Contrarily, for forecasts made with a lead time of 1 month or longer, the deterministic skill of JMA/MRI-CPS2 was comparable to that of the St-SCF, and the probabilistic skill of JMA/MRI-CPS2 remained slightly higher.

Highlights:

• The skill of JMA/MRI-CPS2 for global zero-month lead forecasts was higher than that of the St-SCF.
• For lead forecasts of 1 month or longer, the deterministic skill of JMA/MRI-CPS2 was comparable to that of the St-SCF, and its probabilistic skill was slightly higher.
• Comparison between Dyn-SCFs and St-SCFs enables the determination of potential regions and seasons for the improvement of the forecast skill of Dyn-SCFs.