We aimed to evaluate the effectiveness of ensemble optimal interpolation (EnOI) in improving the analysis of significant wave height (SWH) within wave models using satellite-derived SWH data. Satellite observations revealed higher SWH in mid-latitude regions (30o to 60o in both hemispheres) due to stronger winds, whereas equatorial and coastal areas exhibited lower wave heights, attributed to calmer winds and land interactions. Root mean square error (RMSE) analysis of the control experiment without data assimilation revealed significant discrepancies in high-latitude areas, underscoring the need for enhanced analysis techniques. Data assimilation experiments demonstrated substantial RMSE reductions, particularly in high-latitude regions, underscoring the effectiveness of the technique in enhancing the quality of analysis fields. Sensitivity experiments with varying ensemble sizes showed modest global improvements in analysis fields with larger ensembles. Sensitivity experiments based on different decorrelation length scales demonstrated significant RMSE improvements at larger scales, particularly in the Southern Ocean and Northwest Pacific. However, some areas exhibited slight RMSE increases, suggesting the need for region-specific tuning of assimilation parameters. Reducing the observation error covariance improved analysis quality in certain regions, including the equator, but generally degraded it in others. Rescaling background error covariance (BEC) resulted in overall improvements in analysis fields, though sensitivity to regional variability persisted. These findings underscore the importance of data assimilation, parameter tuning, and BEC rescaling in enhancing the quality and reliability of wave analysis fields, emphasizing the necessity of region-specific adjustments to optimize assimilation performance. These insights are valuable for understanding ocean dynamics, improving navigation, and supporting coastal management practices.

1. Introduction
2. Data and Methods
    2.1. WAVEWATCH III
    2.2. Data Assimilation
    2.3. BEC rescaling
    2.4. Experiment Design
    2.5. Validation
3. Results
    3.1. Ensemble Size
    3.2. Decorrelation Length Scale
    3.3. Observation Error Covariance
    3.4. BEC Rescaling
4. Discussion and Conclusions
Acknowledgments
References

• Hye Min Lim(Pukyong National University, Busan 48513, Republic of Korea)
• Kyeong Ok Kim(Korea Institute of Ocean Science and Technology, Busan 49111, Republic of Korea)
• Hanna Kim(Korea Institute of Ocean Science and Technology, Busan 49111, Republic of Korea)
• Sang Myeong Oh(National Institute of Meteorological Sciences, KMA, Seogwipo 63568, Republic of Korea)
• Young Ho Kim(Pukyong National University, Busan 48513, Republic of Korea) Corresponding author