1. Estimating Ocean Observation Impacts on Coupled Atmosphere‐Ocean Models Using Ensemble Forecast Sensitivity to Observation (EFSO).
- Author
-
Chang, Chu‐Chun, Chen, Tse‐Chun, Kalnay, Eugenia, Da, Cheng, and Mote, Safa
- Subjects
OCEAN ,FORECASTING ,ATMOSPHERIC temperature ,OCEAN temperature ,SEAWATER salinity - Abstract
Ensemble Forecast Sensitivity to Observation (EFSO) is a technique that can efficiently identify the beneficial/detrimental impacts of every observation in ensemble‐based data assimilation (DA). While EFSO has been successfully employed on atmospheric DA, it has never been applied to ocean or coupled DA due to the lack of a suitable error norm for oceanic variables. This study introduces a new density‐based error norm incorporating sea temperature and salinity forecast errors, making EFSO applicable to ocean DA for the first time. We implemented the oceanic EFSO on the CFSv2‐LETKF and investigated the impact of ocean observations under a weakly coupled DA framework. By removing the detrimental ocean observations detected by EFSO, the CFSv2 forecasts were significantly improved, showing the validation of impact estimation and the great potential of EFSO to be extended as a data selection criterion. Plain Language Summary: This study introduces a new method to efficiently estimate the beneficial/detrimental impacts of each oceanic observation in the air‐sea coupled data assimilation (CDA) by incorporating the forecast errors for sea temperature and salinity with a novel density norm. For the first time, we implemented this approach onto the operational‐like CDA system and examined the impacts of ocean observations on the National Centers for Environmental Prediction CFSv2 forecasts. Our findings demonstrate that assimilating ocean profiles and satellite‐retrieved sea surface temperature products significantly improves the CFSv2 forecasts. Moreover, after excluding the detrimental ocean observations identified by our new method, we observed significant improvements in the CFSv2 forecasts. This result validates the accuracy of impact estimation and underscores its great potential as a data selection criterion in CDA. Key Points: A new oceanic Ensemble Forecast Sensitivity to Observation (EFSO) is proposed and implemented on the CFSv2 to investigate observation impactsThe 24‐hr CFSv2 forecasts of sea temperature, salinity, and 2‐m air temperature were improved by 1.5%, 0.8%, and 0.4%, respectively, after removing detrimental ocean observations detected by EFSOThe improvements in the CFSv2 forecast can last for at least 5 days for the ocean and 3 days for the low‐level atmosphere [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF