Submitted as: model evaluation paper 20 Dec 2021

Submitted as: model evaluation paper | 20 Dec 2021

Review status: this preprint is currently under review for the journal GMD.

An Online Ensemble Coupled Data Assimilation Capability for the Community Earth System Model: System Design and Evaluation

Jingzhe Sun5,, Yingjing Jiang1,4,, Shaoqing Zhang1,3,4, Weimin Zhang2, Lv Lu1,4, Guangliang Liu6, Yuhu Chen3, Xiang Xing2, Xiaopei Lin1,3,4, and Lixin Wu1,3,4 Jingzhe Sun et al.
  • 1Key Laboratory of Physical Oceanography, Ministry of Education/Institute for Advanced Ocean Study/Frontiers Science Center for Deep Ocean Multispheres and Earth System (DOMES), Ocean University of China, Qingdao, China
  • 2Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai, China
  • 3Qingdao Pilot National Laboratory for Marine Science and Technology (QNLM), Qingdao, China
  • 4The College of Oceanic and Atmospheric Sciences, Ocean University of China, Qingdao, China
  • 5Beijing Institute of Applied Meteorology, Beijing, China
  • 6Shandong Provincial Key Laboratory of Computer Networks, Qilu University of Technology (Shandong Academy of Sciences), Jinan, China
  • These authors contributed equally to this work.

Abstract. The Community Earth System Model (CESM) developed at the National Center of Atmospheric Research (NCAR) has been used worldwide for climate studies. This study extends the efforts of CESM development to include an online (i.e., in-core) ensemble coupled data assimilation system (CESM-ECDA) to enhance CESM’s capability for climate predictability studies and prediction applications. The CESM-ECDA system consists of an online atmospheric data assimilation (ADA) component implemented to both the finite-volume and spectral-element dynamical cores, and an online oceanic data assimilation (ODA) component. In ADA, surface pressures (Ps) are assimilated, while in ODA, gridded sea surface temperature (SST) and ocean temperature and salinity profiles at real Argo locations are assimilated. The system has been evaluated within a perfect twin experiment framework, showing significantly reduced errors of the model atmosphere and ocean states through “observation”-constraints by ADA and ODA. The weakly CDA in which both the online ADA and ODA are conducted during the coupled model integration shows smaller errors of air-sea fluxes than the single ADA and ODA, facilitating the future utilization of cross-covariance between the atmosphere and ocean at the air-sea interface. A three-year CDA reanalysis experiment is also implemented by assimilating Ps, SST and ocean temperature and salinity profiles from the real world spanning the period 1978 to 1980 using 12 ensemble members. Results show that Ps RMSE is smaller than 20CR and SST RMSE is better than ERA-20C and close to CFSR. The success of the online CESM-ECDA system is the first step to implement a high-resolution long-term climate reanalysis once the algorithm efficiency is much improved.

Jingzhe Sun et al.

Status: open (until 18 Feb 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Jingzhe Sun et al.

Jingzhe Sun et al.


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Short summary
An online ensemble coupled data assimilation system with the Community Earth System Model is designed and evaluated. This system uses the memory-based information transfer approach which avoids frequent i/o operations. The observations of surface pressure, sea surface temperature and in situ temperature and salinity profiles can be effectively assimilated into the coupled model. That will facilitate a long-term high-resolution climate reanalysis once the algorithm efficiency gets much improved.