Observing System Evaluation Based on Ocean Data Assimilation and Prediction Systems: On-Going Challenges and a Future Vision for Designing and Supporting Ocean Observational Networks

Abstract

This paper summarizes recent efforts on Observing System Evaluation (OS-Eval) by the Ocean Data Assimilation and Prediction (ODAP) communities such as GODAE OceanView and CLIVAR-GSOP. It provides some examples of existing OS-Eval methodologies, and attempts to discuss the potential and limitation of the existing approaches. Observing System Experiment (OSE) studies illustrate the impacts of the severe decrease in the number of TAO buoys during 2012-2014 and TRITON buoys since 2013 on ODAP system performance. Multi-system evaluation of the impacts of assimilating satellite sea surface salinity data based on OSEs has been performed to demonstrate the need to continue and enhance satellite salinity missions. Impacts of underwater gliders have been assessed using Observing System Simulation Experiments (OSSEs) to provide guidance on the effective coordination of the western North Atlantic observing system elements. OSSEs are also being performed under H2020 AtlantOS Fujii et al.Observing System Evaluation project with the goal to enhance and optimize the Atlantic in-situ networks. Potential of future satellite missions of wide-swath altimetry and surface ocean currents monitoring is explored through OSSEs and evaluation of Degrees of Freedom for Signal (DFS). Forecast Sensitivity Observation Impacts (FSOI) are routinely evaluated for monitoring the ocean observation impacts in the US Navy's ODAP system. Perspectives on the extension of OS-Eval to coastal regions, the deep ocean, polar regions, coupled data assimilation, and biogeochemical applications are also presented. Based on the examples above, we identify the limitations of OS-Eval, indicating that the most significant limitation is reduction of robustness and reliability of the results due to their system-dependency. The difficulty of performing evaluation in near real time is also critical. A strategy to mitigate the limitation and to strengthen the impact of evaluations is discussed. In particular, we emphasize the importance of collaboration within the ODAP community for multi-system evaluation and of communication with ocean observational communities on the design of OS-Eval, required resources, and effective distribution of the results. Finally, we recommend further developing OS-Eval activities at international level with the support of the international ODAP (e.g., OceanPredict and CLIVAR-GSOP) and observational communities.

Influence of oceanic conditions in the energy transfer efficiency estimation of a micronekton model

“…SEAPODYM-MTL provides a parsimonious approach with only a few parameters and a MLE to estimates these parameters from observations. Among them, the energy transfer efficiency coefficients are of great importance because they directly control the biomass of micronekton functional groups, including those that undergo DVM and contribute to the sequestration of carbon dioxide into the deep ocean (Davison et al, 2013;Giering et al, 2014;Ariza et al, 2015). Therefore, a correct assessment of energy transfer coefficients is crucial for climate studies.…”

“…Through these daily migrations, the mesopelagic micronekton potentially contributes to a substantial transfer of atmospheric CO 2 to the deep ocean, after its metabolization by photosynthesis and export through the food chain (Davison et al, 2013). The understanding and quantification of this mechanism, called the "biological pump", are crucial in the context of climate change (Zaret and Suffern, 1976;Volk and Hoffert, 1985;Benoit-Bird et al, 2009;Davison et al, 2013;Giering et al, 2014;Ariza et al, 2015). However, there is a lack of comprehensive datasets at a global scale to properly estimate micronekton biomass and composition.…”

Observational Needs for Improving Ocean and Coupled Reanalysis, S2S Prediction, and Decadal Prediction

“…Additionally, new and upcoming satellite missions such as the Surface Water and Ocean Topography (SWOT) will provide higher-fidelity SSH observations than ever before. Coordination between international groups such as CLIVAR and GODAE OceanView is needed for significant progress to be made with international observing efforts (Fuiji, 2019). These international efforts, together with Global Ocean Observing System (GOOS) and its expert panels focusing on physics and biogeochemistry need to work together to build an observing system that recognizes user priorities.…”

Ocean Observations to Improve Our Understanding, Modeling, and Forecasting of Subseasonal-to-Seasonal Variability

“…Multi-system evaluation of observation impacts based on international collaboration is effective to deliver fair and robust information to society and observational agencies. Coordination by international groups such as CLIVAR and GODAE OceanView aims to support these efforts to make significant progress (see also Fujii et al, 2019). Here, we provide scientific rationales for ocean observations being important for S2S predictions, discuss gaps in observations, and recommend designs of observational and modeling experiments to evaluate the impact of ocean observations on S2S forecasts.…”