SynObs is one of the Japan-led projects being performed as part of the United Nations Decade of Ocean Science. It aims to propose an efficient ocean observing network that maximizes the synergistic effects of various observational data for predicting the oceans. We expect active participation from Japanese researchers in ocean science.

The United Nations has designated 2021-2030 as the Decade of Ocean Science for Sustainable Development to support various activities utilizing ocean science knowledge to achieve the Sustainable Development Goals (SDGs). In Japan, the Japan National Committee of the UN Ocean Decade1 has been established, and many researchers are participating in related activities. One of the projects led by Japan as part of the UN Decade of Ocean Science is the Synergistic Observing Network for Ocean Prediction (SynObs)2. The project aims to propose an efficient ocean observing network that maximizes the synergistic effects of various observational data for ocean predictions.
Ocean observation data is essential to estimating initial ocean states for ocean numerical models used to predict future changes. At the same time, since ocean prediction is a significant application of ocean observation data in regards to actual societies, it is necessary to demonstrate  positive impacts of ocean observations when making predictions in order to maintain the observing network. This was recognized from the beginning of the Global Ocean Data Assimilation Experiment (GODAE) implemented from 1998 to 2008. In response, the Observing System Evaluation Task Team (OS-Eval TT) was formed in 2007. OS-Eval TT was succeeded by its follow-on programs (currently by the international research program on ocean prediction, OceanPredict), which continued to address this issue. However, there were challenges, such as insufficient collaboration with observation agencies regarding the exchange of detailed observation information and the utilization of evaluation results. Therefore, OS-Eval TT launched SynObs in conjunction with the UN Decade of Ocean Science.
SynObs is operated as a comprehensive project through three UN Decade of Ocean Science programs: ForeSea: The Ocean Prediction Capacity of the Future; Ocean Observing Co-Design; and "CoastPredict: Observing and Predicting the Global Coastal Ocean (Figure 1)3. ForeSea is led by OceanPredict, while the remaining two are led by the Global Ocean Observing System (GOOS) under the UNESCO Intergovernmental Oceanographic Commission (UNESCO-IOC) and the World Meteorological Organization (WMO). There are plans to collaborate with the UN Decade of Ocean Science program "Digital Twins of the Ocean (DITTO)", where the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) plays the leading role in Japan, and the UN Decade of Ocean Science project "Integrated Global, Full-Depth and Multidisciplinary Ocean Observing Array for Beyond 2020 (OneArgo)", which belongs to Ocean Observing Co-Design.

SynObs held a kick-off workshop in Tsukuba City from November 15 to 18, 2022, sponsored by the Meteorological Research Institute of the Japan Meteorological Agency and co-sponsored by JAMSTEC (Figure 2). A total of 53 research presentations were made, with 84 researchers from abroad and 62 from Japan participating, including online participants.
Many workshop presentations focused on research on the impacts of observational data. For example, Dr. Matthieu Le Henaff from the University of Miami presented observation impact experiments related to typhoon prediction. Dr. Marilaure Gregoire from the University of Liège presented on the continuous evaluation of the impact of observations on weather prediction led by the WMO, and confirmed the need for cooperation between WMO and SynObs for evaluating the impact of observations in weather and climate prediction using Earth system models that include the ocean. The workshop participants also discussed the deepening of cooperation with fishermen in obtaining observational data, based on presentations by Dr. Naoki Hirose from Kyushu University and two others. Among the participants, many are involved in OneArgo, Ocean Observing Co-Design, and satellite observation missions, and introduced the current state of ocean observation and future observation plans. Through the workshop, in which numerous discussions were held among experts in ocean predictions and ocean observation, we were able to promote the launch of SynObs to both domestic and international researchers as well as establish a framework for future collaboration.

Currently, SynObs is planning to conduct Observing System Experiments (OSEs) and Observing System Simulation Experiments (OSSEs) simultaneously on more than ten ocean prediction systems, with the cooperation of participating institutions from various countries. An OSE is a set of prediction experiments started from initial ocean states estimated with or without data of a specific observation type in order to evaluating the impact of the observation type from the difference between the two. On the other hand, an OSSE is a similar experiment to an OSE but uses virtual observation data created from high-resolution model simulation results. This allows for assessing the impact of future observation systems that do not yet exist. The performance and characteristics of each system inevitably influence the results of individual OSEs and OSSEs. Through SynObs, the goal is to conduct a system-independent, general and highly reliable evaluation that integrates OSE/OSSE results from many systems, which will contribute to designing a better ocean observation network.
In OSEs, the importance of existing satellite altimeters, Argo floats, and tropical moored buoys will be evaluated. In OSSEs, the impact of future satellite ocean current observation missions, increased density of Argo floats, and continental shelf observations using underwater gliders will be assessed. Experiments are scheduled to be conducted by the end of 2023, with results to be presented at the WMO Observing Impact Workshop, Ocean Predict Symposium, and other events in 2024.
Additionally, SynObs is planning activities called Observing System Evaluation Showcases to widely disseminate the impact assessment of ocean observations to stakeholders and the ocean science community and intends to create web pages and special issues in international academic journals. Furthermore, in collaboration with Ocean Observing Co-Design and the WMO, SynObs aims to create proposals on the importance of existing ocean observations and the design of future observation networks. SynObs' activities are supported through the voluntary participation and support of scientists involved in ocean prediction and observation. Active contributions to SynObs from within Japan are expected as well. (End)

1. https://oceandecade.jp/ja/
2. https://oceanpredict.org/un-decade-of-ocean-science/synobs-2/
3. Nadia PINARDI “CoastPredict: Observing and Predicting the Global Coastal Ocean” No. 514 of this newsletter (published Jan 5, 2022)
https://www.spf.org/opri/newsletter/514_2.html