Teleconnections and the Predictability of Weather and Climate
Introduction (Background and Issues)
The GRENE Arctic Climate Change Research Project (GRENE Arctic) and the Arctic Challenge for Sustainability (ArCS) project have revealed that rapid environmental changes in the Arctic, such as sea ice, snow cover, and ice sheet shrinkage due to Arctic warming will affect cold waves and heavy snowfall in mid-latitude regions, global climate, ocean circulation, and even ecosystems and biological resources. The understanding that changes in the Arctic will affect not only Japan but also other countries has advanced, it is now internationally recognized, not only scientifically but also socially, that "understanding the reality of Arctic warming and its effects and elucidating its mechanisms" is an issue to be urgently addressed. To this end, the Arctic research community is now expected to improve the accuracy of observations to understand the actual changes in the Arctic environment, to improve and refine the Improvement of weather and climate prediction to make quantitative forecasts, to evaluate the impact on the human environment, and to promote legal and policy responses to ensure a sustainable society.
Among these, this Research Program has set "Elucidation of Teleconnection and the Predictability of Weather and Climate" as its main target, which contributes to Strategic Goal 2, "Improvement of Weather and Climate Prediction." Specifically, this project aims to clarify the mechanisms of weather and climate processes that directly contribute to the improvement of weather and climate prediction, by quantitatively evaluating land surface processes, water and heat transport, and to provide basic data and indices that contribute to the evaluation of predictability, as well as to clarify the amplification and progression processes of Arctic warming. In addition, we aim for social implementation that contributes to the prediction of short-term extreme events and disaster prevention and mitigation measures.
Research Outline
In addition to the findings through the GRENE Arctic and ArCS research on "the effects of climate change in the Arctic on mid-latitude climates, including Japan," and with the importance of the occurrence of extreme events and global-scale irreversible change due to rapid changes in the Arctic as an issue to be addressed, this Research Program has been named "Teleconnection and the Predictability of Weather and Climate" and has set the following three research objectives.
(1) Understanding extreme phenomena related to changes in the Arctic
(2) Elucidation of warming amplification in the Arctic and the warming progression process
(3) Contribution to social implementation of extreme phenomena prediction, disaster prevention/mitigation and climate change adaptation measures
The most important feature of this Research Program, which is aimed at achieving Strategic Goal 2, is to focus on actual atmospheric phenomena and extreme events that occur daily, and to capture the links between these phenomena and climate change and climate modulation in the pan-Arctic region, as well as weather and climate in the mid- and low-latitudes. Based on this perspective, we will elucidate the "teleconnection of weather and climate" and accurately assess its "predictability" by continuously capturing the horizontal coupling system of atmosphere-ocean-snow/ice-land, stratosphere-troposphere-ocean-land, and polar-midlatitude-tropics on short- to medium- to long-term time scales. This is a world-leading approach to Arctic research that incorporates a new perspective on extreme phenomena and their modulation, and integrates multispectral coupling, vertical coupling, and horizontal coupling.
To achieve this goal, we have set the following four Sub Programs (Chiefs of Sub Programs) with the objective of this Research Program as "understanding the occurrence of extreme events due to abrupt changes in the Arctic and the process of progressive warming in the Arctic”.
Sub Program 1: Mechanism of Extreme Weathers with Cold Air Mass (Meiji Honda)
Sub Program 2: Pan-Arctic Seasonal-to-Decadal Climate Variability and Its Modulation under Global Warming (Bunmei Taguchi)
Sub Program 3: Mechanism of Arctic Warming Amplification (Masakazu Yoshimori)
Sub Program 4: Weather and Climate Variability Associated with Land Processes (Tomonori Sato)
Each Sub Program consisted of three to eight researchers, and the number of researchers generally remained around 25 throughout the Research Program.
Summary of Overall Research Program Results
The following is a summary of research results from the start of the project in June 2020 to September 2024. Since this Research Program is mainly data analysis and numerical experiments, we were able to carry out the originally planned research plan on schedule, with almost no impact from COVID-19.
Although FY2020 was the peak year for COVID-19, we first strengthened cooperation among Sub Programs, and through close meetings and study groups, we exchanged information and established an initial research structure. In addition, we have shared research meetings with the Research Program on Climate Prediction, which shares Strategic Goal 2, and have worked to build a system in which we can contribute to the refinement and sophistication of models. The collaboration with related Research Programs under Strategic Goals 1, 3 and 4 was based on the individual connections among researchers. We began discussions with Niigata Prefecture as the first stakeholder.
In FY2021, we completed a cutoff low index that objectively indexes the dynamics of Arctic cold air mass, and in September 2021, we published real-time information as a cutoff low (COL) map on the Niigata University website (https://naos.env.sc.niigata-u.ac.jp/~coluser/), laying a solid foundation for the development of the Research Program on the subject “Teleconnection and the Predictability of Weather and Climate Prediction”. Collaboration among Sub Programs has also continued actively, and a system for sharing and analyzing information on notable phenomena, especially those that occur frequently in various parts of the world, has been established. Collaboration with the Research Program on Climate Prediction, which shares Strategic Goal 2, has stabilized, and with related Research Programs of Strategic Goals 1, 3, and 4, a collaboration system has been established through participation in events organized by the Research Program on International Relations and the " Arctic Transdisciplinary Community of Practice". In efforts toward social implementation, discussions with Niigata Prefecture have been continued, and we held a public seminar.
In FY2022, the tracking system (tracking algorithm) for the cutoff low vortex indicator was completed, and the cutoff low index analysis tool was implemented in GitLab, which is now available to anyone who wishes to use it, both in Japan and abroad. Cooperation among Sub Programs and Research Programs continued to be good, and we maintained a system of constant information sharing and collaborative analysis through meetings and research conferences. In terms of international collaboration, a session was held at the 7th International Symposium on Arctic Research (ISAR-7), which was a face-to-face meeting, with four of the Chiefs of Sub Programs as conveners. The Principal Investigator and Deputy Principal Investigator also visited the International Pacific Research Center (IPRC) at the University of Hawaii to exchange views on the impact of cutoff low-induced arctic cold air on mid- and low-latitude North Pacific Ocean weather and climate. For social implementation, discussions with East Japan Railway Company (JR East) and Japan Meteorological Agency (JMA) have been initiated in addition to Niigata Prefecture.
In FY2023, we started to develop an indicator for the occurrence of extreme events, which will be further developed from the cutoff low indicator, and proceeded with the evaluation of its predictability. In addition, with the aim of integrating the efforts of each Sub Program, we have moved toward the proposal of a coupled polar-midlatitude-tropical system, the mechanism of decadal-scale changes, the evaluation of water and heat transport associated with global warming, and the elucidation of the processes of changes in land surfaces including biogeochemical cycles. Collaboration among Sub Programs and Research Programs continued to be active through meetings and workshops. In international collaboration, international meetings and events were held in conjunction with the convergence of COVID-19, and international dissemination of research results was promoted through participation in international conferences and other events. The COL Map website, which is now available to the public, was improved, with an English-language version as the basic version, and a mobile media version, including smartphones, was developed for wider use by stakeholders. The COL Map is now the top-ranked search engine site by typing "col map". The English-language version of the cutoff low index analysis tool is also the basic version. In terms of social implementation, the cutoff low vortex indicator was implemented in the internal analysis tool of the Climate Information Division of the Japan Meteorological Agency in June 2023, and its use began with the analysis materials of the Extreme Weather Analysis Review Meeting in July. We also continued discussions with Niigata Prefecture and other stakeholders through committee meetings and study sessions on the impact of the record-breaking heat wave in the summer of 2023 on the social living environment and agriculture.
In FY2024, we aimed to further integrate the various processes related to weather and climate in the Arctic Circle that have been obtained so far in each Sub Program. For the cutoff low index, we identified extreme weather indicators related to prominent atmospheric phenomena associated with heavy rainfall and heavy snowfall, and are implementing these indicators into the tracking system. The cutoff low index implemented in the JMA Climate Information Division analysis tool since FY2023 was published on the JMA’s Extreme Weather Analysis Website in October 2024.
Summary
The members of the Research Program have been working together to promote this project from an unprecedented new perspective, focusing on real atmospheric phenomena and extreme events that occur daily, with the aim of furthering the clarification of the impact of Arctic climate change on mid-latitude climates, including Japan, which has been the goal of the project since the GRENE Arctic. In particular, we have developed a cutoff low index that objectively measures the dynamics of Arctic cold air mass and disseminated real-time information via a website. In addition, we are developing indicators for extreme phenomena and preparing to release a system for detecting and tracking cutoff lows that cause pronounced extreme weather events and displaying their predicted paths during the final year of the project. We have published 18-24 papers in peer-reviewed English-language journals in each fiscal year, and have maintained a steady flow of 2-8 press releases throughout the research period. With the close collaboration among Sub Programs, we were able to promote our research smoothly according to the originally planned research roadmap without any changes in the research plan, as we were almost unaffected by COVID-19.