Citation for the Award

Professor Sir Brian Hoskins and Professor John Wallace have significantly influenced the development of atmospheric and climate dynamics, the basis of modern numerical weather and climate prediction, Hoskins through his research into theoretical and numerical modelling, and Wallace through his efforts in data analysis. Their research has helped build a scientific foundation that has led to greater understanding and better forecasting of the increasingly anomalous weather and climate events our world is now faced with, and their contributions are deserving of recognition.

In recent years substantial natural variability in the ocean-atmosphere system alongside continued global warming have resulted in more frequent severe weather disasters across the globe. The heat waves and heavy rains experienced in Japan and around the world this past summer clearly demonstrated the immense societal impact of such events. As such anomalous weather and climate events become more extreme, it will become even more important on a societal level to harness numerical weather and climate prediction to forecast such events and prevent and mitigate potential disasters. Numerical weather and climate prediction has become an indispensable part of the soft infrastructure of modern society, and its development has been supported not only by dramatic advancements in computational resources and observational and forecasting technologies, but also by better understanding of atmospheric circulation at various spatiotemporal scales, by a new and deeper understanding of their underlying mechanisms, and by increased knowledge about how to predict their evolution. Over the last five decades, the contributions of both of these scientists have helped make such scientific progress possible.

In the late 1970s, weather prediction still relied mainly on the experience of forecasters. It was then that Hoskins created the first numerical atmospheric model to realistically simulate the development and maturation of extratropical cyclones and weather fronts in the mid-latitude westerlies, foreshadowing the rapid development of numerical weather prediction. During the same period, Wallace’s team harnessed gridded initial data for numerical weather prediction to become the first to clearly demonstrate that cyclones and anticyclones, westerly winds, and other phenomena in the extratropical northern hemisphere can be reproduced in the data according to the principles of large-scale atmospheric dynamics. This encouraged the rapid quantification of observational and analysis research on atmospheric circulation and its variability. In the early 1980s, Hoskins used Rossby wave theory to propose a dynamical basis for teleconnection, which describes how anomalous atmospheric circulation in one region can cause circulation anomalies in distant regions. During the same period, Wallace was the first to statistically identify several teleconnection patterns that occur recurrently in the extratropical northern hemisphere – including the persistent atmospheric circulation anomalies caused by El Niño and La Niña – as interannual variability in the tropical Pacific ocean-atmosphere coupled system. His findings demonstrated that the concept of teleconnection could be useful to study the Pacific decadal variability and other ocean-atmosphere coupled fluctuations in the tropics, especially their potential predictability for extratropical weather conditions a month or even a season in advance. Wallace also identified hemispheric-scale variations in the mid-latitude westerlies from observational data and found that they can cause weather anomalies over extensive areas, and that they can be linked to persistent stratospheric circulation anomalies depending on the season. This suggested that such information could be useful for prediction. Meanwhile, Hoskins advocated for the use of a specific dynamically-conserved quantity in order to understand the evolution of meanders of the upper-tropospheric westerly winds and their impact on anomalous weather conditions, and this is now widely accepted by the research community and weather forecasting agencies.

The research achievements by Hoskins and Wallace convinced the academic community and government agencies of the usefulness of numerical weather and climate prediction, which led to the production of “atmospheric reanalysis data,” an essential tool for climate research and meteorological agencies monitoring climate change and analyzing extreme weather events. Their achievements have led to real advances in clarifying structures, evolution, mechanisms, and predictability of weather and climatic phenomena around the globe at various spatiotemporal scales, including anomalies in atmospheric circulation and precipitation and their interactions with the ocean. The two researchers have contributed immensely to the development of atmospheric and climate dynamics, which serve as the foundation of weather and climate prediction and analyzing extreme weather and climate events.

It is for these reasons that we believe the achievements of Professor Sir Brian Hoskins and Professor John Wallace make them worthy of recognition as recipients of the 2024 Japan Prize in the fields of Resources, Energy, the Environment, and Infrastructure.