Habitable Japan Sustainability of atmospheric and oceanic environment as a survival basis of island country Japan Grant-in-Aid for Transformative Research Areas (A) (2024–2028)

Climate in the mid-latitude, including Japan, is strongly affected by global climate change. Remote forcings of the tropical ocean warming and the Arctic sea ice loss intensify meanders of the westerly wind (jet stream), often causing the extreme weather and climate in East Asia. The local ocean-atmosphere phenomena, such as the East Asian monsoon and the heat/moisture transport from the Kuroshio and Tsushima warm currents, are also important for the climate variability and change in Japan. Given the fact that the ocean warming around Japan is much faster than the global average of surface temperature warming, it needs to be explored how the mid-latitude climate interacts with both the tropics and polar regions in two-way direction. In this project, we will attempt to clarify the following research items, synthesizing the observational analysis and various types of climate model simulations:

1. To investigate how the future changes in the tropical ocean-atmosphere coupling and inter-basin interaction affect the mid-latitude climate, and whether the rapid warming of the extratropical oceans modulates the tropical climate.
2. To identify a role of the extratropical ocean-atmosphere interaction in the blocking highs and amplified meanders of the westerly wind that cause the extreme weather and climate.
3. To explore future changes in the Arctic-mid latitude teleconnection in response to the Arctic sea ice loss, and examine how the interdecadal variability of the extratropical oceans, such as the Pacific decadal variability and the Atlantic multidecadal variability, affects the Arctic climate under the global warming.