5:15 PM - 7:15 PM
[AAS10-P11] Impact of stratospheric sulfate geoengineering on westerly winds and climate of Japan in winter
Keywords:stratospheric sulfate geoengineering, westerly winds, blocking high, East Asian winter monsoon
Stratospheric sulfate geoengineering is a method of mitigating global warming by injecting sulfur dioxide into the stratosphere to generate sulfate aerosols, thereby reducing radiative forcing. This method also has various side effects, one of which is a change in westerly winds in winter. On the other hand, changes in location and frequency of occurrence of blocking high associated with westerly wind meandering and effects of changes in westerly winds and blocking high on the climate of Japan are not known in detail. This study investigates the impact of stratospheric sulfate geoengineering on westerly winds and climate of Japan in winter.
By analyzing the results of sensitivity experiments using climate models, the effects of stratospheric sulfate geoengineering are separated into effects due to weakening of radiative forcing and effects due to tropical lower stratospheric warming. Changes in westerly winds are strongly influenced by the latter, with the polar vortex enhanced in the stratosphere propagating into the troposphere, causing it to shift even more poleward than it did during warming and less likely to meander. This altered sea level pressure and surface winds, resulting in a positive phase of the Arctic Oscillation and the North Atlantic Oscillation, a strengthening of the Siberian High, and a weakening of the Aleutian Low, which shifted the wind direction of the East Asian winter monsoon more northerly. On the other hand, surface air temperatures were strongly influenced by both, and a cold trend was confirmed in East Asia, including Japan, due to increased East Siberian blocking and West and Central Siberian blocking, positive phase of the Arctic Oscillation, and global cooling effects. This study shows that stratospheric sulfate geoengineering affects not only the position of the westerly winds but also their meandering and the frequency of blocking high. These effects on surface atmospheric circulation and temperatures suggest that the direction of the East Asian winter monsoon may change to the north, and that the entire East Asia region, including Japan, may become colder.
By analyzing the results of sensitivity experiments using climate models, the effects of stratospheric sulfate geoengineering are separated into effects due to weakening of radiative forcing and effects due to tropical lower stratospheric warming. Changes in westerly winds are strongly influenced by the latter, with the polar vortex enhanced in the stratosphere propagating into the troposphere, causing it to shift even more poleward than it did during warming and less likely to meander. This altered sea level pressure and surface winds, resulting in a positive phase of the Arctic Oscillation and the North Atlantic Oscillation, a strengthening of the Siberian High, and a weakening of the Aleutian Low, which shifted the wind direction of the East Asian winter monsoon more northerly. On the other hand, surface air temperatures were strongly influenced by both, and a cold trend was confirmed in East Asia, including Japan, due to increased East Siberian blocking and West and Central Siberian blocking, positive phase of the Arctic Oscillation, and global cooling effects. This study shows that stratospheric sulfate geoengineering affects not only the position of the westerly winds but also their meandering and the frequency of blocking high. These effects on surface atmospheric circulation and temperatures suggest that the direction of the East Asian winter monsoon may change to the north, and that the entire East Asia region, including Japan, may become colder.