Open AccessThe Role of Anthropogenic Aerosol Forcing in Interdecadal Variations of Summertime Upper‐Tropospheric Temperature Over East Asia
Author(s) -
Wang Zhili,
Lin Lei,
Yang Meilin,
Guo Zhun
Publication year - 2019
Publication title -
earth's future
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.641
H-Index - 39
ISSN - 2328-4277
DOI - 10.1029/2018ef001052
Subject(s) - westerlies , climatology , environmental science , troposphere , east asia , forcing (mathematics) , aerosol , atmospheric sciences , plateau (mathematics) , monsoon , sea surface temperature , radiative forcing , east asian monsoon , flood myth , geology , geography , china , meteorology , mathematical analysis , mathematics , archaeology
Observations show a significant interdecadal decline of July and August (JA) mean upper‐tropospheric temperature (UTT) over East Asia during the second half of the twentieth century, which is likely responsible for the weakening of the East Asian summer monsoon and the “southern flood and northern drought” phenomenon observed in eastern China. This study investigates the role of anthropogenic aerosol forcing in the interdecadal cooling for the period 1951–2001 and the physical mechanisms involved using a coupled Earth system model, combined with reanalysis data. Our results show that the aerosol forcing leads to a drop of 0.14 °C per decade in JA mean UTT averaged over East Asia (30–45°N, 90–130°E), which significantly contributes to the observed cooling of 0.2 °C per decade. The interdecadal cooling may be attributed to the weakening of interhemispheric differences in JA mean sea surface temperature in response to aerosols. The asymmetric hemispheric change in sea surface temperature alters the local eddy flux, thereby weakening upper‐tropospheric westerlies and the transport of warm air from over the Tibetan plateau into downstream regions between 30°N and 40°N. We further find that changes in the geographic distribution of SO 2 emissions are the dominant cause of differences in JA mean UTT trends over East Asia between decades. The projected decrease in anthropogenic aerosols will lead to a rise of 0.05 °C per decade in JA mean UTT over East Asia during 2010–2050 under the Representative Concentration Pathways 8.5 scenario. This will likely have large impacts on the distribution of summer precipitation in East Asia in the future.