11:00 〜 13:00
[AAS08-P04] Fast and Slow Responses of Surface Air Temperature to the Increasing Anthropogenic Aerosols in the Asia Monsoon Region
キーワード：人為起源エアロゾル、アジアモンスーン、地表気温
The Asian monsoon region is one of the largest sources of anthropogenic aerosols (AAs). AAs reduce incoming solar radiation flux through the aerosol–radiation and –cloud interactions. The climate response to AAs in the Asian monsoon region was separated into the fast and slow responses. The fast response is the direct effect of AAs, whereas the slow response includes the SST feedbacks. This study investigated the surface air temperature (SAT) response to AAs in the South Asian monsoon region.
We used the climate model simulation outputs of Coupled Model Intercomparison Project 6. Compare with or without the AA forcings both in CGCM and AGCM experiments, the fast and slow responses to AAs were analyzed.
There was surface cooling in almost all the Asian monsoon regions due to the increasing AAs obstructing the solar radiations. However, in the regions over and around India, there was relative surface warming, which some models even showed warming anomalies.
Separating into the two responses, the fast response decreased in SAT significantly around the source regions of AAs, whereas the slow response showed the inter-hemispheric SAT gradient, which significantly cooled in the Northern Hemisphere. Focusing on the Asian monsoon region, the fast response notably reduced the SAT, particularly over East Asia. There was a slight reduction in SAT over South Asia, which was contributed by the slow response.
To understand the process that induced these differences, the changes in radiation fluxes at the surface, cloud fraction, and winds due to the increase in AAs were analyzed. The fast response of the downward shortwave radiation at the surface (DSRS) was decreased almost all over Asia, particularly over East Asia. However, the fast response of cloud-related DSRS was increased in northern India, and the cloud fraction was decreased in the same region. The slow response of all-sky and cloud-related DSRS increased over southern India, and the cloud fraction was decreased, which was consistent with the response of SAT.
Therefore, the slow response increased the incoming solar radiation mainly in the southern part of India. Following the response, the SAT cooling was occurred in South Asia.
We used the climate model simulation outputs of Coupled Model Intercomparison Project 6. Compare with or without the AA forcings both in CGCM and AGCM experiments, the fast and slow responses to AAs were analyzed.
There was surface cooling in almost all the Asian monsoon regions due to the increasing AAs obstructing the solar radiations. However, in the regions over and around India, there was relative surface warming, which some models even showed warming anomalies.
Separating into the two responses, the fast response decreased in SAT significantly around the source regions of AAs, whereas the slow response showed the inter-hemispheric SAT gradient, which significantly cooled in the Northern Hemisphere. Focusing on the Asian monsoon region, the fast response notably reduced the SAT, particularly over East Asia. There was a slight reduction in SAT over South Asia, which was contributed by the slow response.
To understand the process that induced these differences, the changes in radiation fluxes at the surface, cloud fraction, and winds due to the increase in AAs were analyzed. The fast response of the downward shortwave radiation at the surface (DSRS) was decreased almost all over Asia, particularly over East Asia. However, the fast response of cloud-related DSRS was increased in northern India, and the cloud fraction was decreased in the same region. The slow response of all-sky and cloud-related DSRS increased over southern India, and the cloud fraction was decreased, which was consistent with the response of SAT.
Therefore, the slow response increased the incoming solar radiation mainly in the southern part of India. Following the response, the SAT cooling was occurred in South Asia.