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| Titel |
Sensitivity study on the impacts of biogenic VOC on the Asian monsoon climate in dry and wet seasons using MIROC5 |
| VerfasserIn |
H. G. Takahashi, H.-J. Kim, K. Tanaka, K. Takata, K. Saito, T. Yasunari |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250061882
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| Zusammenfassung |
| Biogenic volatile organic compounds (BVOC) are a major source of secondary organic
aerosol (SOA), which probably affects regional and global climates. Over the Asian monsoon
region, land-use and land-cover (LULC) has been artificially changed from natural vegetation
to cropland in the last 300 years. Due to the LULC changes, biomass has significantly
reduced, which in turn has reduced BVOC emission. This study estimates the sensitivity of
the impacts of BVOC changes induced by LULC in the Asian monsoon region. Because wet
deposition process is generally dominant for atmospheric burden of aerosols in rainy season,
it is possible that the impacts in wet and dry seasons are different. Thus, we also focus on the
differences between the two seasons. We conducted two experiments. One is with a
standard concentration of SOA from BVOC attached to the GCM (B1), while the
other is with our new estimation (B2), on the basis of Guenther et al. (2006) and
Sakulyanontvittaya et al. (2008). The SOA concentration in B2 is 1.5–2 times higher than that
in B1.
The changes (B2-B1) in direct effects of aerosols showed a localized cooling signal over
the Indochina Peninsula where the concentration of organic carbon (OC) aerosol is
significantly increased in dry season (April), while a wide-spread cooling was calculated over
the Asian region and north Indian Ocean in rainy season (July). Cloud characteristics showed
the changes in dry season that the radius of cloud droplets reduced and that the number of
cloud droplets increased. Those probably induced long-lived clouds. Consequently, cooling
effect of cloud was found over the Indochina Peninsula. In the rainy season, changes in cloud
characteristics are not predominant. We roughly estimated direct and indirect effects
(changes in surface radiation through the changes in cloud characteristics) of all
species of aerosols due to the BVOC changes are 1–2 Wm-2 and 5–8 Wm-2 over
the Indochina Peninsula in April. On the other hand in July, the direct effect was
increased over the whole Asian monsoon region, although the change was small. |
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