The effect of regional changes in anthropogenic aerosols on rainfall of the East Asian Summer Monsoon

The response of East Asian Summer Monsoon (EASM) precipitation to long term changes in regional anthropogenic aerosols (sulphate and black carbon) is explored in an atmospheric general circulation model, the atmospheric component of the UK High-Resolution Global Environment Model v1.2 (HiGAM). Separ...

Full description

Bibliographic Details
Main Authors: L. Guo, E. J. Highwood, L. C. Shaffrey, A. G. Turner
Format: Article
Language:English
Published: Copernicus Publications 2013-02-01
Series:Atmospheric Chemistry and Physics
Online Access:http://www.atmos-chem-phys.net/13/1521/2013/acp-13-1521-2013.pdf
_version_ 1818930742551379968
author L. Guo
E. J. Highwood
L. C. Shaffrey
A. G. Turner
author_facet L. Guo
E. J. Highwood
L. C. Shaffrey
A. G. Turner
author_sort L. Guo
collection DOAJ
description The response of East Asian Summer Monsoon (EASM) precipitation to long term changes in regional anthropogenic aerosols (sulphate and black carbon) is explored in an atmospheric general circulation model, the atmospheric component of the UK High-Resolution Global Environment Model v1.2 (HiGAM). Separately, sulphur dioxide (SO<sub>2</sub>) and black carbon (BC) emissions in 1950 and 2000 over East Asia are used to drive model simulations, while emissions are kept constant at year 2000 level outside this region. The response of the EASM is examined by comparing simulations driven by aerosol emissions representative of 1950 and 2000. The aerosol radiative effects are also determined using an off-line radiative transfer model. During June, July and August, the EASM was not significantly changed as either SO<sub>2</sub> or BC emissions increased from 1950 to 2000 levels. However, in September, precipitation is significantly decreased by 26.4% for sulphate aerosol and 14.6% for black carbon when emissions are at the 2000 level. Over 80% of the decrease is attributed to changes in convective precipitation. The cooler land surface temperature over China in September (0.8 °C for sulphate and 0.5 °C for black carbon) due to increased aerosols reduces the surface thermal contrast that supports the EASM circulation. However, mechanisms causing the surface temperature decrease in September are different between sulphate and BC experiments. In the sulphate experiment, the sulphate direct and the 1st indirect radiative effects contribute to the surface cooling. In the BC experiment, the BC direct effect is the main driver of the surface cooling, however, a decrease in low cloud cover due to the increased heating by BC absorption partially counteracts the direct effect. This results in a weaker land surface temperature response to BC changes than to sulphate changes. The resulting precipitation response is also weaker, and the responses of the monsoon circulation are different for sulphate and black carbon experiments. This study demonstrates a mechanism that links regional aerosol emission changes to the precipitation changes of the EASM, and it could be applied to help understand the future changes in EASM precipitation in CMIP5 simulations.
first_indexed 2024-12-20T04:05:32Z
format Article
id doaj.art-0ed931c8e11247f2bf5a2d39ec6f9760
institution Directory Open Access Journal
issn 1680-7316
1680-7324
language English
last_indexed 2024-12-20T04:05:32Z
publishDate 2013-02-01
publisher Copernicus Publications
record_format Article
series Atmospheric Chemistry and Physics
spelling doaj.art-0ed931c8e11247f2bf5a2d39ec6f97602022-12-21T19:54:02ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242013-02-011331521153410.5194/acp-13-1521-2013The effect of regional changes in anthropogenic aerosols on rainfall of the East Asian Summer MonsoonL. GuoE. J. HighwoodL. C. ShaffreyA. G. TurnerThe response of East Asian Summer Monsoon (EASM) precipitation to long term changes in regional anthropogenic aerosols (sulphate and black carbon) is explored in an atmospheric general circulation model, the atmospheric component of the UK High-Resolution Global Environment Model v1.2 (HiGAM). Separately, sulphur dioxide (SO<sub>2</sub>) and black carbon (BC) emissions in 1950 and 2000 over East Asia are used to drive model simulations, while emissions are kept constant at year 2000 level outside this region. The response of the EASM is examined by comparing simulations driven by aerosol emissions representative of 1950 and 2000. The aerosol radiative effects are also determined using an off-line radiative transfer model. During June, July and August, the EASM was not significantly changed as either SO<sub>2</sub> or BC emissions increased from 1950 to 2000 levels. However, in September, precipitation is significantly decreased by 26.4% for sulphate aerosol and 14.6% for black carbon when emissions are at the 2000 level. Over 80% of the decrease is attributed to changes in convective precipitation. The cooler land surface temperature over China in September (0.8 °C for sulphate and 0.5 °C for black carbon) due to increased aerosols reduces the surface thermal contrast that supports the EASM circulation. However, mechanisms causing the surface temperature decrease in September are different between sulphate and BC experiments. In the sulphate experiment, the sulphate direct and the 1st indirect radiative effects contribute to the surface cooling. In the BC experiment, the BC direct effect is the main driver of the surface cooling, however, a decrease in low cloud cover due to the increased heating by BC absorption partially counteracts the direct effect. This results in a weaker land surface temperature response to BC changes than to sulphate changes. The resulting precipitation response is also weaker, and the responses of the monsoon circulation are different for sulphate and black carbon experiments. This study demonstrates a mechanism that links regional aerosol emission changes to the precipitation changes of the EASM, and it could be applied to help understand the future changes in EASM precipitation in CMIP5 simulations.http://www.atmos-chem-phys.net/13/1521/2013/acp-13-1521-2013.pdf
spellingShingle L. Guo
E. J. Highwood
L. C. Shaffrey
A. G. Turner
The effect of regional changes in anthropogenic aerosols on rainfall of the East Asian Summer Monsoon
Atmospheric Chemistry and Physics
title The effect of regional changes in anthropogenic aerosols on rainfall of the East Asian Summer Monsoon
title_full The effect of regional changes in anthropogenic aerosols on rainfall of the East Asian Summer Monsoon
title_fullStr The effect of regional changes in anthropogenic aerosols on rainfall of the East Asian Summer Monsoon
title_full_unstemmed The effect of regional changes in anthropogenic aerosols on rainfall of the East Asian Summer Monsoon
title_short The effect of regional changes in anthropogenic aerosols on rainfall of the East Asian Summer Monsoon
title_sort effect of regional changes in anthropogenic aerosols on rainfall of the east asian summer monsoon
url http://www.atmos-chem-phys.net/13/1521/2013/acp-13-1521-2013.pdf
work_keys_str_mv AT lguo theeffectofregionalchangesinanthropogenicaerosolsonrainfalloftheeastasiansummermonsoon
AT ejhighwood theeffectofregionalchangesinanthropogenicaerosolsonrainfalloftheeastasiansummermonsoon
AT lcshaffrey theeffectofregionalchangesinanthropogenicaerosolsonrainfalloftheeastasiansummermonsoon
AT agturner theeffectofregionalchangesinanthropogenicaerosolsonrainfalloftheeastasiansummermonsoon
AT lguo effectofregionalchangesinanthropogenicaerosolsonrainfalloftheeastasiansummermonsoon
AT ejhighwood effectofregionalchangesinanthropogenicaerosolsonrainfalloftheeastasiansummermonsoon
AT lcshaffrey effectofregionalchangesinanthropogenicaerosolsonrainfalloftheeastasiansummermonsoon
AT agturner effectofregionalchangesinanthropogenicaerosolsonrainfalloftheeastasiansummermonsoon