The impact of recent changes in Asian anthropogenic emissions of SO<sub>2</sub> on sulfate loading in the upper troposphere and lower stratosphere and the associated radiative changes
<p>Convective transport plays a key role in aerosol enhancement in the upper troposphere and lower stratosphere (UTLS) over the Asian monsoon region where low-level convective instability persists throughout the year. We use the state-of-the-art ECHAM6–HAMMOZ global chemistry–climate model to...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-08-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/9989/2019/acp-19-9989-2019.pdf |
| Summary: | <p>Convective transport plays a key role in aerosol enhancement in the upper
troposphere and lower stratosphere (UTLS) over the Asian monsoon region
where low-level convective instability persists throughout the year. We use
the state-of-the-art ECHAM6–HAMMOZ global chemistry–climate model to
investigate the seasonal transport of anthropogenic Asian sulfate aerosols
and their impact on the UTLS. Sensitivity simulations for <span class="inline-formula">SO<sub>2</sub></span> emission
perturbation over India (48 % increase) and China (70 % decrease) are
performed based on the Ozone Monitoring Instrument (OMI) satellite-observed
trend, rising over India by <span class="inline-formula">∼4.8</span> % per year and decreasing
over China by <span class="inline-formula">∼7.0</span> % per year during 2006–2017. The
enhanced Indian emissions result in an increase in aerosol optical depth
(AOD) loading in the UTLS by 0.61 to 4.17 % over India. These aerosols
are transported to the Arctic during all seasons by the lower branch of the
Brewer–Dobson circulation enhancing AOD by 0.017 % to 4.8 %.
Interestingly, a reduction in <span class="inline-formula">SO<sub>2</sub></span> emission over China inhibits the
transport of Indian sulfate aerosols to the Arctic in summer-monsoon and
post-monsoon seasons due to subsidence over northern India. The region of
sulfate aerosol enhancement shows significant warming in the UTLS over northern India, south China (<span class="inline-formula">0.2±0.15</span> to <span class="inline-formula">0.8±0.72</span> K) and the Arctic
(<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>∼</mo><mn mathvariant="normal">1</mn><mo>±</mo><mn mathvariant="normal">0.62</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="51pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="6b8d82df5c23f66fffe20f5420b1c3f8"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-9989-2019-ie00001.svg" width="51pt" height="10pt" src="acp-19-9989-2019-ie00001.png"/></svg:svg></span></span> to <span class="inline-formula">1.6±1.07</span> K). The estimated seasonal
mean direct radiative forcing at the top of the atmosphere (TOA) induced by
the increase in Indian <span class="inline-formula">SO<sub>2</sub></span> emission is <span class="inline-formula">−</span>0.2 to <span class="inline-formula">−</span>1.5 W m<span class="inline-formula"><sup>−2</sup></span> over northern India. The Chinese <span class="inline-formula">SO<sub>2</sub></span> emission reduction
leads to a positive radiative forcing of <span class="inline-formula">∼0.6</span> to 6 W m<span class="inline-formula"><sup>−2</sup></span> over China. The decrease in vertical velocity and
the associated enhanced stability of the upper troposphere in response to
increased Indian <span class="inline-formula">SO<sub>2</sub></span> emissions will likely decrease rainfall over
India.</p> |
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| ISSN: | 1680-7316 1680-7324 |