Satellite observations of smoke–cloud–radiation interactions over the Amazon rainforest
<p>The Amazon rainforest routinely experiences intense and long-lived biomass burning events that result in smoke plumes that cover vast regions. The spatial and temporal extent of the plumes and the complex pathways through which they interact with the atmosphere have proved challenging to me...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-04-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/23/4595/2023/acp-23-4595-2023.pdf |
| Summary: | <p>The Amazon rainforest routinely experiences intense and long-lived biomass
burning events that result in smoke plumes that cover vast regions. The
spatial and temporal extent of the plumes and the complex pathways through
which they interact with the atmosphere have proved challenging to measure
for purposes of gaining a representative understanding of smoke impacts on the Amazonian
atmosphere. In this study, we use multiple collocated satellite sensors
on board AQUA and TERRA platforms to study the underlying
smoke–cloud–radiation interactions during the diurnal cycle. An 18-year
time series for both morning and afternoon overpasses is constructed,
providing collocated measurements of aerosol optical depth (AOD; column-integrated aerosol extinction), cloud properties, top-of-atmosphere
radiative fluxes, precipitation, and column water vapour content from
independent sources.</p>
<p>The long-term time series reduces the impact of interannual variability and
provides robust evidence that smoke significantly modifies the Amazonian
atmosphere. Low loadings of smoke (AOD <span class="inline-formula">≤</span> 0.4) enhance convective
activity, cloudiness, and precipitation, but higher loadings (AOD <span class="inline-formula">></span> 0.4) strongly suppress afternoon convection and promote
low-level cloud occurrence. Accumulated precipitation increases with
convective activity but remains elevated under high smoke loadings,
suggesting fewer but more intense convective cells. Contrasting morning and
afternoon cloud responses to smoke are observed, in line with recent
simulations. Observations of top-of-atmosphere radiative fluxes support the
findings and show that the response of low-level cloud properties and
cirrus coverage to smoke results in a pronounced and consistent increase in
top-of-atmosphere outgoing radiation (cooling) of up to 50 W m<span class="inline-formula"><sup>−2</sup></span> for an AOD perturbation of <span class="inline-formula">+</span>1.0.</p>
<p>The results demonstrate that smoke strongly modifies the atmosphere over the Amazon via widespread changes to the cloud field properties. Rapid
adjustments work alongside instantaneous radiative effects to drive a
stronger cooling effect from smoke than previously thought, whilst
contrasting morning and afternoon responses of liquid and ice water paths
highlight a potential method for constraining aerosol impacts on climate.
Increased drought susceptibility, land use change, and deforestation will
have important and widespread impacts on the region over the coming decades.
Based on this analysis, we anticipate that further increases in anthropogenic
fire activity will associated with an overall reduction in regional
precipitation and a negative forcing (cooling) on the Earth's energy
budget.</p> |
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| ISSN: | 1680-7316 1680-7324 |