Simulation of the transport, vertical distribution, optical properties and radiative impact of smoke aerosols with the ALADIN regional climate model during the ORACLES-2016 and LASIC experiments
<p>Estimates of the direct radiative effect (DRE) from absorbing smoke aerosols over the southeast Atlantic Ocean (SAO) require simulation of the microphysical and optical properties of stratocumulus clouds as well as of the altitude and shortwave (SW) optical properties of biomass burning aer...
| Main Authors: | , , , , , , , , , , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-04-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/4963/2019/acp-19-4963-2019.pdf |
| Summary: | <p>Estimates of the direct radiative effect (DRE) from absorbing smoke aerosols
over the southeast Atlantic Ocean (SAO) require simulation of the
microphysical and optical properties of stratocumulus clouds as well as of
the altitude and shortwave (SW) optical properties of biomass burning
aerosols (BBAs). In this study, we take advantage of the large number of
observations acquired during the ObseRvations of Aerosols above Clouds and their
intEractionS (ORACLES-2016) and Layered Atlantic Smoke
Interactions with Clouds (LASIC) projects during
September 2016 and compare them with datasets from the ALADIN-Climate
(Aire Limitée Adaptation dynamique Développement
InterNational) regional model. The model provides a good representation of the liquid water
path but the low cloud fraction is underestimated compared to satellite
data. The modeled total-column smoke aerosol optical depth (AOD) and above-cloud
AOD are consistent (<span class="inline-formula">∼0.7</span> over continental sources and
<span class="inline-formula">∼0.3</span> over the SAO at 550 nm) with the Modern-Era Retrospective analysis for
Research and Applications version 2 (MERRA-2), Ozone Monitoring Instrument (OMI)
or Moderate Resolution Imaging Spectroradiometer (MODIS) data. The
simulations indicate smoke transport over the SAO occurs mainly between 2 and 4 km,
consistent with surface and aircraft lidar observations. The BBA single
scattering albedo is slightly overestimated compared to the Aerosol Robotic
Network (AERONET) and more significantly when compared to Ascension Island
surface observations. The difference could be due to the absence of internal
mixing treatment in the ALADIN-Climate model. The SSA overestimate leads to
an underestimation of the simulated SW radiative heating compared to ORACLES
data. ALADIN-Climate simulates a positive (monthly mean) SW DRE of about
<span class="inline-formula">+6</span> W m<span class="inline-formula"><sup>−2</sup></span> over the SAO (20<span class="inline-formula"><sup>∘</sup></span> S–10<span class="inline-formula"><sup>∘</sup></span> N and
10<span class="inline-formula"><sup>∘</sup></span> W–20<span class="inline-formula"><sup>∘</sup></span> E) at the top of the atmosphere and in all-sky
conditions. Over the<span id="page4964"/> continent, the presence of BBA is shown to significantly
decrease the net surface SW flux, through direct and semi-direct effects,
which is compensated by a decrease (monthly mean) in sensible heat fluxes
(<span class="inline-formula">−25</span> W m<span class="inline-formula"><sup>−2</sup></span>) and surface land temperature (<span class="inline-formula">−1.5</span> <span class="inline-formula"><sup>∘</sup></span>C) over
Angola, Zambia and the Democratic Republic of the Congo, notably. The surface
cooling and the lower tropospheric heating decrease the continental planetary
boundary layer height by about <span class="inline-formula">∼200</span> m.</p> |
|---|---|
| ISSN: | 1680-7316 1680-7324 |