Observations and hypotheses related to low to middle free tropospheric aerosol, water vapor and altocumulus cloud layers within convective weather regimes: a SEAC<sup>4</sup>RS case study
<p>The NASA Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC<span class="inline-formula"><sup>4</sup></span>RS) project included goals related to aerosol particle life cycle in convective regimes. Using th...
Main Authors: | , , , , , , , , , , , , , , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2019-09-01
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Series: | Atmospheric Chemistry and Physics |
Online Access: | https://www.atmos-chem-phys.net/19/11413/2019/acp-19-11413-2019.pdf |
Summary: | <p>The NASA Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC<span class="inline-formula"><sup>4</sup></span>RS) project included goals related
to aerosol particle life cycle in convective regimes. Using the University of
Wisconsin High Spectral Resolution Lidar system at Huntsville, Alabama, USA, and the NASA DC-8 research aircraft, we investigate the altitude dependence
of aerosol, water vapor and Altocumulus (Ac) properties in the free
troposphere from a canonical 12 August 2013 convective storm case as a
segue to a presentation of a mission-wide analysis. It stands to reason that
any moisture detrainment from convection must have an associated aerosol
layer. Modes of covariability between aerosol, water vapor and Ac are
examined relative to the boundary layer entrainment zone, 0 <span class="inline-formula"><sup>∘</sup></span>C level,
and anvil, a region known to contain Ac clouds and a complex aerosol
layering structure (Reid et al., 2017). Multiple aerosol layers in regions
warmer than 0 <span class="inline-formula"><sup>∘</sup></span>C were observed within the planetary boundary layer entrainment zone. At
0 <span class="inline-formula"><sup>∘</sup></span>C there is a proclivity for aerosol and water vapor detrainment from
storms, in association with melting level Ac shelves. Finally, at
temperatures colder than 0 <span class="inline-formula"><sup>∘</sup></span>C, weak aerosol layers were identified above Cumulus congestus tops (<span class="inline-formula">∼0</span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>∼</mo><mo>-</mo><mn mathvariant="normal">20</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="8d516c7f10428f65837c03e018b98af2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-19-11413-2019-ie00001.svg" width="32pt" height="10pt" src="acp-19-11413-2019-ie00001.png"/></svg:svg></span></span> <span class="inline-formula"><sup>∘</sup></span>C). Stronger aerosol signals return in association with anvil
outflow. In situ data suggest that detraining particles undergo aqueous-phase or heterogeneous chemical or microphysical transformations, while at
the same time larger particles are being scavenged at higher altitudes
leading to enhanced nucleation. We conclude by discussing hypotheses
regarding links to aerosol emissions and potential indirect effects on Ac
clouds.</p> |
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ISSN: | 1680-7316 1680-7324 |