Quantifying the effect of aerosol on vertical velocity and effective terminal velocity in warm convective clouds
Better representation of cloud–aerosol interactions is crucial for an improved understanding of natural and anthropogenic effects on climate. Recent studies have shown that the overall aerosol effect on warm convective clouds is non-monotonic. Here, we reduce the system's dimensions to its...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-05-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/18/6761/2018/acp-18-6761-2018.pdf |
| Summary: | Better representation of cloud–aerosol interactions is crucial for an
improved understanding of natural and anthropogenic effects on climate.
Recent studies have shown that the overall aerosol effect on warm convective
clouds is non-monotonic. Here, we reduce the system's dimensions to its
center of gravity (COG), enabling distillation and simplification of the
overall trend and its temporal evolution. Within the COG framework, we show
that the aerosol effects are nicely reflected by the interplay of the
system's characteristic vertical velocities, namely the updraft (<i>w</i>) and the
effective terminal velocity (<i>η</i>). The system's vertical velocities can be
regarded as a sensitive measure for the evolution of the overall trends with
time. Using a bin-microphysics cloud-scale model, we analyze and follow the
trends of the aerosol effect on the magnitude and timing of <i>w</i> and <i>η</i>,
and therefore the overall vertical COG velocity. Large eddy simulation (LES)
model runs are used to upscale the analyzed trends to the cloud-field scale
and study how the aerosol effects on the temporal evolution of the field's
thermodynamic properties are reflected by the interplay between the two
velocities. Our results suggest that aerosol effects on air vertical motion
and droplet mobility imply an effect on the way in which water is distributed
along the atmospheric column. Moreover, the interplay between <i>w</i> and <i>η</i>
predicts the overall trend of the field's thermodynamic instability. These
factors have an important effect on the local energy balance. |
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| ISSN: | 1680-7316 1680-7324 |