The response of cloud processes to an aerosol
perturbation is one of the largest uncertainties in the anthropogenic
forcing of the climate. It occurs at a variety of
timescales, from the near-instantaneous Twomey effect to
the longer timescales required for cloud adjustments. Understanding
the temporal evolution of cloud properties following
an aerosol perturbation is necessary to interpret the results of
so-called “natural experiments” from a known aerosol source
such as a ship or industrial site. This work uses reanalysis
wind fields and ship emission information matched to observations
of ship tracks to measure the timescales of cloud
responses to aerosol in instantaneous (or“snapshot”) images
taken by polar-orbiting satellites.
As in previous studies, the local meteorological environment
is shown to have a strong impact on the occurrence and
properties of ship tracks, but there is a strong time dependence
in their properties. The largest droplet number concentration
(Nd) responses are found within 3 h of emission,
while cloud adjustments continue to evolve over periods of
10 h or more. Cloud fraction is increased within the early
life of ship tracks, with the formation of ship tracks in otherwise
clear skies indicating that around 5 %–10%of clear-sky
cases in this region may be aerosol-limited.
The liquid water path (LWP) enhancement and the Nd–
LWP sensitivity are also time dependent and strong functions
of the background cloud and meteorological state. The nearinstant
response of the LWP within ship tracks may be evidence
of a bias in estimates of the LWP response to aerosol
derived from natural experiments. These results highlight
the importance of temporal development and the background cloud field for quantifying the aerosol impact on clouds, even
in situations where the aerosol perturbation is clear.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:74863 |
| Date | 11 May 2021 |
| Creators | Gryspeerdt, Edward, Goren, Tom, Smith, Tristan W. P. |
| Publisher | Copernicus Publications |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:article, info:eu-repo/semantics/article, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | 1680-7316, https://doi.org/10.5194/acp-21-6093-2021 |
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