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| Titel |
Study of Droplet Activation in Thin Clouds Using Ground-based Raman Lidar and Ancillary Remote Sensors |
| VerfasserIn |
Marco Rosoldi, Fabio Madonna, Pilar Guma Claramunt, Gelsomina Pappalardo |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250112974
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| Publikation (Nr.) |
 EGU/EGU2015-13165.pdf |
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| Zusammenfassung |
| Studies on global climate change show that the effects of aerosol-cloud interactions (ACI) on
the Earth’s radiation balance and climate, also known as indirect aerosol effects, are the most
uncertain among all the effects involving the atmospheric constituents and processes (Stocker
et al., IPCC, 2013). Droplet activation is the most important and challenging process in the
understanding of ACI. It represents the direct microphysical link between aerosols and clouds
and it is probably the largest source of uncertainty in estimating indirect aerosol
effects.
An accurate estimation of aerosol-clouds microphysical and optical properties in
proximity and within the cloud boundaries represents a good frame for the study of droplet
activation. This can be obtained by using ground-based profiling remote sensing
techniques.
In this work, a methodology for the experimental investigation of droplet activation, based
on ground-based multi-wavelength Raman lidar and Doppler radar technique, is
presented. The study is focused on the observation of thin liquid water clouds,
which are low or midlevel super-cooled clouds characterized by a liquid water path
(LWP) lower than about 100 gm-2(Turner et al., 2007). These clouds are often
optically thin, which means that ground-based Raman lidar allows the detection of the
cloud top and of the cloud structure above. Broken clouds are primarily inspected to
take advantage of their discontinuous structure using ground based remote sensing.
Observations are performed simultaneously with multi-wavelength Raman lidars, a cloud
Doppler radar and a microwave radiometer at CIAO (CNR-IMAA Atmospheric
Observatory: www.ciao.imaa.cnr.it), in Potenza, Southern Italy (40.60N, 15.72E, 760 m
a.s.l.).
A statistical study of the variability of optical properties and humidity in the transition
from cloudy regions to cloud-free regions surrounding the clouds leads to the identification of
threshold values for the optical properties, enabling the discrimination between clouds and
cloudless regions.
Furthermore, a statistical study of the Doppler radar moments allows to retrieve droplet
size and vertical velocities close to the cloud base. First evidences of a correlation
between updrafts and downdrafts and aerosol effective radius have been found. |
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