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| Titel |
Rain chemistry and cloud composition and microphysics in a Caribbean tropical montane cloud forest under the influence of African dust |
| VerfasserIn |
Elvis Torres-Delgado, Carlos J. Valle-Diaz, Darrel Baumgardner, William H. McDowell, Grizelle González, Olga L. Mayol-Bracero |
| 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 |
250111159
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| Publikation (Nr.) |
 EGU/EGU2015-11245.pdf |
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| Zusammenfassung |
| It is known that huge amounts of mineral dust travels thousands of kilometers from the
Sahara and Sahel regions in Africa over the Atlantic Ocean reaching the Caribbean, northern
South America and southern North America; however, not much is understood about how the
aging process that takes place during transport changes dust properties, and how the presence
of this dust affects cloud’s composition and microphysics. This African dust reaches the
Caribbean region mostly in the summer time. In order to improve our understanding of the
role of long-range transported African dust (LRTAD) in cloud formation processes in a
tropical montane cloud forest (TMCF) in the Caribbean region we had field campaigns
measuring dust physical and chemical properties in summer 2013, as part of the Puerto
Rico African Dust and Cloud Study (PRADACS), and in summer 2014, as a part
of the Luquillo Critical Zone Observatory (LCZO) and in collaboration with the
Saharan Aerosol Long-Range Transport and Aerosol-Cloud-Interaction Experiment
(SALTRACE). Measurements were performed at the TMCF of Pico del Este (PE,
1051 masl) and at the nature reserve of Cabezas de San Juan (CSJ, 60 masl). In
both stations we monitored meteorological parameters (e.g., temperature, wind
speed, wind direction). At CSJ, we measured light absorption and scattering at three
wavelengths (467, 528 and 652 nm). At PE we collected cloud and rainwater and
monitored cloud microphysical properties (e.g., liquid water content, droplet size
distribution, droplet number concentration, effective diameter and median volume
diameter). Data from aerosol models, satellites, and back-trajectories were used
together with CSJ measurements to classify air masses and samples collected at PE
in the presence or absence of dust. Soluble ions, insoluble trace metals, pH and
conductivity were measured for cloud and rainwater. Preliminary results for summer 2013
showed that in the presence of LRTAD (1) the average conductivity of cloud water
was almost twice (81.1 μS/cm) as that in the absence of LRTAD (47.7 μS/cm),
(2) the average conductivity in rainwater was slightly higher (15.0 μS/cm vs 12.8
μS/cm), and (3) the average pH was slightly higher for both cloud and rainwater
samples (average of 6.41 for cloud water and 6.37 for rainwater). Detailed results on
the chemical composition (water-soluble ions, trace metals, total organic carbon
and total nitrogen) of cloud and rainwater, cloud microphysics, and on how these
properties are affected in the presence of dust events will be presented at the meeting. |
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