Abstract
Abstract. The CARRIBA (Cloud, Aerosol, Radiation and tuRbulence in the trade wInd regime over BArbados) project, focused on high resolution and collocated measurements of thermodynamic, turbulent, microphysical, and radiative properties of trade wind cumuli over Barbados, is introduced. The project is based on two one-month field campaigns in November 2010 (climatic wet season) and April 2011 (climatic dry season). Observations are based on helicopter-borne and ground-based measurements in an area of 100 km2 off the coast of Barbados. CARRIBA is accompanied by long-term observations at the Barbados Cloud Observatory located at the East coast of Barbados since early in 2010 and which provides a longer-term context for the CARRIBA measurements. The deployed instrumentation and sampling strategy are presented together with a classification of the meteorological conditions. The two campaigns were influenced by different air masses advected from the Caribbean area, the Atlantic Ocean, and the African continent which led to distinct aerosol conditions. Pristine conditions with low aerosol particle number concentrations of ~100 cm3 were alternating with periods influenced by Saharan dust or aerosol from biomass burning resulting in comparably high number concentrations of ~ 500 cm3. The biomass burning aerosol was originating from both the Caribbean area and Africa. The shallow cumulus clouds responded to the different aerosol conditions with a wide range of mean droplet sizes and number concentrations. Two days with different aerosol and cloud microphysical properties but almost identical meteorological conditions have been analyzed in detail. The differences in the droplet number concentration and droplet sizes appear not to show any significant change for turbulent cloud mixing, but the relative roles of droplet inertia and sedimentation in initiating coalescence, as well as the cloud reflectivity, do change substantially.
Highlights
Introduction and motivationShallow cumulus clouds are a common feature of the trade wind regions
The typical amount of precipitation in November is 170 mm compared with 60 mm in April, based on a 30 yr record measured at the airport
This article provides a general introduction to the two CARRIBA campaigns performed in the climatic wet season (November 2010) and dry season (April 2011) on and nearby Barbados
Summary
Shallow cumulus clouds are a common feature of the trade wind regions (hereafter called the trades). The CARRIBA-project (Cloud, Aerosol, Radiation and tuRbulence in the trade wInd regime over BArbados) was initiated by the Leibniz Institute for Tropospheric Research (TROPOS). Beside fundamental questions like how large droplets form in a turbulent shallow cumulus, the focus is on the question of how the clouds respond to different aerosol conditions observed during the two campaigns. The consequences of the different cloud properties for cloud-turbulence interaction and radiation effects are discussed This example nicely illustrates the unique possibilities of our deployed measurement setup and helps motivate the project as a whole, and the sampling strategies that were employed
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