The Barbados Cloud Observatory: Anchoring Investigations of Clouds and Circulation on the Edge of the ITCZ

Stevens, Björn; Farrell, D. A.; Hirsch, Lutz; Jansen, Friedhelm; Nuijens, Louise; Serikov, Ilya; Brügmann, Björn; Forde, Marvin; Linné, Holger; Lonitz, Katrin; Prospero, Joseph M.

doi:10.1175/bams-d-14-00247.1

Cited by 166 publications

(223 citation statements)

References 67 publications

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“…The TROPOS photometer was operated from June 2013 to July 2014 (with an interruption from October 2013 to February 2014 caused by a damage of the sun photometer). Another photometer of AERONET is installed at Ragged Point (east coast of Barbados) in the vicinity of the Barbados Cloud Observatory (Stevens et al, 2016). The Ragged Point photometer has performed measurements since 2007.…”

Section: Aeronet Photometersmentioning

confidence: 99%

Triple-wavelength depolarization-ratio profiling of Saharan dust over Barbados during SALTRACE in 2013 and 2014

et al. 2017

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Abstract. Triple-wavelength polarization lidar measurements in Saharan dust layers were performed at Barbados (13.1 • N, 59.6 • W), 5000-8000 km west of the Saharan dust sources, in the framework of the Saharan Aerosol Longrange Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE-1, June-July 2013, SALTRACE-3, June-July 2014). Three case studies are discussed. High quality was achieved by comparing the dust linear depolarization ratio profiles measured at 355, 532, and 1064 nm with respective dual-wavelength (355, 532 nm) depolarization ratio profiles measured with a reference lidar. A unique case of long-range transported dust over more than 12 000 km is presented. Saharan dust plumes crossing Barbados were measured with an airborne triple-wavelength polarization lidar over Missouri in the midwestern United States 7 days later. Similar dust optical properties and depolarization features were observed over both sites indicating almost unchanged dust properties within this 1 week of travel from the Caribbean to the United States. The main results of the triple-wavelength polarization lidar observations in the Caribbean in the summer seasons of 2013 and 2014 are summarized. On average, the particle linear depolarization ratios for aged Saharan dust were found to be 0.252 ± 0.030 at 355 nm, 0.280 ± 0.020 at 532 nm, and 0.225 ± 0.022 at 1064 nm after approximately 1 week of transport over the tropical Atlantic. Based on published simulation studies we present an attempt to explain the spectral features of the depolarization ratio of irregularly shaped mineral dust particles, and conclude that most of the irregularly shaped coarse-mode dust particles (particles with diameters > 1 µm) have sizes around 1.5-2 µm. The SALTRACE results are also set into the context of the SAMUM-1 (Morocco, 2006) and SAMUM-2 (Cabo Verde, 2008) depolarization ratio studies. Again, only minor changes in the dust depolarization characteristics were observed on the way from the Saharan dust sources towards the Caribbean.

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Section: Aeronet Photometersmentioning

confidence: 99%

Triple-wavelength depolarization-ratio profiling of Saharan dust over Barbados during SALTRACE in 2013 and 2014

et al. 2017

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“…3): the Barbados Cloud Observatory (BCO, Stevens et al 2016) and a network of research vessels (RVs). Applications for ship measurement time from Germany (Meteor and Maria S. Merian), France (Atalante), The Netherlands (Pelagia), the USA and Spain are pending.…”

Section: Surface and Ship-based Observationsmentioning

confidence: 99%

“…Their response to global warming is thus critical for global-mean cloud feedbacks, and actually it is their differing response to warming that explains most of the spread of climate sensitivity across climate models (Bony et al 2004;Bony and Dufresne 2005;Webb et al 2006;Medeiros et al 2008;Vial et al 2013;Boucher et al 2013;Medeiros et al 2015). Model diversity in the strength of the vertical mixing of water vapour within the first few kilometres above the ocean surface (in association with both convective and large-scale circulations) is thought to explain half of the variance in climate sensitivity estimates across models (Sherwood et al 2014): the lower-tropospheric mixing dehydrates the cloud layer near its base at an increasing rate as the climate warms and this rate scales with the mixing strength in the current climate (Sherwood et al (2014); Gettelman et al (2012); Tomassini et al (2015); Brient et al (2016); Stevens et al (2016); Vial et al (2016), Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

“…1 Vertical profiles of the low-cloud fraction, and of its response to global warming, predicted by two general circulation models (MPI and IPSL) in the trade-wind cumulus regime. For each model, results are shown for two versions differing only by their representation of lower-tropospheric mixing (after Stevens et al 2016;Vial et al 2016) convection and circulation, and their role in climate change: How strong is the convective mixing in regimes of shallow cumulus and how much does it couple to surface turbulent fluxes, radiative effects and water vapour? Is the cloud-base fraction of trade-wind cumuli insensitive to variations in convective mixing and large-scale circulations?…”

Section: Introductionmentioning

confidence: 99%

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EUREC4A: A Field Campaign to Elucidate the Couplings Between Clouds, Convection and Circulation

et al. 2017

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Trade-wind cumuli constitute the cloud type with the highest frequency of occurrence on Earth, and it has been shown that their sensitivity to changing environmental conditions will critically influence the magnitude and pace of future global warming. Research over the last decade has pointed out the importance of the interplay between clouds, convection and circulation in controling this sensitivity. 123Surv Geophys (2017) 38:1529-1568 https://doi.org/10.1007/s10712-017-9428-0 cumuli at cloud base is very sensitive to changes in environmental conditions, while process models suggest the opposite. To understand and resolve this contradiction, we propose to organize a field campaign aimed at quantifying the physical properties of tradecumuli (e.g., cloud fraction and water content) as a function of the large-scale environment. Beyond a better understanding of clouds-circulation coupling processes, the campaign will provide a reference data set that may be used as a benchmark for advancing the modelling and the satellite remote sensing of clouds and circulation. It will also be an opportunity for complementary investigations such as evaluating model convective parameterizations or studying the role of ocean mesoscale eddies in air-sea interactions and convective organization.

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“…NARVAL-2 consisted of roughly twice as many flight hours distributed over ten flights in, around, and across the ITCZ. For NARVAL-1, the configuration of HALO is described by Stevens et al (2016). For NARVAL-2, the configuration was similar.…”

Section: Airborne Measurements and The Barbados Cloud Observatorymentioning

confidence: 99%

Structure and Dynamical Influence of Water Vapor in the Lower Tropical Troposphere

et al. 2017

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In situ, airborne and satellite measurements are used to characterize the structure of water vapor in the lower tropical troposphere-below the height, z Ã ; of the triple-point isotherm, T Ã : The measurements are evaluated in light of understanding of how lowertropospheric water vapor influences clouds, convection and circulation, through both radiative and thermodynamic effects. Lower-tropospheric water vapor, which concentrates in the first few kilometers above the boundary layer, controls the radiative cooling profile of the boundary layer and lower troposphere. Elevated moist layers originating from a preferred level of convective detrainment induce a profile of radiative cooling that drives circulations which reinforce such features. A theory for this preferred level of cumulus termination is advanced, whereby the difference between T Ã and the temperature at which primary ice forms gives a 'first-mover advantage' to glaciating cumulus convection, thereby concentrating the regions of the deepest convection and leading to more clouds and moisture near the triple point. A preferred level of convective detrainment near T Ã implies relative humidity reversals below zÃ which are difficult to identify using retrievals from satellite-borne microwave and infrared sounders. Isotopologues retrievals provide a hint of such features and their ability to constrain the structure of the vertical humidity profile merits further study. Nonetheless, it will likely remain challenging to resolve dynamically -017-9420-8 important aspects of the vertical structure of water vapor from space using only passive sensors.

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The Barbados Cloud Observatory: Anchoring Investigations of Clouds and Circulation on the Edge of the ITCZ

Cited by 166 publications

References 67 publications

Triple-wavelength depolarization-ratio profiling of Saharan dust over Barbados during SALTRACE in 2013 and 2014

Triple-wavelength depolarization-ratio profiling of Saharan dust over Barbados during SALTRACE in 2013 and 2014

EUREC4A: A Field Campaign to Elucidate the Couplings Between Clouds, Convection and Circulation

Structure and Dynamical Influence of Water Vapor in the Lower Tropical Troposphere

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