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1. Isotopic measurements in water vapor, precipitation, and seawater during EUREC ⁴ A

   https://doi.org/10.5194/essd-15-465-2023  

   Bailey, Adriana; Aemisegger, Franziska; Villiger, Leonie; Los, Sebastian A.; Reverdin, Gilles; Quiñones Meléndez, Estefanía; Acquistapace, Claudia; Baranowski, Dariusz B.; Böck, Tobias; Bony, Sandrine; et al (January 2023, Earth System Science Data)

   Abstract. In early 2020, an international team set out to investigatetrade-wind cumulus clouds and their coupling to the large-scale circulationthrough the field campaign EUREC4A: ElUcidating the RolE ofClouds-Circulation Coupling in ClimAte. Focused on the western tropicalAtlantic near Barbados, EUREC4A deployed a number of innovativeobservational strategies, including a large network of water isotopicmeasurements collectively known as EUREC4A-iso, to study the tropicalshallow convective environment. The goal of the isotopic measurements was toelucidate processes that regulate the hydroclimate state – for example, byidentifying moisture sources, quantifying mixing between atmospheric layers,characterizing the microphysics that influence the formation and persistenceof clouds and precipitation, and providing an extra constraint in theevaluation of numerical simulations. During the field experiment,researchers deployed seven water vapor isotopic analyzers on two aircraft,on three ships, and at the Barbados Cloud Observatory (BCO). Precipitationwas collected for isotopic analysis at the BCO and from aboard four ships.In addition, three ships collected seawater for isotopic analysis. All told,the in situ data span the period 5 January–22 February 2020 andcover the approximate area 6 to 16∘ N and 50 to 60∘ W,with water vapor isotope ratios measured from a few meters above sea levelto the mid-free troposphere and seawater samples spanning the ocean surfaceto several kilometers depth. This paper describes the full EUREC4A isotopic in situ data collection– providing extensive information about sampling strategies and datauncertainties – and also guides readers to complementary remotely sensedwater vapor isotope ratios. All field data have been made publicly availableeven if they are affected by known biases, as is the case for high-altitudeaircraft measurements, one of the two BCO ground-based water vapor timeseries, and select rain and seawater samples from the ships. Publication ofthese data reflects a desire to promote dialogue around improving waterisotope measurement strategies for the future. The remaining, high-qualitydata create unprecedented opportunities to close water isotopic budgets andevaluate water fluxes and their influence on cloudiness in the trade-windenvironment. The full list of dataset DOIs and notes on data quality flagsare provided in Table 3 of Sect. 5 (“Data availability”). 

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2. African smoke particles act as cloud condensation nuclei in the wintertime tropical North Atlantic boundary layer over Barbados

   https://doi.org/10.5194/acp-23-981-2023  

   Royer, Haley M.; Pöhlker, Mira L.; Krüger, Ovid; Blades, Edmund; Sealy, Peter; Lata, Nurun Nahar; Cheng, Zezhen; China, Swarup; Ault, Andrew P.; Quinn, Patricia K.; et al (January 2023, Atmospheric Chemistry and Physics)

   Abstract. The number concentration and properties of aerosol particles serving ascloud condensation nuclei (CCN) are important for understanding cloudproperties, including in the tropical Atlantic marine boundary layer (MBL), where marine cumulus clouds reflect incoming solar radiation and obscure thelow-albedo ocean surface. Studies linking aerosol source, composition, andwater uptake properties in this region have been conducted primarily duringthe summertime dust transport season, despite the region receiving a varietyof aerosol particle types throughout the year. In this study, we comparesize-resolved aerosol chemical composition data to the hygroscopicityparameter κ derived from size-resolved CCN measurements made duringthe Elucidating the Role of Clouds–Circulation Coupling in Climate (EUREC4A) and Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC) campaigns from January to February 2020. Weobserved unexpected periods of wintertime long-range transport of Africansmoke and dust to Barbados. During these periods, the accumulation-mode aerosol particle and CCN number concentrations as well as the proportions ofdust and smoke particles increased, whereas the average κ slightlydecreased (κ=0.46±0.10) from marine backgroundconditions (κ=0.52±0.09) when the submicron particles were mostly composed of marine organics and sulfate. Size-resolved chemicalanalysis shows that smoke particles were the major contributor to theaccumulation mode during long-range transport events, indicating that smokeis mainly responsible for the observed increase in CCN numberconcentrations. Earlier studies conducted at Barbados have mostly focused onthe role of dust on CCN, but our results show that aerosol hygroscopicity and CCN number concentrations during wintertime long-range transport events over the tropical North Atlantic are also affected by African smoke. Ourfindings highlight the importance of African smoke for atmospheric processesand cloud formation over the Caribbean. 

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3. Using EUREC4A/ATOMIC field campaign data to improve trade wind regimes in the Community Atmosphere Model

   https://doi.org/10.5194/gmd-17-1627-2024  

   Graap, Skyler; Zarzycki, Colin M (January 2024, Geoscientific Model Development)

   Improving the prediction of clouds in shallow-cumulus regimes via turbulence parameterization in the planetary boundary layer (PBL) will likely increase the global skill of global climate models (GCMs) because this cloud regime is common over tropical oceans where low-cloud fraction has a large impact on Earth's radiative budget. This study attempts to improve the prediction of PBL structure in tropical trade wind regimes in the Community Atmosphere Model (CAM) by updating its formulation of momentum flux in CLUBB (Cloud Layers Unified by Binormals), which currently does not by default allow for upgradient momentum fluxes. Hindcast CAM output from custom CLUBB configurations which permit countergradient momentum fluxes are compared to in situ observations from weather balloons collected during the ElUcidating the RolE of Cloud–Circulation Coupling in ClimAte and Atlantic Tradewind Ocean–Atmosphere Mesoscale Interaction Campaign (EUREC4A/ATOMIC) field campaign in the tropical Atlantic in early 2020. Comparing a version with CAM–CLUBB with a prognostic treatment of momentum fluxes results in vertical profiles that better match large-eddy simulation results. Countergradient fluxes are frequently simulated between 950 and 850 hPa over the EUREC4A/ATOMIC period in CAM–CLUBB. Further modification to the planetary boundary layer (PBL) parameterization by implementing a more generalized calculation of the turbulent length scale reduces model bias and root mean squared error (RMSE) relative to sounding data when coupled with the prognostic momentum configuration. Benefits are also seen in the diurnal cycle, although more systematic model errors persist. A cursory budget analysis suggests the buoyant production of momentum fluxes, both above and below the jet maximum, significantly contributes to the frequency and depth of countergradient vertical momentum fluxes in the study region. This paper provides evidence that higher-order turbulence parameterizations may offer pathways for improving the simulation of trade wind regimes in global models, particularly when evaluated in a process study framework. 

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4. EUREC⁴A

   https://doi.org/10.5194/essd-13-4067-2021  

   Stevens, Bjorn; Bony, Sandrine; Farrell, David; Ament, Felix; Blyth, Alan; Fairall, Christopher; Karstensen, Johannes; Quinn, Patricia K.; Speich, Sabrina; Acquistapace, Claudia; et al (January 2021, Earth System Science Data)

   null (Ed.)

   Abstract. The science guiding the EUREC4A campaign and its measurements is presented. EUREC4A comprised roughly 5 weeks of measurements in the downstream winter trades of the North Atlantic – eastward and southeastward of Barbados. Through its ability to characterize processes operating across a wide range of scales, EUREC4A marked a turning point in our ability to observationally study factors influencing clouds in the trades, how they will respond to warming, and their link to other components of the earth system, such as upper-ocean processes or the life cycle of particulate matter. This characterization was made possible by thousands (2500) of sondes distributed to measure circulations on meso- (200 km) and larger (500 km) scales, roughly 400 h of flight time by four heavily instrumented research aircraft; four global-class research vessels; an advanced ground-based cloud observatory; scores of autonomous observing platforms operating in the upper ocean (nearly 10 000 profiles), lower atmosphere (continuous profiling), and along the air–sea interface; a network of water stable isotopologue measurements; targeted tasking of satellite remote sensing; and modeling with a new generation of weather and climate models. In addition to providing an outline of the novel measurements and their composition into a unified and coordinated campaign, the six distinct scientific facets that EUREC4A explored – from North Brazil Current rings to turbulence-induced clustering of cloud droplets and its influence on warm-rain formation – are presented along with an overview of EUREC4A's outreach activities, environmental impact, and guidelines for scientific practice. Track data for all platforms are standardized and accessible at https://doi.org/10.25326/165 (Stevens, 2021), and a film documenting the campaign is provided as a video supplement. 

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5. Measurements from the RV <i>Ronald H. Brown</i> and related platforms as part of the Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC)

   https://doi.org/10.5194/essd-13-1759-2021  

   Quinn, Patricia K.; Thompson, Elizabeth J.; Coffman, Derek J.; Baidar, Sunil; Bariteau, Ludovic; Bates, Timothy S.; Bigorre, Sebastien; Brewer, Alan; de Boer, Gijs; de Szoeke, Simon P.; et al (January 2021, Earth System Science Data)

   The Atlantic Tradewind Ocean-Atmosphere Mesoscale Interaction Campaign (ATOMIC) took place from 7 January to 11 July 2020 in the tropical North Atlantic between the eastern edge of Barbados and 51∘ W, the longitude of the Northwest Tropical Atlantic Station (NTAS) mooring. Measurements were made to gather information on shallow atmospheric convection, the effects of aerosols and clouds on the ocean surface energy budget, and mesoscale oceanic processes. Multiple platforms were deployed during ATOMIC including the NOAA RV Ronald H. Brown (RHB) (7 January to 13 February) and WP-3D Orion (P-3) aircraft (17 January to 10 February), the University of Colorado's Robust Autonomous Aerial Vehicle-Endurant Nimble (RAAVEN) uncrewed aerial system (UAS) (24 January to 15 February), NOAA- and NASA-sponsored Saildrones (12 January to 11 July), and Surface Velocity Program Salinity (SVPS) surface ocean drifters (23 January to 29 April). The RV Ronald H. Brown conducted in situ and remote sensing measurements of oceanic and atmospheric properties with an emphasis on mesoscale oceanic–atmospheric coupling and aerosol–cloud interactions. In addition, the ship served as a launching pad for Wave Gliders, Surface Wave Instrument Floats with Tracking (SWIFTs), and radiosondes. Details of measurements made from the RV Ronald H. Brown, ship-deployed assets, and other platforms closely coordinated with the ship during ATOMIC are provided here. These platforms include Saildrone 1064 and the RAAVEN UAS as well as the Barbados Cloud Observatory (BCO) and Barbados Atmospheric Chemistry Observatory (BACO). Inter-platform comparisons are presented to assess consistency in the data sets. Data sets from the RV Ronald H. Brown and deployed assets have been quality controlled and are publicly available at NOAA's National Centers for Environmental Information (NCEI) data archive (https://www.ncei.noaa.gov/archive/accession/ATOMIC-2020, last access: 2 April 2021). Point-of-contact information and links to individual data sets with digital object identifiers (DOIs) are provided herein. 

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