Search for: All records

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”). 

Abstract Atmospheric ice nucleating particles (INPs) influence global climate by altering cloud formation, lifetime, and precipitation efficiency. The role of secondary organic aerosol (SOA) material as a source of INPs in the ambient atmosphere has not been well defined. Here, we demonstrate the potential for biogenic SOA to activate as depositional INPs in the upper troposphere by combining field measurements with laboratory experiments. Ambient INPs were measured in a remote mountaintop location at –46 °C and an ice supersaturation of 30% with concentrations ranging from 0.1 to 70 L –1 . Concentrations of depositional INPs were positively correlated with the mass fractions and loadings of isoprene-derived secondary organic aerosols. Compositional analysis of ice residuals showed that ambient particles with isoprene-derived SOA material can act as depositional ice nuclei. Laboratory experiments further demonstrated the ability of isoprene-derived SOA to nucleate ice under a range of atmospheric conditions. We further show that ambient concentrations of isoprene-derived SOA can be competitive with other INP sources. This demonstrates that isoprene and potentially other biogenically-derived SOA materials could influence cirrus formation and properties.