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Shipboard and Unmanned Aerial System (UAS) measurements of aerosol properties in the Coupled Ocean-Atmosphere System of the Northwest Tropical Atlantic

We propose to participate in the ATOMIC field campaign aboard the RV Ronald H. Brown in January/February 2020. Our objective is to improve the understanding of the effects of aerosol particles on clouds and radiation transfer over the Northwest Tropical Atlantic and the related impacts on the upper ocean. Aerosols in this region have both ocean-derived (sea spray and dimethylsulfide) and continental sources (European pollution, African dust, and biomass burning). Our hypothesis is that the temporal variability of atmospheric aerosols, through aerosol-cloud interactions and direct aerosol light scattering and absorption, influence the temporal variability in net radiation reaching the ocean surface and sea surface temperature. We will test this hypothesis with measurements of aerosol properties in the marine boundary layer on the ship and vertically and regionally with a UAS. This proposal directly addresses the call for proposals to study lower atmospheric boundary layer processes and their influence on the ocean. This work contributes to NOAA’s long term climate goal to strengthen scientific understanding of climate.
We will be using the shipboard measurements that have been deployed on many field campaigns (VOCALS, DYNAMO, NEAQS, TexAQS, CalNex) and the UAS aerosol payload that has been deployed in Svalbard, Norway. The shipboard measurements will include aerosol number-size distributions, chemical analysis, cloud condensation nuclei (CCN) potential at supersaturations in the range of 0.1% to 2%, aerosol light scattering and absorption coefficients, and aerosol optical depth. The UAS measurements will include particle number concentration, aerosol absorption coefficient, filter collection for aerosol chemistry (Bates et al., 2013), aerosol size distributions from 130 to 3000 nm (Gao et al., 2016), optical depth measurements from a miniature scanning sun photometer (Murphy et al., 2016), cloud droplet number size distributions (CDP, DMT, Boulder, CO), temperature, and RH. The UAS will also be equipped with a flux measurement system (miniFLux) for the measurement of atmospheric thermodynamic state, turbulence, three dimensional winds, and surface and sky infra-red temperature (Fairall et al., in a separate proposal to this announcement).
The measured aerosol and cloud properties will be regressed against net radiation and SST measured on the ship to test our hypothesis. The time series of these parameters will be analyzed in the context of the larger set of meteorological, oceanographic, and satellite data to investigate the processes and cause-effect relationships between aerosols, radiative transfer, cloud physics, precipitation, and surface ocean properties. Multivariate statistical analysis will be used to determine relationships between aerosol parameters (e.g., concentration, size distribution, composition) and cloud physics parameters, (e.g., thermodynamic profiles, cloud albedo and effective radius, vertical mixing, cloud base, cloud top, and precipitation rate). The products, time series of aerosol parameters and derived empirical relationships, will provide input to the ATOMIC/EUREC4A-OA and EUREC4A modeling communities. The final data sets will be archived on the PMEL Atmospheric Chemistry data server ( and NOAA PMEL’s ERDDAP Data Server.

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