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Published April 16, 2018 | Published + Accepted Version + Supplemental Material
Journal Article Open

Characteristic Vertical Profiles of Cloud Water Composition in Marine Stratocumulus Clouds and Relationships With Precipitation


This study uses airborne cloud water composition measurements to characterize the vertical structure of air‐equivalent mass concentrations of water‐soluble species in marine stratocumulus clouds off the California coast. A total of 385 cloud water samples were collected in the months of July and August between 2011 and 2016 and analyzed for water‐soluble ionic and elemental composition. Three characteristic profiles emerge: (i) a reduction of concentration with in‐cloud altitude for particulate species directly emitted from sources below cloud without in‐cloud sources (e.g., Cl^− and Na^+), (ii) an increase of concentration with in‐cloud altitude (e.g., NO_2− and formate), and (iii) species exhibiting a peak in concentration in the middle of cloud (e.g., non–sea‐salt SO_4^2−, NO_3−, and organic acids). Vertical profiles of rainout parameters such as loss frequency, lifetime, and change in concentration with respect to time show that the scavenging efficiency throughout the cloud depth depends strongly on the thickness of the cloud. Thin clouds exhibit a greater scavenging loss frequency at cloud top, while thick clouds have a greater scavenging loss frequency at cloud base. The implications of these results for treatment of wet scavenging in models are discussed.

Additional Information

© 2018 American Geophysical Union. Received 17 OCT 2017; Accepted 13 FEB 2018; Accepted article online 21 FEB 2018; Published online 13 APR 2018. All data used in this work can be found in the Figshare database (Sorooshian et al., 2017). This work was funded by Office of Naval Research grants N00014‐10‐1‐0811, N00014‐11‐1‐0783, N00014‐10‐1‐0200, N00014‐04‐1‐0118, and N00014‐16‐1‐2567. A. MacDonald acknowledges support from the Mexican National Council for Science and Technology (CONACyT). H. Wang acknowledges support from the United States Department of Energy (DOE) Office of Science, Biological and Environmental Research. The Pacific Northwest National Laboratory (PNNL) is operated for DOE by Battelle Memorial Institute under contract DE‐AC05‐76RLO1830. The authors gratefully acknowledge Jan Kazil for useful discussions.

Attached Files

Published - MacDonald_et_al-2018-Journal_of_Geophysical_Research_3A_Atmospheres.pdf

Accepted Version - nihms-1067826.pdf

Supplemental Material - 2017jd027900-sup-0001-text_si-s01.docx


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