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Characteristic Vertical Profiles of Cloud Water Composition in Marine Stratocumulus Clouds and Relationships With Precipitation
Author(s) -
MacDonald Alexander B.,
Dadashazar Hossein,
Chuang Patrick Y.,
Crosbie Ewan,
Wang Hailong,
Wang Zhen,
Jonsson Haflidi H.,
Flagan Richard C.,
Seinfeld John H.,
Sorooshian Armin
Publication year - 2018
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2017jd027900
Subject(s) - scavenging , marine stratocumulus , altitude (triangle) , environmental science , atmospheric sciences , precipitation , liquid water content , cloud base , cloud top , cloud condensation nuclei , cloud computing , particulates , sulfate , sea salt aerosol , effects of high altitude on humans , seawater , environmental chemistry , sea salt , chemistry , aerosol , meteorology , geology , oceanography , geography , biochemistry , geometry , mathematics , organic chemistry , computer science , antioxidant , operating system
Abstract 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.