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Dispersion of Droplet Size Distributions in Supercooled Non‐precipitating Stratocumulus from Aircraft Observations Obtained during the Southern Ocean Cloud Radiation Aerosol Transport Experimental Study
Author(s) -
Wang Yang,
Zhao Chuanfeng,
McFarquhar Greg M.,
Wu Wei,
Reeves Mike,
Li Jiming
Publication year - 2021
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2020jd033720
Subject(s) - aerosol , marine stratocumulus , cloud base , atmospheric sciences , effective radius , environmental science , radiative transfer , radius , radiative forcing , supercooling , meteorology , cloud computing , physics , astrophysics , optics , computer security , galaxy , computer science , operating system
The characteristics of cloud droplet size distributions and statistical relations of the relative dispersion ( ε ) with the vertical velocity ( w ) and with the interstitial aerosol concentration ( N ia ) are investigated for ubiquitous supercooled shallow stratocumulus observed over the Southern Ocean (SO) using aircraft measurements obtained during the Southern Ocean Cloud Radiation Aerosol Transport Experimental Study. Distinct vertical variations have been found using 36 non‐precipitating cloud profiles. The cloud droplet effective radius ( r e ) increases nearly monotonically from 5.3 ± 1.9 μm at cloud base to 9.4 ± 2.2 μm at cloud top. The ε decreases rapidly from cloud base (0.42 ± 0.13) and then remains relatively constant in the upper cloud layer (0.27 ± 0.09). This study also shows robust dependence of ε on both N ia and w . The ε increases (decreases) with increasing N ia ( w ) at a 95% confidence level when values of w (low N ia ) are restricted to a small range. The important roles of aerosols and dynamics on ε are demonstrated and are crucial to estimating aerosol indirect radiative forcing, especially for pristine SO regions where models almost universally underestimate reflected radiation.