Observations of the boundary layer, cloud, and aerosol variability in the southeast Pacific near-coastal marine stratocumulus during VOCALS-REx
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Authors
Zheng, X.
Albrecht, B.
Jonsson, H.H.
Khelif, D.
Feingold, G.
Minnis, P.
Ayers, K.
Chuang, P.
Donaher, S.
Rossiter, D.
Subjects
Advisors
Date of Issue
2011-09-27
Date
September 27, 2011
Publisher
Copernicus Publications
Language
Abstract
Aircraft observations made off the coast of northern
Chile in the Southeastern Pacific (20° S, 72° W; named
Point Alpha) from 16 October to 13 November 2008 during
the VAMOS Ocean-Cloud- Atmosphere-Land Study-
Regional Experiment (VOCALS-REx), combined with meteorological
reanalysis, satellite measurements, and radiosonde
data, are used to investigate the boundary layer
(BL) and aerosol-cloud-drizzle variations in this region. On
days without predominately synoptic and meso-scale influences,
the BL at Point Alpha was typical of a non-drizzling
stratocumulus-topped BL. Entrainment rates calculated from
the near cloud-top fluxes and turbulence in the BL at Point
Alpha appeared to be weaker than those in the BL over the
open ocean west of Point Alpha and the BL near the coast
of the northeast Pacific. The cloud liquid water path (LWP)
varied between 15 gmˉ² and 160 gmˉ². The BL had a depth
of 1140±120 m, was generally well-mixed and capped by
a sharp inversion without predominately synoptic and mesoscale
influences. The wind direction generally switched from
southerly within the BL to northerly above the inversion. On
days when a synoptic system and related mesoscale costal
circulations affected conditions at Point Alpha (29 October–
4 November), a moist layer above the inversion moved over
Point Alpha, and the total-water mixing ratio above the inversion
was larger than that within the BL.
The accumulation mode aerosol varied from 250 to
700 cmˉ³ within the BL, and CCN at 0.2% supersaturation
within the BL ranged between 150 and 550 cmˉ³. The
main aerosol source at Point Alpha was horizontal advection
within the BL from south. The average cloud droplet number
concentration ranged between 80 and 400 cmˉ³. While
the mean LWP retrieved from GOES was in good agreement
with the in situ measurements, the GOES-derived cloud
droplet effective radius tended to be larger than that from the
aircraft in situ observations near cloud top. The aerosol and
cloud LWP relationship reveals that during the typical well-mixed
BL days the cloud LWP increased with the CCN concentrations.
On the other hand, meteorological factors and
the decoupling processes have large influences on the cloud
LWP variation as well.
Type
Article
Description
The article of record as published may be found at http://dx.doi.org/10.5194/acp-11-9943-2011
Series/Report No
Department
Organization
Naval Postgraduate School (U.S.)
Identifiers
NPS Report Number
Sponsors
Funding
ONR grant N000140810465
NOAA/CPPA Program under grant NA08OAR4320889
ONR grant N000140810438
NASA Modeling, Analysis, and Prediction Porgram
NASA Clouds and the Earth's Radiant Energy System Project
Department of Energy ARM Program through DE-AI02-07ER64546
NOAA's Climate Goal
NOAA/CPPA Program under grant NA08OAR4320889
ONR grant N000140810438
NASA Modeling, Analysis, and Prediction Porgram
NASA Clouds and the Earth's Radiant Energy System Project
Department of Energy ARM Program through DE-AI02-07ER64546
NOAA's Climate Goal
Format
17 p.
Citation
Zheng, X., et al. "Observations of the boundary layer, cloud, and aerosol variability in the southeast Pacific near-coastal marine stratocumulus during VOCALS-REx." Atmospheric Chemistry and Physics 11.18 (2011): 9943-9959.
Distribution Statement
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.