TY - JOUR
T1 - Vertical dependence of horizontal variation of cloud microphysics
T2 - Observations from the ACE-ENA field campaign and implications for warm-rain simulation in climate models
AU - Zhang, Zhibo
AU - Song, Qianqian
AU - Mechem, David
AU - Larson, Vincent
AU - Wang, Jian
AU - Liu, Yangang
AU - K. Witte, Mikael
AU - Dong, Xiquan
AU - Wu, Peng
N1 - Funding Information:
Financial support. This research has been supported by the US De-
Funding Information:
Acknowledgements. Zhibo Zhang acknowledges the financial support from the Atmospheric System Research (grant no. DESC0020057) funded by the Office of Biological and Environmental Research in the US DOE Office of Science. The computations in this study were performed at the UMBC High Performance Computing Facility (HPCF). The facility is supported by the US National Science Foundation through the MRI program (grant nos. CNS-0821258 and CNS-1228778) and the SCREMS program (grant no. DMS-0821311), with substantial support from UMBC. David B. Mechem was supported by subcontract OFED0010-01 from the University of Maryland Baltimore County and the US Department of Energy’s Atmospheric Systems Research grant DE-SC0016522.
Publisher Copyright:
© 2021 Copernicus GmbH. All rights reserved.
PY - 2021/3/2
Y1 - 2021/3/2
N2 - In the current global climate models (GCMs), the nonlinearity effect of subgrid cloud variations on the parameterization of warm-rain process, e.g. the autoconversion rate, is often treated by multiplying the resolved-scale warm-rain process rates by a so-called enhancement factor (EF). In this study, we investigate the subgrid-scale horizontal variations and covariation of cloud water content (qc) and cloud droplet number concentration (Nc) in marine boundary layer (MBL) clouds based on the in situ measurements from a recent field campaign and study the implications for the autoconversion rate EF in GCMs. Based on a few carefully selected cases from the field campaign, we found that in contrast to the enhancing effect of qc and Nc variations that tends to make EF>1, the strong positive correlation between qc and Nc results in a suppressing effect that tends to make EF<1. This effect is especially strong at cloud top, where the qc and Nc correlation can be as high as 0.95. We also found that the physically complete EF that accounts for the covariation of qc and Nc is significantly smaller than its counterpart that accounts only for the subgrid variation of qc, especially at cloud top. Although this study is based on limited cases, it suggests that the subgrid variations of Nc and its correlation with qc both need to be considered for an accurate simulation of the autoconversion process in GCMs.
AB - In the current global climate models (GCMs), the nonlinearity effect of subgrid cloud variations on the parameterization of warm-rain process, e.g. the autoconversion rate, is often treated by multiplying the resolved-scale warm-rain process rates by a so-called enhancement factor (EF). In this study, we investigate the subgrid-scale horizontal variations and covariation of cloud water content (qc) and cloud droplet number concentration (Nc) in marine boundary layer (MBL) clouds based on the in situ measurements from a recent field campaign and study the implications for the autoconversion rate EF in GCMs. Based on a few carefully selected cases from the field campaign, we found that in contrast to the enhancing effect of qc and Nc variations that tends to make EF>1, the strong positive correlation between qc and Nc results in a suppressing effect that tends to make EF<1. This effect is especially strong at cloud top, where the qc and Nc correlation can be as high as 0.95. We also found that the physically complete EF that accounts for the covariation of qc and Nc is significantly smaller than its counterpart that accounts only for the subgrid variation of qc, especially at cloud top. Although this study is based on limited cases, it suggests that the subgrid variations of Nc and its correlation with qc both need to be considered for an accurate simulation of the autoconversion process in GCMs.
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U2 - 10.5194/acp-21-3103-2021
DO - 10.5194/acp-21-3103-2021
M3 - Article
AN - SCOPUS:85102013080
SN - 1680-7316
VL - 21
SP - 3103
EP - 3121
JO - Atmospheric Chemistry and Physics
JF - Atmospheric Chemistry and Physics
IS - 4
ER -