Cloud Adiabaticity and Its Relationship to Marine Stratocumulus Characteristics Over the Northeast Pacific Ocean
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Authors
Braun, Rachel A.
Dadashazar, Hossein
MacDonald, Alexander B.
Crosbie, Ewan
Jonsson, Haflidi H.
Woods, Roy K.
Flagan, Richard C.
Seinfeld, John H.
Sorooshian, Armin
Subjects
Advisors
Date of Issue
2018
Date
Publisher
Monterey, California: Naval Postgraduate School
Language
Abstract
Cloud adiabaticity (α) is defined as the ratio of the actual liquid water path (LWP measured) in a
cloud to its corresponding adiabatic value (LWP ad). Processes such as drizzle and entrainment can lead to
subadiabatic LWP measured. This study examines α and its relationship to microphysical properties for 86
cloud events over the Northeast Pacific Ocean based on data collected during four separate summertime
airborne campaigns. For the study region, α was found to be 0.766 ± 0.134. For most cases, clouds with a
low value of α were found to have lower droplet number concentration (Nd), higher droplet effective
radius (re), higher relative dispersion (d), and higher rain rate (R). The subcloud aerosol concentration (Na)
was often less for the low-α cases. The relationship between α and the vertical profiles and cloud-top
characteristics for both the cloud droplet-only spectrum and full spectrum (cloud and rain droplets) is also
examined. Inclusion of rain droplets produced a larger change in d for the low-α clouds as compared
to the high-α clouds. On average, R increased at cloud top for high-α clouds but decreased at cloud top
for low-α clouds. Accounting for α when estimating Nd from Moderate Resolution Imaging
Spectroradiometer retrievals results in better agreement with in situ Nd values. Results of this work
motivate the need for additional focus on the factors governing α, such as cloud type, and implications of
its value, especially for remote-sensing retrievals.
Type
Article
Description
The article of record as published may be found at http://dx.doi.org/10.1029/2018JD029287
Series/Report No
Department
Meteorology
Organization
Naval Postgraduate School (U.S.)
Identifiers
NPS Report Number
Sponsors
Mexican National Council for Science and Technology (CONACyT)
Funder
Office of Naval Research N00014-10-1-0811
N00014-11-1-0783
N00014-10-1-0200
N00014-04-1-0118
N00014-16-1- 2567
N00014-11-1-0783
N00014-10-1-0200
N00014-04-1-0118
N00014-16-1- 2567
Format
17 p.
Citation
Braun, Rachel A., et al. "Cloud Adiabaticity and Its Relationship to Marine Stratocumulus Characteristics Over the Northeast Pacific Ocean." Journal of Geophysical Research: Atmospheres 123.24 (2018): 13,790-13,806.
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.