Mesoscale variability in coastal stratocumulus clouds observed during UPPEF2012
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Authors
Franklin, Kyle B.
Subjects
Stratocumulus clouds
mesoscale variability
mesoscale cellular convection
UPPEF 2012
aircraft measurements.
mesoscale variability
mesoscale cellular convection
UPPEF 2012
aircraft measurements.
Advisors
Wang, Qing
Date of Issue
2014-03
Date
Mar-14
Publisher
Monterey, California. Naval Postgraduate School
Language
Abstract
Analysis of satellite imagery shows horizontally extensive coastal stratocumulus layers with closed cell mesoscale cellular convection (MCC) near the coast transitioning to open cell MCC further offshore. The nearshore MCC region had a dominant length scale of 8.5 km. The offshore open cell region had larger length scales of 12 km to 20 km. Aircraft transects conducted through the closed cell MCC exhibited variable perturbations on two distinct length scales. Perturbations associated with MCC occurred at lengths scales identical to satellite observations. Perturbations also occurred on smaller length scales due to narrow, sub-kilometer convective downdraft events imbedded within the MCC. These events showed less spatial organization than MCC, with the distance between events ranging from .5 km to 3 km, and typical event widths of 1 km or less. Typical event perturbations include colder, dryer, downdrafts. Analysis of dynamic and thermodynamic variables has shown that typical downward velocities of .25 ms-1 exist in the middle of the cloud layer, but subsequent horizontal mixing of adjacent air reduces the magnitude of thermodynamic perturbations in the downdrafts, reduces negative buoyancy, and slows the downdraft near cloud base. These narrow downdraft events are a significant source of boundary layer vertical temperature and moisture fluxes.
Type
Thesis
Description
Series/Report No
Department
Meteorology
Organization
Identifiers
NPS Report Number
Sponsors
Funder
Format
Citation
Distribution Statement
Approved for public release; distribution is unlimited.
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.