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Title: Joint Synoptic and Cloud Variability over the Northeast Atlantic near the Azores

Abstract

Marine boundary layer clouds are modified by processes at different spatial and temporal scales. To isolate the processes governing aerosol–cloud–precipitation interactions, multiday synoptic variability of the environment must be accounted for. Information on the location of low clouds relative to the ridge–trough pattern gives insight into how cloud properties vary as a function of environmental subsidence and stability. The technique of self-organizing maps (SOMs) is employed to objectively classify the 500-hPa geopotential height patterns for 33 years of reanalysis fields (ERA-Interim) into pretrough, trough, posttrough, ridge, and zonal-flow categories. The SOM technique is applied to a region of prevalent marine low cloudiness over the eastern North Atlantic Ocean that is centered on the Azores island chain, the location of a long-term U.S. Department of Energy observation site. The Azores consistently lie in an area of substantial variability in synoptic configuration, thermodynamic environment, and cloud properties. The SOM method was run in two ways to emphasize multiday and seasonal variability separately. Over and near the Azores, there is an east-to-west sloshing back and forth of the western edge of marine low clouds associated with different synoptic states. The different synoptic states also exhibit substantial north–south variability in the position of highmore » clouds. For any given month of the year, there is large year-to-year variability in the occurrence of different synoptic states. Hence, estimating the climatological behavior of clouds from short-term field campaigns has large uncertainties. Finally, this SOM approach is a robust method that is broadly applicable to characterizing synoptic regimes for any location.« less

Authors:
 [1];  [1];  [2];  [2];  [3]
  1. Univ. of Kansas, Lawrence, KS (United States). Dept. of Geography and Atmospheric Science
  2. North Carolina State Univ., Raleigh, NC (United States). Dept. of Marine, Earth, and Atmospheric Sciences
  3. Oregon State Univ., Corvallis, OR (United States). College of Oceanic and Atmospheric Sciences
Publication Date:
Research Org.:
North Carolina State Univ., Raleigh, NC (United States); Univ. of Kansas, Lawrence, KS (United States); Oregon State Univ., Corvallis, OR (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1441239
Alternate Identifier(s):
OSTI ID: 1541814
Grant/Contract Number:  
SC0006701; SC0006736; SC0006994; SC0016522; C0006994
Resource Type:
Published Article
Journal Name:
Journal of Applied Meteorology and Climatology
Additional Journal Information:
Journal Volume: 57; Journal Issue: 6; Journal ID: ISSN 1558-8424
Publisher:
American Meteorological Society
Country of Publication:
United States
Language:
English
Subject:
meteorology & atmospheric sciences; North Atlantic Ocean; synoptic climatology; stratiform clouds; synoptic-scale processes; cloud cover; climate classification/regimes

Citation Formats

Mechem, David B., Wittman, Carly S., Miller, Matthew A., Yuter, Sandra E., and de Szoeke, Simon P. Joint Synoptic and Cloud Variability over the Northeast Atlantic near the Azores. United States: N. p., 2018. Web. doi:10.1175/jamc-d-17-0211.1.
Mechem, David B., Wittman, Carly S., Miller, Matthew A., Yuter, Sandra E., & de Szoeke, Simon P. Joint Synoptic and Cloud Variability over the Northeast Atlantic near the Azores. United States. doi:10.1175/jamc-d-17-0211.1.
Mechem, David B., Wittman, Carly S., Miller, Matthew A., Yuter, Sandra E., and de Szoeke, Simon P. Tue . "Joint Synoptic and Cloud Variability over the Northeast Atlantic near the Azores". United States. doi:10.1175/jamc-d-17-0211.1.
@article{osti_1441239,
title = {Joint Synoptic and Cloud Variability over the Northeast Atlantic near the Azores},
author = {Mechem, David B. and Wittman, Carly S. and Miller, Matthew A. and Yuter, Sandra E. and de Szoeke, Simon P.},
abstractNote = {Marine boundary layer clouds are modified by processes at different spatial and temporal scales. To isolate the processes governing aerosol–cloud–precipitation interactions, multiday synoptic variability of the environment must be accounted for. Information on the location of low clouds relative to the ridge–trough pattern gives insight into how cloud properties vary as a function of environmental subsidence and stability. The technique of self-organizing maps (SOMs) is employed to objectively classify the 500-hPa geopotential height patterns for 33 years of reanalysis fields (ERA-Interim) into pretrough, trough, posttrough, ridge, and zonal-flow categories. The SOM technique is applied to a region of prevalent marine low cloudiness over the eastern North Atlantic Ocean that is centered on the Azores island chain, the location of a long-term U.S. Department of Energy observation site. The Azores consistently lie in an area of substantial variability in synoptic configuration, thermodynamic environment, and cloud properties. The SOM method was run in two ways to emphasize multiday and seasonal variability separately. Over and near the Azores, there is an east-to-west sloshing back and forth of the western edge of marine low clouds associated with different synoptic states. The different synoptic states also exhibit substantial north–south variability in the position of high clouds. For any given month of the year, there is large year-to-year variability in the occurrence of different synoptic states. Hence, estimating the climatological behavior of clouds from short-term field campaigns has large uncertainties. Finally, this SOM approach is a robust method that is broadly applicable to characterizing synoptic regimes for any location.},
doi = {10.1175/jamc-d-17-0211.1},
journal = {Journal of Applied Meteorology and Climatology},
number = 6,
volume = 57,
place = {United States},
year = {2018},
month = {6}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1175/jamc-d-17-0211.1

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Cited by: 2 works
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