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  • American Meteorological Society
  • Annual Reviews
Collection
Years
  • 1
    Journal cover
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    Annual Reviews
    Online: 1.2008 – 9.2016
    Publisher: Annual Reviews
    Print ISSN: 1936-1327
    Electronic ISSN: 1936-1335
    Topics: Chemistry and Pharmacology
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  • 2
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    Annual Reviews
    Online: 1.1963 – 54.2016
    Publisher: Annual Reviews
    Print ISSN: 0066-4146
    Electronic ISSN: 1545-4282
    Topics: Physics
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  • 3
    Formerly as: Annual Review of Energy and the Environment ; Annual Review of Energy  (1976–2002)
    Publisher: Annual Reviews
    Print ISSN: 0362-1626 , 1056-3466 , 1543-5938
    Electronic ISSN: 1545-2050
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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  • 4
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    Annual Reviews
    Online: 1.1967 – 50.2016
    Publisher: Annual Reviews
    Print ISSN: 0066-4197
    Electronic ISSN: 1545-2948
    Topics: Biology
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  • 5
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    Annual Reviews
    Online: 1.1939 – 78.2016
    Publisher: Annual Reviews
    Print ISSN: 0066-4278
    Electronic ISSN: 1545-1585
    Topics: Biology , Medicine
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  • 6
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    Annual Reviews
    Online: 1.2009 – 5.2013
    Publisher: Annual Reviews
    Print ISSN: 1941-1340
    Electronic ISSN: 1941-1359
    Topics: Economics
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  • 7
    Formerly as: Annual Review of Biophysics and Biomolecular Structure ; Annual Review of Biophysics and Biophysical Chemistry ; Annual Review of Biophysics and Bioengineering  (1972–2007)
    Publisher: Annual Reviews
    Print ISSN: 0084-6589 , 0883-9182 , 1056-8700 , 1936-122X
    Electronic ISSN: 1545-4266 , 1936-1238
    Topics: Biology , Physics
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  • 8
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    Annual Reviews
    Online: 1.1983 – 34.2016
    Publisher: Annual Reviews
    Print ISSN: 0732-0582
    Electronic ISSN: 1545-3278
    Topics: Biology , Medicine
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  • 9
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    Annual Reviews
    Online: 1.2009 – 8.2016
    Publisher: Annual Reviews
    Print ISSN: 1941-1405
    Electronic ISSN: 1941-0611
    Topics: Biology , Geosciences
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  • 10
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    Annual Reviews
    Online: 1.1947 – 70.2016
    Publisher: Annual Reviews
    Print ISSN: 0066-4227
    Electronic ISSN: 1545-3251
    Topics: Biology
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  • 11
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    American Meteorological Society
    Online: 51.1970 –
    Print: 52.1971 – 81(2).1999 (Location: A62, Keller, 2/4-5)
    Publisher: American Meteorological Society
    Corporation: American Meteorological Society, AMS
    Print ISSN: 0003-0007
    Electronic ISSN: 1520-0477
    Topics: Geosciences , Physics
    Acronym: BAMS
    Abbreviation: Bull Am Meteorol Soc
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  • 12
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    American Geophysical Union (AGU) | Association of American Geographers (AAG) | American Meteorological Society | Allen Press
    Online: 1(1).1997 –
    Publisher: American Geophysical Union (AGU) , Association of American Geographers (AAG) , American Meteorological Society , Allen Press
    Electronic ISSN: 1087-3562
    Topics: Geography , Geosciences , Physics
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  • 13
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    American Meteorological Society | Allen Press
    Online: 1.1971 –
    Print: 23.1993 – 41.2011 (Location: A17, Kompaktmagazin, 42/7 - 43/2)
    Publisher: American Meteorological Society , Allen Press
    Corporation: American Meteorological Society, AMS
    Print ISSN: 0022-3670
    Electronic ISSN: 1520-0485
    Topics: Geosciences , Physics
    Acronym: JPO
    Abbreviation: J Phys Oceanogr
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  • 14
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    American Meteorological Society | Allen Press
    Online: 1.1873 –
    Print: 121.1993 – 136.2008 (Location: A43, LZ 9-11 Unten)
    Print: 2.1874 – 122.1994 (Location: A62, Konferenzraum, 2OG)
    Publisher: American Meteorological Society , Allen Press
    Corporation: American Meteorological Society, AMS
    Print ISSN: 0027-0644
    Electronic ISSN: 1520-0493
    Topics: Geography , Geosciences , Physics
    Acronym: MWR
    Abbreviation: Month Weather Rev
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  • 15
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    American Meteorological Society
    Online: 1.2009 – (older than 12 months)
    Publisher: American Meteorological Society
    Print ISSN: 1948-8327
    Electronic ISSN: 1948-8335
    Topics: Geosciences , Physics
    Keywords: Meteorologie, Bioklimatologie
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  • 16
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    Annual Reviews
    Online: 1.1973 –
    Print: 8.1980 – 46.2018 (Location: A17, Kompaktmagazin, 5/6-7)
    Publisher: Annual Reviews
    Print ISSN: 0084-6597
    Electronic ISSN: 1545-4495
    Topics: Geosciences , Physics
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  • 17
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    Annual Reviews
    Online: 1.1969 – 48.2016
    Publisher: Annual Reviews
    Print ISSN: 0066-4189
    Electronic ISSN: 1545-4479
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 18
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    Annual Reviews
    Online: 1.1952 – 66.2016
    Formerly as: Annual Review of Nuclear Science  (1952–1977)
    Publisher: Annual Reviews
    Print ISSN: 0066-4243 , 0163-8998
    Electronic ISSN: 1545-4134
    Topics: Physics
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  • 19
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    Annual Reviews
    Online: 1.1932 – 85.2016
    Publisher: Annual Reviews
    Print ISSN: 0066-4154
    Electronic ISSN: 1545-4509
    Topics: Biology , Chemistry and Pharmacology
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  • 20
    Formerly as: Annual Review of Plant Physiology and Plant Molecular Biology ; Annual Review of Plant Physiology  (1950–2001)
    Publisher: Annual Reviews
    Print ISSN: 0066-4294 , 1040-2519 , 1543-5008
    Electronic ISSN: 1545-2123
    Topics: Biology
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  • 21
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    American Meteorological Society | JSTOR
    Online: 1.1920 – (older than 3 years)
    Publisher: American Meteorological Society , JSTOR
    Print ISSN: 0003-0007
    Electronic ISSN: 1520-0477
    Topics: Geosciences , Physics
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  • 22
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    American Meteorological Society | Allen Press | JSTOR
    Online: 1.1988 –
    Print: 5.1992 – 20.2007 (Location: A43, LZ 10-12 Mitte | RZ)
    Print: 4(9).1991 – 8(1).1995 (Location: A62, Keller, 39/2-3)
    Publisher: American Meteorological Society , Allen Press , JSTOR
    Corporation: American Meteorological Society, AMS
    Print ISSN: 0894-8755
    Electronic ISSN: 1520-0442
    Topics: Geosciences , Physics
    Acronym: JC
    Abbreviation: J Clim
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  • 23
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    American Meteorological Society | Allen Press
    Online: 1.1944 –
    Print: 50.1993 – 64.2007 (Location: A43, LZ 10 Unten -12 Unten)
    Print: 19.1962 – 30.1973 (Location: A62, Keller, 3/2)
    Formerly as: Journal of Meteorology  (1944–1961)
    Publisher: American Meteorological Society , Allen Press
    Corporation: American Meteorological Society, AMS
    Print ISSN: 0022-4928 , 0095-9634
    Electronic ISSN: 1520-0469
    Topics: Geography , Geosciences , Physics
    Acronym: JAS
    Abbreviation: J Atmos Sci
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  • 24
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    American Meteorological Society
    Print: 1.1944 – 18.1961 (Location: A62, Keller, 3/2 ; 46/2 (Vol. 11-13))
    Continued as: Journal of the Atmospheric Sciences  (1962–)
    Publisher: American Meteorological Society
    Corporation: American Meteorological Society, AMS
    Print ISSN: 0095-9634
    Topics: Geosciences
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  • 25
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    Annual Reviews
    Online: 2017 –
    Publisher: Annual Reviews
    Description: What is known? What isn’t known? Knowable Magazine, the digital publication from Annual Reviews, seeks to make that knowledge accessible to all. Knowable Magazine explores the real-world significance of scholarly work through a journalistic lens. We report on the current state of play across a wide variety of fields — from agriculture to high-energy physics; biochemistry to water security; the origins of the universe to psychology. Review articles written by leading scholars from the 50 Annual Reviews journals serve as springboards for stories in Knowable Magazine. Through in-depth features, explainers, articles, essays, interviews, infographics, slideshows, and comics, Knowable Magazine presents insights from research to a broader audience. The content is published under a CC BY-ND copyright license, and the Annual Reviews journal articles featured in Knowable Magazine are free to all for a limited period. Knowable Magazine content is thoroughly researched, reported, edited, copy-edited and fact-checked. Review articles in Annual Review journals provide ideas, but editorial decisions and reporting decisions are made by the magazine staff, guided by what will best inform and intrigue readers.
    Topics: Natural Sciences in General
    Keywords: Allgemeine Naturwissenschaften ; Forschung
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  • 26
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    Annual Reviews
    Online: 1.1972 – 45.2016
    Publisher: Annual Reviews
    Print ISSN: 0084-6570
    Electronic ISSN: 1545-4290
    Topics: Biology , Ethnic Sciences
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  • 27
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    Annual Reviews
    Online: 1.1985 – 32.2016
    Formerly as: Annual Review of Cell Biology  (1985–1994)
    Publisher: Annual Reviews
    Print ISSN: 0743-4634 , 1081-0706
    Electronic ISSN: 1530-8995
    Topics: Biology , Medicine
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  • 28
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    Annual Reviews
    Online: 1.1970 – 47.2016
    Formerly as: Annual Review of Ecology and Systematics  (1970–2002)
    Publisher: Annual Reviews
    Print ISSN: 0066-4162 , 1543-592X
    Electronic ISSN: 1545-2069
    Topics: Biology
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  • 29
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    Annual Reviews
    Online: 1.2000 –
    Publisher: Annual Reviews
    Print ISSN: 1527-8204
    Electronic ISSN: 1545-293X
    Topics: Biology
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  • 30
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    Annual Reviews
    Online: 1.1971 – 46.2016
    Formerly as: Annual Review of Materials Science  (1971–2000)
    Publisher: Annual Reviews
    Print ISSN: 0084-6600 , 1531-7331
    Electronic ISSN: 1545-4118
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 31
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    Annual Reviews
    Online: 1.1999 – 18.2016
    Publisher: Annual Reviews
    Print ISSN: 1523-9829
    Electronic ISSN: 1545-4274
    Topics: Medicine , Technology
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  • 32
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    Annual Reviews
    Online: 1.1986 – 4.1990
    Publisher: Annual Reviews
    Print ISSN: 8756-7016
    Electronic ISSN: 8756-7016
    Topics: Computer Science
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  • 33
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    Annual Reviews | JSTOR
    Online: 1.2009 – 5.2013
    Publisher: Annual Reviews , JSTOR
    Print ISSN: 1941-1367
    Electronic ISSN: 1941-1375
    Topics: Economics
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  • 34
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    Annual Reviews
    Online: 1.1981 – 36.2016
    Publisher: Annual Reviews
    Print ISSN: 0199-9885
    Electronic ISSN: 1545-4312
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 35
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    Annual Reviews
    Online: 1.2010 – 7.2016
    Publisher: Annual Reviews
    Print ISSN: 1947-5454
    Electronic ISSN: 1947-5462
    Topics: Physics
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  • 36
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    Annual Reviews
    Online: 1973 – 1996
    Publisher: Annual Reviews
    Print ISSN: 0084-6597
    Electronic ISSN: 1545-4495
    Topics: Geosciences , Physics
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  • 37
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    Annual Reviews | JSTOR
    Online: 1.2009 – 5.2013
    Publisher: Annual Reviews , JSTOR
    Print ISSN: 1941-1383
    Electronic ISSN: 1941-1391
    Topics: Economics
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  • 38
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    Annual Reviews
    Online: 1.1956 – 61.2016
    Publisher: Annual Reviews
    Print ISSN: 0066-4170
    Electronic ISSN: 1545-4487
    Topics: Biology
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  • 39
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    American Meteorological Society | Allen Press
    Online: 1.2000 – (older than 12 months)
    Print: 3.2002 – 6.2005 (Location: A43, LZ 14 Mitte)
    Publisher: American Meteorological Society , Allen Press
    Corporation: American Meteorological Society, AMS
    Print ISSN: 1525-755X
    Electronic ISSN: 1525-7541
    Topics: Geosciences , Physics
    Acronym: JH
    Abbreviation: J Hydrometeorol
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  • 40
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    American Meteorological Society | Allen Press
    Online: 1.1986 – (older than 12 months)
    Print: 1.1986 – 15(1).2000 (Location: A62, Keller, 38/5)
    Publisher: American Meteorological Society , Allen Press
    Corporation: American Meteorological Society, AMS
    Print ISSN: 0882-8156
    Topics: Geography , Physics
    Acronym: WF
    Abbreviation: Weather Forecast
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  • 41
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    Annual Reviews
    Online: 1.2014 – 3.2016
    Publisher: Annual Reviews
    Print ISSN: 2326-8298
    Electronic ISSN: 2326-831X
    Topics: Mathematics
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  • 42
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    Annual Reviews
    Online: 1.2013 – 4.2016
    Publisher: Annual Reviews
    Print ISSN: 2165-8102
    Electronic ISSN: 2165-8110
    Topics: Biology
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  • 43
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    Annual Reviews
    Online: 1963 – 1995
    Publisher: Annual Reviews
    Print ISSN: 0066-4146
    Electronic ISSN: 1545-4282
    Topics: Physics
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  • 44
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    Annual Reviews
    Online: 1.1978 – 39.2016
    Publisher: Annual Reviews
    Print ISSN: 0147-006X
    Electronic ISSN: 1545-4126
    Topics: Biology , Medicine
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  • 45
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    Annual Reviews
    Online: 1.1950 – 67.2016
    Publisher: Annual Reviews
    Print ISSN: 0066-426X
    Electronic ISSN: 1545-1593
    Topics: Chemistry and Pharmacology , Physics
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  • 46
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    Annual Reviews
    Online: 1.1961 – 56.2016
    Formerly as: Annual Review of Pharmacology  (1961–1975)
    Publisher: Annual Reviews
    Print ISSN: 0066-4251 , 0362-1642
    Electronic ISSN: 1545-4304
    Topics: Chemistry and Pharmacology , Medicine
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  • 47
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    Annual Reviews
    Online: 1.1963 – 54.2016
    Publisher: Annual Reviews
    Print ISSN: 0066-4286
    Electronic ISSN: 1545-2107
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 48
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    American Meteorological Society | Allen Press
    Online: 1.1962 – (older than 12 months)
    Print: 31.1992 – 32.1993 (Location: A43, LZ 10 Mitte)
    Formerly as: Journal of Applied Meteorology  (1988–2005)
    Publisher: American Meteorological Society , Allen Press
    Corporation: American Meteorological Society, AMS
    Print ISSN: 1558-8424
    Electronic ISSN: 1558-8432
    Topics: Geosciences , Physics
    Acronym: JAMC
    Abbreviation: J Appl Meteorol Climatol
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  • 49
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    American Meteorological Society | Allen Press
    Online: 1.1984 – (older than 12 months)
    Publisher: American Meteorological Society , Allen Press
    Corporation: American Meteorological Society, AMS
    Print ISSN: 0739-0572
    Electronic ISSN: 1520-0426
    Topics: Geography , Geosciences , Physics
    Acronym: ATOT
    Abbreviation: J Atmospher Ocean Technol
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  • 50
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    American Meteorological Society
    Online: 2002 –
    Publisher: American Meteorological Society
    Topics: Geography , Physics
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  • 51
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    American Meteorological Society
    In:  Journal of Physical Oceanography, 48 (2). pp. 261-281.
    Publication Date: 2019-02-01
    Description: Multi-year moored velocity observations of the Angola Current near 11°S reveal a weak southward mean flow superimposed by substantial intraseasonal to seasonal variability, including annual and semiannual cycles with distinct baroclinic structures. In the equatorial Atlantic these oscillations are associated with basin-mode resonances of the fourth and second baroclinic modes, respectively. Here, the role of basin-mode resonance and local forcing for the Angola Current seasonality are investigated. A suite of linear shallow-water models for the tropical Atlantic is employed, each model representing a single baroclinic mode forced at a specific period. The annually and semiannually oscillating forcing is given by 1) an idealized zonally uniform zonal forcing restricted to the equatorial band corresponding to a remote equatorial forcing or 2) realistic, spatially-varying Fourier components of wind stress data that include local forcing off Angola, particularly alongshore winds. Model-computed modal amplitudes are scaled to match moored velocity observations from the equatorial Atlantic. The observed annual cycle of alongshore velocity at 11°S is well reproduced by the remote equatorial forcing. Including local forcing slightly improves the agreement between observed and simulated semiannual oscillations at 11°S compared to the purely equatorial forcing. However, the model-computed semiannual cycle lacks amplitude at mid-depth. This could be the result of either underestimating the strength of the second equatorial basin-mode of the fourth baroclinic mode or other processes not accounted for in the shallow-water models. Overall, our findings underline the importance of large-scale linear equatorial wave dynamics for the seasonal variability of the boundary circulation off Angola.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 52
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    American Meteorological Society
    In:  Journal of Physical Oceanography, 23 (11). pp. 2373-2391.
    Publication Date: 2018-03-07
    Description: A sigma-coordinate, primitive equation ocean circulation model is used to explore the problem of the remnant generation of trapped waves about a tall, circular, isolated seamount by an incident oscillatory barotropic current. The numerical solutions are used to extend prior studies into the fully nonlinear regime, and in particular to quantify and interpret the occurrence of residual circulation. Specific attention is also devoted to the dependence of the resonance and rectification mechanisms on stratification, forcing frequency, and choice of subgrid-scale viscous closure. Resonantly generated trapped waves of significant amplitude are found to occur broadly in parameter space; a precise match between the frequency of the imposed incident current and the frequency of the trapped free wave is not necessary to produce substantial excitation of the trapped wave. The maximum amplification factors produced in these numerical solutions, O(100) times the strength of the incident current, are consistent with previous studies. In the presence of nonlinear advection, strong residual currents are produced. The time-mean circulation about the seamount is dominated by a strong bottom-intensified, anticyclonic circulation closely trapped to the seamount. Maximum local time-mean current amplitudes are found to be as large as 37% of the magnitude of the propagating waves. In addition to the strong anticyclonic residual flow, there is a weaker secondary circulation in the vertical-radial plane characterized by downwelling over the top of the seamount at all depths. Maximum vertical downwelling rates of several tens of meters per day occur at the summit of the seamount. The vertical mass flux implied by this systematic downwelling is balanced by a slow radial flux of mass directed outward along the flanks of the seamount. Time-mean budgets for the radial and azimuthal components of momentum show that horizontal eddy fluxes of momentum are responsible for transporting net radial and azimuthal momentum from the far field to the upper flanks of the seamount. There, Coriolis and pressure gradient forces provide the dominant balances in the radial direction. However, the Coriolis force and viscous effects provide the primary balance for the azimuthal component.
    Type: Article , PeerReviewed
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  • 53
    Publication Date: 2018-08-17
    Description: Accurate measurement of fluctuations in temperature and humidity are needed for determination of the surface evaporation rate and the air-sea sensible heat flux using either the eddy correlation or inertial dissipation method for flux calculations. These measurements are difficult to make over the ocean, and are subject to large errors when sensors are exposed to marine air containing spray droplets. All currently available commercial measurement devices for atmospheric humidity require frequent maintenance. Included in the objectives of the Humidity Exchange over the Sea program were testing and comparison of sensors used for measuring both the fluctuating and mean humidity in the marine atmosphere at high wind speeds and development of techniques for the protection of these sensors against contamination by oceanic aerosols. These sensors and droplet removal techniques are described and comparisons between measurements from several different systems are discussed in this paper. To accomplish these goals, participating groups devised and tested three methods of removing sea spray from the sample airstream. The best performance was given by a rotating semen device, the “spray Ringer.” Several high-frequency temperature and humidity instruments, based on different physical principles, were used in the collaborative field experiment. Temperature and humidity fluctuations were measured with sufficient accuracy inside the spray removal devices using Lyman-α hygrometers and a fast thermocouple psychrometer. Comparison of several types of psychrometers (using electric thermometers) and a Rotronic MP-100 humidity sensor for measuring the mean humidity illustrated the hysteresis of the Rotronic MP-100 device after periods of high relative humidity. Confidence in the readings of the electronic psychrometer was established by in situ calibration with repeated and careful readings of ordinary hand-held Assman psychrometers (based on mercury thermometers). Electronic psychrometer employing platinum resistance thermometers perform very well.
    Type: Article , PeerReviewed
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  • 54
    Publication Date: 2019-04-01
    Description: Benthic storms are important for both the energy budget of the ocean and for sediment resuspension and transport. Using 30 years of output from a high-resolution model of the North Atlantic, it is found that most of the benthic storms in the model occur near the western boundary in association with the Gulf Stream and the North Atlantic Current, in regions that are generally co-located with the peak near-bottom eddy kinetic energy. A common feature are meander troughs in the near-surface jets that are accompanied by deep low pressure anomalies spinning up deep cyclones with near-bottom velocities of up to more than 0.5 m/s. A case study of one of these events shows the importance of both baroclinic and barotropic instability of the jet, with energy being extracted from the jet in the upstream part of the meander trough and partly returned to the jet in the downstream part of the meander trough. This motivates examining the 30-year time mean of the energy transfer from the (annual mean) background flow into the eddy kinetic energy. This quantity is shown to be co-located well with the region in which benthic storms and large increases in deep cyclonic relative vorticity occur most frequently, suggesting an important role for mixed barotropic-baroclinic instability driven cyclogenesis in generating benthic storms throughout the model simulation. Regions of largest energy transfer and most frequent benthic storms are found to be the Gulf Stream west of the New England Seamounts and the North Atlantic Current near Flemish Cap.
    Type: Article , PeerReviewed
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  • 55
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    American Meteorological Society
    In:  Bulletin of the American Meteorological Society, 78 (12). pp. 2771-2777.
    Publication Date: 2019-03-07
    Description: A review is given of the meaning of the term “El Niño” and how it has changed in time, so there is no universal single definition. This needs to be recognized for scientific uses, and precision can only be achieved if the particular definition is identified in each use to reduce the possibility of misunderstanding. For quantitative purposes, possible definitions are explored that match the El Niños identified historically after 1950, and it is suggested that an El Niño can be said to occur if 5-month running means of sea surface temperature (SST) anomalies in the Niño 3.4 region (5°N–5°S, 120°–170°W) exceed 0.4°C for 6 months or more. With this definition, El Niños occur 31% of the time and La Niñas (with an equivalent definition) occur 23% of the time. The histogram of Niño 3.4 SST anomalies reveals a bimodal character. An advantage of such a definition is that it allows the beginning, end, duration, and magnitude of each event to be quantified. Most El Niños begin in the northern spring or perhaps summer and peak from November to January in sea surface temperatures.
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  • 56
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    American Meteorological Society
    In:  Journal of Physical Oceanography, 22 (1). pp. 83-92.
    Publication Date: 2018-03-09
    Description: Antarctic Bottom Water flows into the western North Atlantic across the equator, shifting from the western side to the eastern side of the trough between the American continents and the Mid-Atlantic Ridge as it continues north. This is puzzling because such large-scale motion is thought to be controlled by dynamics that disallows an eastern boundary current. Previous explanations for the transposition involve a (necessarily small-scale) density current that changes sides because of the change in sign of rotation across the equator, or a topographic effect that changes the sign of the effective mean vorticity gradient and thus requires an eastern boundary current. Here an alternative explanation for the overall structure of bottom flow is given. A source of mass to a thin bottom layer is assumed to upwell uniformly across its interface into a less dense layer at rest. A simple formula for the magnitude of the upwelling and thickness of the layer is derived that depends on the source strength to the bottom layer. For a strong enough source, the bottom layer thickness is zero along a grounding curve that separates the bottom water from the western boundary and confines it to the east. A band of recirculating interior flow occurs, supplied by an isolated northern and western boundary current. Similar structures appear to exist in the Antarctic Bottom Water of the western North Atlantic.
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  • 57
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    American Meteorological Society
    In:  Journal of Physical Oceanography, 22 (1). pp. 93-104.
    Publication Date: 2018-03-09
    Description: North Atlantic air-sea heat and freshwater flux data from several sources are used to estimate the conversion rate of water from one density to another throughout the range of sea surface density. This cross-isopycnal mass flux varies greatly over the ocean, with a maximum of 32.2 × 106 m3 s−1 at σ = 26.1 kg m−3 (toward greater densities) and a minimum of −7.6 × 106 m3 s−1 (toward lesser densities) at σ = 23.0 kg m−3. The air-sea fluxes force water to accumulate in three density bands: one at the lowest sea surface densities generated by heating; one centered near the density of subtropical mode water; and one spanning subpolar mode water densities. The transfer of water to the highest and lowest densities is balanced by mixing, which returns water to the middle density range, and also by boundary sources or sinks. Integrating the cross-isopycnal flux over all densities gives an annual average sinking of about 9 × 1O6 m3 s−1, which presumably escapes across the equator and must be balanced by a similar inflow. Comparison with estimates from tracer studies suggests that the renewal of tracer characteristics at a given density may occur without the existence of an annual average mass source at that density, because along- and cross-isopycnal mixing can renew a tracer without supplying mass.
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  • 58
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    American Meteorological Society
    In:  Journal of Atmospheric and Oceanic Technology, 11 (4). pp. 982-993.
    Publication Date: 2019-03-14
    Description: Cicosal sea surface height (SSH) data in the tropical and midlatitude North Atlantic are analyzed with and without water vapor (WV) correction to study the WV influence on along-track SSH anomaly profits, mesoscale SSH variability, wavenumber spectra, and objectively mapped fields of SSH anomaly. Three different WV datasets were used, one from the Fleet Numerical Oceanographic Center (FNOC) model and two from the Special Sensor Microwave/Imager (SSM/I) based on different WV retrieval algorithms. These WV dataset show significant differences, in particular in the tropics. However, the method for deriving SSH anomalies from altimeter height data Alters out much of the WV corrections. The residual WV effect on SSH anomaly is shown to be most significant in the seasonally migrating intertropical convergence zone of the tropical Atlantic: there the SSM/I corrections reduce the along-track mesoscale SSH variability by typically 1–1.5 cm. On seasonal timescales the maximum WV effect in this region is characterized by a 2–3-cm rms difference between SSH anomaly with and without SSM/I WV corrections, whereas FNOC corrections have almost no effect. Inferred seasonal velocity variations in the North Equatorial Countercurrent core (4° – 6°N) in the region of maximum WY influence (30° – 40°W) are reduced by about 20% and 30%, depending on whether SSM/I corrections by Emery or Wentz are used
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  • 59
    Publication Date: 2017-12-15
    Description: Warm water of open ocean origin on the continental shelf of the Amundsen and Bellingshausen Seas causes the highest basal melt rates reported for Antarctic ice shelves with severe consequences for the ice shelf/ice sheet dynamics. Ice shelves fringing the broad continental shelf in the Weddell and Ross Seas melt at rates orders ofmagnitude smaller. However, simulations using coupled ice–ocean models forced with the atmospheric output of the HadCM3 SRES-A1B scenario run (CO2 concentration in the atmosphere reaches 700 ppmv by the year 2100 and stays at that level for an additional 100 years) show that the circulation in the southern Weddell Sea changes during the twenty-first century. Derivatives of Circumpolar Deep Water are directed southward underneath the Filchner–Ronne Ice Shelf, warming the cavity and dramatically increasing basal melting. To find out whether the open ocean will always continue to power the melting, the authors extend their simulations, applying twentieth-century atmospheric forcing, both alone and together with prescribed basal mass flux at the end of (or during) the SRES-A1B scenario run. The results identify a tipping point in the southern Weddell Sea: once warm water flushes the ice shelf cavity a positive meltwater feedback enhances the shelf circulation and the onshore transport of open ocean heat. The process is irreversible with a recurrence to twentieth-century atmospheric forcing and can only be halted through prescribing a return to twentieth-century basal melt rates. This finding might have strong implications for the stability of the Antarctic ice sheet.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed , info:eu-repo/semantics/article
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  • 60
    Publication Date: 2018-08-08
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 61
    Publication Date: 2018-04-06
    Description: On 24 and 25 October 1995, high-resolution oceanographic measurements were carried out in the Strait of Messina by using a towed conductivity-temperature-depth chain and a vessel-mounted acoustic Doppler current profiler. During the period of investigation the surface water of the Tyrrhenian Sea north of the strait sill was heavier than the surface water of the Ionian Sea south of the strait sill. As a consequence, during northward tidal flow surface water of the Ionian Sea spread as a surface jet into the Tyrrhenian Sea, whereas during southward tidal flow heavier surface water of the Tyrrhenian Sea spread, after having sunk to a depth of about 100 m, as a subsurface jet into the Ionian Sea. Both jets had the form of an internal bore, which finally developed into trains of internal solitary waves whose amplitudes were larger north than south of the strait sill. These measurements represent a detailed picture of the tidally induced internal dynamics in the Strait of Messina during the period of investigation, which contributes to elucidate several aspects of the general internal dynamics in the area: 1) Associated with the tidal flow are intense water jets whose equilibrium depth strongly depends on the horizontal density distribution along the Strait of Messina; 2) although climatological data show that a large horizontal density gradient in the near-surface layer along the Strait of Messina exists, its reversal can occur; 3) fluctuations in the larger-scale circulation patterns that determine the inflow of the modified Atlantic water into the Eastern Mediterranean Sea can be responsible for this reversal. As the tidally induced internal waves reflect the variability in the horizontal density distribution along the Strait of Messina, it is suggested that from the analysis of synthetic aperture radar imagery showing sea surface manifestations of internal waves in this area fluctuations of larger-scale circulation patterns in the Mediterranean Sea can be inferred.
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  • 62
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    American Meteorological Society
    In:  Journal of Climate, 16 . pp. 2717-2734.
    Publication Date: 2018-07-24
    Description: Synoptic-scale variability in the air–sea turbulent fluxes in the areas of midlatitudinal western boundary currents is analyzed. In the Gulf Stream area, ocean–atmosphere fluxes on synoptic time- and space scales are clearly coordinated with the propagating synoptic-scale atmospheric transients. The statistical analysis of 6-hourly resolution sea level pressure and surface turbulent fluxes from the NCEP–NCAR reanalysis for the period from 1948 to 2000 in the area of strong sea surface temperature gradients in the Gulf Stream gives strong proof for the association between the propagating cyclones and synoptic patterns of surface turbulent fluxes. It is shown that sea–air interaction in this area is controlled by the sharpness of surface temperature gradients in the ocean and by the intensity of the advection of the air masses in different parts of cyclones during the cold-air and warm-air outbreaks. A simple parameter based on the joint consideration of the characteristics of sea surface temperature and sea level pressure fields is used to characterize the synoptic variability of air–sea turbulent fluxes. The effectiveness of the relationship between surface temperature and surface pressure on one side and air–sea flux anomalies on the other vary from year to year in phase with variability in the frequencies of deep atmospheric cyclones in the Gulf Stream area. The limits of applicability of the approach, its sensitivity to higher-resolution sea surface temperature data, and the possibility of its further applications are discussed.
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  • 63
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    American Meteorological Society
    In:  Journal of Physical Oceanography, 32 . pp. 1112-1116.
    Publication Date: 2018-04-06
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  • 64
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    American Meteorological Society
    In:  Journal of Atmospheric and Oceanic Technology, 15 . pp. 1051-1059.
    Publication Date: 2018-07-04
    Description: A new optical disdrometer has been developed that is optimized for use in high wind speeds, for example, on board ships. The minimal detectable size of droplets is 0.35 mm. Each drop is measured separately with regard to its size and residence time within the sensitive volume. From the available information, the drop size distribution can be calculated with a resolution of 0.05 mm in diameter either by evaluation of the residence time of drops or by drop counting knowing the local wind. Experience shows that using the residence time leads to better results. Rain rates can be determined from the droplet spectra by assuming terminal fall velocity of the drops according to their size. Numerical modeling of disdrometer measurements has been performed, allowing the study of the effect of multiple occupancy of the sensitive volume and grazing incidences on disdrometer measurements. Based on these studies an iterative procedure has been developed to eliminate the impact of these effects on the calculated drop size distributions. This technique may also be applied to any other kind of disdrometer. Long-term simultaneous measurements of the disdrometer and a conventional rain gauge have been used to validate this procedure.
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  • 65
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    American Meteorological Society
    In:  Journal of Climate, 15 . pp. 3043-3057.
    Publication Date: 2018-07-24
    Description: Zonally symmetric fluctuations of the midlatitude westerly winds characterize the primary mode of atmospheric variability in the Southern Hemisphere during all seasons. This is true not only in observations but also in an unforced 15 000-yr integration of a coarse-resolution (R15) coupled ocean–atmosphere model. Here it is documented how this mode of atmospheric variability, known as the Southern Annular Mode (SAM), generates ocean circulation and sea ice variations in the model integration on interannual to centennial timescales that are tightly in phase with the SAM. The positive phase of the SAM is associated with an intensification of the surface westerlies over the circumpolar ocean (around 60°S), and a weakening of the surface westerlies farther north. This induces Ekman drift to the north at all longitudes of the circumpolar ocean, and Ekman drift to the south at around 30°S. Through mass continuity, the Ekman drift generates anomalous upwelling along the margins of the Antarctic continent, and downwelling around 45°S. The anomalous flow diverging from the Antarctic continent also increases the vertical tilt of the isopycnals in the Southern Ocean, so that a more intense circumpolar current is also closely associated with positive SAM. In addition, the anomalous divergent flow advects sea ice farther north, resulting in an increase in sea ice coverage. Finally, positive SAM drives increases in poleward heat transport at about 30°S, while decreases occur in the circumpolar region. Ocean and sea ice anomalies of the opposite sign occur when the SAM is negative. The ocean and sea ice fluctuations associated with the SAM constitute a significant fraction of simulated ocean variability poleward of 30°S year-round. The robustness of the mechanisms relating the SAM to oceanic variability suggests that the SAM is likely an important source of large-scale variability in the real Southern Hemisphere ocean.
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  • 66
    Publication Date: 2018-04-10
    Description: Comparisons are made between a time series of meteorological surface layer observational data taken on board the R/V Knorr, and model analysis data from the European Centre for Medium-Range Weather Forecasting (ECMWF) and the National Centers for Environmental Prediction (NCEP). The observational data were gathered during a winter cruise of the R/V Knorr, from 6 February to 13 March 1997, as part of the Labrador Sea Deep Convection Experiment. The surface layer observations generally compare well with both model representations of the wintertime atmosphere. The biases that exist are mainly related to discrepancies in the sea surface temperature or the relative humidity of the analyses. The surface layer observations are used to generate bulk estimates of the surface momentum flux, and the surface sensible and latent heat fluxes. These are then compared with the model-generated turbulent surface fluxes. The ECMWF surface sensible and latent heat flux time series compare reasonably well, with overestimates of only 13% and 10%, respectively. In contrast, the NCEP model overestimates the bulk fluxes by 51% and 27%, respectively. The differences between the bulk estimates and those of the two models are due to different surface heat flux algorithms. It is shown that the roughness length formula used in the NCEP reanalysis project is inappropriate for moderate to high wind speeds. Its failings are acute for situations of large air–sea temperature difference and high wind speed, that is, for areas of high sensible heat fluxes such as the Labrador Sea, the Norwegian Sea, the Gulf Stream, and the Kuroshio. The new operational NCEP bulk algorithm is found to be more appropriate for such areas. It is concluded that surface turbulent flux fields from the ECMWF are within the bounds of observational uncertainty and therefore suitable for driving ocean models. This is in contrast to the surface flux fields from the NCEP reanalysis project, where the application of a more suitable algorithm to the model surface-layer meteorological data is recommended
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  • 67
    Publication Date: 2018-04-05
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  • 68
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    American Meteorological Society
    In:  Journal of Climate, 19 . pp. 5667-5685.
    Publication Date: 2018-06-29
    Description: This paper analyses secular changes and interannual variability in the wind wave, swell, and significant wave height (SWH) characteristics over the North Atlantic and North Pacific on the basis of wind wave climatology derived from the visual wave observations of voluntary observing ship (VOS) officers. These data are available from the International Comprehensive Ocean–Atmosphere Data Set (ICOADS) collection of surface meteorological observations for 1958–2002, but require much more complicated preprocessing than standard meteorological variables such as sea level pressure, temperature, and wind. Visual VOS data allow for separate analysis of changes in wind sea and swell, as well as in significant wave height, which has been derived from wind sea and swell estimates. In both North Atlantic and North Pacific midlatitudes winter significant wave height shows a secular increase from 10 to 40 cm decade−1 during the last 45 yr. However, in the North Atlantic the patterns of trend changes for wind sea and swell are quite different from each other, showing opposite signs of changes in the northeast Atlantic. Trend patterns of wind sea, swell, and SWH in the North Pacific are more consistent with each other. Qualitatively the same conclusions hold for the analysis of interannual variability whose leading modes demonstrate noticeable differences for wind sea and swell. Statistical analysis shows that variability in wind sea is closely associated with the local wind speed, while swell changes can be driven by the variations in the cyclone counts, implying the importance of forcing frequency for the resulting changes in significant wave height. This mechanism of differences in variability patterns of wind sea and swell is likely more realistic than the northeastward propagation of swells from the regions from which the wind sea signal originates.
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  • 69
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    American Meteorological Society
    In:  Journal of Physical Oceanography, 22 . pp. 361-381.
    Publication Date: 2018-04-05
    Description: A primitive equation model of an idealized ocean basin, driven by simple, study wind and buoyancy forcing at the surface, is used to study the dynamics of mesoscale eddies. Model statistics of a six-year integration using a fine grid (1/6° × 0.2°), with reduced coefficients of horizontal friction, are compared to those using a coarser grid (1/3° × 0.4°), but otherwise identical configuration. Eddy generation in both model cases is primarily due to the release of mean potential energy by baroclinic instability. Horizontal Reynolds stresses become significant near the midlatitude jet of the fine-grid case, with a tendency for preferred energy transfers from the eddies to the mean flow. Using the finer resolution, eddy kinetic energy nearly doubles at the surface of the subtropical gyre, and increases by factors of 3–4 over the jet region and in higher latitudes. The spatial characteristics of the mesoscale fluctuations are examined by calculating zonal wavenumber spectra and velocity autocorrelation functions. With the higher resolution, the dominant eddy scale remains approximately the same in the subtropical gyre but decreases by a factor of 2 in the subpolar areas. The wavenumber spectra indicate a strong influence of the model friction in the coarse-grid case, especially in higher latitudes. Using the coarse grid, there is almost no separation between the energetic eddy scale and the scale where friction begins to dominate, leading to steep spectra beyond the cutoff wavenumber. Using the finer resolution an inertial subrange with a k−3 power law begins to emerge in all model regions outside the equatorial belt. Despite the large increase of eddy intensity in the fine-grid model, effects on the mean northward transport of heat are negligible. Strong eddy fluxes of heat across the midlatitude jet are almost exactly compensated by changes of the heat transport due to the mean flow.
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  • 70
    Publication Date: 2018-04-06
    Description: A new numerical two-layer model is presented, which describes the generation of internal tidal bores and their disintegration into internal solitary waves in the Strait of Messina. This model is used to explain observations made by the synthetic aperture radar (SAR) from the European Remote Sensing satellites ERS 1 and ERS 2. The analysis of available ERS 1/2 SAR data of the Strait of Messina and adjacent sea areas show that 1) northward as well as southward propagating internal waves are generated in the Strait of Messina, 2) southward propagating internal waves are observed more frequently than northward propagating internal waves, 3) sea surface manifestations of southward as well as northward propagating internal waves are stronger during periods where a strong seasonal thermocline is known to be present, 4) southward propagating internal bores are released from the sill between 1 and 5 hours after maximum northward tidal flow and northward propagating internal bores are released between 2 and 6 hours after maximum southward tidal flow, and 5) the spatial separation between the first two internal solitary waves of southward propagating wave trains is smaller in the period from July to September than in the period from October to June. The numerical two-layer model is a composite of two models consisting of 1) a hydrostatic “generation model,” which describes the dynamics of the water masses in the region close to the strait’s sill, where internal bores are generated, and 2) a weakly nonhydrostatic “propagation model,” which describes the dynamics of the water masses outside of the sill region where internal bores may disintegrate into internal solitary waves. Due to a technique for movable lateral boundaries, the generation model is capable of simulating the dynamics of a lower layer that may intersect the bottom topography. The proposed generation–propagation model depends on one space variable only, but it retains several features of a fully three-dimensional model by including a realistic channel depth and a realistic channel width. It is driven by semidiurnal tidal oscillations of the sea level at the two open boundaries of the model domain. Numerical simulations elucidate several observed characteristics of the internal wave field in the Strait of Messina, such as north–south asymmetry, times of release of the internal bores from the strait’s sill, propagation speeds, and spatial separations between the first two solitary waves of internal wave trains.
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  • 71
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    American Meteorological Society
    In:  Journal of Climate, 17 (22). pp. 4463-4472.
    Publication Date: 2017-08-23
    Description: On seasonal time scales, ENSO prediction has become feasible in an operational framework in recent years. On decadal to multidecadal time scales, the variability of the oceanic circulation is assumed to provide a potential for climate prediction. To investigate the decadal predictability of the coupled atmosphere–ocean general circulation model (AOGCM) European Centre-Hamburg model version 5/Max Planck Institute Ocean Model (ECHAM5/MPI-OM), a 500-yr-long control integration and “perfect model” predictability experiments are analyzed. The results show that the sea surface temperatures (SSTs) of the North Atlantic, Nordic Seas, and Southern Ocean exhibit predictability on multidecadal time scales. Over the ocean, the predictability of surface air temperature (SAT) is very similar to that of SST. Over land, there is little evidence of decadal predictability of SAT except for some small maritime-influenced regions of Europe. The AOGCM produces predictable signals in lower-tropospheric temperature and precipitation over the North Atlantic, but not in sea level pressure.
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  • 72
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    American Meteorological Society
    In:  Journal of Climate, 19 (23). pp. 6062-6067.
    Publication Date: 2017-08-23
    Description: The influence of the natural multidecadal variability of the Atlantic meridional overturning circulation (MOC) on European climate is investigated using a simulation with the coupled atmosphere–ocean general circulation model ECHAM5/Max Planck Institute Ocean Model (MPI-OM). The results show that Atlantic MOC fluctuations, which go along with changes in the northward heat transport, in turn affect European climate. Additionally, ensemble predictability experiments with ECHAM5/MPI-OM show that the probability density functions of surface air temperatures in the North Atlantic/European region are affected by the multidecadal variability of the large-scale oceanic circulation. Thus, some useful decadal predictability may exist in the Atlantic/European sector.
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  • 73
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    American Meteorological Society
    In:  Journal of Physical Oceanography, 32 . pp. 687-701.
    Publication Date: 2018-04-06
    Description: The quasi-decadal salinity fluctuations in the upper 300 m of the Labrador Sea are investigated by partitioning all available salinity station data since 1948 by region and bottom depth. There are major freshwater anomalies in the early 1970s (the Great Salinity Anomaly), mid-1980s, and early 1990s. These vary in amplitude throughout the region, being least on the shelf and greatest over the slope region near the Labrador Current. The Labrador Sea cannot be considered a simple conduit for freshwater anomalies originating in the East Greenland Current. There is evidence that local processes modulate the anomaly. The freshwater anomalies in the Labrador Current are approximately twice as large as those in the East Greenland Current. The Baffin Island Current flowing southward through the western Davis Strait is the only local source of freshwater with sufficient volume to account for this increase. The propagation speed, 2–3 cm s−1, of the anomaly along the Labrador Sea margin is much less than the advection speed indicating a highly damped system. The connection of the North Atlantic Oscillation (NAO) with these quasi-decadal salinity fluctuations is most obvious in the Labrador Sea interior, where increased surface buoyancy flux during positive NAO drives deep convective mixing and thus terminates the fresh surface anomalies. Less clear are the processes by which NAO-forced changes of lateral freshwater flux modulate the salinity along the margin. The authors propose a feedback mechanism where, during years of low wind speed, freshwater accumulates offshore of the slope front in the surface layer. The increased upper-layer buoyancy prohibits further mixing, and low salinities persist.
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  • 74
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    American Meteorological Society
    In:  Journal of Physical Oceanography, 28 . pp. 1107-1129.
    Publication Date: 2018-04-06
    Description: On the basis of the collection of individual marine observations available from the Comprehensive Ocean–Atmosphere Data Set, major parameters of the sea state were evaluated. Climatological fields of wind waves and swell height and period, as well as significant wave height and resultant period are obtained for the North Atlantic Ocean for the period from 1964 to 1993. Validation of the results against instrumental records from National Data Buoy Center buoys and ocean weather station measurements indicate relatively good agreement for wave height and systematic biases in the visually estimated periods that were corrected. Wave age, which is important for wind stress estimates, was evaluated form wave and wind observations. The climatology of wave age indicates younger waves in winter in the North Atlantic midlatitudes and Tropics. Wave age estimates were applied to the calculations of the wind stress using parameterizations from field experiments. Differences between wave-age-based and traditional estimates are not negligible in wintertime in midlatitudes and Tropics where wave-induced stress contributes from 5% to 15% to the total stress estimates. Importance of the obtained effects for ocean circulation and climate variability is discussed.
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  • 75
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    American Meteorological Society
    In:  Journal of Physical Oceanography, 29 . pp. 145-157.
    Publication Date: 2018-04-06
    Description: As a contribution to the WOCE Deep Basin Experiment, an array of current meters with individual record lengths exceeding ii years was set across the southern boundary of the Brazil Basin between early 1991 and early 1996. The array spanned the Santos Plateau, the Vema Channel, and the Hunter Channel, all areas believed to be important for transport of Antarctic Bottom Water between the Argentine and Brazil Basins. From the combination of geostrophic velocities computed from hydrographic stations and those directly measured, the total transport of bottom water (potential temperature below 2 degrees C) is estimated to be about 6.9 Sv (Sv = 10(6) m(3) s(-1)) northward, with about 4 Sv coming through the Vema Channel and the remainder through the Hunter Channel. Properties of the eddy field are also discussed. Eddy energy levels and their spatial distribution are similar to comparable regimes in the North Atlantic. Integral timescales vary from a few days to several weeks with distance from the Brazil Current and the western boundary. The eddy heat Bur is in the same direction as the heat advection by the mean flow but considerably smaller.
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  • 76
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    American Meteorological Society
    In:  Journal of Climate, 18 (19). pp. 4013-4031.
    Publication Date: 2017-08-23
    Description: Analyses of a 500-yr control integration with the non-flux-adjusted coupled atmosphere–sea ice–ocean model ECHAM5/Max-Planck-Institute Ocean Model (MPI-OM) show pronounced multidecadal fluctuations of the Atlantic overturning circulation and the associated meridional heat transport. The period of the oscillations is about 70–80 yr. The low-frequency variability of the meridional overturning circulation (MOC) contributes substantially to sea surface temperature and sea ice fluctuations in the North Atlantic. The strength of the overturning circulation is related to the convective activity in the deep-water formation regions, most notably the Labrador Sea, and the time-varying control on the freshwater export from the Arctic to the convection sites modulates the overturning circulation. The variability is sustained by an interplay between the storage and release of freshwater from the central Arctic and circulation changes in the Nordic Seas that are caused by variations in the Atlantic heat and salt transport. The relatively high resolution in the deep-water formation region and the Arctic Ocean suggests that a better representation of convective and frontal processes not only leads to an improvement in the mean state but also introduces new mechanisms determining multidecadal variability in large-scale ocean circulation.
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  • 77
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    American Meteorological Society
    In:  Journal of Physical Oceanography, 37 (4). pp. 946-961.
    Publication Date: 2018-04-11
    Description: A model of the subpolar North Atlantic Ocean is used to study different aspects of ventilation and water mass transformation during a year with moderate convection intensity in the Labrador Sea. The model realistically describes the salient features of the observed hydrographic structure and current system, including boundary currents and recirculations. Ventilation and transformation rates are defined and compared. The transformation rate of Labrador Sea Water (LSW), defined in analogy to several observational studies, is 6.3 Sv (Sv ≡ 106 m3 s−1) in the model. Using an idealized ventilation tracer, mimicking analyses based on chlorofluorocarbon inventories, an LSW ventilation rate of 10 Sv is found. Differences between both rates are particularly significant for those water masses that are partially transformed into denser water masses during winter. The main export route of the ventilated LSW is the deep Labrador Current (LC). Backward calculation of particle trajectories demonstrates that about one-half of the LSW leaving the Labrador Sea within the deep LC originates in the mixed layer during that same year. Near the offshore flank of the deep LC at about 55°W, the transformation of LSW begins in January and is at a maximum in February/March. While the export of transformed LSW out of the central Labrador Sea continues for several months, LSW generated near the boundary current is exported more rapidly, with maximum transport rates during March/April within the deep LC.
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    American Meteorological Society
    In:  Journal of Physical Oceanography, 32 (3). pp. 891-902.
    Publication Date: 2018-04-06
    Description: The so-called equatorial stacked jets are analyzed with ship-board observations and moored time series from the Atlantic Ocean. The features are identified and isolated by comparing vertical wavenumber spectra at the equator with those a few degrees from the equator. Mode-filtering gives clear views of the jets in meridional sections, the typical extent being ±1° in latitude. The vertical structure can be well described (explaining 82% of the variance) by N−1-stretched cosines, with a Gaussian amplitude tapering in the vertical. The stretched wavelengths are somewhat variable. Fitting jets of a fixed (stretched) wavelength to four moored sensors in the depth range 1300–1900 m, allows one to track the vertical phase of the jets with an rms error of 30°–45°. The resulting fit from a 20-month moored time series shows long periods of unchanging jet conditions and intermittent times of high variability. There is no significant vertical propagation on these timescales nor a seasonal reversal. Using a composite from many different experiments, interannual variability is visible, however. A possible mechanism for the stacked jets is inertial instability, resulting from background meridional shears at the equator. A condition is that the Ertel potential vorticity becomes zero somewhere, due to meridional asymmetries in the zonal flows. The ship-board observations show that this may be approximately fulfilled by the instantaneous zonal low-mode flows at various depths, resulting from an excess of zonal momentum south of the equator most of the time. Inertial instability should act to redistribute this zonal momentum, and our mooring data show indeed persistent northward momentum flux, but not at the depth levels expected. The momentum transport might suggest that the jets can also flux or mix other properties across the equator.
    Type: Article , PeerReviewed
    Format: text
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  • 79
    Publication Date: 2018-04-05
    Description: The monthly mean wind stress climatology of Hellerman and Rosenstein (HR) is compared with the climatology of Isemer and Hasse (IH), which represents a version of the Bunker atlas (BU) for the North Atlantic based on revised parameterizations. The drag coefficients adopted by IH are 21% smaller than the values of BU and HR, and the calculation of wind speed from marine estimates of Beaufort force (Bft) is based on a revised Beaufort equivalent scale similar to the scientific scale recommended by WMO. The latter choice significantly increases wind speed below Bft 8, and effectively counteracts the reduction of the drag coefficients. Comparing the IH stresses with HR reveals substantially enhanced magnitudes in the trade wind region throughout the year. At 15°N the mean easterly stress increases from about 0.9 (HR) to about 1.2 dyn cm−1 (IH). Annual mean differences are smaller in the region of the westerlies. In winter, the effect due to the reduced drag coefficient dominates and leads to smaller stress values in IH; during summer season the revision of the Beaufort equivalents is more effective and leads to increased stresses. Implications of the different wind stress climatologies for forcing the large-scale ocean circulation are discussed by means of the Sverdrup transport streamfunction (ψs): Throughout the subtropical gyre a significant intensification of ψs takes place with IH. At 27°N, differences of more than 10 Sv (1 Sv ≡ 106 m3 s−1) are found near the western boundary. Differences in the seasonality of ψs are more pronounced in near-equatorial regions where IH increase the amplitude of the annual cycle by about 50%. An eddy-resolving model of the North Atlantic circulation is used to examine the effect of the different wind stresses on the seasonal cycle of the Florida Current. The transport predicted by the numerical model is in much better agreement with observations when the circulation is forced by IH than by HR, regarding both the annual mean (29.1 Sv vs 23.2 Sv) and the seasonal range (6.3 Sv vs 3.4 Sv).
    Type: Article , PeerReviewed
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