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  • 1
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    A case study of an elevated stratopause generated in the Whole Atmosphere Community Climate Model (2011)
    Wiley
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    Publication Date: 2011-04-20
    Description: The Whole Atmosphere Community Climate Model (WACCM) is used to study the influence of gravity waves on the generation and evolution of an elevated stratopause following a sudden stratospheric warming (SSW). By comparing WACCM simulations of two Arctic winters, where one is dynamically undisturbed and one is disturbed, we find that intense planetary wave activity during a SSW drives the reversal of the zonal mean wind in the stratosphere. This alters the penetration of eastward propagating, non-orographic gravity waves into the mesosphere, which determine the extent of cooling in the lower mesosphere and upper stratosphere through the adiabatic effects of the gravity wave-driven residual circulation, and play a crucial role in the reformation of the elevated stratopause in the lower mesosphere. Eventually, the forcing due to gravity waves returns to normal wintertime values as the stratospheric zonal wind recovers, and is then associated with the warming and lowering of the elevated stratopause, by wave induced diabatic descent. We find that SSW followed by an elevated stratopause is a climatologically robust phenomenon in free running WACCM with characteristics closely resembling recently observed events in the Arctic.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    A climatology of elevated stratopause events in the whole atmosphere community climate model (2013)
    Wiley
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    Publication Date: 2013-01-05
    Description: [1]  Elevated stratopause (ES) events occurring during Northern Hemisphere winter are identified in four climate simulations of the period 1953-2005 made with the Whole Atmosphere Community Climate Model (WACCM). We find 68 ES events in 212 winters. These events are found in winters when the middle atmosphere is disturbed and there are zonal wind reversals in the stratosphere at high latitudes. These disturbances can be associated with both major and minor stratospheric sudden warming events (SSWs). The ES events occur under conditions where the stratospheric jet, the gravity wave forcing, and the residual circulation remain reversed longer than in those winters where a SSW occurs without an ES. We compare ES events with the type of SSW (vortex splitting and vortex displacement) and find that 68% of ES events form after vortex splitting events. We also present a climatology of ES events based on NASA's Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis data from 1979 to 2012 and compare it to the model results. WACCM composites of major SSW and ES also show enhanced Eliassen-Palm flux divergences in the upper mesosphere after the stratospheric warming, immediately before the formation of an ES. However, the formation of an ES in WACCM is, due primarily to adiabatic heating from gravity wave-driven downwelling, which follows the re-establishment of the eastward jet in the upper stratosphere. We find nine winters where an ES forms in the absence of any significant planetary wave activity in the upper mesosphere and illustrate one such event.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Chemical Definition of the Mesospheric Polar Vortex (2015)
    Wiley
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    Publication Date: 2015-09-22
    Description: We present a simple chemical definition to demark the edge of the mesospheric polar vortices. Because this vortex definition does not rely on the wind field it is useful in the mesosphere where wind observations are sparse and reanalysis winds are unreliable. The chemical definition is also insensitive to double jets that complicate vortex identification in the mesosphere. The algorithm is based on horizontal gradients of carbon monoxide (CO) and mirrors the widely used vortex edge definition in the stratosphere based on potential vorticity (PV) gradients. Here, the approach is used to identify the Arctic vortex in the mesosphere during a 10-year (2004–2014) record of Microwave Limb Sounder data. Vortex size and shape comparisons are made where the CO and PV methods overlap in the upper stratosphere. A case study is presented during the NH 2008–2009 winter that demonstrates the fidelity of the CO gradient method on individual days and emphasizes the impact of double jets on methods to identify the polar vortex. We recommend transitioning from a PV or stream function-based vortex definition in the stratosphere to using a CO gradient definition above 0.1 hPa (~60 km). The CO gradient method identifies a coherent region of high CO at 80 km that is confined to mid-to-high latitudes 99.8% of the time during Arctic winter. Taking advantage of the CO gradient method to identify the polar vortex adds ~20 km of reliable vortex information (from 60–80 km) in a region of the atmosphere where reanalyses are most suspect.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 4
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    A climatology of cold air outbreaks over North America: WACCM and ERA-40 comparison and analysis (2011)
    Wiley
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    Publication Date: 2011-06-23
    Description: A climatology of cold air outbreaks (CAOs) over North America is presented on the basis of a 50 year simulation of the Whole Atmosphere Community Climate Model (WACCM). This climatology is compared to a similar CAO climatology based on 45 years (1957–2002) of European Centre for Medium-Range Weather Forecasts 40 Year Re-Analysis Project (ERA-40) data. A CAO is identified at a given grid point if the following criteria are met: (1) the surface temperature is lower than 1.5 standard deviations below the 31 day climatological running mean, (2) the standard deviation in temperature is greater than 2 K, and (3) conditions 1 and 2 are satisfied over a contiguous area of ∼5° longitude by 5° latitude. WACCM and ERA-40 comparisons are shown for CAO frequency, temperature anomaly from 31 day climatological mean, geographical location, minimum temperature, and areal extent. Overall, CAOs in WACCM occur ∼30% less frequently than in ERA-40 but cover ∼30% greater area and are 1–2 K lower. In midwinter, WACCM CAOs form at lower latitudes and penetrate to lower latitudes compared to CAOs in ERA-40.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 5
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    Wind and temperature response of midlatitude mesopause region to the 2009 Sudden Stratospheric Warming (2012)
    Wiley
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    Publication Date: 2012-05-09
    Description: In this paper we report winds and temperature in the mesopause region (80–102 km) over full diurnal cycles during the 2009 major Sudden Stratospheric Warming (SSW) at Fort Collins (41°N, 105°W). The measurements were made with the Colorado State University (CSU) sodium Doppler wind-temperature lidar. We deduce the diurnal mean wind and temperature profiles by removing the tidal components from the 24-h continuous observations and present their anomalous behaviors in connection with this event. These mean wind and temperature measurements reveal significant anomalies in the mesopause region: the mean temperature at 80 km was approximately 30 K lower than the climatological mean; the mean zonal wind ranged between ∼ −10 to 0 m/s from 80 to 97 km and then turned eastward in lower thermosphere in a reversal of the climatological mean wind profile. We further use observations from the TIMED/SABER satellite observations and simulations from the WACCM model to investigate the global structure of this dynamical anomaly at Fort Collins. The satellite observations and model reveal that the anomaly is part of a disturbance that extended from the polar region to Fort Collins. These simultaneous wind- and temperature-lidar observations document the direct impact of a major SSW on the dynamic and thermal circulation of the midlatitude mesopause region.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 6
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    A Climatology of Planetary Wave-Driven Mesospheric Inversion Layers in the Extratropical Winter (2014)
    Wiley
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    Publication Date: 2014-12-12
    Description: Mesospheric inversion layers (MILs) are a useful diagnostic to simultaneously investigate middle atmosphere radiation, chemistry, and dynamics in high-top general circulation models. Climatologies of long-lived extratropical winter MILs observed by the Microwave Limb Sounder (MLS) and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) are compared to MILs in the Whole Atmosphere Community Climate Model (WACCM). In general, MIL location, amplitude, and thickness statistics in WACCM are in good agreement with the observations, though WACCM middle and high latitude winter MILs occur 30%-50% more often than in MLS and SABER. This work suggests that planetary wave driven MILs may form as high as 90 km. In the winter, MILs display a wave-1 pattern in both hemispheres, forming most often over the region where the climatological winter stratospheric anticyclones occur. These MILs are driven by the decay of vertically propagating planetary waves in the mesospheric surf zone in both observations and in the model. At the base of polar inversions there is climatological local ascent and cooling situated atop the stratospheric anticyclones, which enhances the cold base of the MILs near 60 km and 120° E longitude.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 7
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    First lidar observation of the mesospheric nickel layer (2015)
    Wiley
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    Publication Date: 2015-01-09
    Description: Ground-based resonance lidar has been used to detect the mesospheric nickel (Ni) layer. The Ni layer is detected through absorption in the 3d 8 ( 3 F)4s 2 3d 9 ( 2 D)4p transition at 337.1 nm and re-emission in both the 3d 9 ( 2 D)4p 3d 8 ( 3 F)4s 2 and 3d 9 ( 2 D)4p 3d 9 ( 2 D)4s transitions at 337.1 and 339.4 nm respectively. Results from wintertime lidar observations on two nights (27-28 November and 20-21 December 2012) at Chatanika, Alaska (65°N, 147°W) are presented. The wintertime Ni layer has a peak concentration of 1.6×10 4 cm -3 at 87 km, with a column abundance of 2.7×10 10 cm -2 , centroid height of 88 km, and rms width of 6.4 km. The midwinter abundance of mesospheric iron (Fe) at Chatanika is 3.4×10 10 cm -2 indicating a ratio of Fe to Ni of 1.2 in the upper atmosphere. This is significantly lower than the value of 18 for the ratio of Fe to Ni in chondrite meteorites..
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
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  • 8
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    Loss of delta-catenin function in severe autism (2015)
    Nature Publishing Group (NPG)
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    Publication Date: 2015-03-26
    Description: Autism is a multifactorial neurodevelopmental disorder affecting more males than females; consequently, under a multifactorial genetic hypothesis, females are affected only when they cross a higher biological threshold. We hypothesize that deleterious variants at conserved residues are enriched in severely affected patients arising from female-enriched multiplex families with severe disease, enhancing the detection of key autism genes in modest numbers of cases. Here we show the use of this strategy by identifying missense and dosage sequence variants in the gene encoding the adhesive junction-associated delta-catenin protein (CTNND2) in female-enriched multiplex families and demonstrating their loss-of-function effect by functional analyses in zebrafish embryos and cultured hippocampal neurons from wild-type and Ctnnd2 null mouse embryos. Finally, through gene expression and network analyses, we highlight a critical role for CTNND2 in neuronal development and an intimate connection to chromatin biology. Our data contribute to the understanding of the genetic architecture of autism and suggest that genetic analyses of phenotypic extremes, such as female-enriched multiplex families, are of innate value in multifactorial disorders.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4383723/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4383723/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Turner, Tychele N -- Sharma, Kamal -- Oh, Edwin C -- Liu, Yangfan P -- Collins, Ryan L -- Sosa, Maria X -- Auer, Dallas R -- Brand, Harrison -- Sanders, Stephan J -- Moreno-De-Luca, Daniel -- Pihur, Vasyl -- Plona, Teri -- Pike, Kristen -- Soppet, Daniel R -- Smith, Michael W -- Cheung, Sau Wai -- Martin, Christa Lese -- State, Matthew W -- Talkowski, Michael E -- Cook, Edwin -- Huganir, Richard -- Katsanis, Nicholas -- Chakravarti, Aravinda -- 1U24MH081810/MH/NIMH NIH HHS/ -- 5R25MH071584-07/MH/NIMH NIH HHS/ -- MH095867/MH/NIMH NIH HHS/ -- MH19961-14/MH/NIMH NIH HHS/ -- R00 MH095867/MH/NIMH NIH HHS/ -- R01 DK075972/DK/NIDDK NIH HHS/ -- R01 MH060007/MH/NIMH NIH HHS/ -- R01 MH074090/MH/NIMH NIH HHS/ -- R01MH074090/MH/NIMH NIH HHS/ -- R01MH081754/MH/NIMH NIH HHS/ -- England -- Nature. 2015 Apr 2;520(7545):51-6. doi: 10.1038/nature14186. Epub 2015 Mar 25.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Center for Complex Disease Genomics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA [2] Predoctoral Training Program in Human Genetics and Molecular Biology, McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA [3] National Institute of Mental Health (NIMH) Autism Centers of Excellence (ACE) Genetics Consortium at the University of California, Los Angeles, Los Angeles, California 90095, USA. ; Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA. ; Center for Human Disease Modeling, Duke University, Durham, North Carolina 27710, USA. ; Center for Human Genetic Research, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA. ; 1] Center for Complex Disease Genomics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA [2] National Institute of Mental Health (NIMH) Autism Centers of Excellence (ACE) Genetics Consortium at the University of California, Los Angeles, Los Angeles, California 90095, USA. ; 1] Center for Human Genetic Research, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA [2] Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 USA. ; 1] National Institute of Mental Health (NIMH) Autism Centers of Excellence (ACE) Genetics Consortium at the University of California, Los Angeles, Los Angeles, California 90095, USA [2] Department of Psychiatry, University of California, San Francisco, San Francisco, California 94158, USA. ; 1] National Institute of Mental Health (NIMH) Autism Centers of Excellence (ACE) Genetics Consortium at the University of California, Los Angeles, Los Angeles, California 90095, USA [2] Department of Psychiatry, Yale University, New Haven, Connecticut 06511, USA. ; Leidos Biomedical Research, Inc., Frederick, Maryland 21702, USA. ; National Human Genome Research Institute, Bethesda, Maryland 20892, USA. ; Baylor College of Medicine, Houston, Texas 77030, USA. ; 1] National Institute of Mental Health (NIMH) Autism Centers of Excellence (ACE) Genetics Consortium at the University of California, Los Angeles, Los Angeles, California 90095, USA [2] Autism &Developmental Medicine Institute, Geisinger Health System, Lewisburg, Pennsylvania 17837, USA. ; University of Illinois at Chicago, Chicago, Illinois 60608, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25807484" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Autistic Disorder/*genetics/*metabolism ; Brain/embryology/*metabolism ; Catenins/*deficiency/*genetics/metabolism ; Cells, Cultured ; Chromatin/genetics/metabolism ; DNA Copy Number Variations/genetics ; Embryo, Mammalian/cytology/metabolism ; Exome/genetics ; Female ; Gene Expression ; Gene Expression Regulation, Developmental ; Hippocampus/pathology ; Humans ; Male ; Mice ; Models, Genetic ; Multifactorial Inheritance/genetics ; Mutation, Missense ; Nerve Net ; Neurons/cytology/metabolism ; Sex Characteristics ; Zebrafish/embryology/genetics/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 9
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    Secondary planetary waves in the middle and upper atmosphere following the stratospheric sudden warming event of January 2012 (2013)
    Wiley
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    Publication Date: 2013-03-21
    Description: [1]  The role of planetary waves in causing stratospheric sudden warmings (SSWs) is well understood and quantified. However, recent studies have indicated that secondary planetary waves are excited in the mesosphere and lower thermosphere (MLT) following SSWs. We use a version of the Whole Atmosphere Community Climate Model (WACCM) constrained by reanalysis data below 50 km to simulate the SSW of January 2012, a minor warming followed by the formation of an elevated stratopause. We document the occurrence of enhanced Eliassen-Palm flux divergence in the MLT associated with faster, secondary westward-propagating planetary waves of wave number 1 and period 〈 10 days. We confirm the presence of these secondary planetary waves using observations made by the SABER instrument onboard NASA's TIMED satellite.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
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  • 10
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    Gravity Wave Dynamics in a Mesospheric Inversion Layer: 1. Reflection, Trapping, and Instability Dynamics (2017)
    Wiley
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    Publication Date: 2017-11-19
    Description: An anelastic numerical model is employed to explore the dynamics of gravity waves (GWs) encountering a mesosphere inversion layer (MIL) having a moderate static stability enhancement and a layer of weaker static stability above. Instabilities occur within the MIL when the GW amplitude approaches that required for GW breaking due to compression of the vertical wavelength accompanying the increasing static stability. Thus MILs can cause large-amplitude GWs to yield instabilities and turbulence below the altitude where they would otherwise arise. Smaller amplitude GWs encountering a MIL do not lead to instability and turbulence, but do exhibit partial reflection and transmission, and the transmission is a smaller fraction of the incident GW when instabilities and turbulence arise within the MIL. Additionally, greater GW transmission occurs for weaker MILs and for GWs having larger vertical wavelengths relative to the MIL depth and for lower GW intrinsic frequencies. These results imply similar dynamics for inversions due to other sources, including the tropopause inversion layer, the high stability capping the polar summer mesopause, and lower-frequency GWs or tides having sufficient amplitudes to yield significant variations in stability at large and small vertical scales. MILs also imply much stronger reflections and less coherent GW propagation in environments having significant fine structure in the stability and velocity fields than in environments that are smoothly varying.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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