171 research outputs found

    Shifting family bilingualism: two South African case studies

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    This ethnographic, sociolinguistic study describes the home language practices of two Afrikaans/English bilingual families, living in two middle-class English-dominant neighbourhoods, with the youngest children attending an English-medium primary school. In this study, I investigate if these families maintain their existing Afrikaans-dominant bilingualism, or shift towards greater use of English. According to the sociolinguistic literature, there is an on-going relationship between the processes of language maintenance and shift. Factors that influence these processes include bilingualism, marriage patterns, socio-economic status, prestige of dominant languages, domains, educational environment, school peer group and attitudes as well as perceptions about languages and language use. The database consists of naturalistic observations, interviews and language diaries. Conversations between family members in their respective homes were audio-recorded (32 hours of observations in total) and open-ended interviews were conducted with family members about their language use and attitudes. The children completed language diaries where they self-reported their language use at home and at school. The findings are as follows: both families speak English, Afrikaans as well as varieties of English and Afrikaans characterised by code-switching, code-mixing and borrowings in the home. The Petersen family presents with intergenerational transmission and maintenance of Afrikaans from the mother and brothers to the younger daughters. ‘Teaching moments’ in this family, characterised by an active interrelationship between English and Afrikaans, result in the transmission and use of Afrikaans and English between the family members. As a result of the domestic Afrikaans maintenance, the two daughters continue to speak Afrikaans and express a positive attitude toward the language in general and their bilingual identity in particular

    Nitrous Oxide in the Atmosphere: First Measurements of a Lower Thermospheric Source

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    Nitrous oxide (N2O) is an important anthropogenic greenhouse gas, as well as one of the most significant anthropogenic ozone-depleting substances in the stratosphere. The satellite-based instrument Atmospheric Chemistry Experiment-Fourier Transform Spectrometer has been observing the Earth\u27s limb since 2004 and derives profiles of N2O volume mixing ratios in the upper troposphere to the lower thermosphere. The resulting climatology shows that N2O is continuously produced in the lower thermosphere via energetic particle precipitation and enhanced N2O is present at all latitudes, during all seasons. The results are consistent with an N2O production source peaking near or above 94 km via low-energy particles, as well as a polar wintertime source near 70 km via medium energy particles. N2O produced in the polar upper atmosphere descends each winter to as far down as ∼40 km. ©2016. American Geophysical Union

    Hydrocarbons in the Upper Troposphere and Lower Stratosphere Observed from ACE-FTS and Comparisons with WACCM

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    Satellite measurements from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) are used to examine the global, seasonal variations of several hydrocarbons, including carbon monoxide (CO), ethane (C2H6), acetylene (C2H2), and hydrogen cyanide (HCN). We focus on quantifying large-scale seasonal behavior from the middle troposphere to the stratosphere, particularly in the tropics, and furthermore make detailed comparisons with the Whole Atmosphere Community Climate Model (WACCM) chemistry climate model (incorporating tropospheric photochemistry, time-varying hydrocarbon emissions, and meteorological fields nudged from reanalysis). Comparisons with Microwave Limb Sounder (MLS) measurements of CO are also included to understand sampling limitations of the ACE-FTS data and biases among observational data sets. Results show similar overall variability for CO, C2H6, and C2H2, with a semiannual cycle in the tropical upper troposphere related to seasonally varying sources and deep tropical convection, plus a maximum during Northern Hemisphere summer tied to the Asian monsoon anticyclone. These species also reveal a strong annual cycle above the tropical tropopause, tied to annual variations in the upward branch of Brewer-Dobson circulation. HCN reveals substantial differences from the other species, due to a longer photochemical lifetime and a chemical sink associated with ocean surface contact, which produces a minimum in the tropical upper troposphere not observed in the other species. For HCN, transport to the stratosphere occurs primarily through the Asian summer monsoon anticyclone. Overall, the WACCM simulation is able to reproduce most of the large-scale features observed in the ACE-FTS data, suggesting a reasonable simulation of sources and large-scale transport. The model is too low in the Southern Hemisphere subtropics during Austral spring, which indicates underestimate of biomass burning emissions and/or insufficient vertical transport in the model. © 2012. American Geophysical Union

    Equivalent linear change in cognition between individuals with bipolar disorder and healthy controls over 5 years

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    ObjectivesCognitive dysfunction is a key feature of bipolar disorder (BD). However, not much is known about its temporal stability, as some studies have demonstrated a neurodegenerative model in BD while others have shown no change in cognitive functioning over time. Building upon our prior work, which examined the natural course of executive functioning, the current study aimed to investigate the natural course of memory, emotion processing, and fine motor dexterity over a 5‐year period in BD and healthy control (HC) samples.MethodsUsing a 5‐year longitudinal cohort, 90 individuals with BD and 17 HCs were administered a battery of neuropsychological tests at study baseline and at 1 and 5 years after study entry that captured four areas of cognitive performance: visual memory, auditory memory, emotion processing, and fine motor dexterity.ResultsLatent growth curve modeling showed no group differences in the slopes of any of the cognitive factors between the BD and HC groups. Age at baseline was negatively associated with visual memory, emotion processing, and fine motor dexterity. Education level was positively associated with auditory and visual memory and fine motor. Female gender was negatively associated with emotion processing.ConclusionsExtending our prior work on longitudinal evaluation of executive functioning, individuals with BD show similar linear change in other areas of cognitive functioning including memory, emotion processing, and fine motor dexterity as compared to unaffected HCs. Age, education, and gender may have some differential effects on cognitive changes.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142144/1/bdi12532.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142144/2/bdi12532_am.pd

    Influence of cognitive reserve on neuropsychological functioning in bipolar disorder: Findings from a 5‐year longitudinal study

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136365/1/bdi12470_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136365/2/bdi12470.pd

    A Multi-Parameter Dynamical Diagnostics for Upper Tropospheric and Lower Stratospheric Studies

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    Ozone trend estimates have shown large uncertainties in the upper troposphere/lower stratosphere (UTLS) region despite multi-decadal observations available from ground-based, balloon, aircraft, and satellite platforms. These uncertainties arise from large natural variability driven by dynamics (reflected in tropopause and jet variations) as well as the strength in constituent transport and mixing. Additionally, despite all the community efforts there is still a lack of representative high-quality global UTLS measurements to capture this variability. The Stratosphere-troposphere Processes And their Role in Climate (SPARC) Observed Composition Trends and Variability in the UTLS (OCTAV-UTLS) activity aims to reduce uncertainties in UTLS composition trend estimates by accounting for this dynamically induced variability. In this paper, we describe the production of dynamical diagnostics using meteorological information from reanalysis fields that facilitate mapping observations from several platforms into numerous geophysically-based coordinates (including tropopause and upper tropospheric jet relative coordinates). Suitable coordinates should increase the homogeneity of the air masses analyzed together, thus reducing the uncertainty caused by spatio-temporal sampling biases in the quantification of UTLS composition trends. This approach thus provides a framework for comparing measurements with diverse sampling patterns and leverages the meteorological context to derive maximum information on UTLS composition and trends and its relationships to dynamical variability. The dynamical diagnostics presented here are the first comprehensive set describing the meteorological context for multi-decadal observations by ozonesondes, lidar, aircraft, and satellite measurements in order to study the impact of dynamical processes on observed UTLS trends by different sensors on different platforms. Examples using these diagnostics to map multi-platform datasets into different geophysically-based coordinate systems are provided. The diagnostics presented can also be applied to analysis of greenhouse gases other than ozone that are relevant to surface climate and UTLS chemistry.</p

    Validation of ACE-FTS Version 3.5 NOy Species Profiles Using Correlative Satellite Measurements

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    The ACE-FTS (Atmospheric Chemistry Experiment - Fourier Transform Spectrometer) instrument on the Canadian SCISAT satellite, which has been in operation for over 12 years, has the capability of deriving stratospheric profiles of many of the NOy (N + NO + NO2 + NO3 + 2 x N2O5 + HNO3 + HNO4 + ClONO2 + BrONO2) species. Version 2.2 of ACE-FTS NO, NO2, HNO3, N2O5, and ClONO2 has previously been validated, and this study compares the most recent version (v3.5) of these five ACE-FTS products to spatially and temporally coincident measurements from other satellite instruments - GOMOS, HALOE, MAESTRO, MIPAS, MLS, OSIRIS, POAM III, SAGE III, SCIAMACHY, SMILES, and SMR. For each ACE-FTS measurement, a photochemical box model was used to simulate the diurnal variations of the NOy species and the ACE-FTS measurements were scaled to the local times of the coincident measurements. The comparisons for all five species show good agreement with correlative satellite measurements. For NO in the altitude range of 25-50 km, ACE-FTS typically agrees with correlative data to within -10%. Instrument-averaged mean relative differences are approximately -10% at 30-40 km for NO2, within ± 7% at 8-30km for HNO3, better than -7 % at 21-34 km for local morning N205, and better than -8% at 21-34 km for ClONO2. Where possible, the variations in the mean differences due to changes in the comparison local time and latitude are also discussed

    MIPAS observations of ozone in the middle atmosphere

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    This work is distributed under the Creative Commons Attribution 4.0 License.In this paper we describe the stratospheric and mesospheric ozone (version V5r-O3-m22) distributions retrieved from MIPAS observations in the three middle atmosphere modes (MA, NLC, and UA) taken with an unapodized spectral resolution of 0.0625 cm from 2005 until April 2012. O is retrieved from microwindows in the 14.8 and 10 μm spectral regions and requires non-local thermodynamic equilibrium (non-LTE) modelling of the O and vibrational levels. Ozone is reliably retrieved from 20 km in the MA mode (40 km for UA and NLC) up to ∼105 km during dark conditions and up to ∼95 km during illuminated conditions. Daytime MIPAS O has an average vertical resolution of 3-4 km below 70 km, 6-8 km at 70-80 km, 8-10 km at 80-90, and 5-7 km at the secondary maximum (90-100 km). For nighttime conditions, the vertical resolution is similar below 70 km and better in the upper mesosphere and lower thermosphere: 4-6 km at 70-100 km, 4-5 km at the secondary maximum, and 6-8 km at 100-105 km. The noise error for daytime conditions is typically smaller than 2% below 50 km, 2-10% between 50 and 70 km, 10-20% at 70-90 km, and ∼30% above 95 km. For nighttime, the noise errors are very similar below around 70 km but significantly smaller above, being 10-20% at 75-95 km, 20-30% at 95-100 km, and larger than 30% above 100 km. The additional major O errors are the spectroscopic data uncertainties below 50 km (10-12 %) and the non-LTE and temperature errors above 70 km. The validation performed suggests that the spectroscopic errors below 50 km, mainly caused by the O air-broadened half-widths of the band, are overestimated. The non-LTE error (including the uncertainty of atomic oxygen in nighttime) is relevant only above ∼85 km with values of 15-20 %. The temperature error varies from ∼3% up to 80 km to 15-20% near 100 km. Between 50 and 70 km, the pointing and spectroscopic errors are the dominant uncertainties. The validation performed in comparisons with SABER, GOMOS, MLS, SMILES, and ACE-FTS shows that MIPAS O has an accuracy better than 5% at and below 50 km, with a positive bias of a few percent. In the 50-75 km region, MIPAS O has a positive bias of ∼10 %, which is possibly caused in part by O spectroscopic errors in the 10 μm region. Between 75 and 90 km, MIPAS nighttime O is in agreement with other instruments by 10 %, but for daytime the agreement is slightly larger, ∼10-20 %. Above 90 km, MIPAS daytime O is in agreement with other instruments by 10 %. At night, however, it shows a positive bias increasing from 10% at 90 km to 20% at 95-100 km, the latter of which is attributed to the large atomic oxygen abundance used. We also present MIPAS O distributions as function of altitude, latitude, and time, showing the major O features in the middle and upper mesosphere. In addition to the rapid diurnal variation due to photochemistry, the data also show apparent signatures of the diurnal migrating tide during both day-and nighttime, as well as the effects of the semi-Annual oscillation above ∼70 km in the tropics and mid-latitudes. The tropical. daytime O at 90 km shows a solar signature in phase with the solar cycle. © Author(s) 2018.The IAA team was supported by the Spanish MICINN under the project ESP2014-54362-P and EC FEDER funds. The IAA and IMK teams were partially supported by ESA O3-CCI and MesosphEO projects. Maya Garcia-Comas was financially supported by MINECO through its >Ramon y Cajal> subprogram. Funding for the Atmospheric Chemistry Experiment comes primarily from the Canadian Space Agency. Work at the Jet Propulsion Laboratory was performed under contract with the National Aeronautics and Space Administration

    Updated merged SAGE-CCI-OMPS+ dataset for the evaluation of ozone trends in the stratosphere

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    In this paper, we present the updated SAGE-CCI-OMPS+ climate data record of monthly zonal mean ozone profiles. This dataset covers the stratosphere and combines measurements by nine limb and occultation satellite instruments – SAGE II (Stratospheric Aerosol and Gases Experiment II), OSIRIS (Optical Spectrograph and InfraRed Imaging System), MIPAS (Michelson Interferometer for Passive Atmospheric Sounding), SCIAMACHY (SCanning Imaging Spectrometer for Atmospheric CHartographY), GOMOS (Global Ozone Monitoring by Occultation of Stars), ACE-FTS (Atmospheric Chemistry Experiment Fourier Transform Spectrometer), OMPS-LP (Ozone Monitor Profiling Suite Limb Profiler), POAM (Polar Ozone and Aerosol Measurement) III, and SAGE III/ISS (Stratospheric Aerosol and Gases Experiment III on the International Space Station). Compared to the original version of the SAGE-CCI-OMPS dataset (Sofieva et al., 2017b), the update includes new versions of MIPAS, ACE-FTS, and OSIRIS datasets and introduces data from additional sensors (POAM III and SAGE III/ISS) and retrieval processors (OMPS-LP). In this paper, we show detailed intercomparisons of ozone profiles from different instruments and data versions, with a focus on the detection of possible drifts in the datasets. The SAGE-CCI-OMPS+ dataset has a better coverage of polar regions and of the upper troposphere and the lower stratosphere (UTLS) than the previous dataset. We also studied the influence of including new datasets on ozone trends, which are estimated using multiple linear regression. The changes in the merged dataset do not change the overall morphology of post-1997 ozone trends; statistically significant trends are observed in the upper stratosphere. The largest changes in ozone trends are observed in polar regions, especially in the Southern Hemisphere
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