Wave forcing of the quasi-biennial oscillation in the Max Planck Institute Earth System Model

This study investigates the resolved wave forcing of the quasi-biennial oscillation (QBO) in the Max Planck Institute Earth System Model truncated at T63 with 95 vertical levels. The model, which parameterizes unresolved gravity waves, internally generates a QBO. The resolved waves contribute up to 50% and 30% to the total wave forcing (resolved plus parameterized) of the QBO westerly and easterly jet, respectively, mostly owing to waves with zonal wavenumbers lower than 20 and frequencies lower than 0.5 cpd. At higher frequencies and wavenumbers, the model underestimates the strength of the tropospheric wave sources when compared to Tropical Rainfall Measuring Mission (TRMM) observations and applies strong horizontal diffusion, which explains the shortage of wave momentum at these scales (relative to recent studies based on high-resolution models). The study further relates the vertical structure of equatorial Kelvin waves, which contribute most to the transport and deposition of westerly wave momentum, to their radiative dissipation and compares the role of longwave radiation and horizontal diffusion in the dissipation of the resolved waves in general. The Kelvin waves adjust their vertical wavelength according to their intrinsic phase speed and are efficiently damped by longwave radiation within westerly flow, where the vertical wavelength strongly decreases. Waves with zonal wavenumbers larger than 10, however, are mostly damped by horizontal diffusion. The latitudinal distribution of the resolved wave forcing reflects the latitudinal structure of the waves and is asymmetric with respect to the equator. © 2014 American Meteorological Society

Seasonal aspects of the quasi-biennial oscillation in the Max Planck Institute Earth System Model and ERA-40

This study investigates seasonal modulations of the quasi-biennial oscillation (QBO) of the tropical stratosphere. For this purpose, the Max Planck Institute Earth System Model (MPI-ESM), which internally generates a realistic QBO compared to the ERA-40 data set, is employed. The modeled QBO is forced with resolved and parametrized waves. At 5 hPa, the seasonal distribution of the onset of QBO westerly jets clusters in spring and fall due to the coupling of the QBO and the semiannual oscillation. This seasonal clustering of the westerly jets extends throughout the stratosphere, shifting to later months with increasing pressure. QBO westerly jets starting in the upper stratosphere in fall propagate to the middle stratosphere more slowly than westerly jets starting in spring. This is attributed to seasonal modulations of the QBO forcing and enhanced wave filtering by the QBO westerly jet in the lower stratosphere in fall and winter compared to spring and summer. The observed stalling of the QBO easterly jet in the lower stratosphere and the accompanied prolonged persistence of the QBO westerly jet in the vicinity of the tropopause are attributed equally to seasonal variations of the resolved and parameterized wave forcing and the advective forcing

The influence of the spectral truncation on the simulation of waves in the tropical stratosphere

Convectively triggered waves are the main driver of the tropical stratospheric circulation. In atmospheric models, the model’s resolution limits the length of the simulated wave spectrum. In this study, the authorscompare the tropical tropospheric wave sources, their projection on the wave field in the lower stratosphere, and the circumstances of their upward propagation in the atmospheric model ECHAM6 with three spectral truncations of T63, T127, and T255. The model internally generates the quasi biennial oscillation (QBO),which dominates the variability in the tropical stratosphere. This analysis focuses on two opposite phases of the QBO to account for the influence of the background wind field on the wave filtering. It is shown that, compared to the high-resolution model versions, the T63 version has less convective variability and less wave momentum in the lower stratosphere at wavenumbers larger than 20, well below the version’s truncation limit.In the low-resolution version, the upward propagation of the waves is further hindered by the highly active (relative to the high-resolution versions) horizontal diffusion scheme. However, even in the T255version of ECHAM6, the convective variability is too small compared to TRMM observations at periods shorter than 2 days and wavelengths shorter than 1000 km. Hence, to model a realistic tropical waveactivity, the convective parameterization of the model has to improve to increase the day-to-day precipitation variability

Urban eddy covariance measurements reveal significant missing NOx emissions in Central Europe

Nitrogen oxide (NOx) pollution is emerging as a primary environmental concern across Europe. While some large European metropolitan areas are already in breach of EU safety limits for NO2, this phenomenon does not seem to be only restricted to large industrialized areas anymore. Many smaller scale populated agglomerations including their surrounding rural areas are seeing frequent NO2 concentration violations. The question of a quantitative understanding of different NOx emission sources is therefore of immanent relevance for climate and air chemistry models as well as air pollution management and health. Here we report simultaneous eddy covariance flux measurements of NOx, CO2, CO and non methane volatile organic compound tracers in a city that might be considered representative for Central Europe and the greater Alpine region. Our data show that NOx fluxes are largely at variance with modelled emission projections, suggesting an appreciable underestimation of the traffic related atmospheric NOx input in Europe, comparable to the weekend-weekday effect, which locally changes ozone production rates by 40%

Study protocol of cost-effectiveness and cost-utility of a biopsychosocial multidisciplinary intervention in the evolution of non-specific sub-acute low back pain in the working population: cluster randomised trial.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Background: Low back pain (LBP), with high incidence and prevalence rate, is one of the most common reasons to consult the health system and is responsible for a significant amount of sick leave, leading to high health and social costs. The objective of the study is to assess the cost-effectiveness and cost-utility analysis of a multidisciplinary biopsychosocial educational group intervention (MBEGI) of non-specific sub-acute LBP in comparison with the usual care in the working population recruited in primary healthcare centres. Methods/design: The study design is a cost-effectiveness and cost-utility analysis of a MBEGI in comparison with the usual care of non-specific sub-acute LBP.Measures on effectiveness and costs of both interventions will be obtained from a cluster randomised controlled clinical trial carried out in 38 Catalan primary health care centres, enrolling 932 patients between 18 and 65 years old with a diagnosis of non-specific sub-acute LBP. Effectiveness measures are: pharmaceutical treatments, work sick leave (% and duration in days), Roland Morris disability, McGill pain intensity, Fear Avoidance Beliefs (FAB) and Golberg Questionnaires. Utility measures will be calculated from the SF-12. The analysis will be performed from a social perspective. The temporal horizon is at 3 months (change to chronic LBP) and 12 months (evaluate the outcomes at long term. Assessment of outcomes will be blinded and will follow the intention-to-treat principle. Discussion: We hope to demonstrate the cost-effectiveness and cost-utility of MBEGI, see an improvement in the patients' quality of life, achieve a reduction in the duration of episodes and the chronicity of non-specific low back pain, and be able to report a decrease in the social costs. If the intervention is cost-effectiveness and cost-utility, it could be applied to Primary Health Care Centres. Trial registration: ISRCTN: ISRCTN5871969

Vascular complications of prosthetic inter-vertebral discs

Five consecutive cases of prosthetic inter-vertebral disc displacement with severe vascular complications on revisional surgery are described. The objective of this case report is to warn spinal surgeons that major vascular complications are likely with anterior displacement of inter-vertebral discs. We have not been able to find a previous report on vascular complications associated with anterior displacement of prosthetic inter-vertebral discs. In all five patients the prosthetic disc had eroded into the bifurcation of the inferior vena cava and the left common iliac vein. In three cases the aortic bifurcation was also involved. The fibrosis was so severe that dissecting out the arteries and veins to provide access to the relevant disc proved impossible. Formal division of the left common iliac vein and artery with subsequent repair was our solution. Anterior inter-vertebral disc displacement was associated with severe vascular injury. Preventing anterior disc displacement is essential in disc design. In the event of anterior displacement, disc removal should be planned with a Vascular Surgeon

Mass models from high-resolution HI data of the dwarf galaxy NGC 1560

We present HI observations performed at the GMRT of the nearby dwarf galaxy NGC 1560. This Sd galaxy is well-known for a distinct "wiggle" in its rotation curve. Our new observations have twice the resolution of the previously published HI data. We derived the rotation curve by taking projection effects into account, and we verified the derived kinematics by creating model datacubes. This new rotation curve is similar to the previously published one: we confirm the presence of a clear wiggle. The main differences are in the innermost ~100 arcsec of the rotation curve, where we find slightly (<~ 5 km/s) higher velocities. Mass modelling of the rotation curve results in good fits using the core-dominated Burkert halo (which however does not reproduce the wiggle), bad fits using the a Navarro, Frenk & White halo, and good fits using MOND (Modified Newtonian Dynamics), which also reproduces the wiggle.Comment: Accepted for publication in MNRAS. 11 pages, 13 figures. High-resolution version available at http://users.ugent.be/~ggianfra/1560_final.pd