A method for estimating the extent of denitrification of Arctic polar vortex air from tracer-tracer scatter plots

A method for estimating the extent of denitrification of Arctic polar vortex air is proposed. Previous estimates of denitrification using tracer-tracer scatter plots have not allowed for mixing-induced changes in tracer-tracer relationships in a sufficiently general way. This difficulty is overcome by constructing an artificial "reference tracer'' from a linear combination of other long-lived tracers. The reference tracer is designed so that, as far as possible, it has a linear canonical relationship with NOy in midlatitudes. A linear relationship is unaffected by mixing, so denitrification is apparent as deviations of vortex measurements from the linear midlatitude relationship. The method is first demonstrated using data from a chemical transport model in which no denitrification processes are present. It is then applied to balloon, aircraft and shuttle-borne measurements made before and during the breakdown of the Arctic vortex in 1992-1993 and 1996-1997. In each case the method indicates that little or no denitrification had occurred in any of the vortex air encountered. When the method is applied to the southern hemisphere vortex in 1994, by contrast, denitrified air is clearly seen to be present around 19-23 km in the vortex

Screening disability insurance applications

This paper investigates the effects of stricter screening of disability insurance applications. A large-scale experiment was setup where in two of the 26 Dutch regions case workers of the disability insurance administration were instructed to screen applications more stringently. The empirical results show that stricter screening reduces long-term sickness absenteeism and disability insurance applications. We find evidence for direct effects of stricter screening on work resumption during the period of sickness absence and for self-screening by potential disability insurance applicants. Stricter screening seems to improve targeting efficiency, without inducing negative spillover effects to the inflow into unemployment insurance. The costs of stricter screening are only a small fraction of the monetary benefits.Disability insurance; experiment; policy evaluation; sickness absenteeism; self-screening

Description and Evaluation of the specified-dynamics experiment in the Chemistry-Climate Model Initiative

We provide an overview of the REF-C1SD specified-dynamics experiment that was conducted as part of phase 1 of the Chemistry-Climate Model Initiative (CCMI). The REF-C1SD experiment, which consisted of mainly nudged general circulation models (GCMs) constrained with (re)analysis fields, was designed to examine the influence of the large-scale circulation on past trends in atmospheric composition. The REF-C1SD simulations were produced across various model frameworks and are evaluated in terms of how well they represent different measures of the dynamical and transport circulations. In the troposphere there are large (∼40 %) differences in the climatological mean distributions, seasonal cycle amplitude, and trends of the meridional and vertical winds. In the stratosphere there are similarly large (∼50 %) differences in the magnitude, trends and seasonal cycle amplitude of the transformed Eulerian mean circulation and among various chemical and idealized tracers. At the same time, interannual variations in nearly all quantities are very well represented, compared to the underlying reanalyses. We show that the differences in magnitude, trends and seasonal cycle are not related to the use of different reanalysis products; rather, we show they are associated with how the simulations were implemented, by which we refer both to how the large-scale flow was prescribed and to biases in the underlying free-running models. In most cases these differences are shown to be as large or even larger than the differences exhibited by free-running simulations produced using the exact same models, which are also shown to be more dynamically consistent. Overall, our results suggest that care must be taken when using specified-dynamics simulations to examine the influence of large-scale dynamics on composition

Acute abdominal pain presenting as a rare appendiceal duplication: a case report

<p>Abstract</p> <p>Introduction</p> <p>Appendiceal duplication is a rare anomaly that can manifest as right lower quadrant pain. There are several variations described for this condition. We recommend aggressive operative management should this anatomical variation present in the presence of acute appendicitis.</p> <p>Case presentation</p> <p>We report the case of a 15-year-old African American girl who presented to our hospital with right lower quadrant pain and was subsequently found to have appendiceal duplication.</p> <p>Conclusion</p> <p>There are two categorical systems that have described and stratified appendiceal duplication. Both classification systems have been outlined and referenced in this case report. A computed tomography scan has been included to provide a visual aid to help identify true vermiform appendiceal duplication. The presence of this anatomical abnormality is not a reason for surgical intervention; however, should this be found in the setting of acute appendicitis, aggressive resection of both appendices is mandatory.</p

Fast and slow responses of Southern Ocean sea surface temperature to SAM in coupled climate models

We investigate how sea surface temperatures (SSTs) around Antarctica respond to the Southern An- nular Mode (SAM) on multiple timescales. To that end we examine the relationship between SAM and SST within unperturbed preindustrial control simulations of coupled general circulation models (GCMs) included in the Climate Modeling Intercomparison Project phase 5 (CMIP5). We develop a technique to extract the re- sponse of the Southern Ocean SST (55◦S−70◦S) to a hypothetical step increase in the SAM index. We demonstrate that in many GCMs, the expected SST step re- sponse function is nonmonotonic in time. Following a shift to a positive SAM anomaly, an initial cooling regime can transition into surface warming around Antarctica. However, there are large differences across the CMIP5 ensemble. In some models the step response function never changes sign and cooling persists, while in other GCMs the SST anomaly crosses over from negative to positive values only three years after a step increase in the SAM. This intermodel diversity can be related to differences in the models’ climatological thermal ocean stratification in the region of seasonal sea ice around Antarctica. Exploiting this relationship, we use obser- vational data for the time-mean meridional and vertical temperature gradients to constrain the real Southern Ocean response to SAM on fast and slow timescales

Reconstruction of the history of anthropogenic CO2 concentrations in the ocean

The release of fossil fuel CO(2) to the atmosphere by human activity has been implicated as the predominant cause of recent global climate change. The ocean plays a crucial role in mitigating the effects of this perturbation to the climate system, sequestering 20 to 35 per cent of anthropogenic CO(2) emissions. Although much progress has been made in recent years in understanding and quantifying this sink, considerable uncertainties remain as to the distribution of anthropogenic CO(2) in the ocean, its rate of uptake over the industrial era, and the relative roles of the ocean and terrestrial biosphere in anthropogenic CO(2) sequestration. Here we address these questions by presenting an observationally based reconstruction of the spatially resolved, time-dependent history of anthropogenic carbon in the ocean over the industrial era. Our approach is based on the recognition that the transport of tracers in the ocean can be described by a Green's function, which we estimate from tracer data using a maximum entropy deconvolution technique. Our results indicate that ocean uptake of anthropogenic CO(2) has increased sharply since the 1950s, with a small decline in the rate of increase in the last few decades. We estimate the inventory and uptake rate of anthropogenic CO(2) in 2008 at 140 +/- 25 Pg C and 2.3 +/- 0.6 Pg C yr(-1), respectively. We find that the Southern Ocean is the primary conduit by which this CO(2) enters the ocean (contributing over 40 per cent of the anthropogenic CO(2) inventory in the ocean in 2008). Our results also suggest that the terrestrial biosphere was a source of CO(2) until the 1940s, subsequently turning into a sink. Taken over the entire industrial period, and accounting for uncertainties, we estimate that the terrestrial biosphere has been anywhere from neutral to a net source of CO(2), contributing up to half as much CO(2) as has been taken up by the ocean over the same period

Revisiting the Relationship among Metrics of Tropical Expansion

There is mounting evidence that the width of the tropics has increased over the last few decades, but there are large differences in reported expansion rates. This is, likely, in part due to the wide variety of metrics that have been used to define the tropical width. Here we perform a systematic investigation into the relationship among nine metrics of the zonal-mean tropical width using preindustrial control and abrupt quadrupling of CO2 simulations from a suite of coupled climate models. It is shown that the latitudes of the edge of the Hadley cell, the midlatitude eddy-driven jet, the edge of the subtropical dry zones, and the Southern Hemisphere subtropical high covary interannually and exhibit similar long-term responses to a quadrupling of CO2. However, metrics based on the outgoing longwave radiation, the position of the subtropical jet, the break in the tropopause, and the Northern Hemisphere subtropical high have very weak covariations with the above metrics and/or respond differently to increases in CO2 and thus are not good indicators of the expansion of the Hadley cell or subtropical dry zone. The differing variability and responses to increases in CO2 among metrics highlights that care is needed when choosing metrics for studies of the width of the tropics and that it is important to make sure the metric used is appropriate for the specific phenomena and impacts being examined

The effects of acute serotonin challenge on executive planning in patients with obsessive-compulsive disorder (OCD), their first-degree relatives, and healthy controls

© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s00213-020-05597-7.Rationale: OCD is characterized by executive function impairment and by clinical responsivity to selective serotonin reuptake inhibitors (SSRIs). Executive planning deficits constitute a candidate endophenotype for OCD. It is not known whether this endophenotype is responsive to acute serotonin manipulation. Objective: To investigate the effects of acute SSRI administration on executive function in patients with OCD, first-degree relatives of patients with OCD and healthy controls. Methods: A randomized double-blind crossover study assessed the effects of single dose escitalopram (20mg) and placebo on executive planning in 24 patients with OCD, 13 clinically unaffected first-degree relatives of patients with OCD and 28 healthy controls. Performance on a Tower of London task measuring executive planning was assessed 4 hours after oral administration of the pharmacological challenge / placebo, and compared across and within groups using a mixed model ANOVA. Results: On the outcome measure of interest, i.e. the mean number of choices to obtain the correct solution, there was a marginally significant effect of group (F(2, 59)=3.1; p=0.052), with patients (Least square [LS] mean: 1.43; Standard Error [SE]: 0.06; 95% confidence interval [CI], 1.31-1.55) and their relatives (LS mean: 1.46; SE: 0.08; 95% CI, 1.30-1.62) performing worse than matched healthy controls (LS mean: 1.26; SE: 0.05; 95% CI, 1.15-1.37) on placebo. There was a trend towards a significant group x treatment interaction (F(2, 58)=2.8, p=0.069), with post hoc tests showing (i) patients (p=0.009; LS mean difference: 0.23; SE: 0.08) and relatives (p=0.03; LS mean difference: 0.22; SE: 0.10) were more impaired compared to controls and (ii) escitalopram was associated with improved executive planning in patients with OCD (p=0.013; LS mean difference: 0.1; SE: 0.04), but not other groups (both p>0.1; controls: LS mean difference: -0.03; SE: 0.04; relatives: LS mean difference: 0.02; SE: 0.05). Conclusion: Our findings are consistent with a view that there is impaired executive planning in OCD, and that this constitutes a behavioral endophenotype. In patients with OCD, but not in relatives, acute SSRI administration ameliorated this deficit. Further investigation is needed to understand common and differential involvement of neurochemical systems in patients with OCD and their relatives.Peer reviewe