Hemispheric asymmetries in recent changes of the stratospheric circulation

Despite the expected opposite effects of ozone recovery, the stratospheric Brewer-Dobson circulation (BDC) has been found to weaken in the Northern hemisphere (NH) relative to the Southern hemisphere (SH) in recent decades, inducing substantial effects on chemical composition. We investigate hemispheric asymmetries in BDC changes since about 2000 in simulations with the transport model CLaMS driven with different reanalyses (ERA5, ERA-Interim, JRA-55, MERRA-2) and contrast those to a suite of free-running climate model simulations. We find that age of air increases robustly in the NH stratosphere relative to the SH in all reanalyses considered. Related nitrous oxide changes agree well between reanalysis-driven simulations and satellite measurements, providing observational evidence for the hemispheric asymmetry in BDC changes. Residual circulation metrics further show that the composition changes are caused by structural BDC changes related to an upward shift and strengthening of the deep BDC branch, resulting in longer transit times, and a downward shift and weakening shallow branch in the NH relative to the SH. All reanalyses agree on this mechanism. Although climate model simulations show that ozone recovery will lead to overall reduced circulation and age of air trends, the hemispherically asymmetric signal in circulation trends is small compared to internal variability. Therefore, the observed circulation trends over the recent past are not in contradiction to expectations from climate models. Furthermore, the hemispheric asymmetry in BDC trends imprints on the composition of the lower stratosphere and the signal might propagate into the troposphere, potentially affecting composition down to the surface.

Impacts of the COVID-19 Pandemic on a Human Research Islet Program

Designated a pandemic in March 2020, the spread of severe acute respiratory syndrome virus 2 (SARS-CoV2), the virus responsible for coronavirus disease 2019 (COVID-19), led to new guidelines and restrictions being implemented for individuals, businesses, and societies in efforts to limit the impacts of COVID-19 on personal health and healthcare systems. Here we report the impacts of the COVID-19 pandemic on pancreas processing and islet isolation/distribution outcomes at the Alberta Diabetes Institute IsletCore, a facility specialising in the processing and distribution of human pancreatic islets for research. While the number of organs processed was significantly reduced, organ quality and the function of cellular outputs were minimally impacted during the pandemic when compared to an equivalent period immediately prior. Despite the maintained quality of isolated islets, recipient groups reported poorer feedback regarding the samples. Our findings suggest this is likely due to disrupted distribution which led to increased transit times to recipient labs, particularly those overseas. Thus, to improve overall outcomes in a climate of limited research islet supply, prioritization of tissue recipients based on likely tissue transit times may be needed.

Evaluation of gastrointestinal transit times and pH in healthy cats using a continuous pH monitoring system

Objectives The aim of this study was to characterize gastrointestinal (GI) transit times and pH in healthy cats. Methods GI transit times and pH were measured in six healthy, colony-housed, purpose-bred spayed female cats using a continuous, non-invasive pH monitoring system in a sequential order design. For the first period (‘pre-feeding’), food was withheld for 20 h, followed by oral administration of a pH capsule. Five hours post-capsule administration, cats were meal-fed by offering them their daily allowance of food for 1 h. For the second period (‘post-feeding’), food was withheld for 24 h and cats were fed for 1 h, after which a pH capsule was orally administered. Studies in both periods were repeated three times. GI transit times and pH were compared between the two periods. Results The median transit times for the pre- and post-feeding periods, respectively, were: gastric –94 mins (range 1–4101) and 1068 mins (range 484–5521); intestinal –1350 mins (range 929–2961) and 1534 mins (range 442–2538); and GI –1732 mins (range 1105–5451) and 2795 mins (range 926–6563). The median GI pH values for the first and second periods, respectively, were: esophageal –7.0 (range 3.5–7.8) and 4.5 (range 2.9–6.4); gastric –2.7 (range 1.7–6.2) and 2.0 (range 1.1–3.3); intestinal –8.2 (range 7.6–8.7) and 7.8 (range 6.7–8.5); first-hour small intestinal –8.2 (range 7.4–8.7) and 8.3 (range 7.9–8.6); and last-hour large intestinal –8.5 (range 7.0–8.9) and 7.8 (range 6.3–8.7). Gastric ( P <0.0020) and intestinal pH ( P <0.0059) were significantly increased in the pre-feeding period compared with the post-feeding period. Conclusions and relevance Gastric and intestinal pH differed significantly when the capsule was administered 5 h prior to feeding compared with 1 h after feeding. Transit times for both periods showed high degrees of intra- and inter-individual variability.

An Integrated System for Simultaneous Monitoring of Traffic and Pollution Concentration—Lessons Learned for Bielsko-Biała, Poland

The challenge of maintaining the required level of mobility and air quality in cities can be met by deploying an appropriate management system in which the immediate vicinity of roads is monitored to identify potential pollution hotspots. This paper presents an integrated low-cost system which can be used to study the impact of traffic related emission on air quality at intersections. The system was used for three months in 2017 at five locations covering intersections in the centre of a mid-sized city. Depending on the location, pollution hotspots with high PM2.5 and PM10 concentrations occurred 5–10% of the time. It was shown that despite the close mutual proximity of the locations, traffic and the immediate surroundings lead to significant variation in air quality. At locations with adverse ventilation conditions a tendency towards more frequent occurrences of moderate and sufficient air quality was observed than at other locations (even those with more traffic). Based on the results, a practical extension of the system was also proposed by formulating a model for the prediction of PM2.5 concentration using a neural network. Information on transit times, meteorological data and the background level of PM10 concentration were used as model input parameters.

Estimating Brewer-Dobson circulation trends from changes in stratospheric water vapour and methane

The stratospheric meridional overturning circulation, also referred to as the Brewer-Dobson circulation (BDC), controls the composition of the stratosphere, which, in turn, affects radiation and climate. As the BDC cannot be directly measured, one has to infer its strength and trends indirectly. For instance, trace gas measurements allow the calculation of average transit times. Satellite measurements provide information on the distributions of trace gases for the entire stratosphere, with measurements of particularly long and dense coverage available for stratospheric water vapour (H2O). Although chemical processes and boundary conditions confound interpretation, the influence of CH4 oxidation on H2O is relatively straightforward, and thus H2O is an appealing tracer for transport analysis despite these caveats. In this work, we explore how mean age of air trends can be estimated from the combination of stratospheric H2O and CH4 data. We carry out different sensitivity studies with the Chemical Lagrangian Model of the Stratosphere (CLaMS) and focus on the analysis of the periods of 1990–2006 and 1990–2017. In particular, we assess the methodological uncertainties related to the two commonly-used approximations of (i) instantaneous stratospheric entry mixing ratio propagation, and (ii) constant correlation between mean age and the fractional release factor of methane. Our results show that the estimated mean age of air trends from the combination of observed stratospheric H2O and CH4 changes may be significantly affected by the assumed approximations. Depending on the investigated stratospheric region and the considered period, the error in estimated mean age of air decadal trends can be large – the discrepancies are up to 10 % per decade or even more at the lower stratosphere. For particular periods, the errors from the two approximations can lead to opposite effects, which may even cancel out. Finally, we propose an improvement to the approximation method by using an idealised age spectrum to propagate stratospheric entry mixing ratios. The findings of this work can be used for improving and assessing the uncertainties in stratospheric BDC trend estimation from global satellite measurements.

Assessment of whole gut motility in adolescents using the wireless motility capsule test

Functional gastrointestinal (GI) disorders are often associated with intestinal dysmotility representing a diagnostic challenge. A relatively new method is the wireless motility capsule (WMC) test, which continuously measures pH, pressure, temperature and regional transit times as it passes through the GI tract. In adults, the WMC test was approved for use in the diagnosis of gastroparesis and constipation by assessing GI transit and contractility. We performed the WMC test in nine adolescent patients aged 12–17 years with functional GI symptoms from July 2017 until February 2019. Abnormal transit times were detected in four patients. Three patients showed abnormal transit times of the upper GI tract: in two cases, contractility analysis revealed prolonged gastric retention, and in one patient, abnormal colonic transit was detected.Conclusion: The WMC test is a minimally invasive procedure with potential to expand future diagnostic opportunities for paediatric patients with functional GI disorders and suspected motility disturbances. What is Known:• The assessment of GI transit and contractility of the whole gut is possible with the WMC test which is approved for use in the diagnosis of gastroparesis and constipation in adults. What is New:• The WMC test is a non-invasive diagnostic tool with the potential to expand diagnostic opportunities in paediatric patients by assessing regional and whole gut motility.• In paediatric patients with functional GI disorders, the WMC test could help to make an adequate diagnosis and initiate appropriate therapy.

Modelling temporal variability of in-situ soil water and vegetation isotopes reveals ecohydrological couplings in a willow plot

The partitioning of water fluxes in the critical zone is of great interest due to the implications for understanding water cycling and quantifying water availability for various ecosystem services. We used the tracer-aided ecohydrological model EcH2O-iso to evaluate water, energy, water stable isotope, and biomass dynamics at an intensively monitored study plot under two willow trees, a riparian species, in Berlin, Germany. Importantly, we assessed the value of in-situ soil and plant water isotope data to quantify xylem water sources and transit times, with coupled estimates of the temporal dynamics and ages of soil and root-uptake water. The willows showed high evapotranspiration water use, with limited percolation of summer precipitation to deeper soil layers due to the dominance of shallow root-uptake (> 80 % in the upper 10 cm). Lower evapotranspiration under grass resulted in higher soil moisture storage, greater soil evaporation and more percolation of soil water. Biomass allocation was predominantly foliage growth (57 % in grass and 78 % in willow). Shallow soil water age under grass was similar to under willows (15–17 days). Considering potential xylem transit times showed a large improvement in the model's capability to estimate xylem isotopic composition and water age, and revealed the high value of in-situ data within modelling. Root-uptake was predominately derived from summer precipitation events (56 %) and had an average age of 35 days, with xylem transport times taking at least 6.2–8.1 days. By evaluating water partitioning, energy and isotope mass-balance, along with biomass allocation, the model revealed multifaceted capabilities for assessing water cycling within the critical zone at high temporal resolution, including xylem water sources and transport, which are all necessary for short and long-term assessment of water availability for plant growth.