Modelling the Antarctic ozone hole

Researchers performed model calculations of the ozone depletions taking place in the Antarctic lower stratosphere. Making the assumption that odd nitrogen is frozen out on stratospheric haze particles, an analysis is given of how much homogeneous reactions can contribute to ozone loss during September-October. Comparisons with observations indicate the potential importance of reactions with HCl in the polar stratospheric cloud particles

Everything should be as simple as possible, but no simpler : towards a protocol for accumulating evidence regarding the active content of health behaviour change interventions

Supplemental data for this article can be accessed here: 10.1080/17437199.2013.848409Peer reviewedPublisher PD

Acute effects of a large bolide impact simulated by a global atmospheric circulation model

The goal is to use a global three-dimensional atmospheric circulation model developed for studies of atmospheric effects of nuclear war to examine the time evolution of atmospheric effects from a large bolide impact. The model allows for dust and NOx injection, atmospheric transport by winds, removal by precipitation, radiative transfer effects, stratospheric ozone chemistry, and nitric acid formation and deposition on a simulated Earth having realistic geography. Researchers assume a modest 2 km-diameter impactor of the type that could have formed the 32 km-diameter impact structure found near Manson, Iowa and dated at roughly 66 Ma. Such an impact would have created on the order of 5 x 10 to the 10th power metric tons of atmospheric dust (about 0.01 g cm(-2) if spread globally) and 1 x 10 to the 37th power molecules of NO, or two orders of magnitude more stratospheric NO than might be produced in a large nuclear war. Researchers ignore potential injections of CO2 and wildfire smoke, and assume the direct heating of the atmosphere by impact ejecta on a regional scale is not large compared to absorption of solar energy by dust. Researchers assume an impact site at 45 N in the interior of present day North America

Everything should be as simple as possible, but this will still be complex : a reply to various commentaries on IPEBA

Peer reviewedPostprin

Targeted and Tailored Pharmacist-led Medication Reviews:Addressing deprescribing and hypoglycaemia in older people and people with type 2 diabetes

In older people, the drawbacks of medication can sometimes outweigh the benefits. It is therefore important that medication that is no longer appropriate is stopped in time. Medication reviews are a valuable tool for community pharmacists to contribute to the drug management of older patients. During a medication review, a pharmacist, together with a patient and their general practitioner, explore whether medication use can be improved. An important part of this is to check whether medication can be stopped. This thesis investigated how various aspects of medication assessments can be improved. In particular, it focused on stopping medication for diabetes and heart disease. Two selection algorithms have been developed to improve selection for medication reviews. The first algorithm distinguishes between medically complex and less complex patients. The second algorithm, developed using machine learning, detects diabetes patients with a high risk of hypoglycaemia. In addition, the views, ideas and experiences of patients about deprescribing and hypoglycaemia were investigated. Furthermore, the barriers and facilitators for healthcare providers to reduce medication have been explored. Based on these studies, a new, personalised form of medication reviews for type 2 diabetes patients at high risk of hypoglycaemia has been developed and tested in practice. This intervention resulted in a clear focus on improving medication for diabetes and heart disease and showed an increase in deprescribing medication for these diseases

Adding effect sizes to a systematic review on interventions for promoting physical activity among European teenagers

This commentary adds effect sizes to the recently published systematic review by De Meester and colleagues and provides a more detailed insight into the effectiveness of interventions to promote physical activity among European teenagers. The main findings based on this evidence were: (1) school-based interventions generally lead to short term improvement in physical activity levels, but there were large differences between interventions with regard to effect sizes; (2) a multi-component approach (including environmental components) generally resulted in larger effect sizes, thereby providing evidence for the assumption that a multi-component approach should produce synergistic results; and (3) if an intervention aimed to affect more health behaviours besides physical activity, then the intervention appeared to be less effective in favour of physical activity

Influence of a solar proton event on stratospheric ozone

Ozone depletion in the stratosphere associated with the solar proton event of August 4, 1972, was observed with the backscattered ultraviolet experiment on the Nimbus 4 satellite. An abrupt ozone decrease in the 75-80 deg N zone of about 0.002 atm-cm above 4 mb was observed to persist throughout the month of August. A decrease was noted in the 55-65 deg N zone on days 219 and 220, but recovery occurred on day 221. Thereafter, a more gradual decrease was observed. The equatorial zone also showed gradual decrease after day 218, but these were not uniquely distinguished from seasonal variations. The observed change in total ozone following the event was -0.003 atm-cm for the 75-80 deg N zone, corresponding to a 1.3 percent reduction in the 0.305 atm-cm zonal average, but within the 0.019 atm-cm standard deviation. Above the 10 mb surface in the 75-80 deg N zone however, a decrease of 0.004 atm-cm may be compared with a standard deviation of 0.001 atm-cm

Model study of multiphase DMS oxidation with a focus on halogens

We studied the oxidation of dimethylsulfide (DMS) in the marine boundary layer (MBL) with a one-dimensional numerical model and focused on the influence of halogens. Our model runs show that there is still significant uncertainty about the end products of the DMS addition pathway, which is especially caused by uncertainty in the product yield of the reaction of the intermediate product methyl sulfinic acid (MSIA) with OH. BrO strongly increases the importance of the addition branch in the oxidation of DMS even when present at mixing ratios smaller than 0.5pmol mol^-1. The inclusion of halogen chemistry leads to higher DMS oxidation rates and smaller DMS to SO₂ conversion efficiencies. The DMS to SO₂ conversion efficiency is also drastically reduced under cloudy conditions. In cloud-free model runs between 5 and 15% of the oxidized DMS reacts further to particulate sulfur, in cloudy runs this fraction is almost 100%. Sulfate production by HOCl_aq and HOBr_aq is important in cloud droplets even for small Br^- deficits and related small gas phase halogen concentrations. In general, more particulate sulfur is formed when halogen chemistry is included. A possible enrichment of HCO₃^- in fresh sea salt aerosol would increase pH values enough to make the reaction of S(IV)^* (=SO_2,aq+HSO₃^-+SO₃^2-) with O₃ dominant for sulfate production. It leads to a shift from methyl sulfonic acid (MSA) to non-sea salt sulfate (nss-SO₄^2-) production but increases the total nss-SO₄^2- only somewhat because almost all available sulfur is already oxidized to particulate sulfur in the base scenario. We discuss how realistic this is for the MBL. We found the reaction MSA_aq+OH to contribute about 10% to the production of nss-SO₄^2- in clouds. It is unimportant for cloud-free model runs. Overall we find that the presence of halogens leads to processes that decrease the albedo of stratiform clouds in the MBL

A discussion on the determination of atmospheric OH and its trends

The oxidation efficiency of the troposphere is largely determined by the hydroxyl radical and its global distribution. Its presence limits the lifetime of most trace gases. Because of the great importance of several of these gases for climate, ozone budget and OH itself, it is of fundamental importance to acquire knowledge about atmospheric OH and possible trends in its concentrations. In the past, average concentrations of OH and trends were largely derived using industrially produced CH₃CCl₃ as a chemical tracer. The analyses have given valuable, but also rather uncertain results. In this paper we describe an idealized computer aided tracer experiment which has as one of its goals to derive tracer concentration weighted, global average <<i>k</i>(OH)>, where the temporal and spatial OH distribution is prescribed and <i>k</i> is the reaction rate coefficient of OH with a hitherto never produced (Gedanken) tracer, which is injected at a number of surface sites in the atmosphere in well known amounts over a given time period. Using a three-dimensional (3-D) time-dependent chemistry transport model, <<i>k</i>(OH)> can be accurately determined from the calculated 3-D tracer distribution. It is next explored how well <<i>k</i>(OH)> can be retrieved solely from tracer measurements at a limited number of surface sites. The results from this analysis are encouraging enough to actually think about the feasibility to carry out a global dedicated tracer experiment to derive <<i>k</i>(OH)> and its temporal trends. However, before that, we propose to test the methods that are used to derive <<i>k</i>(OH)>, so far largely using CH₃CCl₃, with an idealized tracer experiment, in which a global chemistry transport model is used to calculate the ``Gedanken'' tracer distribution, representing the real 3-D world, from which <<i>k</i>(OH)> is derived, using only the tracer information from a limited set of surface sites. We propose here that research groups which are, or will be, involved in global average OH studies to participate in such an inter-comparison of methods, organized and over-seen by a committee appointed by the International Global Atmospheric Chemistry (IGAC) program