Description: We present BrAHMs (BAsal Hydrology Model): a physically based basal hydrology model which represents water flow using Darcian flow in the distributed drainage regime and a fast down-gradient solver in the channelized regime. Switching from distributed to channelized drainage occurs when appropriate flow conditions are met. The model is designed for long-term integrations of continental ice sheets. The Darcian flow is simulated with a robust combination of the Heun and leapfrog–trapezoidal predictor–corrector schemes. These numerical schemes are applied to a set of flux-conserving equations cast over a staggered grid with water thickness at the centres and fluxes defined at the interface. Basal conditions (e.g., till thickness, hydraulic conductivity) are parameterized so the model is adaptable to a variety of ice sheets. Given the intended scales, basal water pressure is limited to ice overburden pressure, and dynamic time stepping is used to ensure that the Courant–Friedrichs–Lewy (CFL) condition is met for numerical stability. The model is validated with a synthetic ice sheet geometry and different bed topographies to test basic water flow properties and mass conservation. Synthetic ice sheet tests show that the model behaves as expected with water flowing down gradient, forming lakes in a potential well or reaching a terminus and exiting the ice sheet. Channel formation occurs periodically over different sections of the ice sheet and, when extensive, displays the arborescent configuration expected of Röthlisberger channels. The model is also shown to be stable under high-frequency oscillatory meltwater inputs.

Description: Background: Alcohol is a major preventable cause of injury, disability and death in young people. Large numbers of young people with alcohol-related injuries and medical conditions present to hospital emergency departments (EDs). Access to brief, efficacious, accessible and cost effective treatment is an international health priority within this age group. While there is growing evidence for the efficacy of brief motivational interviewing (MI) for reducing alcohol use in young people, there is significant scope to increase its impact, and determine if it is the most efficacious and cost effective type of brief intervention available. The efficacy of personality-targeted interventions (PIs) for alcohol misuse delivered individually to young people is yet to be determined or compared to MI, despite growing evidence for school-based PIs.Aim: This paper describes the study protocol of a single blinded randomised controlled superiority trial comparing the efficacy and cost-effectiveness of telephone-delivered MI, PI and an Assessment Feedback/Information (AF/I) only control for reducing alcohol use and related harm in young people. Methods: Participants will be 390 young people aged 16 to 25 years presenting to a crisis support service or ED with alcohol-related injuries and illnesses (including severe alcohol intoxication). Young people are randomized to (i) 2 sessions of MI; (ii) 2 sessions of a new PI or (iii) a 1 session AF/I only control. Participants are reassessed at 1, 3, 6 and 12 months on the primary outcomes of alcohol use and related problems and secondary outcomes of mental health symptoms, functioning, severity of problematic alcohol use, alcohol injuries, alcohol-related knowledge, coping self-efficacy to resist using alcohol, and cost effectiveness.DiscussionThis study will identify the most efficacious and cost-effective telephone-delivered brief intervention for reducing alcohol misuse and related problems in young people presenting to crisis support services or EDs. We expect efficacy will be greatest for PI, followed by MI, and then AF/I at 1, 3, 6 and 12 months on the primary and secondary outcome variables. Telephone-delivered brief interventions could provide a youth-friendly, accessible, efficacious, cost-effective and easily disseminated treatment for addressing the significant public health issue of alcohol misuse and related harm in young people.Trial registration: This trial is registered with the Australian and New Zealand Clinical Trials Registry ACTRN12613000108718.

Description: [1]  Energetic Electron Precipitation (EEP) impacts the chemistry of the middle atmosphere with growing evidence of coupling to surface temperatures at high latitudes. To better understand this link it is essential to have realistic observations to properly characterise precipitation and which can be incorporated into chemistry-climate models. The Polar-orbiting Operational Environmental Satellites (POES) detectors measure precipitating particles but only integral fluxes and only in a fraction of the bounce loss cone. Ground based riometers respond to precipitation from the whole bounce loss cone; they measure the cosmic radio noise absorption (CNA); a qualitative proxy with scant direct information on the energy-flux of EEP. POES observations should have a direct relationship with ΔCNA and comparing the two will clarify their utility in studies of atmospheric change. We determined ionospheric changes produced by the EEP measured by the POES spacecraft in ~250 overpasses of an imaging riometer in northern Finland. The ΔCNA modeled from the POES data is 10-15 times less than the observed ΔCNA when the 〉30 keV flux is reported as 〈10 6  cm -2  sec -1  sr -1 . Above this level there is relatively good agreement between the space-based and ground-based measurements. The discrepancy occurs mostly during periods of low geomagnetic activity and we contend that weak diffusion is dominating the pitch angle scattering into the bounce loss cone at these times. A correction to the calculation using measurements of the trapped flux considerably reduces the discrepancy and provides further support to our hypothesis that weak diffusion leads to underestimates of the EEP.