Gravel threshold of motion: a state function of sediment transport disequilibrium? Earth Surface Dynamics DOI 10.5194/esurf-4-685-2016 29 August 2016 Accurately predicting gravel transport rates in mountain rivers is difficult because of feedbacks with channel morphology. River bed surfaces evolve during floods, influencing transport rates. I propose that the threshold of gravel motion is a state variable for channel reach evolution. I develop a new model to predict how transport thresholds evolve as a function of transport rate, and then use laboratory flume experiments to calibrate and validate the model. Read more
Why CO2 cools the middle atmosphere – a consolidating model perspective Earth System Dynamics DOI 10.5194/esd-7-697-2016 29 August 2016 Carbon dioxide, while warming the Earth’s surface, cools the atmosphere beyond about 15 km (the middle atmosphere). This cooling is considered a fingerprint of anthropogenic global warming, yet the physical reason behind it remains prone to misconceptions. Here we use a simple radiation model to illustrate the physical essence of stratospheric cooling, and a complex climate model to quantify how strongly different mechanisms contribute. Read more
A thermodynamic formulation of root water uptake Hydrology and Earth System Sciences DOI 10.5194/hess-20-3441-2016 29 August 2016 This theoretical paper describes the energy fluxes and dissipation along the flow paths involved in root water uptake, an approach that is rarely taken. We show that this provides useful additional insights for understanding the biotic and abiotic impediments to root water uptake. This approach shall be applied to explore efficient water uptake strategies and help locate the limiting processes in the complex soil–plant–atmosphere system. Read more
Impacts of aviation fuel sulfur content on climate and human health Atmospheric Chemistry and Physics DOI 10.5194/acp-16-10521-2016 24 August 2016 Using a coupled tropospheric chemistry-aerosol microphysics model this research paper investigates the effect of variations in aviation fuel sulfur content (FSC) on surface PM2.5 concentrations, increases in aviation-induced premature mortalities, low-level cloud condensation nuclei and radiative effect. When investigating the climatic impact of variations in FSC the ozone direct radiative effect, aerosol direct radiative effect and aerosol cloud albedo effect are quantified. Read more
Hemispherically asymmetric volcanic forcing of tropical hydroclimate during the last millennium Earth System Dynamics DOI 10.5194/esd-7-681-2016 23 August 2016 A band of intense rainfall exists near the equator known as the intertropical convergence zone, which can migrate in response to climate forcings. Here, we assess such migration in response to volcanic eruptions of varying spatial structure (Northern Hemisphere, Southern Hemisphere, or an eruption fairly symmetric about the equator). We do this using model simulations of the last millennium and link results to energetic constraints and the imprint eruptions may leave behind in past records. Read more
Satellite observations of stratospheric hydrogen fluoride and comparisons with SLIMCAT calculations Atmospheric Chemistry and Physics DOI 10.5194/acp-16-10501-2016 22 August 2016 HF, the dominant stratospheric fluorine reservoir, results from the atmospheric degradation of anthropogenic species such as CFCs, HCFCs, and HFCs. All are strong greenhouse gases, and CFCs and HCFCs deplete stratospheric ozone. We report the comparison of HF global distributions and trends measured by the ACE-FTS and HALOE satellite instruments with the output of SLIMCAT, a chemical transport model. The global HF trends reveal a slowing down in the rate of increase of HF since the 1990s. SLIMCAT calculations">Read more
Annual Greenland accumulation rates (2009–2012) from airborne snow radar The Cryosphere DOI 10.5194/tc-10-1739-2016 11 August 2016 Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet through increasing surface melt, emphasizing the need to closely monitor surface mass balance in order to improve sea-level rise predictions. Here, we quantify the net annual accumulation over the Greenland Ice Sheet, which comprises the largest component of surface mass balance, at a higher spatial resolution than currently available using high-resolution, airborne-radar data. Read more
A review of marine geomorphometry, the quantitative study of the seafloor Hydrology and Earth System Sciences DOI 10.5194/hess-20-3207-2016 9 August 2016 Geomorphometry, the science of quantitative terrain characterization, has traditionally focused on the investigation of terrestrial landscapes. More recently, a suite of geomorphometric techniques have been applied to characterize the seafloor. The dynamic, four-dimensional nature of the marine environment and differences in data collection methods cause issues for geomorphometry that are specific to marine applications. This article offers the first review of marine geomorphometry to date. Read more
Large gain in air quality compared to an alternative anthropogenic emissions scenario Atmospheric Chemistry and Physics DOI 10.5194/acp-16-9771-2016 4 August 2016 Three 30-year simulations of past atmospheric composition changes were performed using different anthropogenic emissions of pollutants accounting or not for the applied air quality legislation and accounting for the year–to–year observed climate and natural emissions variability. The actual benefit of applied legislation along with technological advances is higher than what is usually calculated by a simple comparison of today’s atmosphere against a constant anthropogenic emissions simulation. Read more
Drift simulation of MH370 debris using superensemble techniques Natural Hazards and Earth System Sciences DOI 10.5194/nhess-16-1623-2016 27 July 2016 In March 2014, a commercial airliner vanished without a trace. The main wreckage of the plane was never recovered, except for some small parts that washed up more than 17 months after the disappearance. In this paper we show a method to model the most likely trajectories of floating debris from the aircraft. The results show that the assumed area of the crash site is compatible with the recovered debris and predict that further debris may be found along the African east coast. Read more
