Evaluating the spatial uncertainty of future land abandonment in a mountain valley (Vicdessos, Pyrenees-France) : insights form model parameterization and experiments

International audienceEuropean mountains are particularly sensitive to climatic disruptions and land use changes. The latter leads to high rates of natural reforestation over the last 50 years. Faced with the challenge of predicting possible impacts on ecosystem services, LUCC models offer new opportunities for land managers to adapt or mitigate their strategies. Assessing the spatial uncertainty of future LUCC is crucial for the defintion of sustainable land use strategies. However, the sources of uncertainty may differ, including the input parameters, the model itself, and the wide range of possible futures. The aim of this paper is to propose a method to assess the probability of occurrence of future LUCC that combines the inherent uncertainty of model parameterization and the ensemble uncertainty of the future based scenarios. For this purpose, we used the Land Change Modeler tool to simulate future LUCC on a study site located in the Pyrenees Mountains (France) and 2 scenarios illustratins 2 land use strategies. The model was parameterized with the same driving factors used for its calibration. The defintion of static vs. dynamic and quantitative vs. qualitative (discretized) driving factors, and their combination resulted in 4 parameterizations. The combination of model outcomes produced maps of spatial uncertainty of future LUCC. This work involves literature to future-based LUCC studies. It goes beyond the uncertainty of simulation models by integrating the unceertainty of the future to provide maps to help decision makers and land managers

Thin film diamond Electronic devices for high temperature, high power and high radiation applications

In the ideal form diamond displays extreme physical, optical and electronic properties, making this material interesting for many device applications. However, natural or high pressure, high temperature synthesised forms of diamond are not useful since they are only available as small irregular crystallites and are expensive. The emergence of commercially accessible techniques for the formation of thin films of diamond over relatively large areas has changed this situation, enabling the prospects for the use of diamond as an electronic material to be truly evaluated. Thin film diamond is a defective polycrystalline material. It is difficult to dope n- and p-type and resists conventional chemical etching. Thus, despite the superlative properties of ideal diamond, the realisation of useful devices from this material is far from simple. This thesis considers how the problems may be overcome such that high performance diamond devices can be realised for use in high temperature, high power and high radiation environments. Following a review of the current state-of-the-art in diamond device technology the experimental techniques used throughout this study are summarised. Field effect transistors (FETs) have been designed for operation at high (>300 deg. C) temperatures. Boron-doped (p-type) diamond was used to form the active channel, with insulating diamond acting as the gate to the FET structure. Polycrystalline diamond devices with the highest yet reported transconductance values, which display full turn-off characteristics have been produced. To enable room temperature operation, where boron is an ineffective dopant, a novel doping approach has been established using hydrogen; devices with transconductance, power handling and full pinch-off characteristic have been realised for the first time with this approach. More complex devices require patterning of the diamond substrate material; reactive ion etching using oxygen and chlorinated fluorocarbons have been studied in this context. Finally the use of diamond for the fabrication of ionising radiation detectors has been explored, resulting in the realisation of high collection efficiency structures. (author)SIGLEAvailable from British Library Document Supply Centre-DSC:DXN034480 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

SMOS sea surface salinity prototype processor: Algorithm validation

International audienceThe Soil Moisture and Ocean Salinity (SMOS) mission (launch scheduled for 2008) aims at obtaining global maps of soil moisture and sea surface salinity (SSS). It uses an L-band (1.4 GHz) microwave interferometric radiometer to obtain brightness temperatures (Tb) at the Earth surface at horizontal and vertical polarizations. They will be used to retrieve both geophysical variables, following specifically designed algorithms that will be applied when the satellite field-of-view is covering land or ocean surfaces respectively. The retrieval of salinity is a complex process that requires the knowledge of environmental information and an accurate processing of the radiometer measurements, because of the narrow range of ocean Tb and the strong impact on the measures of geophysical parameters (such as sea state). Here we present the baseline approach chosen to retrieve sea surface salinity from SMOS data, as developed and implemented by the joint team of scientists and engineers responsible for the SMOS Salinity Level 2 Prototype Processor. We present academic tests conducted over homogeneous scenes with the prototype. In these configurations, external perturbation sources (sky radiation, sun glint, ...) are not taken into account. Roughness is the main sea surface signal disturbing SSS retrieval

SMOS calibration and instrument performance after one year in orbit

This paper summarizes the rationale for the European Space Agency's Soil Moisture and Ocean Salinity (SMOS) mission routine calibration plan, including the analysis of the calibration parameter annual variability, and the performances and stability of SMOS images after one year of data. SMOS spends 1.68% of the total observation time in calibration. The instrument performs well within expectations with regard to accuracy and radiometric sensitivity, although spatial ripples are present in SMOS images. Several mechanisms are currently used or under investigation to mitigate this problem. Also, a loss antenna model has recently been introduced to correct for physical temperature-induced effects. This antenna model successfully corrects observed orbital variations, but has difficulties in correcting brightness temperature long-term drifting, as assessed using relatively well-known targets other than the external calibration region-cold space.Peer Reviewe

Assessing the potential for improving public transport in rural areas by using driverless vehicles

Driverless vehicles might fundamentally change the transport system in multiple ways. Reducing driver costs in mobility services could create opportunities for new mobility concepts. Research on driverless vehicles have previously concentrated on urban areas, though driverless vehicles in rural areas could have greater positive effects. Hence, the aim of the study is to see how driverless vehicles can be used in rural areas to contribute to a more sustainable transport system. Three rural mobility concepts for driverless vehicles are developed and by applying these to different case locations, the feasibility of the concepts is discussed. Interviews with local actors in Sweden were conducted to learn about general and local challenges with specific case locations. What rural mobility concept for driverless vehicles to use depends on access to public transport, distance to main roads and spatial density of travel demand. A modelling approach of a first and last mile feeder service is used to evaluate the feasibility of this mobility concept further. Model results show that driverless shuttles can feed travel demands of 100-150 passengers daily and still perform alternative tasks. Even though rural areas have general challenges, local issues also need consideration to optimize the benefits of the services. Public transport authorities are experts on local challenges and could take more responsibility in questions regarding driverless vehicles. For instance, flexibility, accessibility and equality could be improved by merging routes and shorten travel times for entire bus routes. Furthermore, other societal functions can be developed by reinvesting capital in other areas.

A new generation of Tropical Cyclone Size measurements from space

Combined microwave brightness temperature measurements from recent L- and dual C-band satellite radiometers provide new estimates of surface wind speed structure in Tropical Cyclones which enhances temporal sampling capability for gale (34-knots), damaging (50-knots) and destructive (64-knots) wind radii. Wind radii estimates in Tropical Cyclones (TC) are crucial to help determine the TC wind structure for the production of effective warnings and to constrain initial conditions for a number of applications. In that context, we report on the capabilities of a new generation of satellite microwave radiometers operating at L-band frequency (~1.4 GHz) and dual C-band (~6.9 and 7.3 GHz). These radiometers provide wide swath (> 1000 km) coverage at a spatial resolution of ~40 km and revisit of ~3 days. L-band measurements are almost unaffected by rain and atmospheric effects, while dual C-band data offer an efficient way to significantly minimize these impacts. During storm conditions, increasing foam coverage and thickness at the ocean surface sufficiently modify the surface emissivity at these frequencies, and in turn the brightness temperature (Tb) measurements. Based on aircraft measurements, new geophysical model functions have been derived to infer reliable ocean surface wind speeds from measured Tb variations. Data from these sensors collected over 2010-2015 are shown to provide reliable estimates of the gale-force (34-kt), damaging (50-kt), and destructive winds (64-kt), within the Best-track wind radii uncertainty. Combined, and further associated with other available observations, these measurements can now provide regular quantitative and complementary surface wind information of interest for operational TC forecasting operations