Estimating spatial and temporal patterns of urban anthropogenic heat fluxes for UK cities: the case of Manchester

A model is proposed for determining the temporal and spatial patterns of anthropogenic heat fluxes in UK urban areas. It considers buildings, traffic, and metabolic heat flux sources and has been evaluated to a good accuracy against alternative data for the Greater Manchester area in the UK. Results are presented at spatial resolution of 200 ×?200 m although the model itself is scalable depending on data availability. In this paper, results are generated using a set of urban morphology units so that detailed and time-consuming accounting of individual building and road emissions is not required. The model estimates a mean heat emission of 6.12 Wm^-2 across Greater Manchester, with values in the region of 10 Wm^-2 for non central urbanized areas and 23 Wm^-2 in city center areas. Despite this difference, the results are not described by a simple distance decay function, as has been reported for other cities, due to the influence of satellite towns and the influence of the road network. Buildings are the dominant emitter, contributing some 60% of total emissions across the city compared to around 32% for road traffic and 8% for metabolic sources.     

An objective method for mapping hazardous flow deposits from the stratigraphic record of stratovolcanoes: a case example from Montagne Pelée

A method is described that enables a variety of maps, which indicate the probabilities of deposition, to be constructed in a reproducible manner from the stratigraphie information typically available at well-studied stratovoicanoes. These maps can then be used as a basis for hazard assessment. The sampling of the deposits of previous eruptions is subject to uncertainties due to erosion, sectoral deposition and non-exposure. A model-based, iterative algorithm is used to compensate for the incomplete sampling. For each site, the available evidence from the other sites is used to estimate the probability of deposition for missing deposits. A geographical information system (GIS)-based method that uses Thiessen polygons to represent the presence or absence of deposits, together with simple cartographic rules based on depositional processes, then defines the extent of deposition. The combined operation of these two techniques is presented for Montagne Pelée in Martinique, using the amended stratigraphic record of Smith and Roobol (1990) for the past 6000 years. Three types of maps are created: maps for individual depositional events (the 1902 block-and-ash flow and surge deposits are used to verify the technique); maps for different deposit types aggregated over 6000 years of activity; and scenario maps which, in Montagne Pelée’s case, recognise that during the next Peléean or Plinian eruption a variety of hazards will have to be confronted.     

Images of the edges of aeromagnetic anomalies as an aid to geological mapping: The case history of Tobago,West Indies

Tobago consists chiefly of Mesozoic igneous and metamorphic rocks of oceanic island arc affinity. During a four year programme of geological mapping of the island we had access to aeromagnetic data which showed large amplitude, E-W trending linear anomalies mainly associated with highly magnetic plutonic rocks. Using the pseudogravity transform and a subsequent mapping of local maxima of the horizontal gradients we created raster images of the edges or boundaries of the causative magnetic bodies. Thresholding of the boundary pixels allowed noise to be filtered and the most significant boundaries to be chosen. When combined with digitised field-mapped geological boundaries a useful format was created that allowed us to validate some of the field boundaries, investigate unexplained features and interpret structures.     

The storage and release of magma on Mount Etna

The eruptive history of Etna during the past 450 years provides data on effusion rates, volumes of magma involved, and the nature of the eruptive conduits. These data are interpreted in terms of a two-part intravolcanic magma reservoir which feeds the flank eruptions through dike-like conduits. The structural framework of the volcano which controls the spatial distribution of eruptive sites is partly inherited from the basement and partly controlled by the central magma column and the surrounding caldera boundary faults. Hydraulic fracturing theory predicts that the central magma column will fail at depths below 1 km if the tensile strength of the conduit rocks is about 100 bars and that a peak fracturing capability will be reached between 1 and 2 km depth. This inference agrees well with the peak of flank eruptive activity at 1.4 km below the summit observed in the data on the loci of eruptions. The average flank-eruption feeding dike is defined and shown to be capable of the observed maximum effusion rates (20–100 m³ s⁻¹) from magmatic pressure differences of 30–150 bars     

Towards Operational Repeat-Pass SAR Interferometry at Active Volcanoes

Measurement of volcanic surface movement is an operational technique at many volcano observatories to help understand internal processes and to aid in eruption forecasting. The potential of differential radar interferometry (DInSAR) to map patterns of surface deformation on volcanoes is well-proven. However, the technique has not yet become operational, partly because current spaceborne radars were not designed for the task. We discuss the limitations of the European Space Agency's ERS SARs for this purpose in terms of: radar system constraints, volcano surface characteristics, interpretational uncertainties and the operational context. We illustrate the drawbacks at typical stratovolcanoes in South America, chosen to represent a range of conditions. For non expert users of DInSAR, knowing how well DInSAR will work on a particular volcano is important. Freely-available global datasets of vegetation cover and atmospheric water vapour content can be used as proxy measures of coherence and path delay effects, which are the two main determinants of data quality. Operational volcano DInSAR is still years away, but many of the characteristics of such a system can be specified based on the experience learned from earlier radars.     

Supply limited sediment transport in a high-discharge event of the tropical Burdekin River, North Queensland, Australia

Interactions between catchment variables and sediment transport processes in rivers are complex, and sediment transport behaviour during high‐flow events is not well documented. This paper presents an investigation into sediment transport processes in a short‐duration, high‐discharge event in the Burdekin River, a large sand‐ and gravel‐bed river in the monsoon‐ and cyclone‐influenced, semi‐arid tropics of north Queensland. The Burdekin's discharge is highly variable and strongly seasonal, with a recorded maximum of 40 400 m³ s^?1. Sediment was sampled systematically across an 800 m wide, 12 m deep and straight reach using Helley‐Smith bedload and US P‐61 suspended sediment samplers over 16 days of a 29‐day discharge event in February and March 2000 (peak 11 155 m³ s^?1). About 3·7 × 10⁶ tonnes of suspended sediment and 3 × 10⁵ tonnes of bedload are estimated to have been transported past the sample site during the flow event. The sediment load was predominantly supply limited. Wash load included clay, silt and very fine sand. The concentration of suspended bed material (including very coarse sand) varied with bedload transport rate, discharge and height above the bed. Bedload transport rate and changes in channel shape were greatest several days after peak discharge. Comparison between these data and sparse published data from other events on this river shows that the control on sediment load varies between supply limited and hydraulically limited transport, and that antecedent weather is an important control on suspended sediment concentration. Neither the empirical relationships widely used to estimate suspended sediment concentrations and bedload (e.g. Ackers & White, 1973) nor observations of sediment transport characteristics in ephemeral streams (e.g. Reid & Frostick, 1987) are directly applicable to this river.