Abstract.We consider various aspects of the link between solar-modulated geomagnetic activity and the Northern Annular Mode (NAM). Our results indicate that the geomagnetic forcing of atmospheric circulation in the Northern Hemisphere is temporally and seasonally restricted, modulated by the Quasi-Biennial Oscillation (QBO), and reliant on stratosphere-troposphere coupling. When the data are restricted to January values after 1965, for years in which the January QBO is eastwards, the correlation coefficient between the geomagnetic AA index and the NAM is 0.85. These results can account for many of the enigmatic features of Northern Hemisphere circulation.

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As an initial evaluation of the potential of digital elevation models (DEMs) and geographic information systems (GISs) for geomorphic characterization of rocky shorelines, airborne laser scan (ALS) data have been used to characterize shore platforms around Shag Point, southeastern New Zealand. The platforms have been characterized using field-based techniques in previously published research, and therefore offer an ideal site for evaluation purposes. The main challenge involved the delineation of the shore platform area in terms of landward and seaward extents. The cliff top and landward edge of the shore platform was readily mapped, whereas the seaward edge of platforms was mapped with lesser precision due to difficulties associated with tidal inundation and the interference of wave action and surface water. In the central region of the study area (~0·1 km 2 ) higher platform elevations and dense point cloud data enabled the generation of a high-resolution (1 m) DEM. In analysing the DEM, ALS offered an advantage over the previous field survey in respect of the ability to assess continuous topography in plan-view. The extent and form of two distinctive erosional surfaces is clearly apparent and was revealed through classifications based on slope and elevation. The spatial continuity of the upper surface implies that, in addition to the role of rock structure described in previous work, sea level and wave exposure may have been important factors in the generation and preservation of platform morphology at Shag Point. Figure 2.Derivation of the landward edge of the shore platforms using surface slope. It is possible to manually extract the landward edge (cliff toe) from the slope map. Pixel size is 1 m.Defining shore platform boundaries using airborne laser scan data 949 Figure 3. The results of the platform delineation process. The platform outline is shown in black. The landward edge of the platform, derived using a slope calculation on the 1 m DEM, is also indicated. The landward edge of the platform is well defined, whereas the seaward edge is in some cases overestimated (on the eastern portion) due to (a) difficulties in separating ground and water strikes, or (b) tidal inundation (on the western portion). Image sourced from Land Information New Zealand, NZMG Orthophoto J43 Palmerston 2001/2002, Crown Copyright Reserved. Pixel size is 2·5 m. This figure is available in colour online at www.interscience.wiley.com/journal/espl data into ground and non-ground points was undertaken by the data provider and details of the filtering algorithm are unknown. However, because shore-platform areas are highly unlikely to contain either buildings or vegetation, but may contain subtle terrain variations corresponding with features such as concretions and gullies, the judicious inclusion of non-ground points may be justified. As with the previous DEM, the boundary of the landward platform edge was refined by once again including only pixels with heights below 5 m. A comparison of the platform DEMs 950 Figure 4. A comparison...

The accurate mapping of coalmine subsidence is necessary for the continued management of potential subsidence impacts. The use of airborne laser scan (ALS) data for subsidence mapping provides an alternative method to traditional ground-based approaches that affords increased accessibility and complete spatial coverage. This paper evaluates the suitability and potential of ALS data for subsidence mapping, primarily through the examination of two pre-mining surveys in a rugged, densely vegetated study site. Data quality, in terms of mean point spacing and coverage, is evaluated, along with the impact of interpolation methods, resolution, and terrain. It was assumed that minimal surface height changes occurred between the two premining surfaces. Therefore any height changes between digital elevation models of the two ALS surveys were interpreted as errors associated with the use of ALS data for subsidence mapping. A mean absolute error of 0.23 m was observed, though this error may be exaggerated by the presence of a systematic 0.15 m offset between the two surveys. Very large (several metres) errors occur in areas of steep or dynamic terrain, such as along cliff lines and watercourses. Despite these errors, preliminary subsidence mapping, performed using a third, post-mining dataset, clearly demonstrates the potential benefits of ALS data for subsidence mapping, as well as some potential limitations and the need for further careful assessment and validation concerning data errors.