Relative Radiometric Correction of Multitemporal Satellite Imagery Using Fourier and Wavelet Transform

Remotely sensed multitemporal, multisensor data are often required in Earth observation applications. A common problem associated with the use of multisource image data is the grey value differences caused by non-surface factors such as different illumination, atmospheric, or sensor conditions. Image normalization is required to reduce the radiometric influences caused by non-surface factors and to ensure that the grey value differences between temporal images reflect actual changes on the surface of the Earth. This paper proposes new approaches to radiometric correction of multitemporal satellite imagery using wavelet analysis and Fourier transform. The results obtained are compared with commonly used NO-change regression (NC) normalization and Histogram Matching spatial domain methods. Both visual inspection and statistical accuracy assessment show that proposed transform domain approaches are valid.     

Upper Water Column Nitrous Oxide Distributions in the Northeast Subarctic Pacific Ocean

This is the first study to investigate the magnitude and distribution of N₂O concentrations along the Line P oceanographic transect in the Northeast (NE) subarctic Pacific Ocean. Concentrations of N₂O were measured from the surface to 600 m depth at five stations between 126°W and 145°W. Although nitrification within the mixed layer may produce some N₂O, we conclude that mixing and diffusion processes, which vertically transport N₂O upwards from below the mixed layer, are the primary sources of N₂O to the surface waters of the NE subarctic Pacific Ocean. Below the mixed layer, nitrification appears to be the dominant source of N₂O, and based on correlations of excess N₂O (ΔN₂O) versus apparent oxygen utilization and NO₃ ^? concentrations, we estimated that the N₂O yield from nitrification was approximately 0.028 to 0.040%. The longitudinal distributions of N₂O concentrations below the mixed layer were variable and we consider the potential role that different transiting water masses may play in contributing to this variability. Finally, we estimated that the regional average sea-to-air N₂O flux was 4.37 mol of N₂O km^?2 d^?1, a value which is approximately four times that of the global average seawater-to-air flux rate. Our N₂O yield estimates are within the range of those expected under oxic conditions, leading us to conclude that decreasing dissolved O₂ concentrations in the NE subarctic Pacific Ocean, and the water masses that influence this region, over the past 50 years have yet to produce a substantial increase in N₂O production. Given the expectation that dissolved O₂ concentrations in the subarctic Pacific Ocean will continue to decrease during this century, this study has provided an important baseline from which future studies will be able to track changes in seawater N₂O concentrations and fluxes to the atmosphere.

[Traduit par la rédaction] La présente étude est la première à s'intéresser à la valeur et à la distribution des concentrations de N₂O le long du transect océanographique de la ligne P dans le Pacifique Nord-Est subarctique. Les concentrations de N₂O ont été mesurées de la surface jusqu’à une profondeur de 600 m à cinq stations entre 126°O et 145°O. Bien que la nitrification à l'intérieur de la couche de mélange puisse produire du N₂O, nous concluons que le mélange et les processus de diffusion, qui transportent verticalement le N₂O vers le haut à partir d'en dessous de la couche de mélange, sont les sources principales de N₂O pour les eaux de surface du Pacifique Nord-Est subarctique. En dessous de la couche mélange, la nitrification semble être la principale source de N₂O, et d'après les corrélations de l'excès de N₂O (ΔN₂O) par rapport à l'utilisation apparente d'oxygène et aux concentrations de NO₃ ^?, nous avons estimé que le rendement en N₂O de la nitrification était approximativement de 0,028 à 0,040%. Les distributions longitudinales des concentrations de N₂O en dessous de la couche de mélange étaient variables et nous considérons le rôle possible que des différentes masses d'eau transitoires peuvent avoir à jouer dans cette variabilité. Finalement, nous avons estimé que la moyenne régionale du flux mer–air de N₂O était de 4,37 moles de N₂O km^?2 j^?1, une valeur qui est environ quatre fois celle du taux planétaire moyen du flux eau de mer–air. Nos estimations du rendement en N₂O sont de l'ordre de celles attendues dans des conditions oxyques, ce qui nous amène à conclure que la diminution des concentrations d'oxygène dissout dans le Pacifique Nord–Est subarctique, et dans les masses d'eau qui influencent cette région, au cours des cinquante dernières années ont encore à produire une augmentation substantielle de production de N₂O. Étant donné qu'on s'attend à ce que les concentrations d'oxygène dissout dans le Pacifique subarctique continuent à diminuer durant le présent siècle, cette étude a fourni une importante base de référence à partir de laquelle de futures études pourront suivre les changements dans les concentrations de N₂O dans l'eau de mer et dans ses flux vers l'atmosphère.     

OSCILLATIONS IN THERMALLY-CONDUCTING POLYTROPIC ATMOSPHERES IN THE PRESENCE OF A VERTICAL MAGNETIC FIELD

We have investigated the normal modes of subadiabatic and superadiabatic polytropic atmospheres with constant vertical magnetic field and constant thermal conductivity. In the subadiabatic case, we found the lowest, third and fifth modes were always damped, however overstability was detected in the second and fourth modes at low values of the background magnetic field. In the superadiabatic case, instability was detected in several modes, however the effect of the change from sub to superadiabatic had little effect on the frequencies of the modes. The introduction of a variety of boundary conditions varying the degree of thermal and mechanical isolation altered the decay rates of the modes from moderately damped with rigid boundary conditions toward zero decay with the less restrictive conditions, again with essentially no effect on the oscillation frequencies. In both types of atmosphere, modes with periods in the 3-min and 5-min bands were present with magnetic fields around 3000 G, whereas only the 5-min modes were present at 2000 G.     

Aquifer Discharge Drives Microbial Community Change in Karst Estuaries

Karst estuaries are unique systems governed by freshwater inputs that flow directly to the sea through karst conduits and/or matrices. Because they are found at the interface between terrestrial and marine environments, they can act as sentinels to climate change and as indicators of aquifer health. The physical and geochemical gradients formed in karst estuaries are a direct result of the interactions between inland hydrological conditions and sea level. To examine the influence these gradients have on microbial communities in the water column and sediment of a karst estuary, we studied the spring-fed Double Keyhole Karst Estuary in west central Florida for a 2-year period. Four sites were monitored within this system starting at the Double Keyhole Spring Conduit extending 2 km west through the estuary toward the Gulf of Mexico. Water column and sediment samples were collected quarterly at all sites from September 2011 through September 2013. Archaeal, bacterial, and microbial eukaryote communities were analyzed using quantitative PCR and length-heterogeneity PCR. The biological communities were analyzed in the context of hydrological, physical, and geochemical parameters in order to determine which factor(s) governed the observed changes of microbial abundance and richness. The major finding of this study was that microbial community change in this karst estuary was primarily driven by the volume of aquifer discharge and associated physical gradients, and less by the geochemical fluctuations within the system.     

Growth,feed conversion and faecal discharge of yellowtail kingfish (Seriola lalandi) fed three commercial diets

Abstract

A study was undertaken to provide data on growth, feed conversion ratio (FCR) and faecal discharge of yellowtail kingfish (Seriola lalandi) fed three commercial diets used previously to culture this species in New Zealand. Fish were raised in tanks from 0.4 to 1.2 kg over the spring (water temperature 14–17°C) and summer (17–22°C) periods. There were considerable differences in volumetric and mass‐specific feed intake, and energy intake amongst diets. Daily crude protein intake was similar amongst diets, although it increased from the cold (4.05–4.50 g protein kg^?1 day^?1) to warm period (6.48–7.67 g protein kg^?1 day^?1). The biological and economical FCR varied with diet (BFCR 1.22–2.17, EFCR 1.30–2.62), as did the cost of feed per unit biomass produced (NZ$38–3.78 kg^?1). Growth rates were broadly similar amongst diets, and the warmer summer temperature period greatly improved both growth (increase from 0.51–0.64% to 1.18–1.23% mass gain day^?1) and BFCR (decrease from 1.37–2.17 to 1.22–1.46). The Salmofood ESF diet resulted in only half of the faecal setüeable solids and settleable total nitrogen (T N) and total phosphorus (T P) output compared with Skretting NME, which was in turn only half or less of that of Reliance SF     

Assessing adequacy of spectrum‐matched ground motions for response history analysis

Response spectrum matching is commonly used to generate ground motions with response spectra matching a scenario target spectrum. There is some debate in the literature about whether spectrum‐matched motions lead to biased structural analysis results. Furthermore, there are no objective, quantitative criteria available for deciding whether a ground motion has been manipulated excessively by spectrum matching, and whether large modification may also lead to bias. This study investigates both of these issues by presenting the results of structural analysis using two reinforced concrete moment frame models and two earthquake scenarios, with suites of unmatched and matched ground motions. Through comparison with a robust benchmark, it is shown that no significant bias is introduced by spectrum matching. The period range and target damping values for matching are also investigated, and matching up to three times the fundamental period is shown to be beneficial in reducing dispersion in the results. Finally, these analyses were also used to investigate whether large changes in the ground motion lead to biased analysis results. Several potential measures of change are investigated, including those based on peak absolute ground motion, cumulative squared ground motion (absolute or normalized), and input energy into single‐degree‐of‐freedom systems. Although no systematic, statistically significant correlation is found for the analysis results in terms of any of these measures of change, tentative criteria are proposed, which may be used by analysts to aid in the decision of whether to accept or reject a spectrum‐matched motion. Copyright © 2012 John Wiley & Sons, Ltd.     

Place attachment and community activism at the coast: The case of Ngunguru,Northland

The politics of place precipitated by a development proposal for a privately owned sandspit in Ngunguru, Northland, is examined in this article. It centres on residents' place attachment and the ways in which this helped to inform community resistance to development. A framing analysis of 23 stakeholder interviews conducted in 2008–2009 was carried out by the authors. Place attachment was centred on holistic appreciation of the sandspit's special values. A widespread view that exercise of private property rights over the site was deeply problematic was informed by this appreciation. Community ties were enhanced by shared perceptions of a threat to the sandspit.     

Geomorphic covariance structure of a confined mountain river reveals landform organization stage threshold

Significant growth in mountain rivers research since 1990 has promoted the concept that canyon-confined mountain rivers have complex topographic features nested from base- to flood-stages due to canyon structure and abundant large bed elements. Nesting means literally structures inside of structures. Mathematically, nesting means that multiple individual features and repeating patterns exist at different frequency, amplitude, and phasing, and can be added together to obtain the complete structure. Until now, subreach-scale landform structure, including nesting, has not been quantified sufficiently to understand morphodynamic mechanisms that control and respond to such organization. Geomorphic covariance structure analysis offers a systematic framework for evaluating nested topographic patterns. In this study, a threshold stage in mountain river inundation was hypothesized to exist. Above this stage landform structure is organized to be freely self-maintaining via flow convergence routing morphodynamics. A 13.2 km segment of the canyon-confined Yuba River, California, was studied using 2944 cross-sections. Geomorphic covariance structure analysis was carried out on a meter-resolution topographic model to test the hypothesis. River width and bed elevation had significantly less variability than previously reported for lower slope, partially confined gravel/cobble river reaches. A critical stage threshold governing flow convergence routing morphodynamics was evident in several metrics. Below this threshold, narrow/high “nozzle” and wide/low “oversized” were the dominant landforms (excluding “normal channel”), while above it wide/high “wide bar” and narrow/low “constricted pool” were dominant. Three-stage nesting of base-bankfull-flood landforms was dictated by canyon confinement, with nozzle–nozzle–nozzle nesting as the top permutation, excluding normal channel.     

Nuances of neighbourhood: Children’s perceptions of the space between home and school in Auckland, New Zealand

This paper examines primary school children’s experiences of travelling between home and school within three neighbourhoods. Our investigation is set in Auckland, New Zealand, where parental practices such as chauffeuring are commonplace, yet are increasingly recognised as limiting children’s physical fitness and environmental awareness. Drawing on children’s voices, writing and photographs, we investigate how children currently travel to school, how they would like to travel, and how their perspectives on neighbourhood space vary by age, socio-economic status and school location. Findings reveal that over half of the participants did not like the way they travelled to school. Most desire to travel independently within public space, but are limited in their ability to do so, given the fears and obstacles that prevail within their neighbourhoods. We contend that restricted use of public space diminishes children’s agency in inner suburbs. Our analysis reveals that children favour ‘active travel’ for many of the same reasons as health professionals and transport planners. We conclude that as long as children are seen as innocents in need of protection, they will have limited agency in travel decisions and highly contingent access to public space.