The Obduction of Equatorial 13 degrees C Water in the Pacific Identified by a Simulated Passive Tracer

The obduction of equatorial 13 degrees C Water in the Pacific is investigated using a simulated passive tracer of the Consortium for Estimating the Circulation and Climate of the Ocean (ECCO). The result shows that the 13 degrees C Water initialized in the region 8 degrees N-8 degrees S, 130 degrees-90 degrees W enters the surface mixed layer in the eastern tropical Pacific, mainly through upwelling near the equator, in the Costa Rica Dome, and along the coast of Peru. Approximately two-thirds of this obduction occurs within 10 years after the 13 degrees C Water being initialized, with the upper portion of the water mass reaching the surface mixed layer in only about a month. The obduction of the 13 degrees C Water helps to maintain a cool sea surface temperature year-round, equivalent to a surface heat flux of about -6.0 W m(-2) averaged over the eastern tropical Pacific (15 degrees S-15 degrees N, 130 degrees W-eastern boundary) for the period of integration (1993-2006). During El Nino years, when the thermocline deepens as a consequence of the easterly wind weakening, the obduction of the 13 degrees C Water is suppressed, and the reduced vertical entrainment generates a warming anomaly of up to 10 W m(-2) in the eastern tropical Pacific and in particular along the coast of Peru, providing explanations for the warming of sea surface temperature that cannot be accounted for by local winds alone. The situation is reversed during La Nina years.

Origin and Pathway of Equatorial 13 degrees C Water in the Pacific Identified by a Simulated Passive Tracer and Its Adjoint

The origin and pathway of the thermostad water in the eastern equatorial Pacific Ocean, often referred to as the equatorial 13 degrees C Water, are investigated using a simulated passive tracer and its adjoint, based on circulation estimates of a global general circulation model. Results demonstrate that the source region of the 13 degrees C Water lies well outside the tropics. In the South Pacific, some 13 degrees C Water is formed northeast of New Zealand, confirming an earlier hypothesis on the water's origin. The South Pacific origin of the 13 degrees C Water is also related to the formation of the Eastern Subtropical Mode Water (ESTMW) and the Sub-Antarctic Mode Water (SAMW). The portion of the ESTMW and SAMW that eventually enters the density range of the 13 degrees C Water (25.8 < sigma(theta) < 26.6 kg m(-3)) does so largely by mixing. Water formed in the subtropics enters the equatorial region predominantly through the western boundary, while its interior transport is relatively small. The fresher North Pacific ESTMW and Central Mode Water (CMW) are also important sources of the 13 degrees C Water. The ratio of the southern versus the northern origins of the water mass is about 2 to 1 and tends to increase with time elapsed from its origin. Of the total volume of initially tracer-tagged water in the eastern equatorial Pacific, approximately 47.5% originates from depths above sigma(theta) = 25.8 kg m(-3) and 34.6% from depths below sigma(theta) = 26.6 kg m(-3), indicative of a dramatic impact of mixing on the route of subtropical water to becoming the 13 degrees C Water. Still only a small portion of the water formed in the subtropics reaches the equatorial region, because most of the water is trapped and recirculates in the subtropical gyre.

A review of the methodologies used in the computer simulation of evacuation from the built environment

Computer based analysis of evacuation can be performed using one of three different approaches, namely optimisation, simulation or risk assessment. Furthermore, within each approach different means of representing the enclosure, the population, and the behaviour of the population are possible. The myriad of approaches which are available has led to the development of some 22 different evacuation models. This article attempts to describe each of the modelling approaches adopted and critically review the inherent capabilities of each approach. The review is based on available published literature.

Macroecology of Calanus finmarchicus and C. helgolandicus in the North Atlantic Ocean and adjacent seas

Global climate change is expected to modify the spatial distribution of marine organisms. However, projections of future changes should be based on robust information on the ecological niche of species. This paper presents a macroecological study of the environmental tolerance and ecological niche (sensu Hutchinson 1957, i.e. the field of tolerance of a species to the principal factors of its environment) of Calanus finmarchicus and C. helgolandicus in the North Atlantic Ocean and adjacent seas. Biological data were collected by the Continuous Plankton Recorder (CPR) Survey, which samples plankton in the North Atlantic and adjacent seas at a standard depth of 7 m. Eleven parameters were chosen including bathymetry, temperature, salinity, nutrients, mixed-layer depth and an index of turbulence compiled from wind data and chlorophyll a concentrations (used herein as an index of available food). The environmental window and the optimum level were determined for both species and for each abiotic factor and chlorophyll concentration. The most important parameters that influenced abundance and spatial distribution were temperature and its correlates such as oxygen and nutrients. Bathymetry and other water-column-related parameters also played an important role. The ecological niche of C. finmarchicus was larger than that of C. helgolandicus and both niches were significantly separated. Our results have important implications in the context of global climate change. As temperature (and to some extent stratification) is predicted to continue to rise in the North Atlantic sector, changes in the spatial distribution of these 2 Calanus species can be expected. Application of this approach to the 1980s North Sea regime shift provides evidence that changes in sea temperature alone could have triggered the substantial and rapid changes identified in the dynamic regimes of these ecosystems. C. finmarchicus appears to be a good indicator of the Atlantic Polar Biome (mainly the Atlantic Subarctic and Arctic provinces) while C. helgolandicus is an indicator of more temperate waters (Atlantic Westerly Winds Biome) in regions characterised by more pronounced spatial changes in bathymetry.

Navigation assistance for wayfinding in the virtual environments: taxonomy and a survey

Efficient Navigation is essential for the user-acceptance of the Virtual Environments (VEs), but it is also inherently, a difficult task to perform. Resulting research in the area provides users with great variety of navigation assistance in VEs however it is still known to be inadequate, complex and suffers through many limitations. In this paper we discuss the task of navigation in the virtual environments and record the wayfinding assistance currently available for the VEs. The paper introduces taxonomy of navigation and categorizes the aids on basis of the functions performed. The paper provides views on current work performed in the area of non-speech auditory aids. Further we conclude by providing views on the important areas that require further investigation and research.

Obesity and diabetes, the built environment, and the ‘local’ food economy in the United States, 2007

Obesity and diabetes are increasingly attributed to environmental factors, however, little attention has been paid to the influence of the ‘local’ food economy. This paper examines the association of measures relating to the built environment and ‘local’ agriculture with U.S. county-level prevalence of obesity and diabetes. Key indicators of the ‘local’ food economy include the density of farmers’ markets and the presence of farms with direct sales. This paper employs a robust regression estimator to account for non-normality of the data and to accommodate outliers. Overall, the built environment is associated with the prevalence of obesity and diabetes and a strong local’ food economy may play an important role in prevention. Results imply considerable scope for community-level interventions.

The challenge of self-regulation in commercial property leasing: a study of lease codes in the UK.

Purpose – UK Government policy to address perceived market failure in commercial property leasing has largely been pursued through industry self-regulation. Yet, it is proving difficult to assess whether self-regulation on leasing has been a “success”, or even to determine how to evaluate this. The purpose of this paper is to provide a framework for this and a clearer understanding of self-regulation in commercial leasing. Design/methodology/approach – A literature review suggests key criteria to explain the (in)effectiveness of self-regulation. UK lease codes are analysed in the light of this literature, drawing on previous research carried out by the authors on the operation of these codes. Findings – Lease codes appear to be failing as an effective system of self-regulation. While there are influential market actors championing them, the fragmentation of the leasing process lessens this influence. The structures are not there to ensure implementation, monitor compliance and record views of affected stakeholders. Research limitations/implications – This work adds to the literature on self-regulation in general, and provides an insight into its operation in a previously unexplored industry. Research is needed into the experience of other countries in regulating the property industry by voluntary means. Social implications – There are institutional limitations to self-regulation within the property industry. This has implications for policy makers in considering the advantages and limitation of using a voluntary solution to achieve policy aims within the commercial leasing market. Originality/value – This paper provides a first step in considering the lease codes in the wider context of industry self-regulation and is relevant to policy makers and industry bodies.

Multi-scale sensible heat fluxes in the urban environment from large aperture scintillometry and eddy covariance

Sensible heat fluxes (QH) are determined using scintillometry and eddy covariance over a suburban area. Two large aperture scintillometers provide spatially integrated fluxes across path lengths of 2.8 km and 5.5 km over Swindon, UK. The shorter scintillometer path spans newly built residential areas and has an approximate source area of 2-4 km2, whilst the long path extends from the rural outskirts to the town centre and has a source area of around 5-10 km2. These large-scale heat fluxes are compared with local-scale eddy covariance measurements. Clear seasonal trends are revealed by the long duration of this dataset and variability in monthly QH is related to the meteorological conditions. At shorter time scales the response of QH to solar radiation often gives rise to close agreement between the measurements, but during times of rapidly changing cloud cover spatial differences in the net radiation (Q*) coincide with greater differences between heat fluxes. For clear days QH lags Q*, thus the ratio of QH to Q* increases throughout the day. In summer the observed energy partitioning is related to the vegetation fraction through use of a footprint model. The results demonstrate the value of scintillometry for integrating surface heterogeneity and offer improved understanding of the influence of anthropogenic materials on surface-atmosphere interactions.

Infrared and millimetre-wave scintillometry in the suburban environment – Part 1: Structure parameters

Scintillometry, a form of ground-based remote sensing, provides the capability to estimate surface heat fluxes over scales of a few hundred metres to kilometres. Measurements are spatial averages, making this technique particularly valuable over areas with moderate heterogeneity such as mixed agricultural or urban environments. In this study, we present the structure parameters of temperature and humidity, which can be related to the sensible and latent heat fluxes through similarity theory, for a suburban area in the UK. The fluxes are provided in the second paper of this two-part series. A millimetre-wave scintillometer was combined with an infrared scintillometer along a 5.5 km path over northern Swindon. The pairing of these two wavelengths offers sensitivity to both temperature and humidity fluctuations, and the correlation between wavelengths is also used to retrieve the path-averaged temperature–humidity correlation. Comparison is made with structure parameters calculated from an eddy covariance station located close to the centre of the scintillometer path. The performance of the measurement techniques under different conditions is discussed. Similar behaviour is seen between the two data sets at sub-daily timescales. For the two summer-to-winter periods presented here, similar evolution is displayed across the seasons. A higher vegetation fraction within the scintillometer source area is consistent with the lower Bowen ratio observed (midday Bowen ratio < 1) compared with more built-up areas around the eddy covariance station. The energy partitioning is further explored in the companion paper.