Night sky brightness at sites from DMSP-OLS satellite measurements

We apply the sky brightness modelling technique introduced and developed by Roy Garstang to high-resolution DMSP-OLS satellite measurements of upward artificial light flux and to GTOPO30 digital elevation data in order to predict the brightness distribution of the night sky at a given site in the primary astronomical photometric bands for a range of atmospheric aerosol contents. This method, based on global data and accounting for elevation, Earth curvature and mountain screening, allows the evaluation of sky glow conditions over the entire sky for any site in the World, to evaluate its evolution, to disentangle the contribution of individual sources in the surrounding territory, and to identify main contributing sources. Sky brightness, naked eye stellar visibility and telescope limiting magnitude are produced as 3-dimensional arrays whose axes are the position on the sky and the atmospheric clarity. We compared our results to available measurements.Comment: 14 pages, 12 figures, accepted for publication in MNRAS, 17 june 200

Examination of the spectral features of vegetation in 1987 AVIRIS data

Equations for converting AVIRIS digital numbers to percent reflectance were developed using a set of three calibration targets. AVIRIS reflectance spectra from five plant communities exhibit distinct spectral differences

Earth’s polar night boundary layer as an analogue for dark side inversions on synchronously rotating terrestrial exoplanets

A key factor in determining the potential habitability of synchronously rotating planets is the strength of the atmospheric boundary layer inversion between the dark side surface and the free atmosphere. Here we analyse data obtained from polar night measurements at the South Pole and Alert Canada, which are the closest analogues on Earth to conditions on the dark sides of synchronously rotating exoplanets without and with a maritime influence, respectively. On Earth, such inversions rarely exceed 30 K in strength, because of the effect of turbulent mixing induced by phenomena such as so-called mesoscale slope winds, which have horizontal scales of 10s to 100s of km, suggesting a similar constraint to near-surface dark side inversions. We discuss the sensitivity of inversion strength to factors such as orography and the global-scale circulation, and compare them to a simulation of the planet Proxima Centauri b. Our results demonstrate the importance of comparisons with Earth data in exoplanet research, and highlight the need for further studies of the exoplanet atmospheric collapse problem using mesoscale and eddy-resolving models

A Route Map to an Enabling State

This document is the final report of a thematic research carried out by The Carnegie UK Trust. In this document, Sir John Elvidge presents the Enabling State and sets out eight steps that governments can take to improve the well-being of all sections of our society to support individuals and communities to achieve positive change and ensure that the most vulnerable people are not left behind

Polar föhn winds and warming over the Larsen C Ice Shelf, Antarctica

Recent hypotheses that the foehn effect is partly responsible for warming to the east of the Antarctic Peninsula (AP) and enhanced melt rates on the Larsen C Ice Shelf are supported in a study combining the analysis of observational and high resolution model data. Leeside warming and drying during foehn events is observed in new aircraft, radiosonde and automatic weather station data and simulated by the UK Met Office Unified Model at ~1.5 km grid spacing (MetUM 1.5 km). Three contrasting cases are investigated. In Case A relatively weak southwesterly flow induces a nonlinear foehn event. Strongly accelerated flow above and a hydraulic jump immediately downwind of the lee slopes lead to high amplitude warming in the immediate lee of the AP, downwind of which the warming effect diminishes rapidly due to the upward ‘rebound’ of the foehn flow. Case C defines a relatively linear case associated with strong northwesterly winds. The lack of a hydraulic jump enables foehn flow to flood across the entire ice shelf at low levels. Melt rates are high due to a combination of large radiative heat flux, due to dry, clear leeside conditions, and sensible heat flux downward from the warm, well-mixed foehn flow. Climatological work suggests that such strong northwesterly cases are often responsible for high Larsen C melt rates. Case B describes a weak, relatively non-linear foehn event associated with insignificant daytime melt rates. Previously unknown jets – named polar foehn jets – emanating from the mouths of leeside inlets are identified as a type of gap flow. They are cool and moist relative to adjacent calmer regions, due to lower-altitude upwind source regions, and are characterised by larger turbulent heat fluxes both within the air column and at the surface. The relative importance of the three mechanisms deemed to induce leeside foehn warming (isentropic drawdown, latent heating and sensible heating) are quantified using a novel method analysing back trajectories and MetUM 1.5 km model output. It is shown that, depending on the linearity of the flow regime and the humidity of the air mass, each mechanism can dominate. This implies that there is no dominant foehn warming mechanism, contrary to the conclusions of previous work

Spectral Identification of Lighting Type and Character

We investigated the optimal spectral bands for the identification of lighting types and the estimation of four major indices used to measure the efficiency or character of lighting. To accomplish these objectives we collected high-resolution emission spectra (350 to 2,500 nm) for forty-three different lamps, encompassing nine of the major types of lamps used worldwide. The narrow band emission spectra were used to simulate radiances in eight spectral bands including the human eye photoreceptor bands (photopic, scotopic, and “meltopic”) plus five spectral bands in the visible and near-infrared modeled on bands flown on the Landsat Thematic Mapper (TM). The high-resolution continuous spectra are superior to the broad band combinations for the identification of lighting type and are the standard for calculation of Luminous Efficacy of Radiation (LER), Correlated Color Temperature (CCT) and Color Rendering Index (CRI). Given the high cost that would be associated with building and flying a hyperspectral sensor with detection limits low enough to observe nighttime lights we conclude that it would be more feasible to fly an instrument with a limited number of broad spectral bands in the visible to near infrared. The best set of broad spectral bands among those tested is blue, green, red and NIR bands modeled on the band set flown on the Landsat Thematic Mapper. This set provides low errors on the identification of lighting types and reasonable estimates of LER and CCT when compared to the other broad band set tested. None of the broad band sets tested could make reasonable estimates of Luminous Efficacy (LE) or CRI. The photopic band proved useful for the estimation of LER. However, the three photoreceptor bands performed poorly in the identification of lighting types when compared to the bands modeled on the Landsat Thematic Mapper. Our conclusion is that it is feasible to identify lighting type and make reasonable estimates of LER and CCT using four or more spectral bands with minimal spectral overlap spanning the 0.4 to 1.0 um region

Captive breeding programmes for nocturnal prosimians

Due to the nocturnal and arboreal nature of nocturnal prosimians field research on these species is limited. Maintaining populations in zoos provides an opportunity to increase our knowledge of these elusive species. This study aimed to update and contribute to the limited research on captive populations of nocturnal prosimians. The study consists of two parts. Part one aimed to identify the current European captive population of six nocturnal prosimian species (aye-aye, fat-tailed dwarf lemur, Goodman’s mouse lemur, grey mouse lemur, grey slender loris and pygmy slow loris) and determine their demographic self-sustainability. To achieve this aim studbook data was analysed. The difference between birth and death rates, infant mortality rates, age structure and sex composition were investigated. The study concludes populations of aye-aye, fat-tailed dwarf lemur, grey slender loris and pygmy slow loris were not self-sustaining whereas Goodman’s mouse lemur are self-sustaining and grey mouse lemur were found to have an increasing population trend. Part two focussed on the European captive population of pygmy slow loris and grey slender loris. This section sort to determine if husbandry methods affect breeding success. This involved conducting a survey of the current husbandry methods used in 20 European zoos. Statistical tests were carried out to determine if there was a correlation between institution breeding success and the husbandry methods used. The study concludes that there was a significant correlation between institution breeding success and the interval duration between cleaning the fixed enclosure furniture (P=0.030). Results also strongly suggested pygmy slow lorises housed with another species have a higher breeding success than those housed as a single-species exhibit

How Does Aristotle Understand the Paradox of the Meno?

I focus on the distinction between universal and particular knowledge or knowledge simpliciter in APr 2.21 and APo 1.1 as Aristotle’s explicit response to the paradox of the Meno. I attempt to derive a picture of Aristotle’s understanding of the philosophical problem underlying that paradox by asking what that problem would have to be in order for this distinction to make sense as a response to it. I consider two ways of taking the distinction, and argue that both point towards a problem about deriving knowledge of particulars from knowledge of universals as the fundamental problem underlying Aristotle’s understanding of the Meno paradox