Temperature of an active lava channel from spectral measurements,Kilauea Volcano,Hawaii

A narrow band spectroradiometer was used to determine the characteristic temperatures of a very active channeled lava flow for the phase 50 eruption of Pu'u 'O'o on the East Rift Zone of Kilauea Volcano, Hawaii. During the twilight of 19 February 1992, 14 spectra of this activity were acquired over a 51 minute interval [18.29 to 19.20 Hawaiian Standard Time (HST)], from which the thermal distribution of energy of two 18 m² areas, one near the center and one near the margin of the flow, may be investigated. A twocomponent thermal mixing model applied to the data taken of the center of the channel gave, in the most powerful instance (1.8x10⁵ W/m²), a crust temperature of 940° C, a hot component temperature of 1120°C and a hot radiating area of 60% of the total area. A simultaneous spectrum acquired near the channeled flow margin yielded a crust temperature of 586° C and a hot area of only 1.2% of the total area radiating at 1130° C. Average radiant flux densities recorded for the center of the lava channel (1.3x10⁵ W/m² average) are much greater than previous measurements of lava lakes (4.9x10³ W/m²) or recently emplaced lava flows (maximum of 7.2x10⁴ W/m²). The energetic nature of this eruption is shown by satellite measurements made at 02.33 HST on 22 February 1992 by the Advanced Very High Resolution Radiometer in Band 2 (0.72–1.10 m). These show the utility of using existing satellites with moderate resolution (1 km x 1 km pixels) and high temporal coverage (eight overpasses each day for Hawaii) as potential thermal alarms for rapidly assessing the hazard potential of large volcanic eruptions.     

A stochastic model describing the impact of daily rainfall depth distribution on the soil water balance

Simplified, vertically-averaged soil moisture models have been widely used to describe and study eco-hydrological processes in water-limited ecosystems. The principal aim of these models is to understand how the main physical and biological processes linking soil, vegetation, and climate impact on the statistical properties of soil moisture. A key component of these models is the stochastic nature of daily rainfall, which is mathematically described as a compound Poisson process with daily rainfall amounts drawn from an exponential distribution. Since measurements show that the exponential distribution is often not the best candidate to fit daily rainfall, we compare the soil moisture probability density functions obtained from a soil water balance model with daily rainfall depths assumed to be distributed as exponential, mixed-exponential, and gamma. This model with different daily rainfall distributions is applied to a catchment in New South Wales, Australia, in order to show that the estimation of the seasonal statistics of soil moisture might be improved when using the distribution that better fits daily rainfall data. This study also shows that the choice of the daily rainfall distributions might considerably affect the estimation of vegetation water-stress, leakage and runoff occurrence, and the whole water balance.     

Quantifying the largest aggregation of giant trevally Caranx ignobilis (Carangidae) on record: implications for management

The giant trevally Caranx ignobilis (Forsskål) is an important apex predatory fish typically associated with coral reef communities. It is prized in recreational and commercial fisheries, yet little is known about its aggregation dynamics and susceptibility to fishing pressure. This study reports on a previously undocumented aggregation of mature giant trevally observed over a period of eight years (2010–2017) at Ponta do Ouro Partial Marine Reserve in southern Mozambique. The aggregation is one of the few recorded for this carangid in the western Indian Ocean and represents the first subtropical aggregation of giant trevally. The aggregation is also the largest recorded for this species, with up to 2 413 individuals representing an estimated biomass of approximately 30 tonnes. The size and predictability of this annual aggregation make it vulnerable to overexploitation and point towards the need for an appropriate conservation management strategy.     

Bypassing the ‘ratification straitjacket’: reviewing US legal participation in a climate agreement

The issue of US ratification of international environmental treaties is a recurring obstacle for environmental multilateralism, including the climate regime. Despite the perceived importance of the role of the US to the success of any future international climate agreement, there has been little direct coverage in terms of how an effective agreement can specifically address US legal participation. This article explores potential ways of allowing for US legal participation in an effective climate treaty. Possible routes forward include the use of domestic legislation such as section 115 (S115) of the Clean Air Act (CAA) and the use of sole–executive agreements, instead of Senate ratification. Legal participation from the US through sole–executive agreements is possible if the international architecture is designed to allow for their use. Architectural elements such as varying legality and participation across an agreement (variable geometry) could allow for the use of sole–executive agreements. Two broader models for a 2015 agreement with legal participation through sole–executive agreements are constructed based upon these options: a modified pledge and review system and a form of variable geometry composed of number of opt-out, voting-based protocols on specific issues accompanied by bilateral agreements on mitigation commitments with other major emitters through the use of S115 and sole–executive agreements under the Montreal Protocol and Chicago Convention (‘Critical Mass Governance'). While there is no single solution, Critical Mass Governance appears to provide the optimum combination of tools to effectively allow for US legal participation whilst ensuring an effective treaty.

Policy relevance

This article provides some recommendations on how to create an effective, legally binding treaty that allow for US legal participation without Senate approval. Given the recent election of a Republican majority in the US Senate and Congress, increasing willingness of the President to utilize his executive powers, as well as a strong shift in negotiations to appease US interests, the insights of this research are timely and relevant to delegations and other United Nations Framework Convention on Climate Change (UNFCCC) actors. It will also be of use to domestic US actors involved with climate policy by illustrating how to allow for effective and sustainable US multilateral engagement that bypasses domestic political gridlock.     

Ecological assessment to detect imminent change in coral reefs of Admiral Cockburn Land and Sea National Park,Turks and Caicos Islands

Coral reefs of the Turks and Caicos Islands (TCIs) (Caribbean Sea) constitute some of the few pristine coral reef systems in the world and play a crucial role in the islands’ economy because they support rich fisheries catches and tourism development. Ambitious development plans involving increase in fishing and tourism pressures are about to bring changes in coastal zone resources of the TCIs associated with increased sediments and nutrients and reduced predation by herbivorous fish on coral reefs. Understanding change is critical when attempting to protect the resources that these coral reefs support and to adopt proper management strategies. Yet, an environmental assessment program to detect imminent human‐induced changes on the surrounding reefs of the TCIs is lacking. Thus, (i) we obtained baseline data on benthic composition and coral community structure at seven reef sites of representative reefs of the TCIs within the Admiral Cockburn Land and Sea National Park (ACLSNP) of South Caicos Island and (ii) performed a priori statistical power analysis to calculate replication requirements for safely and confidently detecting small (δ = 0.1), medium (δ = 0.3), and large (δ = 0.5) effect sizes for a number of relevant to anticipated changes, univariate, benthic indices and for power β = 0.95. The platforms of the margin reefs studied (9–12 m depth) appeared rather variable regarding benthic composition but quite homogeneous regarding hard coral community structure. Mean percent cover of algal functional groups was 0.1 ± 0.3 (mean ± sd) percent for coralline algae and Halimeda, 0.1 ± 0.6 (mean ± sd) percent for macroalgae, 21.7 ± 33 (mean ± sd) percent for turf algae and 4.8 ± 4.0 (mean ± sd) percent for hard coral cover. The dominant benthic component, however, was carbonate substrate (mean ± sd = 30.4 ± 34.3), thus indicating an accreting reef framework. Mean hard coral density, colony size and recruit density were 5.5 ± 1.8 (mean ± sd) corals per 20‐m line transect, 13.0 ± 2.3 (mean ± sd) cm maximum colony diameter, and 1.3 ± 1.4 (mean ± sd) recruits per square foot, respectively. Due to high natural variance, hard coral colony size and density were practically the most sensitive indices in detecting even small size changes on benthos. Also, the geometric mean of log‐transformed colony size‐frequency distributions of the most abundant hard coral taxa, i.e. Montastrea annularis, Agaricia spp., Siderastrea spp. and Porites asteroides were practically sensitive for the same purpose. We hope that the study will optimize the spatial component of a necessary environmental impact assessment program on coral reefs of the TCIs once the natural spatial variability of the system has been assessed and sensitive, benthic, univariate indices have been identified for representative reference coral reef sites of the TCIs.     

The opposition effect in the outer Solar system: A comparative study of the phase function morphology

In this paper, we characterize the morphology of the disk-integrated phase functions of satellites and rings around the giant planets of our solar system. We find that the shape of the phase function is accurately represented by a logarithmic model [Bobrov, M.S., 1970. Physical properties of Saturn's rings. In: Dollfus, A. (Ed.), Surfaces and Interiors of Planets and Satellites. Academic, New York, pp. 376-461]. For practical purposes, we also parametrize the phase curves by a linear-exponential model [Kaasalainen, S., Muinonen, K., Piironen, J., 2001. Comparative study on opposition effect of icy solar system objects. Journal of Quantitative Spectroscopy and Radiative Transfer 70, 529-543] and a simple linear-by-parts model [Lumme, K., Irvine, W.M., 1976. Photometry of Saturn's rings. Astronomical Journal 81, 865-893], which provides three morphological parameters: the amplitude A and the half-width at half-maximum (HWHM) of the opposition surge, and the slope S of the linear part of the phase function at larger phase angles.Our analysis demonstrates that all of these morphological parameters are correlated with the single-scattering albedos of the surfaces.By taking more accurately into consideration the finite angular size of the Sun, we find that the Galilean, Saturnian, Uranian and Neptunian satellites have similar HWHMs (?0.5^°), whereas they have a wide range of amplitudes A. The Moon has the largest HWHM (∼2^°). We interpret that as a consequence of the “solar size bias”, via the finite angular size of the Sun which varies dramatically from the Earth to Neptune. By applying a new method that attempts to morphologically deconvolve the phase function to the solar angular size, we find that icy and young surfaces, with active resurfacing, have the smallest values of A and HWHM, whereas dark objects (and perhaps older surfaces) such as the Moon, Nereid and Saturn's C ring have the largest A and HWHM.Comparison between multiple objects also shows that solar system objects belonging to the same planet have comparable opposition surges. This can be interpreted as a “planetary environmental effect” that acts to locally modify the regolith and the surface properties of objects which are in the same environment.     

A theoretical model for gas adsorption-induced coal swelling

Swelling and shrinkage (volumetric change) of coal during adsorption and desorption of gas is a well-known phenomenon. For coalbed methane recovery and carbon sequestration in deep, unminable coal beds, adsorption-induced coal volumetric change may cause significant reservoir permeability change. In this work, a theoretical model is derived to describe adsorption-induced coal swelling at adsorption and strain equilibrium. This model applies an energy balance approach, which assumes that the surface energy change caused by adsorption is equal to the elastic energy change of the coal solid. The elastic modulus of the coal, gas adsorption isotherm, and other measurable parameters, including coal density and porosity, are required in this model. Results from the model agree well with experimental observations of swelling. It is shown that the model is able to describe the differences in swelling behaviour with respect to gas species and at very high gas pressures, where the coal swelling ratio reaches a maximum then decreases. Furthermore, this model can be used to describe mixed-gas adsorption induced-coal swelling, and can thus be applied to CO₂-enhanced coalbed methane recovery.     

Particle sieving and sorting under simulated martian conditions

We report on sorting of small grained material under simulated martian conditions in order to better understand the nature of particle movement in the acquisition-to-analysis chain for future martian missions. We find that triboelectric charging when material is sieved is a major phenomenon that has to be understood and mitigation strategies explored in order to be able to successfully move particles under these types of conditions while minimizing cross sample talk. In different experimental set-ups, we have observed such phenomena as caking of the sieve, adhesion of particles to hardware, clodding of dry fines, and electrostatic repulsion. These phenomena occur when different experimental testing is performed with varied configurations and environmental conditions. Identifying these electrostatic effects can help us understand potential bias in the analytical instruments and to define the best operational protocols to collect samples on the surface of Mars. These experiments demonstrate the need for end-to-end system testing under the most realistic environmental conditions and platforms before mission configurations can be demonstrated before launch.     

Wake studies of a 1/30th scale horizontal axis marine current turbine

A 0.4 m diameter (1:30th scale) horizontal axis marine current turbine (MCT) was tested in a circulating water channel. The turbine performance and wake characteristics were determined over a range of flow speeds and rotor thrust coefficients. Measurements of the water surface elevation profiles indicated increasing variation and surface turbulence with increasing flow speeds. Blockage-type effects (where the measured point velocity was greater than the inflow velocity) occurred around the sides of the rotor for all flow speeds. Although the effects were exaggerated at model scale, it is expected that reasonable variations in water level and flow velocity could also occur over a full scale MCT array.