Halley and the London Queen Anne Churches

Edmond Halley's work on two London churches makes them the first buildings planned using modern scientific techniques, argue Jason R Ali and Peter Cunich.     

Rainfall intensity–duration thresholds for postfire debris-flow emergency-response planning

Following wildfires, emergency-response and public-safety agencies can be faced with evacuation and resource-deployment decisions well in advance of coming winter storms and during storms themselves. Information critical to these decisions is provided for recently burned areas in the San Gabriel Mountains of southern California. A compilation of information on the hydrologic response to winter storms from recently burned areas in southern California steeplands is used to develop a system for classifying magnitudes of hydrologic response. The four-class system describes combinations of reported volumes of individual debris flows, consequences of debris flows and floods in an urban setting, and spatial extents of the hydrologic response. The range of rainfall conditions associated with different magnitude classes is defined by integrating local rainfall data with the response magnitude information. Magnitude I events can be expected when within-storm rainfall accumulations (A) of given durations (D) fall above the threshold A = 0.4D ^0.5 and below A = 0.5D ^0.6 for durations greater than 1 h. Magnitude II events will be generated in response to rainfall accumulations and durations between A = 0.4D ^0.5 and A = 0.9D ^0.5 for durations less than 1 h, and between A = 0.5D ^0.6 and A = 0.9D ^0.5 or durations greater than 1 h. Magnitude III events can be expected in response to rainfall conditions above the threshold A = 0.9D ^0.5. Rainfall threshold-magnitude relations are linked with potential emergency-response actions as an emergency-response decision chart, which leads a user through steps to determine potential event magnitudes and identify possible evacuation and resource-deployment levels. Use of this information in planning and response decision-making process could result in increased safety for both the public and emergency responders.     

The current and future capabilities of MCP based UV detectors

At the heart of future space-based astronomical UV instruments will be a sensitive UV detector. Though there has been a death of new UV mission opportunities, detector development has continued. Improvements have been made in spatial resolution, dynamic range, detector size, quantum efficiency and background. At the same time the power and mass required to achieve these goals have decreased. We review the current capabilities of microchannel plate based detectors at Berkeley, both in the laboratory and aboard current on-orbit spacecraft. We also discuss what can be expected from the next generation of UV detectors over the next decade.     

Vegetation-related dry deposition of global PM2.5 from satellite observations

Journal of Geographical Sciences - Vegetation plays an important role in the dry deposition of particles with significant spatial variability, but the magnitude remains unclear at the global scale....     

Geomorphological characteristics of slope failures in northeast Viti Levu island,Fiji, triggered by Tropical Cyclone Winston in February 2016

The highways circumnavigating Viti Levu play a pivotal role in Fiji's socioeconomic development, and are a crucial link to transport aid during disasters. Slope failures triggered by heavy rainfall and tropical cyclones have led to considerable damage and fatalities along Viti Levu's main roads in the past. Knowledge of slope instability mechanisms is key for the successful identification and management of slope failure hazards, however, there is a paucity of such information for Fiji's main roads. Severe Tropical Cyclone (STC) Winston was the strongest cyclone on record to make landfall in Fiji and affected the Fiji Islands from the early hours of 20 February until 3 am, 21 February, 2016. We present a field reconnaissance examining the characteristics and mechanisms of slope failures induced by STC Winston along a 35 km stretch of the northern part of the Viti Levu's ring road, “Kings Road”. Approximately 61 distinct shallow, small‐scale slope failures were identified most of which were of a complex type and included earth and debris slides (planar and rotational) with a minor flow component. The trigger for the slope failures was the ~258 mm of rainfall in 24 hours after 30‐days of antecedent rainfall totalling 482 mm. This caused rapid increases in porewater pressures, especially at the contact of residual soils and the underlying weathered basement rock. Evidence of recurring slips along Kings Road indicates that contemporary slope instability is likely caused by elevated porewater pressure during high intensity rainfall events in clay‐dominated soils.     

Cyanobacterial influence on diatom community lifeform dynamics in shallow subtropical lakes of Florida USA

Fragilarioid diatom taxa are often deemed ubiquitous in shallow lake systems. Their presence has been described as contributing to statistical noise in paleolimnological studies of cold-temperate lakes. In shallow, warm-temperate lakes of Florida, long-term transitions from assemblages dominated by Aulacoseira spp. to fragilarioid taxa, particularly Pseudostaurosira brevistriata, Staurosira construens var. venter, and Staurosirella pinnata, often occur. Distinctly higher limnetic nutrient optima are demonstrated by these fragilarioid taxa than by planktonic Aulacoseira spp. Community successions occur during eutrophication, and progressive replacement of Aulacoseira spp. and other planktonic taxa by fragilarioid taxa is concurrent with and apparently related to the onset of cyanobacterial dominance. We examine successions from Aulacoseira-dominated to fragilarioid-dominated assemblages in sediment cores from subtropical Florida lakes that have undergone eutrophication. Diatom profiles are compared with sedimented pigments, nitrogen stable isotopes of organic matter, and with silica accumulation rates. These study lakes have little if any macrophyte presence. Their light-extinction depths are extremely shallow, yet diatom communities are dominated by bottom-dwelling rather than planktonic taxa. Frequent wind-generated mixing, sometimes to lake bottoms, is sufficient to sustain the light needs of benthic and tychoplanktonic taxa. We conclude that assemblage changes generally are not caused by reduced water depths, silica limitation, nor increased incipient stratification, but that cyanobacteria are responsible for reducing planktonic Aulacoseira in favor of fragilarioid taxa. Cyanobacteria blooms persist over a wide seasonal range because of warm climate and high limnetic nutrient concentrations in Florida lakes. Cyanobacteria progressively displace and outcompete Aulacoseira and other planktonic taxa as eutrophication proceeds. Reduced light availability, changes in mineral/nutrient availability, and other aspects of competitive exclusion, such as cyanobacterial allelotoxins, might contribute to observed changes. Climate warming is not likely to account for Aulacoseira reduction as in colder regions because it is less pronounced in this subtropical district. Lakes with low nutrient levels and less cyanobacteria still sustain large Aulacoseira populations, and decreases in limnetic nutrients sometimes lead to the return of planktonic Aulacoseira. Rather than simply representing statistical noise for paleolimnological reconstructions, shifts to certain fragilarioid taxa indicate when subtropical Florida lakes progressed to hypereutrophic conditions that were marked by cyanobacterial proliferation.     

Event sedimentation in low‐latitude deep‐water carbonate basins,Anegada passage,northeast Caribbean

The Virgin Islands and Whiting basins in the Northeast Caribbean are deep, structurally controlled depocentres partially bound by shallow‐water carbonate platforms. Closed basins such as these are thought to document earthquake and hurricane events through the accumulation of event layers such as debris flow and turbidity current deposits and the internal deformation of deposited material. Event layers in the Virgin Islands and Whiting basins are predominantly thin and discontinuous, containing varying amounts of reef‐ and slope‐derived material. Three turbidites/sandy intervals in the upper 2 m of sediment in the eastern Virgin Islands Basin were deposited between ca. 2000 and 13 600 years ago, but do not extend across the basin. In the central and western Virgin Islands Basin, a structureless clay‐rich interval is interpreted to be a unifite. Within the Whiting Basin, several discontinuous turbidites and other sand‐rich intervals are primarily deposited in base of slope fans. The youngest of these turbidites is ca. 2600 years old. Sediment accumulation in these basins is low (<0.1 mm year^?1) for basin adjacent to carbonate platform, possibly due to limited sediment input during highstand sea‐level conditions, sediment trapping and/or cohesive basin walls. We find no evidence of recent sediment transport (turbidites or debris flows) or sediment deformation that can be attributed to the ca. M7.2 1867 Virgin Islands earthquake whose epicentre was located on the north wall of the Virgin Islands Basin or to recent hurricanes that have impacted the region. The lack of significant appreciable pebble or greater size carbonate material in any of the available cores suggests that submarine landslide and basin‐wide blocky debris flows have not been a significant mechanism of basin margin modification in the last several thousand years. Thus, basins such as those described here may be poor recorders of past natural hazards, but may provide a long‐term record of past oceanographic conditions in ocean passages.     

The benefits of quantifying climate model uncertainty in climate change impacts assessment: an example with heat-related mortality change estimates

The majority of climate change impacts assessments account for climate change uncertainty by adopting the scenario-based approach. This typically involves assessing the impacts for a small number of emissions scenarios but neglecting the role of climate model physics uncertainty. Perturbed physics ensemble (PPE) climate simulations offer a unique opportunity to explore this uncertainty. Furthermore, PPEs mean it is now possible to make risk-based impacts estimates because they allow for a range of estimates to be presented to decision-makers, which spans the range of climate model physics uncertainty inherent from a given climate model and emissions scenario, due to uncertainty associated with the understanding of physical processes in the climate model. This is generally not possible with the scenario-based approach. Here, we present the first application of a PPE to estimate the impact of climate change on heat-related mortality. By using the estimated impacts of climate change on heat-related mortality in six cities, we demonstrate the benefits of quantifying climate model physics uncertainty in climate change impacts assessment over the more common scenario-based approach. We also show that the impacts are more sensitive to climate model physics uncertainty than they are to emissions scenario uncertainty, and least sensitive to whether the climate change projections are from a global climate model or a regional climate model. The results demonstrate the importance of presenting model uncertainties in climate change impacts assessments if the impacts are to be placed within a climate risk management framework.     

Wave constraints for Titan’s Jingpo Lacus and Kraken Mare from VIMS specular reflection lightcurves

Stephan et al. (Stephan, K. et al. [2010]. Geophys. Res. Lett. 37, 7104-+.) first saw the glint of sunlight specularly reflected off of Titan’s lakes. We develop a quantitative model for analyzing the photometric lightcurve generated during a flyby in which the specularly reflected light flux depends on the fraction of the solar specular footprint that is covered by liquid. We allow for surface waves that spread out the geographic specular intensity distribution. Applying the model to the VIMS T58 observations shows that the waves on Jingpo Lacus must have slopes of no greater than 0.15°, two orders of magnitude flatter than waves on Earth’s oceans. Combining the model with theoretical estimates of the intensity of the specular reflection allows a tighter constraint on the waves: ?0.05°. Residual specular signal while the specular point lies on land implies that either the land is wetted, the wave slope distribution is non-Gaussian, or that 5% of the land off the southwest edge of Jingpo Lacus is covered in puddles. Another specular sequence off of Kraken Mare acquired during Cassini’s T59 flyby shows rapid flux changes that the static model cannot reproduce. Points just 1 min apart vary in flux by more than a factor of two. The present dataset does not uniquely determine the mechanism causing these rapid changes. We suggest that changing wind conditions, kilometer-wavelength waves, or moving clouds could account for the variability. Future specular observations should be designed with a fast cadence, at least 6 points per minute, in order to differentiate between these hypotheses. Such new data will further constrain the nature of Titan’s lakes and their interactions with Titan’s atmosphere.