Ski areas, weather and climate: Time series models for New England case studies

Wintertime warming trends experienced in recent decades, and predicted to increase in the future, present serious challenges for ski areas and whole regions that depend on winter tourism. Most research on this topic examines past or future climate-change impacts at yearly to decadal resolution, to obtain a perspective on climate-change impacts. We focus instead on local-scale impacts of climate variability, using detailed daily data from two individual ski areas. Our analysis fits ARMAX (autoregressive moving average with exogenous variables) time series models that predict day-to-day variations in skier attendance from a combination of mountain and urban weather, snow cover and cyclical factors. They explain half to two-thirds of the variation in these highly erratic series, with no residual autocorrelation. Substantively, model results confirm the backyard hypothesis that urban snow conditions significantly affect skier activity; quantify these effects alongside those of mountain snow and weather; show that previous-day conditions provide a practical time window; find no monthly effects net of weather; and underline the importance of a handful of high-attendance days in making or breaking the season. Viewed in the larger context of climate change, our findings suggest caution regarding the efficacy of artificial snowmaking as an adaptive strategy, and of smoothed yearly summaries to characterize the timing-sensitive impacts of weather (and hence, high-variance climate change) on skier activity. These results elaborate conclusions from our previous annual-level analysis. More broadly, they illustrate the potential for using ARMAX models to conduct integrated, dynamic analysis across environmental and social domains

West Greenland\u27s Cod-to-Shrimp Transition: Local Dimensions of Climatic Change

Abstract West Greenland\u27s transition from a cod-fishing to a shrimp-fishing economy, ca. 1960-90, provides a case study in the human dimensions of climatic change. Physical, biological, and social systems interacted in complex ways to affect coastal communities. For this integrated case study, we examine linkages between atmospheric conditions (including the North Atlantic Oscillation), ocean circulation, ecosystem conditions, fishery activities, and the livelihoods and population changes of two West Greenland towns: Sisimiut, south of Disko Bay, and Paamiut, on the southwest coast. Sisimiut prospered as a fishing center through the cod-to-shrimp transition. Paamiut, more specialized in cod fishing, declined. Their stories suggest two general propositions about the human dimensions of climatic change. First, socially important environmental changes result not simply from climatic change, but from interactions between climate, ecosystem, and resource usage. Second, environmental changes affect people differentially and through interactions with social factors. Social networks and cohesion (social capital) are important, in addition to skills (human capital), investments (physical capital), and alternative resources (natural capital): all shape how the benefits and costs are distributed

Identifying the difficulties experienced by year 10 high school students when attempting to solve genetic pedigree problems

Teachers rate genetics as one of the most difficult biology topics for high school students to understand (Finley, Stewart & Yarroch, 1982). It has been observed that some students are able to solve genetics problems using routine algorithmic methods, without understanding the basic underlying concepts (Stewart, 1982). The aim of this study was to identify the procedural errors and conceptual misunderstandings that the students had when attempting to solve genetic pedigree problems. Genetic pedigrees are diagrammatic representations of the members and ancestral relationships in a family (Cummings, 1991). Two male and two female students were selected from each of four Year 10 classes. They were required to solve three genetic pedigree problems, identifying the most likely mode of inheritance for each problem. The interviews were tape-recorded and transcribed, and these were followed up with a debriefing session in which each subject’s knowledge of the conceptual basis of these problems was probed. The results showed that many students made similar errors in procedure and many lacked the conceptual knowledge to produce meaningful solutions. The most common procedural error was the failure to falsify all the possible hypotheses, which resulted in students failing to provide complete and conclusive solutions. Other procedural errors included the incorrect use of genotypes. the failure to identity and correctly interpret critical patterns, and the misinterpretation of non-critical patterns. The conceptual misunderstandings included the lack of knowledge regarding the meanings of dominant and recessive, and the mechanisms of X-linkage. The recommendations for improved teaching of this topic focus on making procedural steps more explicit, and making the link between the procedural steps and underlying conceptual knowledge clearer

Local re-acceleration and a modified thick target model of solar flare electrons

The collisional thick target model (CTTM) of solar hard X-ray (HXR) bursts has become an almost 'Standard Model' of flare impulsive phase energy transport and radiation. However, it faces various problems in the light of recent data, particularly the high electron beam density and anisotropy it involves.} {We consider how photon yield per electron can be increased, and hence fast electron beam intensity requirements reduced, by local re-acceleration of fast electrons throughout the HXR source itself, after injection.} {We show parametrically that, if net re-acceleration rates due to e.g. waves or local current sheet electric (${\cal E}$) fields are a significant fraction of collisional loss rates, electron lifetimes, and hence the net radiative HXR output per electron can be substantially increased over the CTTM values. In this local re-acceleration thick target model (LRTTM) fast electron number requirements and anisotropy are thus reduced. One specific possible scenario involving such re-acceleration is discussed, viz, a current sheet cascade (CSC) in a randomly stressed magnetic loop.} {Combined MHD and test particle simulations show that local ${\cal E}$ fields in CSCs can efficiently accelerate electrons in the corona and and re-accelerate them after injection into the chromosphere. In this HXR source scenario, rapid synchronisation and variability of impulsive footpoint emissions can still occur since primary electron acceleration is in the high Alfv\'{e}n speed corona with fast re-acceleration in chromospheric CSCs. It is also consistent with the energy-dependent time-of-flight delays in HXR features.Comment: 8 pages, 2 figure

Heating Methods and Detection Limits for Infrared Thermography Inspection of Fiber-Reinforced Polymer Composites

The use of fiber-reinforced polymer (FRP) composites to strengthen existing civil infrastructure is expanding rapidly. Many FRP systems used to strengthen reinforced concrete are applied using a wet lay-up method in which dry fibers are saturated on site and then applied to the surface. This research investigated using infrared thermography (IRT) as a nondestructive evaluation (NDE) tool for detecting air voids and epoxy-filled holes in FRP systems bonded to a concrete substrate. Four small-scale specimens with FRP thicknesses ranging from 1 to 4 mm (0.04 to 0.16 in.) containing fabricated defects were constructed and inspected in a laboratory setting. Three heating methods (flash, scan, and long pulse) were employed and a quantitative analysis of resulting IRT data was used to establish detection limits for each method. Scan heating was shown to be most effective for basic defect detection. Air-filled defects at the FRP/concrete interface as small as 2.9 cm2 (0.45 in.2) were detected in a 4 mm (0.16 in.) thick FRP system. Defects as small as 0.3 cm2 (0.05 in.2) were detected in a 1 mm (0.04 in.) thick FRP system