Typical features of atmospheric turbulence profiles associated with Chinooks

Abstract

Winter operation of an acoustic sounder at Calgary, Alberta, has led to some unique observations during Chinook periods. Acoustic backscatter records obtained in these periods reveal an identifiable pattern of events in the atmospheric boundary layer. Descending turbulent structures are observed in pre‐Chinook conditions; the arrival of these structures near ground is associated with the onset of ground‐level warming. When ground‐level temperatures have risen to near 0°C, a deep (200–500 m thick) characteristic region of turbulence is generated in the boundary layer. The correlation of these features with surface wind and temperature data is discussed.     

Inducing fractures and increasing cleat apertures in a bituminous coal under isotropic stress via application of microwave energy

For the degassing of coal seams, either prior to mining or in un-minable seams to obtain coalbed methane, it is the combination of cleat frequency, aperture, connectivity, stress, and mineral occlusions that control permeability. Unfortunately, many potential coalbeds have limited permeability and are thus marginal for economic methane extraction. Enhanced coalbed methane production, with concurrent CO₂ sequestration is also challenging due to limited CO₂ injectivity. Microwave energy can, in the absence of confining stress, induce fractures in coal. Here, creation of new fractures and increasing existing cleat apertures via short burst, high-energy microwave energy was evaluated for an isotropically stressed and an unstressed bituminous coal core. A microwave-transparent argon gas pressurized (1000 psi) polycarbonate vessel was constructed to apply isotropic stress simulating ~ 1800 foot depth. Cleat frequency and distribution was determined for the two cores via micro-focused X-ray computed tomography. Evaluation occurred before and after microwave exposure with and without the application of isotropic stress during exposure. Optical microscopy was performed for tomography cleat aperture calibration and also to examine lithotypes influences on fracture: initiation, propagation, frequency, and orientation. It was confirmed that new fractures are induced via high-energy microwave exposure in an unconfined bituminous core and that the aperture increased in existing cleats. Cleat/fracture volume, following microwave exposure increased from 1.8% to 16.1% of the unconfined core volume. For the first time, similar observations of fracture generation and aperture enhancement in coal were also determined for microwave exposure under isotropic stress conditions. An existing cleat aperture, determined from calibrated X-ray computed tomography increased from 0.17 mm to 0.32 mm. The cleat/fracture volume increased from 0.5% to 5.5%. Optical microscopy indicated that fracture initiated likely occurred in at least some cases at fusain microlithotypes. Presumably this was due to the open pore volumes and potential for bulk water presence or steam pressure buildup in these locations. For the major induced fractures, they were mostly horizontal (parallel to the bedding plane) and often contained within lithotype bands. Thus it appears likely that microwaves have the potential to enhance the communication between horizontal wellbore and existing cleat network, in coal seams at depth, for improved gas recovery or CO₂ injection.     

Latitudinal Variations of Diurnal Meteor Rates

The presence of a diurnal variation in meteor activity is well established. The sporadic meteor count rates are higher on the local dawn side and lower on the local dusk side. This phenomenon is caused by the Earth’s orbital motion and rotation. Meteor radar measurements have been compared from Esrange, Kiruna, Sweden, at 68° N, from Juliusruh, Germany, at 55° N, and from Ascension Island, at 8° S, to investigate how the diurnal variation depends on season at different latitudes. Data have been used from vernal and autumnal equinoxes and summer and winter solstices to locate the largest seasonal differences.     

Intoxifying gentrification: brew pubs and the geography of post-industrial heritage

This paper traces one craft brewery (Mill Street Brewery) across two industrial heritage properties—in Toronto’s Distillery District and Ottawa’s LeBreton Flats—to investigate the extent to which alcohol functions as a catalyst of urban change. Using an analysis of both planning and policy documents, as well as media coverage for the two properties, we explore the role that alcohol plays in recalibrating industrial landscapes into spaces of consumption, and the potential for craft breweries to alter the meanings of industrial heritage. We argue that craft beer works as a vehicle in the manufacture of new spaces of cultural consumption. Specifically, craft beer production and consumption are used to aestheticize the industrial past and pacify resistance to central-city gentrification.     

Location‐based social media behavior and perception: Views of university students

Location‐based social media (LBSM), a specific type of volunteered geographic information (VGI), is increasingly being used as a spatial data source for researchers in geography and related disciplines. Many questions, though, have been raised about VGI data in terms of its quality and its contributors. While a number of studies have explored users’ demographics and motivations for contribution to explicitly geographic forms of VGI, such as OpenStreetMap and Wikimapia, few have focused on these aspects with implicitly geographic forms of VGI, such as LBSM (for example, Twitter and Instagram). This study, through use of an online survey, specifically assesses the LBSM behavior and perceptions of 253 university students, noting differences found in gender, race, and academic standing. We find that the greatest differences are those between males and females, rather than through race or academic standing, and LBSM appears less biased than other forms of VGI.     

Diffusion of a multi-component plasma

Diffusion in a weakly ionized plasma composed of negative ions as well as positive ions is examined using appropriate linearized fluid equations. For initial, electrically neutral, density perturbations of the form exp(ikx) the diffusion process is characterized by electrical non-neutrality and by three stages or time scales. For equal positive and negative ion diffusion coefficients these stages are in general (1) equilibration of the electron gas so that pressure gradient and electric forces are balanced (2) ambipolar-like diffusion of all three species, and concluding with (3) free ion diffusion. The details of the process are governed by the product kλ_e (wave number times electron Debye length) and the ambient ratio of negative ion to electron number density. Numerical and analytic results for separate positive and negative diffusion coefficients show added complexity which is briefly described. These results or the more complete numerical solutions find application to the lower D region of the ionosphere.     

Effect of refraction of sound on bistatic doppler sodar measurements of wind profiles

Comparisons of wind profiles measured with bistatic Doppler sodars below 100 m with in-situ measurements have shown that these sodars underestimate the winds. The possibility of refracted sound contaminating the scattered signals has been investigated both experimentally and theoretically. It was found that it is unlikely that refraction of the initial sound burst is the cause of the underestimation of winds at low levels.