Mid-Mountain Clouds at Whistler During the Vancouver 2010 Winter Olympics and Paralympics     

Ruping Mo  Paul Joe  George A. Isaac  Ismail Gultepe  Roy Rasmussen  Jason Milbrandt  Ron McTaggart-Cowan  Jocelyn Mailhot  Melinda Brugman  Trevor Smith  Bill Scott 《Pure and Applied Geophysics》2014,171(1-2):157-183

A comprehensive study of mid-mountain clouds and their impacts on the Vancouver 2010 Winter Olympics and Paralympics is presented. Mid-mountain clouds were frequently present on the Whistler alpine venue, as identified in an extensive archive of webcam images over a 45-day period from February 5 to March 21, 2010. These clouds posed serious forecast challenges and had significant impacts on some Olympic and Paralympic alpine skiing competitions. Under fair weather conditions, a diurnal upslope (anabatic) flow can work in concert with a diurnal temperature inversion aloft to produce a localized phenomenon known as “Harvey’s Cloud” at Whistler. Two detailed case studies in this paper suggest that mid-mountain clouds can also develop in the area as a result of a moist valley flow interacting with a downslope flow descending from the mountaintop. A southerly inflow through the Sea-to-Sky corridor can be channeled by the local topography into a westerly upslope flow toward Whistler Mountain, resulting in orographic clouds on the alpine venue. Under favorable circumstances, these clouds are trapped to the mid-mountain zone by the leeward subsidence of an elevated southerly flow. The presence of the downslope subsidence was manifested by a distinguished dry layer observed on the top of the mid-mountain clouds in both cases. It is the subsidence-induced adiabatic warming that imposes a strong buoyant suppression to trap the mid-mountain cloud. On the other hand, the subsidence-induced dry layer has the potential to trigger evaporative instability to periodically breakup the mid-mountain cloud.  相似文献   

Performance evaluation of active wireline heave compensation systems in marine well logging environments     

Tanzhuo Liu  Gerardo Iturrino  David Goldberg  Eric Meissner  Kerry Swain  Clayton Furman  Peter Fitzgerald  Nathan Frisbee  Joe Chlimoun  John Van Hyfte  Ron Beyer 《Geo-Marine Letters》2013,33(1):83-93

The basic functionality and performance of a new Schlumberger active wireline heave compensation system on the JOIDES Resolution was evaluated during the sea trial and a 3-year period of the IODP Phase II operations. A suite of software programs was developed to enable real-time monitoring of the dynamics of logging tools, and assess the efficiency of wireline heave compensation during downhole operations. The evaluation of the system effectiveness was performed under normal logging conditions as well as during stationary tests. Logging data were analyzed for their overall quality and repeatability, and to assess the reliability of high-resolution data such as formation microscanner (FMS) electrical images. This revealed that the system reduces 65–80 % of displacement or 88–98 % variance of downhole tool motion in stationary mode under heave conditions of ±0.2–1.5 m and water depths of 300–4,500 m in open holes. Under similar water/heave conditions, the compensator system reduces tool displacement by 50–60 %, or 75–84 % variance in downhole tool motion during normal logging operations. Such compensation efficiency (CE) is comparable to previous compensation systems, but using advanced and upgradeable technologies, and provides 50–85 % heave motion and heave variance attenuation. Moreover, logging down/up at low speeds (300–600 m/h) reduces the system’s CE values by 15–20 %, and logging down at higher speeds (1,000–1,200 m/h) eliminates CE values by 55–65 %. Considering the high quality of the logging data collected, it is concluded that the new system can provide an improved level of compensation over previous systems. Also, if practically feasible, future integration of downhole cable dynamics as an input feedback into the current system could further improve its compensation efficiency during logging operations.  相似文献   

Sediment supply: The main driver of shelf-margin growth   总被引：1，自引：0，他引：1  

Cristian Carvajal  Ron Steel  Andrew Petter 《Earth》2009,96(4):221-248

Despite the obvious importance of sediment supply to shelf-margin architecture and to the potential of margins to contain and bypass deep-water sands, the role of supply in shelf-margin growth has received limited attention. High cross-shelf sediment flux is critically important for the occurrence of deep-water sands, not least on Greenhouse or rapidly subsiding margins where the impact of eustatic sea-level fall may be insufficient to drive sediment delivery out across the shelf into deep-water areas. To draw greater attention to the supply parameter we review a number of shelf margins that have grown chiefly through supply by shelf-edge deltas and associated sediment-gravity flows. Based on structural style and water depth, we recognize two broad types of shelf-margin. Moderately deep-water margins produce clinoforms < 1000 m high and show rates of shelf-edge progradation < 60 km/My and aggradation < 270 m/My, and consequently, infill their basins relatively rapidly, and develop more progradational architectures with morphologically smooth and relatively undeformed slopes. Very deep-water margins produce clinoforms > 1000 m high and generally show rates of shelf-edge progradation < 40 km/My and aggradation < 2500 m/My, and therefore infill their basins more slowly and develop more aggradational architectures with much gravity-driven slope deformation, proneness to failure and ponded architectures (salt or shale driven). On both margin types, long-term (> 1 My) rates of shelf-edge progradation of several tens of km/My tend to be linked to the delivery of relatively large volumes of sand into the deep-water basin. Delivery of this sand beyond the shelf-edge happens despite Greenhouse conditions and is likely recurrent and periodic (delivery cycles in the order of 100′s ky). Such prominent margin growth is a strong indication that sediment influx was relatively high and we refer to these margins as “supply-dominated” shelf margins. The Gulf of Mexico margin is a well-known and data-rich example of a “supply-dominated” shelf-margin during certain times (e.g., Paleocene). In contrast, on both margin types, low rates of shelf-edge progradation are linked to diminished (or even non-existent) and less frequently recurrent deep-water sediment delivery suggestive of relatively low sediment influx. Occurrence of deep-water sand delivery under low sediment influx probably requires fall of relative sea level. The differences between rapidly and slowly prograding margins indicate that sediment supply (and not sea level) is likely to be the key limiting factor on the growth of shelf margins and that sediment supply, as interpreted through progradation rate, can therefore be used to make a first-order prediction of relative amounts of sand passed to deep-water areas.  相似文献   

Geology, failure conditions, and implications of seismogenic avalanches of the 1944 eruption at Vesuvius, Italy     

Richard W. Hazlett  David Buesch  James L. Anderson  Ron Elan  Robert Scandone 《Journal of Volcanology and Geothermal Research》1991,47(3-4)

Widespread avalanching occurred at Mt. Vesuvius during its 1944 eruption, the latest activity of this volcano. The 1944 avalanche deposits display many of the morphological and structural features shown by common slides of the slump-earth flow variety, including levees, transverse ridge-and-trough topography, and preserved stratigraphy. The longest avalanche travelled 1.3 km, with an estimated volume of slightly more than one million cubic meters. Avalanches came to rest on moderately-inclined slopes. Internal structure includes low- and high-angle shears and tensional fractures. Deposits are poorly consolidated. Two lithologic types are observed; avalanches composed of both blocks and ash, with blocky rubble forming a capping layer, and avalanches composed almost wholly of ash. Block-and-ash avalanches were triggered where slopes of loose tephra had been preloaded with lava flows. Ash avalanches formed where heavy accumulations of ash were deposited by prevailing winds. Seismic activity accompanying eruption served as a trigger for avalanching.  相似文献   

Structural analysis of soil microrelief in palaeosols of the Lower Jurassic “Laterite Derivative Facies” (Mishhor and Ardon formations) Makhtesh Ramon,Israel     

Ron Goldbery 《Sedimentary Geology》1982,31(2):119-140

A sequence of palaeosols developed on exposed overbank sediments of successive alluvial cycles of the Lower Jurassic “Laterite Derivative Facies” (LDF) at Makhtesh Ramon, contains well-developed, penecontemporaneous soil microrelief structures. The folded structures commonly show overthrusting, and vary in wave length and amplitude.They are characterized by slickensided surfaces, cuspate in cross section with the curviplanar deformed surfaces oriented concave up. The palaeosol stratigraphy is well established over the entire Makhtesh Ramon area and this afforded the opportunity of obtaining controlled structural measurements on the folded surfaces and their associated slickensided striae as a means of providing data for reconstruction of the fold geometry.Stereographic projection of the poles to the LDF fold surfaces, on two separate palaeosol horizons from several localities, together with the slickensided striae, were plotted on the lower hemisphere of a Schmidt equal-area net. The LDF folds were seen to be symmetrical and asymmetrical structures with a gently plunging fold axis of 4–10°. Maximum and minimum dip values of the cuspate curviplanar surface (SP₁) were well emphasized by the plots (20° and 30° for symmetrical structures) and data from the two horizons obtained from several localities showed remarkable uniformity.A second slickensided, curviplanar surface of deformation (SP₂) shows the same range of dip values as SP₁ and intersects the SP₁ surface normal to the SP₂ fold axis. The internal arrangement of symmetry elements within the LDF folds remains approximately constant regardless of the large variation between the gross morphological parameters such as amplitude and wavelength, and this appears to be a reflection of the response of a soil with inherent anisotropies, to stress.The geometry of the LDF structure resembles that of linear or wavy gilgai. The SP₁ surface therefore is most likely the result of upthrusting on the edges of drainage rills affected by differential wetting. The SP₂ surface bears a constant geometric relationship with SP₁ and is therefore considered to have formed penecontemporaneously during the upthrusting of the SP₁ blocks. A rectangular surface fracture pattern parallel to and normal to topographic slope, is considered to be an alternative means of initiating the upward growth of the soil microrelief features.  相似文献   

Downscaling Landsat-8 land surface temperature maps in diverse urban landscapes using multivariate adaptive regression splines and very high resolution auxiliary data     

Joanna Zawadzka  Ron Corstanje  Jim Harris  Ian Truckell 《International Journal of Digital Earth》2020,13(8):899-914

ABSTRACT

We propose a method for spatial downscaling of Landsat 8-derived LST maps from 100(30?m) resolution down to 2–4?m with the use of the Multiple Adaptive Regression Splines (MARS) models coupled with very high resolution auxiliary data derived from hyperspectral aerial imagery and large-scale topographic maps. We applied the method to four Landsat 8 scenes, two collected in summer and two in winter, for three British towns collectively representing a variety of urban form. We used several spectral indices as well as fractional coverage of water and paved surfaces as LST predictors, and applied a novel method for the correction of temporal mismatch between spectral indices derived from aerial and satellite imagery captured at different dates, allowing for the application of the downscaling method for multiple dates without the need for repeating the aerial survey. Our results suggest that the method performed well for the summer dates, achieving RMSE of 1.40–1.83?K prior to and 0.76–1.21?K after correction for residuals. We conclude that the MARS models, by addressing the non-linear relationship of LST at coarse and fine spatial resolutions, can be successfully applied to produce high resolution LST maps suitable for studies of urban thermal environment at local scales.  相似文献   

Some curious thermomagnetic curves and their interpretation     

Ron Day 《Earth and Planetary Science Letters》1975,27(1):95-100

A study of the thermomagnetic curves of synthetic titanomagnetite powders, heated in air, in non-saturation applied magnetic fields showed that the shape of the curves was related to the magnitude of the applied field, the coercivity of the samples, and the effects of oxidation. The most important result to emerge from this study was the occurrence of reproducible peaks at low temperatures (～100–200°C). The temperature at which the peaks occur was found to increase with increasing coercive force or decreasing applied field. It is suggested that the peaks are the result of the “unblocking” of the magnetization, and should not be confused with thermomagnetic characteristics used to classify ferrites. The “unblocking” temperature is dependent on both the coercive force and the applied magnetic field, as is predicted by most models of thermo-remanent magnetization.  相似文献   

Velocity analysis after migration   总被引：1，自引：0，他引：1  

Ron Silva  Yanghua Wang 《Geophysical Prospecting》2002,50(5):539-545

The double‐square‐root (DSR) equation used in pre‐stack migration is formulated in terms of velocity‐dependent and velocity‐independent terms. The velocity‐dependent term is shown to be the hyperbolic normal moveout (NMO) correction, whereas the velocity‐independent term is related to the recording geometry only. This separation of the velocity‐dependent term offers a means of applying vertical corrections to an initial migration velocity field. Using this concept, procedures are described both for velocity determination and for achieving improved structural imaging.
This decoupling is accurate both for constant‐velocity media and for media whose velocity varies as a function of depth. In media whose velocity varies as a function of both space and depth, a procedure is described for building velocity models through common‐image gather (CIG) stacking following prestack depth migration (PSDM) and time conversion (TC). This so‐called PSDM‐TC stack procedure provides a means of (a) incorporating both vertical and lateral velocity updates into an initial velocity model, (b) obtaining improved structural imaging by using a non‐optimal velocity model for the prestack depth migration, and (c) updating velocity by flattening CIGs and maximizing stack energy. The procedure can be applied to both P‐P wave and P‐SV wave migration.  相似文献   

Reflections on Nigel Thrift's optimism: political strategies to implement his vision     

Ron Johnston   《Geoforum》2002,33(4):421-425

This response to Nigel Thrift's recent paper (2002, Geoforum 33, 291–298) develops two of his points: the need for geography to remain buoyant within school curricula and a potential split of physical from human geography within the universities. I argue that political strategies are necessary for both if geography is to remain the large, intellectually vibrant discipline that Thrift identifies.  相似文献   

Ethnic Residential Segregation Across an Urban System: The Maori in New Zealand, 1991–2001     

Ron Johnston  Michael Poulsen  James Forrest 《The Professional geographer》2005,57(1):115-129

In New Zealand there are substantial variations across the urban system in the degree of residential segregation of those claiming Maori ethnicity. Analyses of those variations, using measures particularly relevant to comparative study, show that Maori segregation was greatest in both 1991 and 2001 in larger urban areas and, especially, in those with relatively large Maori populations. A major deviation from this general pattern was in Auckland; further analysis suggests that this was because of considerable sharing of residential space involving Maori and Pacific Islanders. If the total population claiming a Polynesian identity is studied, the relationships between segregation and both size and Polynesian population share are clarified.  相似文献