A GIS-based method for defining snow zones: application to the western United States     

Cara Moore  Brandon Stone  Eric Richer 《国际地球制图》2015,30(1):62-81

This study maps the geographic extent of intermittent and seasonal snow cover in the western United States using thresholds of 2000–2010 average snow persistence derived from moderate resolution imaging spectroradiometer snow cover area data from 1 January to 3 July. Results show seasonal snow covers 13% of the region, and intermittent snow covers 25%. The lower elevation boundaries of intermittent and seasonal snow zones increase from north-west to south-east. Intermittent snow is primarily found where average winter land surface temperatures are above freezing, whereas seasonal snow is primarily where winter temperatures are below freezing. However, temperatures at the boundary between intermittent and seasonal snow exhibit high regional variability, with average winter seasonal snow zone temperatures above freezing in west coast mountain ranges. Snow cover extent at peak accumulation is most variable at the upper elevations of the intermittent snow zone, highlighting the sensitivity of this snow zone boundary to climate conditions.  相似文献   

Using geodetic GPS receivers to measure vegetation water content   总被引：1，自引：0，他引：1  

Wei Wan  Kristine M. Larson  Eric E. Small  Clara C. Chew  John J. Braun 《GPS Solutions》2015,19(2):237-248

  相似文献   

Formation of the enigmatic Matoush uranium deposit in the Paleoprotozoic Otish Basin,Quebec, Canada     

Paul Alexandre  Kurt Kyser  Daniel Layton-Matthews  Steve R. Beyer  Eric E. Hiatt  Jonathan Lafontaine 《Mineralium Deposita》2015,50(7):825-845

  相似文献   

Benchmarks for multicomponent reactive transport across a cement/clay interface     

Nicolas C. M. Marty  Olivier Bildstein  Philippe Blanc  Francis Claret  Benoit Cochepin  Eric C. Gaucher  Diederik Jacques  Jean-Eric Lartigue  Sanheng Liu  K. Ulrich Mayer  Johannes C. L. Meeussen  Isabelle Munier  Ingmar Pointeau  Danyang Su  Carl I. Steefel 《Computational Geosciences》2015,19(3):635-653

  相似文献   

High-order finite difference modeling of tsunami generation in a compressible ocean from offshore earthquakes   总被引：1，自引：0，他引：1  

Gabriel C. Lotto  Eric M. Dunham 《Computational Geosciences》2015,19(2):327-340

  相似文献   

Climate variability and trends in downscaled high-resolution simulations and projections over Metropolitan France   总被引：2，自引：1，他引：1  

Robert Vautard  Thomas Noël  Laurent Li  Mathieu Vrac  Eric Martin  Philippe Dandin  Julien Cattiaux  Sylvie Joussaume 《Climate Dynamics》2013,41(5-6):1419-1437

In order to fulfill the society demand for climate information at the spatial scale allowing impact studies, long-term high-resolution climate simulations are produced, over an area covering metropolitan France. One of the major goals of this article is to investigate whether such simulations appropriately simulate the spatial and temporal variability of the current climate, using two simulation chains. These start from the global IPSL-CM4 climate model, using two regional models (LMDz and MM5) at moderate resolution (15–20 km), followed with a statistical downscaling method in order to reach a target resolution of 8 km. The statistical downscaling technique includes a non-parametric method that corrects the distribution by using high-resolution analyses over France. First the uncorrected simulations are evaluated against a set of high-resolution analyses, with a focus on temperature and precipitation. Uncorrected downscaled temperatures suffer from a cold bias that is present in the global model as well. Precipitations biases have a season- and model-dependent behavior. Dynamical models overestimate rainfall but with different patterns and amplitude, but both have underestimations in the South-Eastern area (Cevennes mountains) in winter. A variance decomposition shows that uncorrected simulations fairly well capture observed variances from inter-annual to high-frequency intra-seasonal time scales. After correction, distributions match with analyses by construction, but it is shown that spatial coherence, persistence properties of warm, cold and dry episodes also match to a certain extent. Another aim of the article is to describe the changes for future climate obtained using these simulations under Scenario A1B. Results are presented on the changes between current and mid-term future (2021–2050) averages and variability over France. Interestingly, even though the same global climate model is used at the boundaries, regional climate change responses from the two models significantly differ.  相似文献   

Large-Scale Structures over a Single Street Canyon Immersed in an Urban-Type Boundary Layer   总被引：2，自引：2，他引：0  

Laurent Perret  Eric Savory 《Boundary-Layer Meteorology》2013,148(1):111-131

An analysis of the dynamics of the flow over a street canyon immersed in an atmospheric boundary layer is presented, using particle image velocimetry measurements in a wind tunnel. Care was taken to generate a 1:200 model scale urban type boundary layer that is correctly scaled to the size of the canyon buildings. Using proper orthogonal decomposition (POD) of the velocity field and conditional averaging techniques, it is first shown that the flow above the opening of the canyon consists of a shear layer separating from the upstream obstacle, animated by a coherent flapping motion and generating large-scale vortical structures. These structures are alternately injected into the canyon or shed off the obstacle into the outer flow. It is shown that unsteady fluid exchanges between the canyon and the outer flow are mainly driven by the shear layer. Finally, using POD, the non-linear interaction between the large-scale structures of the oncoming atmospheric boundary layer and the flow over the canyon is demonstrated.  相似文献   

Investigation of the Flow Structure in Step-Up Street Canyons—Mean Flow and Turbulence Statistics     

Bhagirath Addepalli  Eric R. Pardyjak 《Boundary-Layer Meteorology》2013,148(1):133-155

A step-up street canyon is a characteristic urban element composed of two buildings in which the height of the upwind building ( $H_\mathrm{u}$ ) is less than the height of the downwind building ( $H_\mathrm{d}$ ). Here, the effect of canyon geometry on the flow structure in isolated step-up street canyons is investigated through isothermal wind-tunnel measurements. The measurements were acquired along the vertical symmetry plane of model buildings using two-dimensional particle image velocimetry (PIV) for normal approach flow. The building-height ratios considered were: $H_\mathrm{d}/ H_\mathrm{u} \approx 3$ , and $H_\mathrm{d}/ H_\mathrm{u} \approx 1.67$ . For each building-height ratio, the along-wind lengths (L) of the upwind and downwind buildings, and the street-canyon width (S) were kept constant, with $L \approx S$ . The cross-wind widths (W) of the upwind and downwind buildings were varied uniformly from $W/S \approx 1$ through $W/S \approx 4$ , in increments of $W/S \approx 1$ . The objective of the work was to characterize the changes in the flow structure in step-up canyons as a function of W/S, for fixed L, S, and $H_\mathrm{d}/H_\mathrm{u}$ values. The results indicate that the in-canyon flow structure does not vary significantly for $H_\mathrm{d}/H_\mathrm{u} \approx 3$ for the W/S values considered. Qualitatively, for $H_\mathrm{d}/H_\mathrm{u} \approx 3$ , the upwind building behaves as an obstacle in the upwind cavity of the downwind building. In contrast, the flow patterns observed for the $H_\mathrm{d}/H_\mathrm{u} \approx 1.67$ configurations are unique and counter-intuitive, and depend strongly on building width (W/S). For $W/S \approx 1$ and $W/S \approx 2$ , the effect of lateral flow into the canyon is so prominent that even the mean flow patterns are highly ambiguous. For $W/S \approx 3$ and 4, the flow along the vertical symmetry plane is more shielded from the lateral flow, and hence a stable counter-rotating vortex pair is observed in the canyon. In addition to these qualitative features, a quantitative analysis of the mean flow field and turbulence stress field is presented.  相似文献   

Similarity Scaling Over a Steep Alpine Slope   总被引：5，自引：5，他引：0  

Daniel F. Nadeau  Eric R. Pardyjak  Chad W. Higgins  Marc B. Parlange 《Boundary-Layer Meteorology》2013,147(3):401-419

In this study, we investigate the validity of similarity scaling over a steep mountain slope (30–41 $^\circ $ ). The results are based on eddy-covariance data collected during the Slope Experiment near La Fouly (SELF-2010); a field campaign conducted in a narrow valley of the Swiss Alps during summer 2010. The turbulent fluxes of heat and momentum are found to vary significantly with height in the first few metres above the inclined surface. These variations exceed by an order of magnitude the well-accepted maximum 10 % required for the applicability of Monin–Obukhov similarity theory in the surface layer. This could be due to a surface layer that is too thin to be detected or to the presence of advective fluxes. It is shown that local scaling can be a useful tool in these cases when surface-layer theory breaks down. Under convective conditions and after removing the effects of self-correlation, the normalized standard deviations of slope-normal wind velocity, temperature and humidity scale relatively well with $z/\varLambda $ , where $z$ is the measurement height and $\varLambda (z)$ the local Obukhov length. However, the horizontal velocity fluctuations are not correlated with $z/\varLambda $ under all stability regimes. The non-dimensional gradients of wind velocity and temperature are also investigated. For those, the local scaling appears inappropriate, particularly at night when shallow drainage flows prevail and lead to negative wind-speed gradients close to the surface.  相似文献   

Evolution of the Parisian urban climate under a global changing climate     

Aude Lemonsu  Raphaëlle Kounkou-Arnaud  Julien Desplat  Jean-Luc Salagnac  Valéry Masson 《Climatic change》2013,116(3-4):679-692

The evolution of the Parisian urban climate under a changing climate is analyzed from long-term offline numerical integrations including a specific urban parameterization. This system is forced by meteorological conditions based on present-climate reanalyses (1970–2007), and climate projections (2071–2099) provided by global climate model simulations following two emission scenarios (A1B and A2). This study aims at quantifying the impact of climate change on air temperature within the city and in the surroundings. A systematic increase of 2-meter air temperature is found. In average according to the two scenarios, it reaches +?2.0/2.4°C in winter and +?3.5/5.0°C in summer for the minimum and maximum daily temperatures, respectively. During summer, the warming trend is more pronounced in the surrounding countryside than in Paris and suburbs due to the soil dryness. As a result, a substantial decrease of the strong urban heat islands is noted at nighttime, and numerous events with negative urban heat islands appear at daytime. Finally, a 30% decrease of the heating degree days is quantified in winter between present and future climates. Inversely, the summertime cooling degree days significantly increase in future climate whereas they are negligible in present climate. However, in terms of accumulated degree days, the increase of the demand in cooling remains smaller than the decrease of the demand in heating.  相似文献