Lithologic control of bedrock meander dimensions in the Appalachian Valley and Ridge province     

Duane D. Braun 《地球表面变化过程与地形》1983,8(3):223-237

Marked differences in bedrock meander dimensions in the Appalachian Valley and Ridge province, at times in adjacent reaches of a single stream, are related to differences in relative erodability of the bedrock. Meanders cut in thick-bedded to massive lithologies, typically carbonates, are distinctly smaller overall than meanders cut into shaly lithologies. Other factors that could affect bedrock meander dimensions were considered and none appeared to offer any help in explaining the dimensional differences observed above. In plateau regions underlain by essentially horizontal strata, the meander form characteristic of one lithology may become superimposed upon another as incision progresses, producing anomalous relationships between bedrock meander dimensions and lithology. Empirical relations developed from meander geometry measurements and estimated bedrock erodability for 78 bedrock meander reaches, containing a total of 1089 individual meander loops, show that meanders cut in shaly lithologies (ML = 105 Q^0.50_f, where ML = meander length and Q_f = most probable annual flood) are about twice the length of meanders cut in non-shaly lithologies (ML = 39.3^0.56_f). The valley floor width of the meanders cut in shaly bedrock (VF = 28 Q^0.43_f) is two to three times wider than the valley floor width of the meanders cut in the more resistant non-shaly bedrock (VF = 8 Q^0.43_f). The mean and median meander length values for individual reaches typically differ by less than 10 per cent.  相似文献   

Evaluation of the CORDEX-Africa multi-RCM hindcast: systematic model errors   总被引：4，自引：3，他引：1  

J. Kim  Duane E. Waliser  Chris A. Mattmann  Cameron E. Goodale  Andrew F. Hart  Paul A. Zimdars  Daniel J. Crichton  Colin Jones  Grigory Nikulin  Bruce Hewitson  Chris Jack  Christopher Lennard  Alice Favre 《Climate Dynamics》2014,42(5-6):1189-1202

Monthly-mean precipitation, mean (T_AVG), maximum (T_MAX) and minimum (T_MIN) surface air temperatures, and cloudiness from the CORDEX-Africa regional climate model (RCM) hindcast experiment are evaluated for model skill and systematic biases. All RCMs simulate basic climatological features of these variables reasonably, but systematic biases also occur across these models. All RCMs show higher fidelity in simulating precipitation for the west part of Africa than for the east part, and for the tropics than for northern Sahara. Interannual variation in the wet season rainfall is better simulated for the western Sahel than for the Ethiopian Highlands. RCM skill is higher for T_AVG and T_MAX than for T_MIN, and regionally, for the subtropics than for the tropics. RCM skill in simulating cloudiness is generally lower than for precipitation or temperatures. For all variables, multi-model ensemble (ENS) generally outperforms individual models included in ENS. An overarching conclusion in this study is that some model biases vary systematically for regions, variables, and metrics, posing difficulties in defining a single representative index to measure model fidelity, especially for constructing ENS. This is an important concern in climate change impact assessment studies because most assessment models are run for specific regions/sectors with forcing data derived from model outputs. Thus, model evaluation and ENS construction must be performed separately for regions, variables, and metrics as required by specific analysis and/or assessments. Evaluations using multiple reference datasets reveal that cross-examination, quality control, and uncertainty estimates of reference data are crucial in model evaluations.  相似文献   

Predictability and prediction skill of the boreal summer intraseasonal oscillation in the Intraseasonal Variability Hindcast Experiment   总被引：2，自引：0，他引：2  

Sun-Seon Lee  Bin Wang  Duane E. Waliser  Joseph Mani Neena  June-Yi Lee 《Climate Dynamics》2015,45(7-8):2123-2135

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Structure and components for the emergency response and warning system on Turtle Mountain,Alberta, Canada   总被引：1，自引：0，他引：1  

Corey R. Froese  Francisco Moreno 《Natural Hazards》2014,70(3):1689-1712

Since 2003, a series of over eighty sensors has been installed at Turtle Mountain, site of the 1903 Frank Slide. The purpose of these instruments is to both characterize and provide warning for a second large rock avalanche from the eastern face of the mountain, where various unstable masses have been identified. Although studies continue on the mountain to better understand the deformation patterns and interpretations of the slope kinematics, significant effort has been expended to develop a structure for the warning and emergency response that clearly outlines not only responsibilities and communications protocols during an emergency, but also day-to-day operational responses and procedures to ensure that the system remains operational. From a day-to-day operational perspective, a systematic and repeatable set of procedures is required in order to ensure that not only are data trends reviewed and reported on, but scheduled checks of system functionality are undertaken. An internal Roles and Responsibilities Manual has been developed to clearly outline responsibilities for geoengineering, information technology (IT), and management staff to ensure that system checks are completed and that support is in place on a 24/7 basis should components of the system cease to operate properly or should unacceptable deformations require review. In addition to that, a clear and concise troubleshooting manual has been developed. This document provides simple diagnoses of problems within the system and a clear roadmap of how to fix each component. From a warning and emergency response perspective, a series of color-coded alert conditions has been developed should unacceptable deformations be observed. At each alert level, clear responsibilities for actions and communications have been identified for geoengineering staff, provincial emergency management authorities, municipal officials, and first responders. This has been documented in the emergency response protocol. All documents described here are “living” documents that are updated on a regular basis as changes to the system are made. An annual mock warning exercise has been developed and run in order to test responses to a hypothetical emergency and generate updates to the system documentation.  相似文献   

The Exxon and BP oil spills: a comparison of psychosocial impacts     

Duane A. Gill  Liesel A. Ritchie  J. Steven Picou  Jennifer Langhinrichsen-Rohling  Michael A. Long  Jessica W. Shenesey 《Natural Hazards》2014,74(3):1911-1932

We address the research question: ‘Did the 2010 BP Deepwater Horizon oil spill have similar psychosocial impacts as the 1989 Exxon Valdez oil spill?’ We answer this question by comparing survey results from a random sample of Cordova, Alaska, residents collected 18 months after the Exxon spill with a random sample of residents in the Alabama coastal counties of Baldwin and south Mobile 1 year after the BP disaster. Analysis revealed similarly high levels of psychological stress for survivors of both disasters. For residents of coastal Alabama, the strongest predictors of psychosocial stress were exposure to oil, ties to renewable resources, concerns about their economic future, worries about air quality, and safety issues regarding seafood harvests in oiled areas. Differences between south Mobile and Baldwin counties were related to the former community’s economic ties to renewable resources and Baldwin County’s dependence on tourism for economic sustainability.  相似文献