Book reviews     

Richard J. Reed  Hanna J. Cortner  Peter M. Morrisette  A. J. Pitman 《Climatic change》1990,16(3):357-366

  相似文献   

The role of geological heterogeneity and variability in water infiltration on non-aqueous phase liquid migration   总被引：2，自引：1，他引：1  

Zhibing Yang  Hanna Zandin  Auli Niemi  Fritjof Fagerlund 《Environmental Earth Sciences》2013,68(7):2085-2097

This study investigates the influence of two factors—geological heterogeneity and variability in water infiltration—on non-aqueous phase liquid (NAPL) migration in the unsaturated zone. NAPL migration under three-phase flow conditions resulting from a ground surface spill is modeled for multiple heterogeneous realizations of a porous medium with various water infiltration scenarios. Increased water infiltration before the spill has two counteracting effects: NAPL relative permeability (k _rn) increases with increasing water saturation (S _w) for a given NAPL saturation, while higher S _w in the soil near the NAPL source zone leads to less NAPL mass infiltration. It is found that the former effect is overwhelmed by the latter effect, the net effect being that with longer infiltration durations before the spill, both the infiltrated NAPL mass and the depth of the front migration decrease. Simulation results also show strong effect of the medium heterogeneity. Results suggest that total infiltrated mass, front depth and plume spread increase with an increasing standard deviation of log-permeability. Also variability in modeling results among realizations is largely impacted by the log-permeability standard deviation. Spatial correlation in permeability also strongly influences NAPL infiltration. An increase in the isotropic correlation length from 0.75 to 1.5 m leads to a decrease in total infiltrated mass, plume migration depth as well as vertical spread. Lateral spread in this case is not shown to be affected by the correlation length.  相似文献   

Book reviews     

T. Hanna  R. J. Fowell  I. W. Farmer 《Geotechnical and Geological Engineering》1986,4(3):253-255

  相似文献   

A least sensitive multichannel optimum filter for sensor arrays     

Hanna  M.T. Simaan  M. 《Oceanic Engineering, IEEE Journal of》1988,13(2):64-69

A family of multichannel filters that can provide complete suppression of coherent interference for almost all frequencies is characterized. The authors then determine the particular member in this family that yields an output that is least sensitive to estimation errors in the parameters which characterize the coherent interference. This filter, called the absolutely optimum array filter (AOAF), is described. This robustness property of the AOAF filter is considered particularly important in applications where imperfect estimates of the parameters are used in the filter design. An example illustrating the results is presented  相似文献   

Characteristics of Stable Flows over Southern Greenland     

Andrew Orr  Edward Hanna  Julian C.R. Hunt  John Cappelen  Konrad Steffen  AG Stephens 《Pure and Applied Geophysics》2005,162(10):1747-1778

The main characteristic features of stable atmospheric flows over a large mountain plateau are summarised and then compared with mesoscale and synoptic scale numerical simulation, meteorological analysis, satellite imagery, and surface observations for the cases of flows over Southern Greenland for four wind directions. The detailed features are identified using the concepts and scaling of stably stratified flow over large mountains with variations in surface roughness, elevation, and heating. For westerly and easterly winds detached jets form at the southern tip, where coastal jets converge, which propagate large distances across the ocean. Near coasts katabatic winds can combine with barrier jets and wake flows generated by synoptic winds. Note how the approach flow rises/falls over southern Greenland for easterly/westerly winds, leading in both cases to more cloud on the western side. Some conclusions are drawn about the large-scale influences of these flows; detached jets in the atmosphere; air-sea interaction; formation of low pressure systems. For accurate simulations of these flows, mesoscale models are necessary with resolutions of order of 20 km or less.  相似文献   

Glaciodynamically upthrusted bands of englacially transported debris in the Pleistocene of central Poland     

Hanna Ruszczy&#;ska-Szenajch 《Sedimentology》2001,48(3):585-597

Two kinds of buried structures are described from Dzirżenin, north-east of Warsaw, where they occur within a glaciofluvial landform: (1) narrow till ridges, showing vertically oriented structures, excavated from stratified gravel and sands; and (2) a narrow vertical zone of massive gravelly/sandy material, involving vertically oriented lens-like layers composed of massive sand with pebbles, or of diamicton. The gravelly/sandy zone is also closely surrounded by stratified glaciofluvial sediments. In spite of their vertical position and internal deformation, the till ridges and gravelly/sandy zone show non-tectonic contacts with the surrounding, stratified, undisturbed sediments. The glaciofluvial sediments that occur immediately next to the structures under discussion are characterized by the occurrence of comparatively coarse material and interbeddings of diamicton, which wedge out away from these structures. The gravelly/sandy zone separates different kinds of water-laid deposits. The buried structures are interpreted as former debris-laden bands, thrust upwards within the frontal part of the ice sheet and then transformed into still-frozen debris ridges projecting over the already dead ice. Further melting of the decaying ice resulted in abundant glaciofluvial sedimentation, and the debris ridges also supplied material for the deposition of the neighbouring stratified deposits. One of the ridges separated different glaciofluvial environments. The glaciofluvial sediments completely buried the ice-cemented ridges, which were finally transformed by a melting-out process into the till ridges and the gravelly/sandy zone. The former are interpreted as having been transformed from upturned debris-laden bands with a high concentration of debris or from the bands composed of frozen-up sediment slabs. The gravelly/sandy zone is interpreted as having (most probably) been deposited from upturned bands characterized by a lesser concentration of debris.  相似文献   

Late Quaternary Stratigraphy, Glacial Limits, and Paleoenvironments of the Marresale Area, Western Yamal Peninsula, Russia     

Steven L. Forman   lafur Inglfsson  Valery Gataullin  William Manley  Hanna Lokrantz 《Quaternary Research》2002,57(3):355

Stratigraphic records from coastal cliff sections near the Marresale Station on the Yamal Peninsula, Russia, yield new insight on ice-sheet dynamics and paleoenvironments for northern Eurasia. Field studies identify nine informal stratigraphic units from oldest to youngest (the Marresale formation, Labsuyakha sand, Kara diamicton, Varjakha peat and silt, Oleny sand, Baidarata sand, Betula horizon, Nenets peat, and Chum sand) that show a single glaciation and a varied terrestrial environment during the late Pleistocene. The Kara diamicton reflects regional glaciation and is associated with glaciotectonic deformation from the southwest of the underlying Labsuyakha sand and Marresale formation. Finite radiocarbon and luminescence ages of ca. 35,000 to 45,000 yr from Varjakha peat and silt that immediately overlies Kara diamicton place the glaciation >40,000 yr ago. Eolian and fluvial deposition ensued with concomitant cryogenesis between ca. 35,000 and 12,000 cal yr B.P. associated with the Oleny and the Baidarata sands. There is no geomorphic or stratigraphic evidence of coverage or proximity of the Yamal Peninsula to a Late Weichselian ice sheet. The Nenets peat accumulated over the Baidarata sand during much of the past 10,000 yr, with local additions of the eolian Chum sand starting ca. 1000 yr ago. A prominent Betula horizon at the base of the Nenets peat contains rooted birch trees ca. 10,000 to 9000 cal yr old and indicates a >200-km shift northward of the treeline from the present limits, corresponding to a 2° to 4°C summer warming across northern Eurasia.  相似文献   

Examining the Variability of Crossing Times for Canadian Trucks at the Three Major Canada–U.S. Border Crossings     

Hanna Maoh  Kevin Gingerich  Rahaf Husein  William Anderson 《The Professional geographer》2018,70(3):350-362

Land borders connecting Canada and the United States are vital transportation facilities for the two countries. Truck crossing times at these facilities can have a significant impact on the performance of the economy. To date, knowledge about border crossing times has been limited due to lack of detailed data on the Canadian border. This article explores and models the patterns of crossing times at the three major land crossings connecting Canada to the United States: Ambassador Bridge, Blue Water Bridge, and Peace Bridge. The analysis is based on 387,775 border crossing truck trips that were generated between Canada and the United States over a course of twelve months. Seemingly unrelated regression (SUR) models are estimated to evaluate the seasonal and hourly crossing times of Canada- and U.S.-bound trips on each border crossing, controlling for traffic intensity in the models. The SUR modeling approach is chosen to control for potential cross-model correlations. The results suggest that crossing times at the border vary by season and hour of the day. Crossing times also vary by direction of traffic and by type of day (i.e., weekday vs. weekend). Traffic intensity has a significant influence on crossing times at two of the crossings but not the Blue Water Bridge. Finally, crossing times are more variable during the summer season and tend to be higher during the late evening hours and past midnight.  相似文献   

Reply to comments by D. Netterville     

Steven R. Hanna 《Boundary-Layer Meteorology》1986,34(1-2):209-209

  相似文献   

Twenty-one years of German geomorphology     

Hanna Bremer 《地球表面变化过程与地形》1984,9(3):281-287

In recent decades, German geomorphology has been mainly concerned with climatic and climato-genetic geomorphology. The first is the study of processes, especially of process combinations in different climato-morphological zones. The second is concerned with the way exogenic forces control the evolution of relief in a certain region. This study of relief generations differs fundamentally from denudation chronology. Certain principles developed as knowledge of these fields has grown, such as the variability of rock resistance with climate and discontinuity of processes in both space and time, are considered. In recent years new trends, based mainly on climatic geomorphology, have been towards greater specialization in fields such as quantitative geomorphology, geomorphological mapping, and laboratory analysis of regolith and soil samples.  相似文献