A climatology of high wind events (HWEs) affecting Sable Island (44°N, 60°W) and Halifax (44.5°N, 63.5°W) was constructed for the period 1979--1995. We then focussed on HWEs at Sable Island in more detail because of their high frequency relative to Halifax. Events were stratified into four groups based on the direction of the peak speed: NE (1°--90°), SE (91°--180°), SW (181°--270°), and NW (271°--360°). Synoptic structures and statistically significant atmospheric anomalies were identified in composites for each group. More detailed structures were found in composites constructed with the aid of a cluster analysis. / NW HWEs were associated with rapidly deepening marine cyclones and lacked clear atmospheric predecessors. NE HWEs were linked to a slow moving offshore cyclone and prominent anticyclone near Labrador. An anomalously weak Icelandic Low was a dominant precursor signal and an important feature found in each of the groups. SE HWEs were related to the strong pressure gradient between a cyclone-anticyclone couplet. The anticyclone was evident four days before the HWE and played a crucial role in the development of the cyclone. SW HWEs were related to a variety of cyclone types, but were typically related to a low-frequency cold surge over eastern North America. / The storms most difficult to predict may be NW HWEs, since they lack clear atmospheric precursor signals. They are also among the most dangerous storms affecting Atlantic Canada, since they move and develop rapidly, and have some of the highest wind speeds.

Conceptual urban runoff (CUR) models are commonly used in the Planning and design of urban drainage systems. These models often require a large number of variables and parameters in order to accurately describe, the complex relationships between rainfall, runoff and watershed characteristics. This requirement has often become a barrier to the use of such models, because of the difficulties involved in the estimation of these parameters. Hence, there is a great need to develop a robust and reliable automatic calibration procedure to assist in the identification of the best set of optimal parameters for a CUR model. The present study is therefore concerned with the automatic calibration of a typical and well-known CUR model, the U.S. Environmental Protection Agency Storm Water Management Model, or SWMM. / In this study, two automatic calibration methods were considered based an two different optimization algorithms: the Downhill Simplex (DHS), a popular local optimization technique, and the Shuffled Complex Evolution (SCE), a global optimization procedure. The consistency of SCE in estimating the SWMM model parameters was assessed under two different scenarios: (1) using "error-free" synthetic data, and (2) using observed data available an the Upper Bukit Timah catchment in Singapore. (Abstract shortened by UMI.)

Side-scan sonar imagery, 40 in$ sp3$ sleeve gun and 3.5 kHz high-resolution profiles reveal a dichotomy of the upper Labrador Slope into (i) a low-relief sector off Hudson Strait that is dominated by mass-transport deposits resulting from the direct input of subglacially derived debris, and (ii) a high-relief sector to the south resulting mainly from deposition out of turbid surface plumes, and headward canyon erosion. This dichotomy continues in the Labrador Basin, where the leveed Northwest Atlantic Mid-Ocean Channel (NAMOC) is flanked by a sandy submarine braidplain in the east, which is the basinward extension of the differences on the upper slope. The floodplain west of NAMOC contains extensive debris-flow deposits generated on the Labrador Slope. / The meandering low-sinuosity, low-gradient NAMOC contains three segments: In the upper equilibrium channel, channel morphology is in equilibrium with spill-over from low-velocity, low-density upper portions of turbidity currents flowing in the channel; in the middle modified equilibrium channel, equilibrium morphology is altered by the confluence with tributary channels, and in the lower segment, channel morphology and position is controlled by basement topography (oceanic fracture zones and seamounts). The NAMOC levees interfinger with the braidplain deposits to the east and prograde southeastward in 7-8 packages. Most packages show a strong cross-channel decrease in thickness, and a strong asymmetry between the left and the right levee, as a Coriolis effect. The braidplain east of the NAMOC, which developed simultaneously with and prior to the NAMOC, shows a north to south gradient from laterally very extensive to highly channelized deposits. In the channelized part, channel positions change rapidly and deposits vary from sandy to gravelly. Extensive sheet-like turbidity currents on the braidplain may have been caused by catastrophic outbursts of subglacial lakes during times of ice-stream surges. / Quantitative morphological analysis shows that the NAMOC is characterized by particularly low sinuosities due to very low channel-gradients compared to other submarine channels. The channel displays several features not recognized before in the deep-sea, or not in the same detail; including submarine hanging valleys and chute pools, submarine point-bars within the channel, coarse-grained wash-over fans on the lee-side of the levees, and terraces within the channel. The talweg is variable in depth and meanders within the channel. An up to 80 m deep talweg is present in the distal NAMOC resulting from flow restrictions due to seamounts. Channel morphology as well as grain size of spill-over deposits suggest that the flow tops of turbidity currents in the NAMOC are slow ($<$0.7 m/s) and dilute ($<$12 kg/m$ sp3$). Gravel deposits in the channel require velocities of 6.5-8 m/s for suspension transport, suggesting a strong vertical velocity and density gradient.

<p> Suisun Marsh is a 470 km² wetland situated between the Sacramento-San Joaquin Delta and San Pablo Bay in the San Francisco Estuary. Today, about 80 percent of the marsh plain is privately owned by duck hunting clubs and managed in accordance with conservation agreements. A complex network of sloughs weaves through the Marsh, providing habitat for numerous aquatic species. Together the waterways and marsh plain support a stunning array of species, provide exurban open space, and are increasingly called upon to meet regional conservation objectives. The Marsh is vulnerable to sea level rise impacts, pollution, and other human impacts, so understanding how it functions so it can be successfully managed to meet the lofty objectives set out for it will be critically important in the decades ahead. This study reviews landscape-scale historical ecology of Suisun Marsh and examines recent variation in fish populations from a geographical perspective.</p><p> Chapter 1 presents the geomorphic and physical history of the landscape, explaining processes driving wetland development and contributing to unique functional subregions within the Marsh. Chapter 2 examines human- and animal-landscape interactions. Ecologically significant shifts in human and animal populations during the Spanish and Mexican eras, followed by agricultural development in the late 1800s and duck club management starting around 1900, have kept the Marsh landscape continually changing. The rate and magnitude of landscape change has intensified since European contact in 1769 and even more since the Gold Rush of 1849. Chapter 3 explores landscape-scale variation in species distribution and abundance based on a long-term study of Suisun Marsh fishes and invertebrates and presents these data in novel animations. Animated maps are used to explore shifting populations of fishes and invertebrates from 1980 to 2013, demonstrating the value of long-term biogeographical datasets in understanding biological communities at the landscape scale.</p><p> Understanding both the deep and recent history of the Marsh provides insights and inspiration, informs management approaches, points to potential restoration and rehabilitation targets, and affects attitudes about appropriate human interactions with this dynamic biological system and landscape.</p>

To better understand the role of mountains in lee cyclogenesis, two such cases which occurred during BASE (Beaufort and Arctic Storms Experiment) are simulated using the Mesoscale Compressible Community model (MC2). Both cases are shown to satisfy criteria for lee cyclogenesis, despite some ambiguity in its definition. The successful simulations reveal that lee cyclogenesis involves several processes: (1) formation of an upper-level short wave, (2) column stretching, (3) enhanced convergence and increased relative vorticity resulting from adiabatic warming, (4) latent heat release and, in one case, increased baroclinicity due to low-level blocking by topography. / The results of sensitivity experiments indicate that removal of topography (latent heat) produces a stronger (weaker) lee cyclone. Topography significantly influences the distribution of precipitation with climatological consequences for areas in the lee. It is found that cyclogenesis can still occur in the absence of mountains in the two cases studied, although mountains modify the cyclogenetic processes.

No description available.

Thesis (Ph.D.)--University of Washington, 2005. / (UnM)AAI3183424. Source: Dissertation Abstracts International, Volume: 66-07, Section: B, page: 3606. Chair: Charles F. Raymond.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 135-139). Also available via the Internet.

Thèse--Université de Paris. / "Bibliographie": p. [5]-10.

Habilitationsschrift--Hamburg. / Some legends also in Spanish. Includes bibliographical references (p. 139-165).