Hurricane Wind Power Spectra, Cospectra, and Integral Length Scales   总被引：1，自引：0，他引：1  

Bo Yu  Arindam Gan Chowdhury  Forrest James Masters 《Boundary-Layer Meteorology》2008,129(3):411-430

Atmospheric turbulence is an important factor in the modelling of wind forces on structures and the losses they produce in extreme wind events. However, while turbulence in non-hurricane winds has been thoroughly researched, turbulence in tropical cyclones and hurricanes that affect the Gulf and Atlantic coasts has only recently been the object of systematic study. In this paper, Florida Coastal Monitoring Program surface wind measurements over the sea surface and open flat terrain are used to estimate tropical cyclone and hurricane wind spectra and cospectra as well as integral length scales. From the analyses of wind speeds obtained from five towers in four hurricanes it can be concluded with high confidence that the turbulent energy at lower frequencies is considerably higher in hurricane than in non-hurricane winds. Estimates of turbulence spectra, cospectra, and integral turbulence scales presented can be used for the development in experimental facilities of hurricane wind flows and the forces they induce on structures.  相似文献   

Performance evaluation of underwater platforms in the context of space exploration     

A.L. Forrest  B.E. Laval  D.R. Williams  M.M. Marinova  A.L. Brady  M.L. Gernhardt 《Planetary and Space Science》2010,58(4):706-716

Robotic platforms are essential for future human planetary and lunar exploration as they can operate in more extreme environments with a greater endurance than human explorers. In this era of space exploration, a terrestrial analog that can be used for development of the coordination between manned and robotic vehicles will optimize the scientific return of future missions while concurrently minimizing the downtime of both human explorers and robotic platforms. This work presents the use of underwater exploratory robots - autonomous underwater vehicles (AUV), remotely operated vehicles (ROV), and manned submersibles - as analogues for mixed human-robot exploration of space. Subaqueous settings present diverse challenges for navigation, operation and recovery that require the development of an exploration model of a similar complexity as required for space exploration. To capitalize on the strengths of both robotic and human explorers this work presents lessons learnt with respect to the fields of human-robotic interface (HRI) and operator training. These are then used in the development of mission evaluation tools: (1) a task efficiency index (TEI), (2) performance metrics, and (3) exploration metrics. Although these independent evaluations were useful for specific missions, further refinement will be required to fully evaluate the strengths and capabilities of multiple platforms in a human-robotic exploration campaign in order to take advantage of unforeseen science opportunities in remote settings.  相似文献   

Sulfur- and oxygen-isotopes in sediment-hosted stratiform barite deposits   总被引：2，自引：0，他引：2  

Craig A. Johnson  Poul Emsbo  Forrest G. Poole  Robert O. Rye 《Geochimica et cosmochimica acta》2009,73(1):133-99

Sulfur- and oxygen-isotope analyses have been obtained for sediment-hosted stratiform barite deposits in Alaska, Nevada, Mexico, and China to examine the environment of formation of this deposit type. The barite is contained in sedimentary sequences as old as Late Neoproterozoic and as young as Mississippian. If previously published data for other localities are considered, sulfur- and oxygen-isotope data are now available for deposits spanning a host-rock age range of Late Neoproterozoic to Triassic. On a δ³⁴S versus δ¹⁸O diagram, many deposits show linear or concave-upward trends that project down toward the isotopic composition of seawater sulfate. The trends suggest that barite formed from seawater sulfate that had been isotopically modified to varying degrees. The δ³⁴S versus δ¹⁸O patterns resemble patterns that have been observed in the modern oceans in pore water sulfate and water column sulfate in some anoxic basins. However, the closest isotopic analog is barite mineralization that occurs at fluid seeps on modern continental margins. Thus the data favor genetic models for the deposits in which barium was delivered by seafloor seeps over models in which barium was delivered by sedimentation of pelagic organisms. The isotopic variations within the deposits appear to reflect bacterial sulfate reduction operating at different rates and possibly with different electron donors, oxygen isotope exchange between reduction intermediates and H₂O, and sulfate availability. Because they are isotopically heterogeneous, sediment-hosted stratiform barite deposits are of limited value in reconstructing the isotopic composition of ancient seawater sulfate.  相似文献   

Comparisons of two global built area land cover datasets in methods to disaggregate human population in eleven countries from the global South     

Forrest R. Stevens  Andrea E. Gaughan  Jeremiah J. Nieves  Adam King  Alessandro Sorichetta  Catherine Linard 《International Journal of Digital Earth》2020,13(1):78-100

ABSTRACT

Mapping built land cover at unprecedented detail has been facilitated by increasing availability of global high-resolution imagery and image processing methods. These advances in urban feature extraction and built-area detection can refine the mapping of human population densities, especially in lower income countries where rapid urbanization and changing population is accompanied by frequently out-of-date or inaccurate census data. However, in these contexts it is unclear how best to use built-area data to disaggregate areal, count-based census data. Here we tested two methods using remotely sensed, built-area land cover data to disaggregate population data. These included simple, areal weighting and more complex statistical models with other ancillary information. Outcomes were assessed across eleven countries, representing different world regions varying in population densities, types of built infrastructure, and environmental characteristics. We found that for seven of 11 countries a Random Forest-based, machine learning approach outperforms simple, binary dasymetric disaggregation into remotely-sensed built areas. For these more complex models there was little evidence to support using any single built land cover input over the rest, and in most cases using more than one built-area data product resulted in higher predictive capacity. We discuss these results and implications for future population modeling approaches.  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   

Vent fluid chemistry in Bahía Concepción coastal submarine hydrothermal system, Baja California Sur, Mexico     

R.M. Prol-Ledesma  C. Canet  M.A. Torres-Vera  M.J. Forrest  M.A. Armienta 《Journal of Volcanology and Geothermal Research》2004,137(4):102

Shallow submarine hydrothermal activity has been observed in the Bahía Concepción bay, located at the Gulf coast of the Baja California Peninsula, along faults probably related to the extensional tectonics of the Gulf of California region. Diffuse and focused venting of hydrothermal water and gas occurs in the intertidal and shallow subtidal areas down to 15 m along a NW–SE-trending onshore–offshore fault. Temperatures in the fluid discharge area vary from 50 °C at the sea bottom up to 87 °C at a depth of 10 cm in the sediments.Chemical analyses revealed that thermal water is enriched in Ca, As, Hg, Mn, Ba, HCO₃, Li, Sr, B, I, Cs, Fe and Si, and it has lower concentrations of Cl, Na, SO₄ and Br than seawater. The chemical characteristics of the water samples indicate the occurrence of mixing between seawater and a thermal end-member. Stable isotopic oxygen and hydrogen composition of thermal samples plot close to the Local Meteoric Water Line on a mixing trend between a thermal end-member and seawater. The composition of the thermal end-member was calculated from the chemistry of the submarine samples data by assuming a negligible amount of Mg for the thermal end-member. The results of the mixing model based on the chemical and isotopic composition indicate a maximum of 40% of the thermal end-member in the submarine vent fluid.Chemical geothermometers (Na/Li, Na–K–Ca and Si) were applied to the thermal end-member concentration and indicate a reservoir temperature of approximately 200 °C. The application of K–Mg and Na/Li geothermometers for vent fluids points to a shallow equilibrium temperature of about 120 °C.Results were integrated in a hydrogeological conceptual model that describes formation of thermal fluids by infiltration and subsequent heating of meteoric water. Vent fluid is generated by further mixing with seawater.  相似文献   

The effects of local campaign spending on the geography of the flow‐of‐the‐vote at the 1991 New South Wales state election     

James Forrest 《The Australian geographer》1997,28(2):229-240

There is a tendency to assume that election campaigning at the local electorate level has little or no impact on voters subject to the influence of highly centralised campaigns and an increasingly nationalised media. However, as applied to the flow‐of‐the‐vote, this study concludes that local campaign spending has real consequences for vote shifts. For the 1991 New South Wales state election, it is established that any major commitment to local electorate spending by one of the major parties relative to the other increases flows to that party and reduces flows from it. However, incumbency of individual seats as such does not appear to have any significant effect. There is a strong suggestion that, for this election, the Liberal‐National Coalition in government was at a distinct disadvantage compared with the Labor Party in opposition, the spending of the former having a much reduced impact on retaining or attracting votes compared with spending by Labor.  相似文献   

Hydro-economic analysis of groundwater pumping for irrigated agriculture in California’s Central Valley,USA     

Josué Medellín-Azuara  Duncan MacEwan  Richard E. Howitt  George Koruakos  Emin C. Dogrul  Charles F. Brush  Tariq N. Kadir  Thomas Harter  Forrest Melton  Jay R. Lund 《Hydrogeology Journal》2015,23(6):1205-1216

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Communicating Climate Change: Reinforcing Comprehension and Personal Ties to Climate Change Through Maps     

Irene M. Johannsen  Karla A. Lassonde  Forrest Wilkerson 《The Cartographic journal》2018,55(1):85-100

Although climate change is highly prevalent in the media, people in Europe and the United States are often unsure about climate change terms, processes, and its personal consequences. In other words, climate change communication seems to be largely failing so far. Among other communication tools, maps are widely used for explanatory purposes by scientists and the media. Here two questions arise: first, whether high map complexity may be too intricate to be understood and discourage people from deciphering the map; and second, whether personal interest in climate change can be influenced by the phenomenon depicted or the map’s scale. In a survey conducted among 109 students in the USA, 63% of respondents preferred a simple map, but a substantial subset, 37%, asked for complexity to receive more information. Regional phenomena evoked more concern than far-off phenomena (concern level index difference of 0.93 on a 5-ranked Likert scale). The advantage of maps showing local areas could not be statistically confirmed.  相似文献   

The geography of same-sex couples and families in Australia: an empirical review     

James Forrest  Andrew Gorman-Murray  Frank Siciliano 《The Australian geographer》2019,50(4):493-509

ABSTRACT

Much has changed since the first mapping of single-sex couples and families from the 2006 Australian census. An increasing willingness to allow their identification in the census has accompanied increasing public acceptance of same-sex couples culminating in significant support for legalising same-sex marriage in a 2017 national survey. Technological advances permit complex cross-tabulations of Australian census data and more detailed characterisations of same-sex couples. New geographies differentiate between male and female couples with children, showing same-sex couples are not just a feature of some inner-city areas, though these remain important, but also of suburban, regional and some rural areas. Drawing on the 2016 census, contemporary geographies of same-sex couples with and without children in Australia and changes over the past decade in Sydney are analysed at a time of increased interest in this demographic.  相似文献