Effects of Roof-Edge Roughness on Air Temperature and Pollutant Concentration in Urban Canyons     

Amir A. Aliabadi  E. Scott Krayenhoff  Negin Nazarian  Lup Wai Chew  Peter R. Armstrong  Afshin Afshari  Leslie K. Norford 《Boundary-Layer Meteorology》2017,164(2):249-279

The influence of roof-edge roughness elements on airflow, heat transfer, and street-level pollutant transport inside and above a two-dimensional urban canyon is analyzed using an urban energy balance model coupled to a large-eddy simulation model. Simulations are performed for cold (early morning) and hot (mid afternoon) periods during the hottest month of the year (August) for the climate of Abu Dhabi, United Arab Emirates. The analysis suggests that early in the morning, and when the tallest roughness elements are implemented, the temperature above the street level increases on average by 0.5 K, while the pollutant concentration decreases by 2% of the street-level concentration. For the same conditions in mid afternoon, the temperature decreases conservatively by 1 K, while the pollutant concentration increases by 7% of the street-level concentration. As a passive or active architectural solution, the roof roughness element shows promise for improving thermal comfort and air quality in the canyon for specific times, but this should be further verified experimentally. The results also warrant a closer look at the effects of mid-range roughness elements in the urban morphology on atmospheric dynamics so as to improve parametrizations in mesoscale modelling.  相似文献   

Storm surge evolution and its relationship to climate oscillations at Duck,NC     

Robert?Munroe  Scott?CurtisEmail author 《Theoretical and Applied Climatology》2017,129(1-2):185-200

Coastal communities experience increased vulnerability during storm surge events through the risk of damage to coastal infrastructure, erosion/deposition, and the endangerment of human life. Policy and planning measures attempt to avoid or mitigate storm surge consequences through building codes and setbacks, beach stabilization, insurance rates, and coastal zoning. The coastal emergency management community and public react and respond on shorter time scales, through temporary protection, emergency stockpiling, and evacuation. This study utilizes time series analysis, the Kolmogorov-Smirnov (K-S) test, Pearson’s correlation, and the generalized extreme value (GEV) theorem to make the connection between climate oscillation indices and storm surge characteristics intra-seasonally to inter-annually. Results indicate that an El Niño (+ENSO), negative phase of the NAO, and positive phase of the PNA pattern all support longer duration and hence more powerful surge events, especially in winter. Increased surge duration increases the likelihood of extensive erosion, inland inundation, among other undesirable effects of the surge hazard.  相似文献   

The volcanic history of Volcán Alcedo,Galápagos Archipelago: A case study of rhyolitic oceanic volcanism     

Dennis Geist  Keith A. Howard  A. Mark Jellinek  Scott Rayder 《Bulletin of Volcanology》1994,56(4):243-260

Volcán Alcedo is one of the seven western Galápagos shields and is the only active Galápagos volcano known to have erupted rhyolite as well as basalt. The volcano stands 4 km above the sea floor and has a subaerial volume of 200 km³, nearly all of which is basalt. As Volcán Alcedo grew, it built an elongate domal shield, which was partly truncated during repeated caldera-collapse and partial-filling episodes. An outward-dipping sequence of basalt flows at least 250 m thick forms the steepest (to 33°) flanks of the volcano and is not tilted; thus a constructional origin for the steep upper flanks is favored. About 1 km³ of rhyolite erupted late in the volcano's history from at least three vents and in 2–5 episodes. The most explosive of these produced a tephra blanket that covers the eastern half of the volcano. Homogeneous rhyolitic pumice is overlain by dacite-rhyolite commingled pumice, with no stratigraphic break. The tephra is notable for its low density and coarse grain size. The calculated height of the eruption plume is 23–30 km, and the intensity is estimated to have been 1.2x10⁸ kg/s. Rhyolitic lavas vented from the floor of the caldera and from fissures along the rim overlie the tephra of the plinian phase. The age of the rhyolitic eruptions is 120 ka, on the basis of K-Ar ages. Between ten and 20 basaltic lava flows are younger than the rhyolites. Recent faulting resulted in a moat around part of the caldera floor. Alcedo most resently erupted sometime between 1946 and 1960 from its southern flank. Alcedo maintains an active, transient hydrothermal system. Acoustic and seismic activity in 1991 is attributed to the disruption of the hydrothermal system by a regional-scale earthquake.  相似文献   

A numerical study of the interaction of tidal oscillations and non-linearities in an estuary     

C.F. Scott 《Estuarine, Coastal and Shelf Science》1994,39(6)

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Winter-to-winter recurrence of sea surface temperature, salinity and mixed layer depth anomalies     

Michael A. Alexander  Michael S. Timlin  James D. Scott 《Progress in Oceanography》2001,49(1-4)

The mean seasonal cycle of mixed layer depth (MLD) in the extratropical oceans has the potential to influence temperature, salinity and mixed layer depth anomalies from one winter to the next. Temperature and salinity anomalies that form at the surface and spread throughout the deep winter mixed layer are sequestered beneath the mixed layer when it shoals in spring, and are then re-entrained into the surface layer in the subsequent fall and winter. Here we document this ‘re-emergence mechanism’ in the North Pacific Ocean using observed SSTs, subsurface temperature fields from a data assimilation system, and coupled atmosphere–ocean model simulations. Observations indicate that the dominant large-scale SST anomaly pattern that forms in the North Pacific during winter recurs in the following winter. The model simulation with mixed layer ocean physics reproduced the winter-to-winter recurrence, while model simulations with observed SSTs specified in the tropical Pacific and a 50 m slab in the North Pacific did not. This difference between the model results indicates that the winter-to-winter SST correlations are the result of the re-emergence mechanism, and not of similar atmospheric forcing of the ocean in consecutive winters. The model experiments also indicate that SST anomalies in the tropical Pacific associated with El Niño are not essential for re-emergence to occur.The recurrence of observed SST and simulated SST and SSS anomalies are found in several regions in the central North Pacific, and are quite strong in the northern (>50°N) part of the basin. The winter-to-winter autocorrelation of SSS anomalies exceed those of SST, since only the latter are strongly damped by surface fluxes. The re-emergence mechanism also has a modest influence on MLD through changes in the vertical stratification in the seasonal thermocline.  相似文献   

Predicting satellite visibility     

Diana W. Scott 《Planetary and Space Science》1967,15(12):1895-1911

An Earth satellite can only be observed by optical methods when it is illuminated by sunlight and the observing station is in darkness, with the result that the satellite is in general only visible on two fairly small arcs of its orbit.

In this paper, a graphical method has been developed for predicting the latitudes from which a satellite in a circular orbit is visible, with the particular aim of discovering periods when a satellite may be observed in mid-latitudes in both the northern and southern hemispheres. For near-polar orbits the occurrence of such periods depends critically on the position of the ascending node of the orbit; but for lower inclinations, the periods of visibility become shorter and more frequent, and the orientation of the orbit is less significant.  相似文献   

A revaluation of the rotational speed of the upper atmosphere     

D. G. King-Hele  Diana W. Scott 《Planetary and Space Science》1966,14(12):1339-1365

In this paper the rotational speed of the upper atmosphere, mainly at heights of 200–300 km, is evaluated from the changes in the orbital inclinations of thirteen satellites. The values obtained represent the mean rotational speed over the latitudes covered by the satellites, at dates between late 1962 and early 1966, i.e. when solar activity was low.

If the angular velocity of the atmosphere is taken as Λ times that of the Earth, the values of Λ found are mostly between 1.0 and 1.6 with estimated S.D. between 0.1 and 0.25. If we exclude two values at heights above 300 km and one anomalous value, the mean of the remaining ten values of Λ obtained is 1.27, with r.m.s. scatter 0.18: this would correspond to an average west-to-east wind of about 100 m/sec in mid-latitudes.  相似文献   

The sedimentary record of the Issyk Kul basin,Kyrgyzstan: climatic and tectonic inferences          下载免费PDF全文

Euan A. Macaulay  Edward R. Sobel  Alexander Mikolaichuk  Michael Wack  Stuart A. Gilder  Andreas Mulch  Alla B. Fortuna  Scott Hynek  Farid Apayarov 《Basin Research》2016,28(1):57-80

A broad array of new provenance and stable isotope data are presented from two magnetostratigraphically dated sections in the south‐eastern Issyk Kul basin of the Central Kyrgyz Tien Shan. The results presented here are discussed and interpreted for two plausible magnetostratigraphic age models. A combination of zircon U‐Pb provenance, paleocurrent and conglomerate clast count analyses is used to determine sediment provenance. This analysis reveals that the first coarse‐grained, syn‐tectonic sediments (Dzhety Oguz formation) were sourced from the nearby Terskey Range, supporting previous thermochronology‐based estimates of a ca. 25–20 Ma onset of deformation in the range. Climate variations are inferred using carbonate stable isotope (δ¹⁸O and δ¹³C) data from 53 samples collected in the two sections and are compared with the oxygen isotope compositions of modern water from 128 samples. Two key features are identified in the stable isotope data set derived from the sediments: (1) isotope values, in particular δ¹³C, decrease between ca. 26.0 and 23.6 or 25.6 and 21.0 Ma, and (2) the scatter of δ¹⁸O values increased significantly after ca. 22.6 or 16.9 Ma. The first feature is interpreted to reflect progressively wetter conditions. Because this feature slightly post‐dates the onset of deformation in the Terskey Range, we suggest that it has been caused by orographically enhanced precipitation, implying that surface uplift accompanied late Cenozoic deformation and rock uplift in the Terskey Range. The increased scatter could reflect variable moisture source or availability caused by global climate change following the onset of Miocene glaciations at ca. 22.6 Ma, or enhanced evaporation during the Mid‐Miocene climatic optimum at ca. 17–15 Ma.  相似文献   

Spatio-temporal changes in heat waves and cold spells: an analysis of 55 U.S. cities     

Michael J. Allen  Scott C. Sheridan 《自然地理学》2016,37(3-4):189-209

With observed increases in global temperatures indicating changes to anomalous temperature events (ATE), few studies have considered the changes associated with both heat and cold together. This study evaluates the changes in heat waves and cold spells for 55 U.S. metropolitan areas (1948–2012). Using surface observations, thresholds of mean apparent temperature were used to define heat, extreme heat, cold, and extreme cold events. Days that exceeded the 95th temperature percentile were considered heat days. Similar values were used to define extreme heat (97.5th), cold (5th), and extreme cold (2.5th). Thresholds were calculated independently for each of the locations, incorporating spatial variability into the ATE definition. Changes in duration, seasonal timing, and frequency, all of which have been shown to be important characteristics in regard to heat and cold events, were evaluated. Significant changes in some characteristics were found. Across many locations, heat events have become more frequent, longer lasting, and earlier occurring, while cold spells have experienced an opposite trend. Since heat and cold events impact a range of ecological and bioclimatological processes, understanding the variability and changes associated with ATE remains an important aspect to consider as society prepares for future events.  相似文献   

Modelling the alongshore variability of optimum rip current escape strategies on a multiple rip-channelled beach     

Bruno Castelle  R. Jak McCarroll  Robert W. Brander  Timothy Scott  Benjamin Dubarbier 《Natural Hazards》2016,81(1):663-686

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