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1.
The Role of Planetary Boundary-Layer Parameterizations in the Air Quality of an Urban Area with Complex Topography 总被引:3,自引:1,他引:2
Elizabeth Bossioli Maria Tombrou Aggeliki Dandou Eleni Athanasopoulou Kostas V. Varotsos 《Boundary-Layer Meteorology》2009,131(1):53-72
The effect of different planetary boundary-layer (PBL) parameterization schemes on the spatial distribution of atmospheric
pollution over the complex topography of the greater Athens area is investigated. Four PBL schemes originally implemented
in a numerical meteorological model and a fifth one simulating the urban effect are examined. Two different atmospheric conditions
are analyzed; a typical summer and a typical winter pollution episode. The relative importance of chemical and physical processes
of the pollution predictions is discussed using process analysis. It is revealed that, for primary pollutants, a local scheme
seems more adequate to represent the maximum observed concentrations while, completely different in structure, a non-local
scheme reproduces the mean observed values in the basin. Concerning secondary pollutants, peak concentration differences,
due to the different PBL schemes, are smoothed out. Nevertheless, the PBL scheme selection shapes the horizontal and the vertical
extension of maximum values. The non-local and semi non-local schemes are superior to the others, favouring strong vertical
mixing and transport towards the surface. The stronger turbulence accommodated effectively by the semi non-local urban scheme
enhances ozone production along the sea-breeze axis and preserves the high ozone concentrations during the nighttime hours
in the urban core. 相似文献
2.
Aggeliki Adamaki Eleftheria E. Papadimitriou George M. Tsaklidis Vassilios Karakostas 《Acta Geophysica》2011,59(4):748-769
Aftershock rates seem to follow a power law decay, but the assessment of the aftershock frequency immediately after an earthquake,
as well as during the evolution of a seismic excitation remains a demand for the imminent seismic hazard. The purpose of this
work is to study the temporal distribution of triggered earthquakes in short time scales following a strong event, and thus
a multiple seismic sequence was chosen for this purpose. Statistical models are applied to the 1981 Corinth Gulf sequence,
comprising three strong (M = 6.7, M = 6.5, and M = 6.3) events between 24 February and 4 March. The non-homogeneous Poisson process outperforms the simple Poisson process
in order to model the aftershock sequence, whereas the Weibull process is more appropriate to capture the features of the
short-term behavior, but not the most proper for describing the seismicity in long term. The aftershock data defines a smooth
curve of the declining rate and a long-tail theoretical model is more appropriate to fit the data than a rapidly declining
exponential function, as supported by the quantitative results derived from the survival function. An autoregressive model
is also applied to the seismic sequence, shedding more light on the stationarity of the time series. 相似文献
3.
Aggeliki Dandou Maria Tombrou Klaus Schäfer Stefan Emeis Anna P. Protonotariou Elissavet Bossioli Nikolaos Soulakellis Peter Suppan 《Boundary-Layer Meteorology》2009,131(3):425-440
An attempt is made to correlate the mixing heights, derived from ceilometer and Sodar measurements, to those simulated by
different atmospheric boundary-layer parameterization schemes. The comparison is performed at two sites (one suburban and
one rural) close to Munich, Germany for two spring and two winter days. It is found that, under convective conditions, the
mixing height determined, by both Sodar and ceilometer, corresponds to the middle or the top of the entrainment zone, respectively,
as calculated from the eddy-viscosity profiles. Under stable conditions, the measured mixing height is related to the height
where eddy viscosities attain their minimum values (Sodar) or to the height of residual mechanical turbulence (ceilometer).
During a foehn case with weak turbulence, the measured mixing height from both Sodar and ceilometer is better inferred by
considering the eddy-viscosity profiles during daytime and the height of the low-level jet during nighttime. 相似文献
4.
In the present study, we examine the dynamics of a sea-breeze front and the urban heat island interacting with the heavily
urbanized city of Athens. For this reason, simulations were performed with a modified version of the PSU/NCAR Mesoscale Model
(MM5), whereby urban features are considered, and the model results were compared with surface routine meteorological data.
An unrealistic run was also performed, where the city of Athens was replaced by dry cropland and pasture surface, as in the
surrounding area. A delay in the sea-breeze front was found during daytime, together with frictional retardation concerning
its penetration, as well as inland displacement of the heat island as the air moved over the city of Athens. During nighttime,
the wind speed increased over the lower atmosphere in the city centre due to the enhanced urban heat island. 相似文献
5.
Aggeliki Georgiopoulou Russell B. Wynn Douglas G. Masson Michael Frenz 《Marine and Petroleum Geology》2009,26(10):2021-2031
The northwest African margin has been affected by numerous large-scale landslides during the late Quaternary. This study focuses on a recent collapse of the Sahara Slide headwall and characterises the resulting flow deposit. Core and seismic data from the base of the upper headwall reveal the presence of blocky slide debris, comprising heavily deformed hemipelagic slope sediments. The blocky slide debris spilled over a lower headwall 60 km downslope and formed a thick transparent debris flow unit. Cores recovered 200–250 km farther downslope contain a surficial turbidite that is interpreted to be linked to the headwall collapse event based on timing and composition. One core located approximately 200 km from the headwall scar (C13) contains debrite encased in turbidite. The debrite comprises sheared and contorted hemipelagic mudstone clasts similar as those seen in the vicinity of the Sahara Slide headwall, and lacks matrix. This debrite pinches out laterally within 25 km of C13, whereas the accompanying turbidite can be correlated across 700 km of the northwest African margin. The linked turbidite–debrite bed is interpreted to have formed through recent failure of the steep Sahara Slide headwall that either 1) generated both a debris flow and a turbidity current almost simultaneously, or 2) generated a debris flow which with entrainment of water and progressive dilution led to formation of an accompanying turbidity current. 相似文献
6.
Maria Kakavas Konstantinos G. Nikolakopoulos Aggeliki Kyriou Helen Zagana 《Arabian Journal of Geosciences》2018,11(14):388
The purpose of this work is to present the detection and qualification of natural karst depressions in southern Ksiromero, SW Aitoloakarnania Prefecture, Western Greece, by the use of freely available digital surface model (DSM) data in line with the geographical information systems—GIS. The study area is a part of the Ionian geotectonic zone whose geological background consists of the Triassic evaporates and Triassic carbonate breccias. The after-Triassic carbonate series, which consist of the Jurassic limestones, the Cretaceous limestones and the Eocene limestones, are also presented in the study area. Several DSMs such as ASTER GDEM, SRTM DEM, ALOS Global DSM, and a DSM generated from Sentinel-1 data were evaluated so as to be used for the automatic karst detection. Furthermore, a karst detection procedure applied on DSMs was performed with the aid of analogue and digital air photos. Additionally, the aforementioned procedure was applied also on DEM with the aid of digitized contours referring to topographic maps characterized by a scale of 1/50,000. All the detected features have been also validated via in situ observations. Finally, all DSMs presented herein are characterized by similar percentage of success in terms of automatic karst detection, regardless their spatial resolution and height accuracy. Their rate varies from 66 to 73%. 相似文献
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9.
Martin Piringer Sylvain Joffre Alexander Baklanov Andreas Christen Marco Deserti Koen De Ridder Stefan Emeis Patrice Mestayer Maria Tombrou Douglas Middleton Kathrin Baumann-Stanzer Aggeliki Dandou Ari Karppinen Jerzy Burzynski 《Boundary-Layer Meteorology》2007,124(1):3-24
The specific problems of determining and simulating the surface energy balance (SEB) and the mixing height (MH) over urban
areas are examined. The SEB and MH are critical components of algorithms and numerical models for the urban boundary layer,
though the constituent parts of the SEB and the MH are not routinely measured by national weather services. Parameterisations
are thus needed in applications. In this investigation, several recently developed algorithms and models for estimating the
SEB and MH were applied to new datasets and assessed. Results are discussed in terms of the need for spatial resolution and
the parameters needed to describe the urban atmosphere. Limitations of models are identified and recommendations for further
development and observations are given. Having identified gaps in knowledge, key findings from new urban experiments and numerical
modelling for the SEB and MH are given. The diurnal cycle for the SEB is significantly different from rural conditions—urban
heat storage is needed in urban parameterisations. The urban MH is increased over the rural MH, as shown by several numerical
schemes and careful sodar analyses. This work has been carried out within the COST-715 Action “Meteorology applied to urban
air pollution problems (1998–2004). COST 715 reached a consensus proposing representatively sited measurements of meteorological
parameters and turbulent fluxes above roof-tops, and recognised that such data are needed to improve numerical models of the
urban surface processes. 相似文献
10.
Aggeliki Barberopoulou Mark R. Legg Burak Uslu Costas E. Synolakis 《Natural Hazards》2011,58(1):479-496
We assess tsunami hazards in San Diego Bay, California, using newly identified offshore tsunami sources and recently available
high resolution bathymetric/topographic data. Using MOST (Titov and Synolakis, J Waterways Port Coastal Ocean Eng ASCE 124(4):57–171,
1998), we simulate locally, regionally and distant-generated tsunamis. Local tsunami source models use more realistic fault
and landslide data than previous efforts. With the exception of the Alaska-Aleutian Trench, modeling results suggest that
local sources are responsible for the largest waves within the San Diego Bay and Mission Bay. Because San Diego Bay is relatively
well protected by North Island and the Silver Strand, the wave heights predicted are consistently smaller inside the harbor
than outside. However, historical accounts, recent tsunamis and our predictions show that San Diego Bay is vulnerable to strong
tsunami induced currents. More specifically, large currents are expected inside the harbor for various distant and local tsunami
sources with estimated flow velocities exceeding 100 cm/s. Such currents have been damaging to harbor facilities, such as
wharves and piers, and may cause boats to break from moorings and ram into adjacent harbor structures, as observed in recent
historic tsunamis. More recently, following the M
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8.8 February 27, 2010 Chile earthquake, tsunami-currents damaged docks/piers in Shelter Island confirming our findings. We
note that the first generation of inundation maps in use in San Diego County by emergency management was based on much larger
“worst case but realistic scenarios” (Synolakis et al. 2002a), which reflected the understanding of offshore hazards pervasive ten years ago. Large inundation and overland flow depths
were observed primarily in local tsunami source simulations. In particular, locally induced tsunamis appear capable to overtop
the Silver Strand. The results suggest that further work needs to be carried out with respect to local tsunami sources as
they seem to have worse impact in the San Diego region than previously thought but probably low probability of occurrence.
We also predict that a coastal community can be devastated simultaneously by large waves inundating shores and large currents
in locations with small flow depths. 相似文献