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1.
Observations from two SOund Detection And Ranging (SODAR) units, a 10 m micrometeorological tower and five Automated Surface Observing Stations (ASOS) were examined during several synoptic scale flow regimes over New York City after the World Trade Center disaster on September 11, 2001. An ARPS model numerical simulation was conducted to explore the complex mesoscale boundary layer structure over New York City. The numerical investigation examined the urban heat island, urban roughness effect and sea breeze structure over the New York City region. Estimated roughness lengths varied from 0.7 m with flow from the water to 4 m with flow through Manhattan. A nighttime mixed layer was observed over lower Manhattan, indicating the existence of an urban heat island. The ARPS model simulated a sea-breeze front moving through lower Manhattan during the study period consistent with the observations from the SODARs and the 10-m tower observations. Wind simulations showed a slowing and cyclonic turning of the 10-m air flow as the air moved over New York City from the ocean. Vertical profiles of simulated TKE and wind speeds showed a maximum in TKE over lower Manhattan during nighttime conditions. It appears that this TKE maximum is directly related to the influences of the urban heat island. 相似文献
2.
The effect of coastal upwelling on the sea-breeze circulation at Cabo Frio, Brazil: a numerical experiment 总被引：1，自引：0，他引：1
The effect of coastal upwelling on sea-breeze circulation in Cabo Frio (Brazil) and the feedback of sea-breeze on the upwelling signal in this region are investigated. In order to study the effect of coastal upwelling on sea-breeze a non-linear, three-dimensional, primitive equation atmospheric model is employed. The model considers only dry air and employs boundary layer formulation. The surface temperature is determined by a forcing function applied to the Earths surface. In order to investigate the seasonal variations of the circulation, numerical experiments considering three-month means are conducted: January-February-March (JFM), April-May-June (AMJ), July-August-September (JAS) and October-November-December (OND). The model results show that the sea-breeze is most intense near the coast at all the seasons. The sea-breeze is stronger in OND and JFM, when the upwelling occurs, and weaker in AMJ and JAS, when there is no upwelling. Numerical simulations also show that when the upwelling occurs the sea-breeze develops and attains maximum intensity earlier than when it does not occur. Observations show a similar behavior. In order to verify the effect of the sea-breeze surface wind on the upwelling, a two-layer finite element ocean model is also implemented. The results of simulations using this model, forced by the wind generated in the sea-breeze model, show that the sea-breeze effectively enhances the upwelling signal. 相似文献
3.
在能量平衡方程中引入气溶胶的吸收和散射作用,并与三维行星边界层运动方程组相耦合,根据温度分布显式求解运动场,探讨三维行星边界层内温度、运动、气溶胶浓度分布特征.结果表明,城市人为热释放直接决定了城市热岛效应的强度,城市面积越大,城市热岛效应的强度也越强,城市面积固定时,城市越分散,城市热岛效应的强度越弱,这为城市建设多采取卫星城的方式提供了一定的理论支撑.气溶胶的散射作用要大于吸收作用,其对城市热岛效应的强度主要起削弱作用,当气溶胶浓度较大时,吸收作用更显著一些,此时城市热岛效应的强度会有一定的增强,但是幅度不大.当城市热岛效应的强度增强时,其所驱动的环流也会增强,造成城区中心气溶胶浓度略有下降. 相似文献
4.
An intelligent data-driven method is used in the present study for investigating, analyzing and quantifying the urban heat island phenomenon in the major Athens region where hourly ambient air-temperature data are recorded at twenty-three stations. The heat island phenomenon has a serious impact on the energy consumption of buildings, increases smog production, while contributing to an increasing emission of pollutants from power plants, including sulfur dioxide, carbon monoxide, nitrous oxides and suspended particulates. The intelligent method is an artificial neural network approach in which the urban heat island intensity at day and nighttime are estimated using as inputs several climatic parameters. Various neural network architectures are designed and trained for the output estimation, which is the daytime and nighttime urban heat island intensity at each station for a two-year time period. The results are tested with extensive sets of non-training measurements and it is found that they correspond well with the actual values. Furthermore, the influence of several input climatic parameters measured at each station, such as solar radiation, daytime and nighttime air temperature, and maximum daily air temperature, on the urban heat island intensity fluctuations is investigated and analyzed separately for the day and nighttime period. From this investigation it is shown that heat island intensity is mainly influenced by urbanization factors. A sensitivity investigation has been performed, based on neural network techniques, in order to adequately quantify the impact of the above input parameters on the urban heat island phenomenon. 相似文献
5.
A mesoscale non-hydrostatic atmospheric model has been coupled with a mesoscale oceanic model. The case study is a four-day simulation of a strong storm event observed during the SEMAPHORE experiment over a 500 × 500 km2 domain. This domain encompasses a thermohaline front associated with the Azores current. In order to analyze the effect of mesoscale coupling, three simulations are compared: the first one with the atmospheric model forced by realistic sea surface temperature analyses; the second one with the ocean model forced by atmospheric fields, derived from weather forecast re-analyses; the third one with the models being coupled. For these three simulations the surface fluxes were computed with the same bulk parametrization. All three simulations succeed well in representing the main oceanic or atmospheric features observed during the storm. Comparison of surface fields with in situ observations reveals that the winds of the fine mesh atmospheric model are more realistic than those of the weather forecast re-analyses. The low-level winds simulated with the atmospheric model in the forced and coupled simulations are appreciably stronger than the re-analyzed winds. They also generate stronger fluxes. The coupled simulation has the strongest surface heat fluxes: the difference in the net heat budget with the oceanic forced simulation reaches on average 50 Wm−2 over the simulation period. Sea surface-temperature cooling is too weak in both simulations, but is improved in the coupled run and matches better the cooling observed with drifters. The spatial distributions of sea surface-temperature cooling and surface fluxes are strongly inhomogeneous over the simulation domain. The amplitude of the flux variation is maximum in the coupled run. Moreover the weak correlation between the cooling and heat flux patterns indicates that the surface fluxes are not responsible for the whole cooling and suggests that the response of the ocean mixed layer to the atmosphere is highly non-local and enhanced in the coupled simulation. 相似文献
6.
将区域气候模式RegCM2与中国科学院大气物理研究所的9层全球格点大气环流模式IAP AGCM单向嵌套,对东亚现代气候进行数值模拟研究,同时检验和分析该嵌套模式的性能.已完成的10年积分结果表明,单向嵌套RegCM2由于具有较高分辨率和较完善的物理过程,因此对地面气温和降水的空间分布形势和季节变化趋势都有较好的模拟能力,且较与之嵌套的IAP AGCM的模拟效果有较大改善,如在中国区域,它模拟的年均地面气温与实况的空间相关系数由全球环流模式的092提高到094,模拟的年均降水由05提高到07. 这与嵌套RegCM2能模拟出IAP AGCM所不能分辨的中尺度信号有很大关系. 相似文献
7.
Mesoscale eddy plays an important role in the ocean circulation. In order to improve the simulation accuracy of the mesoscale eddies, a three-dimensional variation (3DVAR) data assimilation system called Ocean Variational Analysis System (OVALS) is coupled with a POM model to simulate the mesoscale eddies in the Northwest Pacific Ocean. In this system, the sea surface height anomaly (SSHA) data by satellite altimeters are assimilated and translated into pseudo temperature and salinity (T-S) profile data. Then, these profile data are taken as observation data to be assimilated again and produce the three-dimensional analysis T-S field. According to the characteristics of mesoscale eddy, the most appropriate assimilation parameters are set up and testified in this system. A ten years mesoscale eddies simulation and comparison experiment is made, which includes two schemes: assimilation and non-assimilation. The results of comparison between two schemes and the observation show that the simulation accuracy of the assimilation scheme is much better than that of non-assimilation, which verified that the altimetry data assimilation method can improve the simulation accuracy of the mesoscale dramatically and indicates that it is possible to use this system on the forecast of mesoscale eddies in the future. 相似文献
8.
An integrated fuzzy-stochastic modeling approach for assessing health-impact risk from air pollution 总被引：4，自引：4，他引：0
Heng L. Li Guo H. Huang Yun Zou 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(6):789-803
High concentrations of air pollutants in the ambient environment can result in breathing problems with human communities.
Effective assessment of health-impact risk from air pollution is important for supporting decisions of the related detection,
prevention, and correction efforts. However, the quality of information available for environmental/health risk assessment
is often not satisfactory enough to be presented as deterministic numbers. Stochastic method is one of the methods for tackling
those uncertainties, by which uncertain information can be presented as probability distributions. However, if the uncertainties
can not be presented as probabilities, they can then be handled through fuzzy membership functions. In this study, an integrated
fuzzy-stochastic modeling (IFSM) approach is developed for assessing air pollution impacts towards asthma susceptibility.
This development is based on Monte Carlo simulation for the fate of SO2 in the ambient environment, examination of SO2 concentrations based on the simulation results, quantification of evaluation criteria using fuzzy membership functions, and
risk assessment based on the combined fuzzy-stochastic information. The IFSM entails (a) simulation for the fate of pollutants
in ambient environment, with the consideration of source/medium uncertainties, (b) formulation of fuzzy air quality management
criteria under uncertain human-exposure pathways, exposure dynamics, and SPG-response variations, and (c) integrated risk
assessment under complexities of the combined fuzzy/stochastic inputs of contamination level and health effect (i.e., asthma
susceptibility). The developed IFSM is applied to a study of regional air quality management. Reasonable results have been
generated, which are useful for evaluating health risks from air pollution. They also provide support for regional environmental
management and urban planning. 相似文献
9.
Vegetation constitutes one of the fundamental types of land use on Earth. The presence of trees in urban areas can decrease local winds and exchange sensible and latent heat with the surrounding environments, thus exerting notable influences on the urban microenvironment. A better understanding of the turbulent transfer of momentum and scalars around vegetation canopy could significantly contribute to improvement of the urban environment. This work develops a large-eddy simulation(LES) method that is applicable to model the flow and scalar transport over the forest canopy. We study the atmospheric flow over complex forested areas under typical weather conditions by coupling LES to the mesoscale model. Models of radiation and energy balance have been developed with explicit treatment of the vegetation canopy. By examining the flow over a forest canopy under a range of stability conditions, we found that buoyancy enhances or suppresses turbulent mixing in unstable or stable atmosphere respectively, with decreasing or increasing wind shear, respectively. From the multiscale modeling of the Beijing Olympic Forest Park, the present coupling scheme proves to better resolve the diurnal variations in wind speed,temperature, and relative humidity over complex urban terrains. The coupling scheme is superior to the traditional mesoscale model in terms of wind field simulation. This is mainly because the coupling scheme not only takes the influences of external mesoscale flow into consideration, but also resolves the heterogeneous urban surface at a fine scale by downscaling, thus better reproducing the complex flow and turbulent transport in the urban roughness sublayer. 相似文献
10.
The simplified hydraulic two-layer model for a katabatic flow is analysed using the outputs from a high-resolution mesoscale
simulation. A stably stratified night is simulated for the Duero basin, a complex terrain area located in the northern Spanish
plateau, with large vertical and horizontal spatial resolution. Well-defined katabatic flows on the basin slopes are generated
by the simulation, that are relatively stationary and quasi-bidimensional for some areas in the central part of the night.
The bulk quantities used in the two-layer approach as well as the different terms in the equations are computed from the three-dimensional
information provided by the mesoscale simulation. This method allows to inspect how well the simplified approach represents
the katabatic flow generated by the mesoscale model. The study shows that the hydraulic model allows for a comprehensive analysis
of the basic mechanisms of the slope flows but is not able to close the budget equations, since the residuals are large. 相似文献
11.
本文采用RAMS（Regional Atmospheric Modeling System）模式模拟研究了没有背景风的情况下,土壤湿度非均匀分布的长度尺度分别为40km逐渐减小到2km时,地表通量的分布和大气边界层的响应.运用二维傅里叶变换,分析了地表通量、中尺度脉动量和中尺度通量的二维幅度谱分布,初步探讨大尺度模式中非均匀地表条件下的边界层参数化问题.分析结果显示各试验的地表水、热通量和中尺度脉动量的幅度谱的极大值都出现在与各自非均匀尺度相对应的波数处,当有不同尺度的非均匀斑块共存时,最大的非均匀尺度占主导.但是中尺度水、热通量的结果有所不同,除了在与各自非均匀尺度相对应的波数处有峰值之外,在其他波数还有多个峰值.这些结果表明地表水、热通量的空间分布尺度与非均匀尺度之间存在较好的对应关系,而中尺度水、热通量与非均匀尺度的关系并不明显,说明地表水、热通量的网格平均值的代表性较好,但是不能反映次网格脉动的影响,而中尺度通量的网格平均值的代表性较差. 相似文献
12.
Distributed modeling of monthly air temperatures over the rugged terrain of the Yellow River Basin 总被引：1，自引：0，他引：1
Our analyses of the monthly mean air temperature of meteorological stations show that altitude, global solar radiation and
surface effective radiation have a significant impact on air temperature. We set up a physically-based empirical model for
monthly air temperature simulation. Combined the proposed model with the distributed modeling results of global solar radiation
and routine meteorological observation data, we also developed a method for the distributed simulation of monthly air temperatures
over rugged terrain. Spatial distribution maps are generated at a resolution of 1 km×1 km for the monthly mean, the monthly
mean maximum and the monthly mean minimum air temperatures for the Yellow River Basin. Analysis shows that the simulation
results reflect to a considerable extent the macro and local distribution characteristics of air temperature. Cross-validation
shows that the proposed model displays good stability with mean absolute bias errors of 0.19°C–0.35°C. Tests carried out on
local meteorological station data and case year data show that the model has good spatial and temporal simulation capacity.
The proposed model solely uses routine meteorological data and can be applied easily to other regions.
Supported by China Meteorological Administration key Project on New Technique Diffusion (Grant No. CMATG2006Z10) and Jiangsu
Key Laboratory of Meteorological Disasters (Grant No. KLME050102) 相似文献
13.
The gutenberg-richter law for earthquakes in air pollution episodes: A case study for Athens, Greece 总被引：1，自引：0，他引：1
Maria Efstathiou Chris Tzanis Costas Varotsos Despina Deligiorgi 《Acta Geophysica》2012,60(1):280-290
The main aim of this study is to investigate whether the main components of the photochemical smog episodes over megacities
obey the Gaussian distribution or do they follow the distribution of the Gutenberg-Richter law. To this end, a case study
has been implemented for Athens, Greece, which is among the most densely populated capitals in the middle latitudes of the
Northern Hemisphere. The data employed are hourly mean values of surface ozone and nitrogen dioxide concentrations collected
by the National Air Pollution Monitoring Network during the period 1988–2008. The results obtained show that the surface ozone
and nitrogen dioxide concentrations obey the Gutenberg-Richter law, while their extreme values follow the Generalized Pareto
distribution. This finding is important for current efforts to reliably forecast the air pollutants concentrations and to
quantify their contribution to climate change. Finally, the plausible mechanisms involved in air pollution dynamics leading
to the above-mentioned behaviour are also discussed, assuming the air pollution system governed by non-linear processes. 相似文献
14.
LIU ShuHua ? LIU HePing HU Yu ZHANG ChengYi LIANG FuMing & WANG JianHua Department of Atmospheric Sciences School of Physics Peking University Beijing China Laboratory of Climate Research National Climatic Center China Meteorological Administration Beijing China 《中国科学D辑(英文版)》2007,50(2):290-295
A land-surface physical process model was coupled with a mesoscale atmospheric model. This cou- pled model was then used to simulate the interactions between land and the atmosphere, including surface temperature, net radiation, sensible heat flux and latent heat flux over a desert/Gobi with an oasis in northwestern semiarid regions in China. Comparisons between observations and simulations were made over the oasis and the desert/Gobi, respectively. Both cold island effect and wet island ef- fect, the so-called oasis effect, were observed and simulated. Lower temperature, higher specific hu- midity and weaker turbulent transfer were present over the oasis than the desert/Gobi. A subsidence occurred over the oasis, leading to a thermally-generated mesoscale circulation. 相似文献
15.
《Journal of Atmospheric and Solar》2005,67(16):1524-1532
This work estimates the Ångström turbidity coefficients and investigates the variation of the aerosol optical depth (AOD) in the Athens area, during different atmospheric conditions. The AOD is estimated in the wavelength band of 400–670 nm from direct-beam spectral irradiance measurements using ground-based instrumentation, during an experimental campaign performed in the period 22 September–1 October 2002. All data were collected under clear-sky conditions near the city center of Athens; the AODs were estimated relative to the local zenith to avoid the influence of the optical air mass. The study shows that the AOD is influenced by wind regime and traffic in the Athens area. The Angstrom's turbidity coefficients and the AOD values were found to be higher under the influence of South-sector winds compared to those from the North-sector. Under South-sector low winds, the pollutants are accumulated in the Athens basin. On the contrary, the North-sector winds clean the atmosphere. 相似文献
16.
Interannual modulation of mesoscale eddy activity at the intraseasonal timescale in the southeastern tropical Indian Ocean
and its relation to the Indian Ocean dipole mode (IOD) events are investigated using results from a high-resolution ocean
general circulation model. The model reproduces observed characteristics of the intraseasonal variability and its interannual
modulation fairly well, with large variances of the intraseasonal variability during the 1994 and 1997/1998 IOD events. Large
negative temperature anomaly off the coasts of Java and the Lesser Sunda Islands in boreal summer, due to seasonal variation
and interannual anomaly, extended further to the east in 1994, and the associated strong Indonesian throughflow enhanced the
baroclinic instability in the upper layer, generating anomalously large mesoscale eddy activity. The eddy heat transport,
in turn, significantly affected decaying phase of the 1994 IOD event. On the other hand, the development of the cold region
off the Java Island associated with the 1997/1998 IOD event occurred in boreal winter, causing weaker baroclinic instability
and hence weaker eddy activity off Java. This led to little influence on the heat budget in the southeastern tropical Indian
Ocean for the 1997/1998 IOD event. 相似文献
17.
生产油井井下温度场数值模拟分析 总被引：1，自引：0，他引：1
An improved numerical simulation method is presented to calculate the downhole temperature distribution for multiple pay zones in producing oil wells. Based on hydrodynamics and heat transfer theory, a 2-D temperature field model in cylindrical coordinates is developed. In the model, we considered general heat conduction as well as the heat convection due to fluid flow from porous formation to the borehole. We also take into account the fluid velocity variation in the wellbore due to multiple pay zones. We present coupled boundary conditions at the interfaces between the wellbore and adjacent formation, the wellbore and pay zone, and the pay zone and adjacent formation. Finally, an alternating direction implicit difference method （ADI） is used to solve the temperature model for the downhole temperature distribution. The comparison of modeled temperature curve with actual temperature log indicates that simulation result is in general quite similar to the actual temperature log. We found that the total production rate, production time, porosity, thickness of pay zones, and geothermal gradient, all have effects on the downhole temperature distribution. 相似文献
18.
The numerical modeling of the impacts of urban buildings in mesoscale meteorological models has gradually improved in recent years. Correctly representing the latent heat flux from urban surfaces is a key issue in urban land-atmosphere coupling studies but is a common weakness in current urban canopy models. Using the surface energy balance data at a height of 140 m from a 325 m meteorological tower in Beijing, we conducted a 1-year continuous off-line simulation by using a coupled land surface model and a single-layer urban canopy model and found that this model has a relatively large systematic error for simulated latent heat flux. To improve the numerical method for modeling latent heat flux from urban surfaces, we combined observational analysis and urban land surface model to derive an oasis effect coefficient for urban green areas; to develop a temporal variation formula for water availability in urban impervious surfaces; and to specify a diurnal profile and the maximum values of anthropogenic latent heat release for four seasons. These results are directly incorporated into the urban land surface model to improve model performance. In addition, this method serves as a reference for studies in other urban areas. 相似文献
19.
This work investigates the spectral atmospheric transmittance due to aerosols in the urban environment of Athens during a period of one year. The spectral transmittance due to aerosols is derived using measurements of spectral direct-beam solar irradiance in the 310–575 nm spectral band. This derivation is accomplished by using a radiative transfer model for estimating the partial spectral atmospheric transmittance functions due to Rayleigh scattering, and absorption by ozone, nitrogen dioxide and water vapor. The seasonal and diurnal variation of the aerosol transmittance is investigated and the results are discussed with a view to air pollution sources, meteorological factors and topographic characteristics of the Athens basin. 相似文献
20.
Mesoscale processes that form due to changes in surface characteristics play a dominant role in the development of the planetary boundary layer structure and the formation of convection. In this study, effects of the Sandhills region of North and South Carolina on mesoscale processes are examined. Climatological analyses indicate increased convective precipitation in this location as compared to the surrounding region. This is believed to be due to enhanced convection induced by horizontal heat flux gradients caused by sharp changes in soil type and hence the heat capacity of the soil. Simulations using a non-hydrostatic mesoscale model (MM5 version 3.3) were made for a non-precipitation case with a 5-km resolution domain centered over the Carolinas from August 15, 2000 to August 18, 2000. The results showed the existence of a mesoscale circulation over the Sandhills region. Differential heating induced by contrasting soil types dividing the Coastal Plain from the central Piedmont causes this circulation. Sea-breeze circulation often combines with the Sandhills circulation to initiate convection in this region. Diurnal variations are handled well by the model indicating that the thermodynamic structure of the atmosphere is well simulated. 相似文献