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991.
CSAMT法对低阻薄层结构分辨能力的探讨 总被引:8,自引:0,他引:8
用一维有限元法实现可控源音频大地电磁(CSAMT)法的数值模拟技术,分别计算了TM 和TE两种模式下,电性层厚固定、中间低阻薄层电阻率发生变化时的频率-电阻率曲线;以及电性参数确定、但中间低阻薄层结构的厚度发生变化的一系列频率-电阻率曲线;当顶层厚度发生变化时,获得一系列的频率,电阻率曲线。分析了各曲线的特征,归纳了CSAMT法对薄层结构的分辨能力,为正确认识薄层结构的CSAMT频率电阻率响应提供很好的帮助。 相似文献
992.
该文从f平面线性无粘的二维Boussinesq方程组出发, 通过求取函数的极小值, 提出了从实测风场资料中提取基本气流的方案。用该方案提取的基本气流既满足控制方程, 同时又与实测风场之差其模的平方在垂直方向取平均后达到最小; 将实测风场与该基本气流相减, 可提取出扰动风场, 从而能研究基流的失稳问题和扰动场随时间的演变。该文还给出了该方案实际操作的数值计算方法, 并对实际个例进行了计算和分析, 实践表明用该方案提取基本气流是切实可行的。 相似文献
993.
The objective of the present study was to better understand the impacts of the additional sources of nitrous acid (HONO) on visibility, which is an aspect not considered in current air quality models. Simulations of HONO contributions to visibility over the North China Plain (NCP) during August 2007 using the fully coupled Weather Research and Forecasting/Chemistry (WRF/Chem) model were performed, including three additional HONO sources: (1) the reaction of photo-excited nitrogen dioxide (NO~) with water vapor; (2) the NO2 heterogeneous reaction on aerosol surfaces; and (3) HONO emissions. The model generally reproduced the spatial patterns and diurnal variations of visibility over the NCP well. When the additional HONO sources were included in the simulations, the visibility was occasionally decreased by 20%-30% (3-4 km) in local urban areas of the NCP. Monthly-mean concentrations of NO3, NH+, SO]- and PM2.5 were increased by 20%-52% (3-11μg m-3), 10%-38%, 6%-10%, and 6%-11% (9-17 μg m-3), respectively; and in urban areas, monthly-mean accumulation- mode number concentrations (AMNC) and surface concentrations of aerosols were enhanced by 15%-20% and 10%-20%, respectively. Overall, the results suggest that increases in concentrations of PM2.5, its hydrophilic components, and AMNC, are key factors for visibility degradation. A proposed conceptual model for the impacts of additional HONO sources on visibility also suggests that visibility estimation should consider the heterogeneous reaction on aerosol surfaces and the enhanced atmospheric oxidation capacity due to additional HONO sources, especially in areas with high mass concentrations of NOx and aerosols. 相似文献
994.
分析洪峰、洪量和历时三变量联合分布与风险概率及其设计分位数,为水利工程规划设计和风险评估提供参考依据。以珠江流域西江高要站52年洪水数据为例,采用非对称阿基米德M6 Copula函数与Kendall分布函数计算三变量洪水联合分布的“或”重现期、“且”重现期和二次重现期及其最可能的设计分位数。结果表明:“或”重现期的风险率偏高,“且”重现期的风险率偏低,二次重现期更准确地反映了特定设计频率情况下三变量洪水要素遭遇的风险率;按三变量“或”重现期或三变量同频率设计值推算的洪水设计值偏高,以最大可能概率推算的三变量洪水要素的二次重现期设计值可为防洪工程安全与风险管理提供新的选择。 相似文献
995.
The urban environment affects human behavior and health. Most studies on the feelings of street spaces have not considered a specific kind of realistic scene, such as running. To overcome this limitation, we explored the relationship between the urban environment and the pleasure of running. We collected 8260 street view images from 153 running routes in Beijing and invited more than 400 volunteers of different genders and ages to rate their sense of pleasure in street view images of the urban running environment through an online survey. Then, the proportion of visual elements in street images was extracted based on semantic segmentation, and the landscape was divided. Finally, a linear mixed model was used to predict the pleasure scores of different gender and age groups for different landscapes. The results show significant differences in the pleasure scores for different landscapes and age groups. Middle-aged people's sense of pleasure was lower than that of the young and the elderly. More greenery was associated with a higher pleasure score, while the proportion of urban elements such as buildings was negatively correlated with the pleasure score. The results indicate that running in a natural landscape is pleasurable and beneficial for mental health. 相似文献
996.
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998.
Jong-Seong Kug Soon-Il An Yoo-Geun Ham In-Sik Kang 《Theoretical and Applied Climatology》2010,100(3-4):275-282
The change in the teleconnections of both El Niño and La Niña over the North Pacific and American regions due to a future greenhouse warming has been analyzed herein by means of diagnostics of the Intergovernmental Panel on Climate Change-Fourth Assessment Report (IPCC-AR4) coupled general circulation models (CGCMs). Among the IPCC-AR4 CGCM simulations, the composites of the eight-member multimodel ensemble are analyzed. In most CGCMs, the tropical Pacific warming due to the increase of CO2 concentration in the atmosphere promotes the main convection centers in the equatorial Pacific associated with both El Niño and La Niña to the east. The eastward shift of the convection center causes a systematic eastward shift of not only El Niño but also La Niña teleconnection patterns over the North Pacific and America, which is demonstrated in the composite maps of 500 hPa circulation, surface temperature, and the precipitation against El Niño and La Niña, as observed in a comparison between the pre-industrial and CO2 doubling experiments. Thus, a systematic eastward migration of convection centers in the tropical Pacific associated with both El Niño and La Niña due to a future global warming commonly causes the eastward shift of the atmospheric teleconnection patterns over the Northern Hemisphere. 相似文献
999.
江西省区域性平流雾气象要素特征分析及预报思路 总被引:1,自引:3,他引:1
利用江西省2000—2012年常规地面观测资料及探空资料,采用合成和统计方法,分析了54次区域性平流雾的天气形势及气象要素,得到了平流雾逆温层、温湿条件、低层风场及影响系统等统计特征。结果表明:(1)江西省区域性平流雾主要发生于2—3月,北部多于南部。(2)其形势特征为:江南地区低层有较明显的暖湿平流。850 hPa上的切变线或辐合区位于长江流域到江淮一带,925和850 hPa西南风速分别达3~8和7~15 m·s~(-1)。地面形势多为弱低压倒槽和锋面前部的低压,其次为高压底部。(3)850 hPa以下低层有相对湿度≥80%的湿层,500 hPa中层多数有相对湿度≤50%的干层。地面气温和露点多在10~16℃,且达到近饱和。(4)平流雾的逆温结构以单层逆温为主,多数比辐射雾逆温层高、厚度大。逆温强度主要在1~3℃。最后给出了江西平流雾(我国南方)的预报着眼点或预报思路。 相似文献
1000.