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91.
More Americans now reside in Canada than at any time since the Vietnam War. Of particular note is the surprisingly large population of immigrants from the United States who now reside in Montreal—Francophone Canada's largest and most diverse city. This article documents and analyzes the migration experiences, spatial patterns, and “sense of belonging” of Americans in Montreal during the post–Vietnam era framed within the larger political and linguistic context of the city's “Two Solitudes.” Findings are based on information compiled from archival materials, census records, structured and unstructured interviews, survey questionnaires, participant observation, and fieldwork. My overarching goal is to embed the experiences and patterns of this English‐speaking group of immigrants in predominately French‐speaking Montreal during the past five decades—one of the most dramatic and divisive periods of time in Montreal and in Quebec as a whole.  相似文献   
92.
European Union expansion over the last decade has generated many studies, surpassed in number only by governmental comment and media headlines following this general theme. Issues and knowledge explored and expressed have been many, one being a hard to evidence crime-migration nexus leading to constructive empirical studies focussing on the accession to the EU of predominantly East European nations and ensuing migratory patterns. Appertaining to this study is geographic focus on crime committed by inter-EU migrants in England, resulting from holistic research of a contemporary EU statute concerning inter-state sharing of bio-informatics, seeking contextual knowledge to the benefit of policy makers. The geography of inter-EU crime in England identifies spatial dispersion and regional areas of activity on a meso scale. The activity of individual nationalities is examined in a spatial manner displaying distinct differences in movements on a regional (meso) scale. Results improve on current knowledge of the criminality of inter-EU migrants but also identify and call for further research in a conceptual development as localised criminal activity draws an international investigatory perspective.  相似文献   
93.
Precipitation samples were collected by filtrating bulk sampler in Kitakyushu City, Japan, from January 1988 to December 1990. Volume weighted annual mean of pH was 4.93, but the pH distribution indicated that most probable value lay in the range pH 6.0–6.4. Volume weighted annual mean concentrations of major ionic components were as follows; SO 4 2– : 84.2, NO 3 : 28.1, Cl: 86.3, NH 4 + : 45.5, Ca2+: 63.3, Mg2+: 27.0, K+: 3.4, Na+: 69.0 µ eq l–1. The highest concentrations of these ionic components were observed in winter and the lowest occurred in the rainy season. The ratio of ex-SO 4 2– /NO 3 exhibited the lowest ratio in summer, and the highest ratio in winter. Good correlations were obtained between Cl and Na+, ex-SO 4 2+ and ex-Ca2+, NO 3 and ex-Ca2+, and NH 4 + and ex-SO 4 2– , respectively. However, no correlation between Cl and Na+ with Ca2+ was observed. The relationship of H+ with (ex-SO 4 2– + NO 3 ) - (ex-Ca2+ + NH 4 + ) indicated positive correlation.  相似文献   
94.
The four-dimensional empirical orthogonal function (4D-EOF), which in reality is a simple combination of three-dimensional EOF (3D-EOF) and extended EOF (EEOF), is put forward in this paper to test the ability of numerical model to simulate climate and its change. The 4D-E0F analysis is able to reveal not only the horizontal characteristic pattern of analyzed variable, and its corresponding annual and inter-annual variations, but also the vertical structural characteristics. The method suggested is then used to analyze the monthly mean 100-, 500-, 70G-, and 1000-hPa geopotential height fields (4941 grids and grid spacing 60 km) and their anomaly fields in 1989-1998 simulated by the MM5V3 from the RMIP (Regional Climate Model Inter-comparison Project for East Asia)-II, as well as their counterparts (used as the observed fields) from the NCEP/NCAR re-analysis dataset in the same period. The ability of MM5V3 in simulating East Asian climate and its change is tested by comparing the 4D-EOF analysis results of the simulated and observed datasets. The comparative analyzed results show that the horizontal pattern of the first eigenvector of the observed monthly mean geopotential height fields and its vertical equivalent barotropic feature were well simulated; the simulations of the first two eigenvectors of the observed monthly mean geopotential height anomaly fields were also successful for their horizontal abnormal distributions and significant equivalent barotropic features in the vertical were well reproduced; and furthermore, the observed characteristics, such as the variation with height, the annual and inter-annual variations of the monthly mean geopotential height/anomaly fields were also well reflected in the simulation. Therefore, the 4D-EOF is able to comprehensively test numerical model's ability of simulating the climate and its change, and the simulation ability of MM5V3 for the climate and its change in East Asia in the 1990s was satisfactory.  相似文献   
95.
多普勒雷达资料4DVAR同化反演的模拟研究   总被引:21,自引:5,他引:21  
利用Sun等建立的同化模式和四维变分同化方法对多普勒雷达资料反演大气风场、热力场和微物理场进行了模拟试验研究.反演的基本思路是将4DVAR同化方法应用到三维云模式,定义价值函数表征雷达资料与模式预报结果之间的差别,通过极小化价值函数得到反演场,价值函数相对模式控制变量的梯度由伴随模式求取.试验结果表明,4DVAR同化技术能够从单(双)多普勒雷达资料反演大气三维风场、热力场和微物理场.各个变量反演精度高低与同化过程中变量受约束的大小程度呈正相关.速度场和雨水场反演精度较高,温度场、云水和水汽的反演精度次之,温度场的准确反演需要较长的同化时间.价值函数中加入背景场,哪怕是单点探空给出的平均场信息也有利于提高反演精度.在采用单部多普勒雷达资料进行反演时,速度场的反演误差较大.反演区相对雷达站的位置变化对速度场反演结果有一定的影响,而对其他变量的反演影响很小.两个时次的雷达观测资料基本足够提供反演所需的时间演变信息,同化更多时次的雷达资料,反演效果改进很小.雷达观测资料的缺值会显著降低同化效果,甚至可能导致同化失败,引入背景场可以改善这一状况.4DVAR同化技术对于雷达观测资料误差不太敏感.利用双多普勒雷达合成风场提供水平风场边界条件是比较准确可靠的.在反演主体离边界较远时,VAD风场也基本可用作水平风场边界条件.微物理场的反演对模式中的微物理参数化方案较敏感.  相似文献   
96.
中国南京与美国德克萨斯稻田甲烷排放的比较   总被引:8,自引:0,他引:8  
Field measurements of methane emission from rice paddies were made in Nanjing, China and in Texas, USA, respectively. Soil temperature at approximately 10 cm depth of the flooded soils was automatically recorded. Aboveground biomass of rice crop was measured approximately every 10 days in Nanjing and every other week in Texas. Seasonal variation of soil temperature in Nanjing was quite wide with a magnitude of 15.3℃ and that in Texas was narrow with a magnitude of 2.9℃. Analysis of methane emission fluxes against soil temperature and rice biomass production demonstrated that the seasonal course of methane emission in Nanjing was mostly attributed to soil temperature changes, while that in Texas was mainly related to rice biomass production. We concluded that under the permanent flooding condition, the seasonal trend of methane emission would be determined by the soil temperature where there was a wide variation of soil temperature, and the seasonal trend would be mainly determined by rice biomass production if there are no additional organic matter inputs and the variation of soil temperature over the rice growing season is small.  相似文献   
97.
CCSM4模式对东北气温和降水的模拟及预估   总被引:1,自引:0,他引:1  
利用东北地区162个气象观测站逐月气温和降水资料对CCSM4模式的模拟性能进行了评价,并预估了2021—2050年东北地区的气候变化情景。结果表明:CCSM4模式长期历史气候模拟实验模拟的1961—2005年月平均气温、降水量值能较好地再现东北区域年平均气温、降水量的空间分布形态,但气温模拟值比观测偏低,91. 4%站点误差在1. 5℃以内;降水中心比观测略偏北,全区平均偏多35. 18 mm。2021—2050年东北区域年平均气温呈增温趋势,高纬度地区的增温幅度明显大于低纬度地区,与基准年相比,RCP2. 6、RCP4. 5和RCP8. 5情景下全区分别偏高6. 00℃、5. 86℃和6. 42℃。年降水量分布呈东南向西北递减的形态,降水大值中心出现在东南部吉林与辽宁交界处,RCP2. 6、RCP4. 5和RCP8. 5情景下全区分别偏多15. 2%、3. 1%和2. 0%。  相似文献   
98.
针对青藏高原地区雷电短临预报缺乏雷达资料的问题,采用FY-4A卫星多通道数据、欧洲中心第5代再分析资料(ERA5)中的对流指数、闪电定位仪资料等多源监测数据,根据雷电的发生、发展机理,提出了18个关键预报因子,利用随机森林算法建立了适用于西藏山南地区的雷电短临预报模型。统计分析各预报因子在有无雷电天气样本中的概率密度分布与随机森林模型得到的特征重要度指标,结果表明提出的预报因子物理意义明确,建立的模型可信度较高。利用随机森林算法分别对未来10 min、20 min、30 min建立雷电预报模型,并与光流外推预报方法进行对比检验,结果表明:随机森林模型预报效果命中率(POD)、临界成功指数(CSI)均高于光流法,空报率(FAR)也相对较低;未来20 min的随机森林预报模型CSI评分最高,整体预报效果最佳。  相似文献   
99.
The output of 25 models used in the Coupled Model Intercomparison Project phase 3 (CMIP3) were evaluated, with a focus on summer precipitation in eastern China for the last 40 years of the 20th century. Most models failed to reproduce rainfall associated with the East Asian summer monsoon (EASM), and hence the seasonal cycle in eastern China, but provided reasonable results in Southwest (SW) and Northeast China (NE). The simulations produced reasonable results for the Yangtze-Huai (YH) Basin area, although the Meiyu phenomenon was underestimated in general. One typical regional phenomenon, a seasonal northward shift in the rain belt from early to late summer, was completely missed by most models. The long-term climate trends in rainfall over eastern China were largely underestimated, and the observed geographical pattern of rainfall changes was not reproduced by most models. Precipitation extremes were evaluated via parameters of fitted GEV (Generalized Ex- treme Values) distributions. The annual extremes were grossly underestimated in the monsoon-dominated YH and SW regions, but reasonable values were calculated for the North China (NC) and NE regions. These results suggest a general failure to capture the dynamics of the EASM in current coupled climate models. Nonetheless, models with higher resolution tend to reproduce larger decadal trends and annual extremes of precipitation in the regions studied.  相似文献   
100.
文章提出了一个四维经验正交函数(4D-EOF)方法,原理是三维经验正交函数(3D-EOF)与扩展经验正交函数(EEOF)简单的组合,此方法不仅提供空间水平分布特征场及其对应的月际变化特征和年际变化特征,而且还提供空间垂直结构特征.利用这个新方法分析东亚季风国际区域模式比较计划(RMIP)MM5V3模拟的1989-1998年10 a积分结果--包括中国大部分区域(4941个格点,格距60 km)月平均100,500,700,1000 hPa 4个位势高度场(模拟场)及其距平场;同时分析对应的NCAR/NCEP再分析资料(观测场),进而对比两者检验模式模拟东亚季风气候及其变化能力.对比分析结果表明:对于月平均高度场的第一特征向量场,模式能比较准确地模拟出平均气候场的分布及其垂直相当正压性的结构特征;对于月平均高度距平场第一、二特征向量场,模式对于距平场的模拟也较成功,垂直方向有明显的相当正压性特征;月平均高度场及其距平场相应的月际变化和年际变化特征也在模拟中得到较好的反映.本研究表明:4D-EOF具有综合检验数值模式模拟气候及其变化的能力,而MM5V3模拟20世纪90年代东亚气候及其变化能力是令人满意的.  相似文献   
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