The role of periodic boundary forcing in plankton pattern formation

We consider one and two-dimensional minimal models in plankton dynamics. The influence of oscillating boundary forcing functions as agents for triggering pattern formation is discussed. In particular it is found that in these conditions population waves arise for one dimensional models, while for two dimensional models, different amplitudes and frequencies in the boundary forcing generate definite patterns, mimicking the boundary term. This happens even though the model we investigate is very simple. The emergence of these features is an interesting metaphor for the fundamental biological problem of how pattern formation processes may be inevitable in natural heterogeneous ecosystems.     

大气污染排放窗口机制研究

以2种典型的污染排放源(点污染源和线污染源)为基础,提出排污窗口的概念,通过参数转换分解源强对污染扩散进行研究。首先在高斯污染扩散模型的基础上,对非持续性污染源强建模,然后以某烟囱的周期性排污分析,检验排污窗口设置的合理性。对于单双号限行的窗口性质的污染排放研究中,首先对交通流建立线污染扩散模型,然后融合元胞自动机(9元胞互影响)模拟区域多角度污染的扩散平衡,最后对"单双号限行"下北京市不同区域空气质量指标进行分析与仿真。分析结果表明,合理的排污窗口能够减轻污染程度及对人们日常生活的影响。     

武汉市一次污染过程的局地流场和边界层结构的数值模拟

利用2013年11月武汉市逐日空气质量资料、地面气象观测资料、NCEP/NCAR再分析资料和L波段雷达探空资料,通过WRF模式模拟空气污染生消过程中的局地气象条件变化,探讨特殊地形条件下边界层结构变化和局地环流在污染物生消过程中的作用和影响。结果表明：（1）武汉地区当背景环流场强的时候,由地形引起的局地流场对污染物扩散的影响就弱,反之当背景环流场弱的时候, 地形对流场影响明显:夜间为山风,白天为谷风。夜间山风与偏西北气流及偏东气流在武汉及周边地区辐合,形成气流汇聚带,在武汉地区形成一个反复污染带,即由地形引起的局地流场对污染物扩散的贡献就大;（2）武汉地区发生空气污染时,地面湿度较高,边界层呈上干下湿状态,其特征为暖而干且有偏东小风,这导致污染物不断堆积和重污染过程的形成。     

黄河中上游能源化工区大气污染跨界环境影响分析

对黄河中上游能源化工区近地面和边界层顶气象流场及该区域大气污染长距离输送产生的跨界环境影响趋势特征进行了分析。结果表明,该区域近地面和边界层顶的流场总体上为西北向东南流动,大气污染物长距离输送可能影响的区域主要为华中地区;区域冷空气的活动对其大气污染物的清除起重要作用;通过CALPUFF模型的模拟结果表明,该区域SO2的影响程度和范围明显大于NO2,在区域内部存在污染物浓度较高的区域,但未对区外造成显著跨界环境影响。     

Hydraulic fracturing as an interpretive policy problem: lessons on energy controversies in Europe and the U.S.A.

This special issue addresses hydraulic fracturing for shale gas extraction as an interpretive policy problem. Bringing together empirical cases from the U.S.A., the Netherlands, the U.K., Poland, and Germany, we identify three approaches to the interpretation of hydraulic fracturing in the article: understanding its meaning, contextual explanation of the institutionalization of its meaning, and policy design as intervention to alter its meaning. By exploring differences and similarities across these cases, we identified two central tensions in the meaning of shale gas in all cases: (1) economic opportunity or environmental threat and (2) transition toward a more carbon-free energy future or perpetuation of a fossil fuel system. We found that when actors shift the meaning of hydraulic fracturing to consider it predominantly an issue of threat, this explains the dominance of risk governance as an approach to managing the controversy. Alternately, when the meaning of fracking shifts from consideration as an economic opportunity or a bridge fuel to consideration of it as a barrier to an energy transition, this explains the decision to ban fracking. Therefore, a comparative assessment of the papers demonstrates the ways interpretive dimensions of politics can influence the governance of public policy.     

东北玉米低温冷害时空分布与多时间尺度变化规律分析

利用东北地区48个农业气象观测站1961-2010年逐日温度资料和近20多年玉米生育期资料,基于热量指数构建生育阶段冷害指数,采用EOF分析、Mann-Kendall法、子波变换等方法系统分析了近50年东北玉米4个生育阶段低温冷害时空分布及周期特征。结果表明:整个生育期全区平均冷害强度呈极显著的减弱趋势,地区间冷害变化趋势呈现差异化特征,冷害强度减弱趋势由西南向东北方向呈阶梯状递增;4个生育阶段冷害指数EOF第一模态均呈冷害空间变化趋势一致的特征;冷害强度呈较明显的减弱趋势,第1到第4生育阶段减弱趋势逐渐增大,突变均发生在1990年代中期;冷害强度具有较强的周期性,出苗—七叶、出苗—抽雄存在明显的23、25年周期,出苗—乳熟、出苗—成熟均具有较明显的3年周期振荡。     

激发剂作用下的盐石膏废渣的水化过程

运用Kondo模型,研究了在激发剂硫酸钠作用下盐石膏废渣的水化过程.盐石膏废渣的水化过程分为3个阶段,第1、第3阶段受扩散作用控制;第2阶段受相边界反应控制.分别研究了激发剂溶液浓度和温度对相边界反应阶段水化速率的影响,结果表明,在0—0.60 mol.L-1范围内,增大激发剂溶液浓度可使水化速率常数k增大,在12℃≤...     

太阳活动与四川盆地气候资源波动

本文应用四川省气象局提供的气候资料,借助于电子计算机,统计分析了太阳黑子位相与四川盆地热量资源、降水资源波动的关系;采用文献[2]的公式,计算了太阳黑子相对数年均值与热量、降水资源的同期及延后相关系数,并进行了周期分析,进而分析其演变趋势及其对农业生产的影响和应采取的对策。     

Potential and Shortcomings of Numerical Weather Prediction Models in Providing Meteorological Data for Urban Air Pollution Forecasting

The last decade progress in numericalweather prediction (NWP) modelling and studies of urbanatmospheric processes for providing meteorological data forurban air pollution forecasting is analysed on examples ofseveral European meteorological centres. Modern nested NWP models are utilising land-use databasesdown to 1 km resolution or finer, and are approaching thenecessary horizontal and vertical resolution suitable forcity scale. The recent scientific developments in the fieldof urban atmospheric physics and the growing availabilityof high-resolution urban surface characteristics datapromise further improvements of the capability of NWPmodels for this aim. A strategy to improve NWP data forthe urban air pollution forecasting is suggested.