Accounting for the Mesoscale Effects on the Air Pollution in Some Cases of Large Sulfur Pollution in Bulgaria or Northern Greece

The objective of the present work is to demonstrate the influence of the meso-scale dynamic phenomena on the larger scale air pollution characteristics. A limited set of episodes with very large sulphur pollution in Bulgaria or Northern Greece is chosen for the study. A 3D quasi-hydrostatic model of the meso-scale dynamics, based on the Businesque approximation (the formulation of Guthman) is used for the purpose. Some numerical experiments for the Balkan Peninsula are carried out under different background (synoptic) conditions. The simulated flow systems outline the main topography effects, typical for the region, such as slope winds, channelling of the air flows or blocking effects. Numerical simulations of the air pollution transport are also carried out, with and without accounting for the meso-scale deformations of the wind field. The comparison of the air pollution characteristics, obtained in both the cases demonstrates that the underlying surface heterogeneity in some of the synoptic situations may have influence not only on the detailed air pollution field in the region, but also on some larger scale pollution characteristics – the total pollution quantity in the air above the countries, the mean surface concentration, the pollution fluxes trough the country boundaries, dry and wet deposition.     

基于细观模拟的轻骨料混凝土破坏行为及尺寸效应研究∗

轻骨料混凝土由于其轻质高强及保温隔热性能好等优点,越来越多被应用于实际工程结构。从细观角度出发,将混凝土材料看作由骨料颗粒、砂浆基质及界面过渡区组成的三相复合材料,建立了考虑混凝土材料非均质性影响的二维细观数值分析模型,模拟研究了轻骨料混凝土与普通混凝土压缩和劈拉破坏行为及尺寸效应的异同,并揭示两者破坏机理。结果表明:轻骨料混凝土压缩及劈拉破坏均造成骨料颗粒的断裂,而普通混凝土破坏时骨料很少破坏;轻骨料混凝土由于脆性较强,与普通混凝土相比有更加明显的压缩强度尺寸效应现象;轻骨料混凝土与普通混凝土存在相似的劈拉强度尺寸效应现象。     

陕西暴雨若干特征的综合分析

以1970年以来发生在陕西的暴雨、大暴雨为研究对象,使用高空及地面探测资料、卫星云图等监测信息,采用天气学分析、动力学诊断、数值模拟等方法,对陕西持续性暴雨、暴雨的高空和地面中尺度系统、暴雨中尺度对流系统(MCS)、近海台风对陕西暴雨的影响等多方面的特征进行了总结分析.加深了对青藏高原东部暴雨实例和理论的进一步认识和理...     

Investigating the Surface Energy Balance in Urban Areas – Recent Advances and Future Needs

Recent advances in understanding of the surface energy balance of urban areas, based on both experimental investigations andnumerical models, are reviewed. Particular attention is directedto the outcome of a COST-715 Expert Meeting held in April 2000,as well as experiments initiated by that action. In addition, recentcomplete parameterisations of urban effects in meso-scalemodels are reviewed. Given that neither the surface energybalance, nor its components, normally are directly measuredat meteorological stations, nor are there guidelines for theset-up of representative meteorological stations in urbanareas, this paper also provides recommendations to closethese gaps.     

北京城区"7.10"灾害性强降水分析

对2004年7月10日发生在北京城区的灾害性强降水过程进行了分析.结果发现,造成本次城区暴雨的天气系统为一中β尺度对流云团,它生成于河北西北部的偏南暖湿气流中,在移到北京城区发展并停留的1～2h内,造成了本次强降水过程.大尺度背景场分析表明,暴雨发生前北京即处于有利降水的形势场中,地面中尺度辐合线可能是强对流的触发系统.此外还初步分析了城市环境对强降水的增幅作用.     

杭州湾地区核电厂大气中尺度扩散特征研究

采用拉格朗日随机粒子扩散模式和当地实际气象资料,模拟以秦山核电厂为排放源的大气污染物在杭州湾地区的中尺度扩散情况.对代表性年份(1996)各季中月整4个月模拟结果的分析表明,各季平均扩散输送特征受季节变化和当地海陆地形分布的影响明显.春夏季(4,7月)以溯杭州湾往偏西和偏北内陆方向的输送为主,冬秋季(1,10月)主要为向杭州湾南岸及外海诸方向的输送.区域平均扩散能力以春季(4月)为强,秋季(10月)较弱.污染物扩散输送出模拟区域的平均时间春季略小于15h,秋季约24h,冬夏季约20h.     

福建惠安沿海中尺度大气流动和扩散特征研究

采用拉格朗日随机粒子扩散模式和三维风场诊断模式以及实际气象观测资料,模拟分析了福建惠安核电厂所在沿海地区的大气流动和气载污染物的中尺度扩散情况。结果表明:①该区域低层大气的流动决定于各季盛行风背景、天气系统和局地海陆-山谷风环流系统的共同作用。②冬、春、秋季区域中尺度扩散总体沿西南海岸或偏西内陆方向,夏季总体沿东北海岸线方向进行。局地中尺度环流带来的向岸流和离岸流对具体扩散形态有重要影响。③污染物扩散输送出模拟区域的平均去除时间约为18～21h。污染物在200km×200km模拟区域内滞留24h以上的情况在各季分别可占1 4～1 3。