大气物理过程方案对PM2.5预报的敏感性试验

利用WRF-Chem大气化学模式,选择2015年12月中旬发生在我国的大范围空气污染过程,在采用同样化学方案条件下,针对模式中不同物理过程及其参数化方案开展了地面PM_(2.5)预报的敏感性试验。结果表明:该模式能较好展示此次PM_(2.5)污染的演变过程,与实况也较接近,但对青海经宁夏至内蒙的PM_(2.5)高值区出现了漏报现象,这可能是模式外边界未对污染物做更新所致。对地面PM_(2.5)的预报,各物理过程的敏感度不同,边界层(含近地面层)过程的影响要明显大于积云对流及微物理过程的影响,不同的参数化方案会造成不同的预报误差。边界层过程QNSE和与其配套的近地面层方案的组合是预报的较佳组合;而TEMF和与其配套的组合以及ACM2和Pleim-X的组合则不佳。合理的物理过程参数化方案有助于提高PM_(2.5)预报质量。模式预报对排放源也有适应过程,其Spin-up时间较气象要素长。     

THE CHARACTERISTICS OF HIGH WIND DISTRIBUTION IN CHINA'S COASTAL REGION AND THEIR CAUSES

This work investigates the distribution of high winds above Beaufort scale 6 in the offshore zones of China using high-resolution satellite measurements.A numerical experiment is carried out in order to find out the effects of Taiwan Island on the formation of strong winds.The analysis indicates that the distribution of high wind occurrence is similar to that of the average wind velocity in winter.High winds tend to be anchored in special topographical regions,such as the Taiwan Strait,the Bashi Channel and the southeast coast of Vietnam.High winds occur much more frequently over the warmer than the colder flank of Kuroshio front as it meanders from Taiwan to Japan.The frequency of high winds decreases drastically in spring.The Taiwan Strait maintains the largest high wind occurrence.Besides,high winds remain frequent in the Bashi Channel,the southeast tip of Taiwan Island and the warmer flank of Kuroshio front.In summer,high winds generally occur infrequently except over a broad region off the southeast coast of Vietnam near 10°N and the frequency there decreases from southwest to northeast.High winds around Taiwan Island present near axisymmetric distribution with larger frequency along southeast-northwest direction and smaller frequency along southwest-northeast direction.The dominant direction of high winds exhibits a counterclockwise circulation surrounding the island.The frequency of high winds increases rapidly in autumn and almost repeats the distribution that appears in winter.The simulation results suggest that the effects of Taiwan Island topography on high winds vary with seasons.In winter,topography is the major cause of high winds in the surrounding oceanic zones.High winds in both Taiwan Strait and the southeast corner of the island disappear and the frequency decreases gradually from south to north when the terrain is removed.However,in summer,high wind frequency derived from two simulations with and without terrain is almost identical.We attribute this phenomenon to the factors which are responsible for the formation of high winds.     

青藏高原大地形对华南持续性暴雨影响的数值试验

利用新一代中尺度数值预报模式WRF3.2及NCEP/NCAR 逐日4次1°×1°的FNL再分析资料,通过有、无青藏高原以及将高原高度降低到临界高度的数值试验,研究了青藏高原大地形对我国华南地区2010 年5 月一次持续性暴雨过程的影响。试验结果表明:高原大地形对降水的影响显著,随着高原高度的升高,降水增多,高原以东地区的雨带也由北向南移动;高原地形的机械阻挡作用使迎风坡一侧的近地面层附近为强上升运动,背风坡为下沉运动,并分别对应降水的峰值和谷值区;高原对西风气流的爬流、绕流作用明显,高原升高后爬坡作用减弱,以绕流作用为主;高原的加热作用使气流过高原时南支减弱,北支加强,并加强了高原及其东部地区低层的正涡度和高层的负涡度,使高原上空为强烈的上升运动;高原的热力作用使西太平洋副热带高压位置偏南、偏西并稳定维持;高原大地形对形成稳定的高原季风环流圈有重要作用;高原地形高度的作用有利于定常波的形成,波动中心对应强上升运动,形成降水的大值区,稳定维持的定常波使得降水持续集中在同一地区,造成持续性暴雨。     

动力因子对地形影响下的四川暴雨落区的诊断分析

本文分析了2010年7月16～18日地形作用下四川盆地的一次持续性暴雨过程,指出此次暴雨过程是在高低层系统配置较好的情况下发生的。并以NCEP资料为初值场对此次暴雨过程进行了数值模拟,结合实况对模拟结果进行对比分析。分析表明:模式对本次四川暴雨过程的模拟较为成功,能很好地再现此次暴雨的降水落区以及强降水中心。运用广义湿位温、广义对流涡度矢量垂直分量的垂直积分和质量垂直螺旋度对受大巴山脉影响的四川东北部的暴雨落区进行了诊断分析。分析指出,广义湿位温纬向平均的垂直剖面图上,等湿位温线的倒Ω区域与四川东北部的强降水落区吻合较好,等湿位温线的倾斜程度以及湿位温异常的高度可以定性地指示降水的强弱;对广义湿位温从800 hPa到500 hPa垂直积分,用得到的湿位温的水平分布来指示东北部的暴雨落区效果较 好;用改进垂直积分区间后的广义对流涡度矢量垂直分量比用传统的对流涡度矢量垂直分量来示踪四川东北部的暴雨落区效果更好;质量垂直螺旋度能有效刻画出四川东北部地区强降水系统的典型动力场垂直结构,因此与四川东北部的地面强降水具有很好的对应关系。     

不同参数化方案对风预报效果影响个例研究

中尺度气象模式对风场的预报效果与参数化方案的适应性紧密相关.以内蒙古高原丘陵地形、江苏平缓的海陆交界地形2种典型下垫面试验风电场为模拟区域,分别用WRFV3.2 （Weather Research and Forecast Model）模式自带的6种物理过程参数化组合方案预报了2010年1月和7月两个风电场区域的风速和风向,对比分析了参数化组合方案差异对风场预报的影响.结果表明：①内蒙古试验区,边界层MRF方案描述的边界层结构较MYJ方案合理;微物理方案WSM3在夏季的风速预报能力优于WSM6,而冬季相反;复杂地形区域的风场预报需考虑陆面过程参数化方案,尤其是夏季降水发生后,陆面过程对于边界层结构的影响增大,选用Noah优于无陆面过程.②江苏试验区,边界层MRF方案描述的边界层结构较MYJ方案合理;1月陆面过程RUC方案优于陆面热量扩散和Noah;7月陆面热量扩散方案优于RUC和Noah.③风向预报6个方案的预报风向统计与实际记录风向统计有较好的一致性,风向概率分布相似,盛行风向一致且稳定.     

用前期海温预报四川夏季气温的EOF迭代方案

应用ＥＯＦ（经验正交函数）迭代方案，考虑多时次历史资料，在全球海区海温与四川盆地气温非同步联系的基础上，以海温为预报因子进行了夏季气温的长期预报。结果表明：西太平洋高温区等关键海区海温的异常对未来四川盆地夏季气温变化有重要影响，由此建立的引入多时次海温的ＥＯＦ迭代长期温度预报方法，具有较强的预报能力     

Evaluation of spatial variability in snow water equivalent for a high mountain catchment

Multivariate statistical analysis was used to explore relationships between catchment topography and spatial variability in snow accumulation and melt processes in a small headwater catchment in the Spanish Pyrenees. Manual surveys of snow depth and density provided information on the spatial distribution of snow water equivalent (SWE) and its depletion over the course of the 1997 and 1998 melt seasons. A number of indices expressing the topographic control on snow processes were extracted from a detailed digital elevation model of the catchment. Bivariate screening was used to assess the relative importance of these topographic indices in controlling snow accumulation at the start of the melt season, average melt rates and the timing of snow disappearance. This suggested that topographic controls on the redistribution of snow by wind are the most important influence on snow distribution at the start of the melt season. Furthermore, it appeared that spatial patterns of snow disappearance were largely determined by the distribution of snow water equivalent (SWE) at the start of the melt season, rather than by spatial variability in melt rates during the melt season. Binary regression tree models relating snow depth and disappearance date to terrain indices were then constructed. These explained 70–80% of the variance in the observed data. As well as providing insights into the influence of topography on snow processes, it is suggested that the techniques presented herein could be used in the parameterization of distributed snowmelt models, or in the design of efficient stratified snow surveys. Copyright © 2003 John Wiley & Sons, Ltd.     

劳动争议案件时效制度的法律思考

针对我国劳动争议案件处理的时效制度和仲裁前置程序的规定直接影响劳动争议的解决,提出取消仲裁前置程序,由当事人自愿选择仲裁或诉讼;或者,可以保留劳动争议仲裁的前置程序,但应将仲裁时效与诉讼时效严格区分。