南京冬季浓雾的演变特征及爆发性增强研究   总被引：5，自引：2，他引：3  

刘霖蔚  牛生杰  刘端阳  陆春松 《南京气象学院学报》2012,35(1):103-112

2007年12月18—19日,南京地区出现了一次持续20h的浓雾过程,其中能见度低于50m的强浓雾几乎占到整个雾过程的1／3。利用同期在南京市北郊的外场观测数据,结合NCEP再分析资料,分析了该次雾的演变过程、微物理结构及边界层特征,探讨了地面雾爆发性增强的成因。结果表明：本次雾在西南平流的增湿作用下触发生成;日出后,平流输送和地表蒸发提供了充足水汽来源,贴地层逆温因高空下沉增温而向上抬升且稳定存在,因此大雾得以维持;整个雾过程中雾滴数浓度、平均直径、含水量随时间的变化趋势基本一致,平均谱曲线均呈指数下降分布,雾滴集中在小滴端;两次地面雾爆发性增强均发生在夜间,其特征为各微物理参量明显增大,滴谱上抬拓宽;爆发性增强的原因是地表气温陡降、贴地层逆温增强及可充当雾滴凝结核的气溶胶大粒子数增多。  相似文献   

A Numerical Study of the Urban Intensity Effect on Fog Evolution in the Beijing-Tianjin-Hebei Region   总被引：2，自引：0，他引：2       下载免费PDF全文

LIANG Zhao-Ming  GAO Shou-Ting  SUN Ji-Song 《大气和海洋科学快报》2012,5(3):240-245

The influence of urban intensity on fog evolution in the Beijing-Tianjin-Hebei (BTH) region (China) is investigated numerically with the the Weather Research and Forecasting (WRF) model coupled with the urban canopy parameterization-building energy model (UCP- BEM) urban physics scheme. The experiments were designed with a focus on the influence of different urban intensities, which are represented by a different fractional coverage of natural land, buildings, and energy consumption inside buildings in an urban environment. The results of this study indicate that urban areas notably influence fog evolution when natural land is reduced to a small fraction (e.g., less than 10%). Developed land changes fog evolution through urban effects. Higher urban intensity (HUI) generally results in warmer temperatures and lower wind speeds throughout the day, while inhibiting morning specific humidity loss and afternoon specific humidity gain because of the HUI effect on surface heat flux, surface roughness, and surface moisture flux. HUI leads to later and weaker liquid water content formation, with a higher liquid water content base, primarily due to its effect on near surface temperatures. This finding implies that HUI may inhibit the conditions for fog formation. In addition, urban areas with equal natural and developed land coverage seem to greatly enhance the upward surface moisture flux, which is attributed to the combination of a relatively large potential evaporation on developed land and an ample moisture supply from natural land. As a result, the specific humidity increases in the afternoon.  相似文献   

Fog Detection over China’s Adjacent Sea Area by using the MTSAT Geostationary Satellite Data   总被引：1，自引：0，他引：1       下载免费PDF全文

LI Jun  HAN Zhi-Gang  CHEN Hong-Bin  ZHAO Zeng-Liang  WU Hong-Yi 《大气和海洋科学快报》2012,5(2):128-133

A fog threshold method for the detection of sea fog from Multi-function Transport Satellite (MTSAT1R) infrared (IR) channel data is presented.This method uses principle component analysis (PCA),texture analysis,and threshold detection to extract sea fog information.A heavy sea fog episode that occurred over China’s adjacent sea area during 7 8 April 2008 was detected,indicating that the fog threshold method can effectively detect sea fog areas nearly 24 hours a day.MTSAT-1R data from March 2006,June 2007,and April 2008 were processed using the fog threshold method,and sea fog coverage information was compared with the meteorological observation report data from ships.The hit rate,miss rate,and false alarm rate of sea fog detection were 66.1%,27.3%,and 33.9%,respectively.The results show that the fog threshold method can detect the formation,evolution,and dissipation of sea fog events over period of time and that the method has superior temporal and spatial resolution relative to conventional ship observations.In addition,through MTSAT-1R data processing and a statistical analysis of sea fog coverage information for the period from 2006 to 2009,the monthly mean sea fog day frequency,spatial distribution and seasonal variation characteristics of sea fog over China’s adjacent sea area were obtained.  相似文献   

北京市持续重污染天气分析   总被引：7，自引：0，他引：7  

李国翠  范引琪  岳艳霞  张玉凤 《气象科技》2009,37(6):656-659

通过对2004-2008年北京市空气持续重污染过程的统计及其对非沙尘型持续重污染天气形势的特征分析,得到以下结论：持续重污染过程具有明显的季节分布特征,主要包括春季沙尘型污染和秋冬季节非沙尘型污染;非沙尘型持续重污染过程期间多对应着大雾、轻雾、霾、烟等低能见度天气,过程后期对应的天气现象多为大风或降水天气。其中大雾天气更易引发长时间持续的空气重污染事件。非沙尘型持续重污染的天气形势特点为：高空多为纬向环流,850 hPa多为暖脊控制,地面多处于弱气压场,鞍形场型污染尤为严重。北京持续重污染多对应区域性污染。  相似文献   

RESEARCH ON AUTOMATIC FOG IDENTIFICATION TECHNOLOGY BY METEOROLOGICAL SATELLITE REMOTE SENSING     

周红妹  葛伟强  柏桦  刘冬韡  杨引明 《热带气象学报(英文版)》2009,15(1):28-37

There is an urgent need for the development of a method that can undertake rapid, effective, and accurate monitoring and identification of fog by satellite remote sensing, since heavy fog can cause enormous disasters to China’s national economy and people's lives and property in the urban and coastal areas. In this paper, the correlative relationship between the reflectivity of land surface and clouds in different time phases is found, based on the analysis of the radiative and satellite-based spectral characteristics of fog. Through calculation and analyses of the relative variability of the reflectivity in the images, the threshold to identify quasi-fog areas is generated automatically. Furthermore, using the technique of quick image run-length encoding, and in combination with such practical methods as analyzing texture and shape fractures, smoothness, and template characteristics, the automatic identification of fog and fog-cloud separation using meteorological satellite remote sensing images are studied, with good results in application.  相似文献   

北京地区一次辐射雾的数值模拟   总被引：6，自引：2，他引：4  

何晖  金华  刘建忠  张天明  高燕虎 《气候与环境研究》2009,14(4):390-398

利用非静力中尺度模式MM5V3对2006年11月20日北京地区的一次大雾天气过程进行了数值研究。模拟结果与极轨卫星监测图像以及十二通道微波辐射计观测资料的对比表明,模式对此次雾的模拟是比较成功的,尤其是在雾区的分布位置、雾的高度以及雾的维持时间等方面。针对不同的云物理方案、长波辐射项、短波辐射项以及模式的垂直分辨率进行了4组敏感性实验。结果表明,地面的长波辐射冷却促使辐射雾的形成,而短波辐射的加热是辐射雾消散的主要原因。另外,增加模式的垂直分辨率以及选取更加详细的云微物理方案可以使模式模拟的辐射雾的结果有明显的改善。  相似文献   

2050年前中国雾日变化趋势的预估          下载免费PDF全文

刘赫男  罗勇 《气候变化研究进展》2009,5(5):266-270

 利用1971-2005年中国591个气象台站的雾日资料以及逐日最低气温、相对湿度、平均风速资料,分析了35 a来中国各区域年雾日数与这些因子的相关关系,并利用IPCC第四次评估报告所提供的模式数据资料,针对3种不同的排放情景,对21世纪上半叶各区域年平均雾日进行预估。结果表明：对划分的9个雾区的年雾日数的回归方程的拟合效果较好,可以用来进行预估;未来50 a中国大部分地区雾日呈明显减少的变化趋势,在A1B,A2和B1情景下,雾日减少的平均幅度分别为16.2%,13.4%和12.9%。未来50 a中国雾日预估结果的空间分布显示：3种情景下未来中国大部分雾区雾日数都将减少,个别地区雾日数有增加趋势,其中A1B情景下雾日减少区的减少趋势最明显,而B1情景下雾日增加区的增加趋势最明显。  相似文献   

一次广东省大雾过程的数值模拟分析   总被引：1，自引：0，他引：1  

樊琦  王东海  黄聪敏  范绍佳  王安宇  冯瑞权 《热带气象学报》2009,25(5):589-595

利用美国国家大气研究中心（NCAR）和宾夕法尼亚州立大学联合研制的第5代中尺度气象模式系统MM5,对广东省地区春季出现的一次大雾过程进行了数值模拟研究。模式模拟结果与实际温湿探空的对比表明,模式很好地模拟了大雾过程的流场变化特征及表征大雾的液态水含量分布。对这次大雾生消过程起决定性作用的是925 hPa风场的变化。当925 hPa转为偏南风控制时,暖湿的海洋性空气流经较冷的下垫面从而形成大范围的平流雾;而当925 hPa转为干冷的偏北风控制时,原本形成的大雾很快就消散了。同时模式也很好地模拟了伴随此次平流雾出现的逆温过程。逆温层高度约在900 hPa附近,具有相当的厚度,这对于大雾的形成和维持有一定作用。另外,利用模式模拟的液态水含量值估算的能见度水平分布情况与实况的观测结果也较为一致。  相似文献   

河南省北部一次大雾天气过程分析   总被引：1，自引：0，他引：1  

张永涛  谷秀杰  王友贺  高媛媛 《河南气象》2009,(3):29-31

利用地面观测和探空资料以及NCEP1°×1°再分析资料,分析了2007年12A25-27日河南省北部大雾的成因,结果表明：由于降水后低层相对湿度较大,大气层结稳定,地面处在均压场里,风速较小,且大气低层为弱的上升运动、中高层为强的下沉运动,有利于低层水汽聚集,使湿层达到一定的厚度,从而使垂直能见度变差,雾的浓度变大。  相似文献   

石河子地区一次大雾天气的诊断分析     

安冬亮  魏勇  于瑞波 《沙漠与绿洲气象(新疆气象)》2009,3(1):24-26

应用实测资料、NCEP／NCAR再分析资料对2007年2月8—13日石河子地区出现的大雾天气进行诊断分析。结果显示：地面高压、高空暖脊与大雾的形成与消散有着直接的关系;逆温层的存在是大雾出现的必要条件;与大气层结稳定度有关的物理量对大雾天气也有一定的指示意义。  相似文献