陕西强沙尘暴、特强沙尘暴天气气候特征分析   总被引：1，自引：8，他引：1  

雷向杰  李亚丽  王小宁  许新田 《中国沙漠》2005,25(1):118-122

 从陕西1954—2003年所有沙尘暴记录所对应的3次或4次定时能见度观测资料中挑出最小能见度小于500 m的作为强沙尘暴记录,小于200 m的作为特强沙尘暴记录。然后挑取在一次过程中有3个或3个以上气象站出现强沙尘暴的过程共41次作为强沙尘暴过程,有3个或3个以上气象站出现特强沙尘暴的过程共6次作为特强沙尘暴过程。分析结果表明,20世纪90年代是陕西强沙尘暴、特强沙尘暴过程最少的时期。陕西强沙尘暴过程主要发生在春季,冬季次之,其中春季4月最多, 冬季2月最多。除春季、冬季外,6、11月也有发生。根据41次强沙尘暴过程出现前一日08时500 hPa环流形势分析,将造成陕西强沙尘暴天气的环流形势及影响系统分为蒙古冷（横）槽型、脊前下滑槽型、短波槽东移型和西北气流型4类,其中蒙古冷（横）槽型是造成陕西强沙尘暴天气最多的一种形势,占总次数的44%。陕西6次特强沙尘暴过程的环流形势及影响系统全为蒙古冷（横）槽型。根据地面冷空气入侵陕西的路径分析,将造成陕西强沙尘暴天气的冷空气路径分为西路、西北路、北路三条。  相似文献   

Effects of additional HONO sources on visibility over the North China Plain   总被引：1，自引：1，他引：0  

Ying Li  Junling An  Ismail Gultepe 《大气科学进展》2014,31(5):1221-1232

The objective of the present study was to better understand the impacts of the additional sources of nitrous acid （HONO） on visibility, which is an aspect not considered in current air quality models. Simulations of HONO contributions to visibility over the North China Plain （NCP） during August 2007 using the fully coupled Weather Research and Forecasting/Chemistry （WRF/Chem） model were performed, including three additional HONO sources： （1） the reaction of photo-excited nitrogen dioxide （NO~） with water vapor; （2） the NO2 heterogeneous reaction on aerosol surfaces; and （3） HONO emissions. The model generally reproduced the spatial patterns and diurnal variations of visibility over the NCP well. When the additional HONO sources were included in the simulations, the visibility was occasionally decreased by 20%-30% （3-4 km） in local urban areas of the NCP. Monthly-mean concentrations of NO3, NH＋, SO]- and PM2.5 were increased by 20%-52% （3-11μg m-3）, 10%-38%, 6%-10%, and 6%-11% （9-17 μg m-3）, respectively; and in urban areas, monthly-mean accumulation- mode number concentrations （AMNC） and surface concentrations of aerosols were enhanced by 15%-20% and 10%-20%, respectively. Overall, the results suggest that increases in concentrations of PM2.5, its hydrophilic components, and AMNC, are key factors for visibility degradation. A proposed conceptual model for the impacts of additional HONO sources on visibility also suggests that visibility estimation should consider the heterogeneous reaction on aerosol surfaces and the enhanced atmospheric oxidation capacity due to additional HONO sources, especially in areas with high mass concentrations of NOx and aerosols.  相似文献   

一次苏南大暴雨过程数值模拟及其对交通能见度的影响     

汤继涛  袁成松  包云轩  谢晓金 《气象科学》2014,34(3):275-281

利用0.5°×0.5°的GFS分析场数据和中尺度数值模式WRF,对2011年6月17—18日发生在江苏省南部地区覆盖沪宁、沿江及宁常高速公路的一次大暴雨天气过程进行了数值模拟和诊断分析。经过AWMS实测数据及常规气象观测资料的验证,得到如下结论:(1)WRF模式对此次大暴雨过程的模拟结果较为理想,具有良好的预报能力;(2)高低空急流的耦合是本次降水过程爆发的主要动力机制,西南低空急流为此次降水提供了水汽输送通道;(3)雨区上空的垂直螺旋度在低层为正、高层为负;(4)干空气的活动对强降水的形成具有一定的指示作用;(5)强降水是导致公路交通能见度降低的重要因素,且水平能见度与降水强度成负指数关系。  相似文献   

Assessing the visual impacts of new urban features: coupling visibility analysis with 3D city modelling     

Sepideh Saeidi  Marjan Mohammadzadeh  Abdolrassoul Salmanmahiny  Colin Arrowsmith 《国际地球制图》2013,28(12):1315-1331

Abstract

Land use changes associated with urbanization often have negative impacts on scenic beauty. In this paper, we explore and compare the visual impact of two different scenarios of urban growth including historical urban growth (HUG) and aesthetically sound urban growth (AUG) with two different categories of height for buildings in the city of Gorgan, Iran. This was done by viewshed and landscape metric analysis of different viewpoints and 3D representation of each scenario. The results show that with the AUG scenario, viewsheds are less impacted by new developments than the HUG scenario in all the viewpoints. It can be concluded that building locations can considerably affect the landscape visibility while building height does not impact to the same degree as location. The results of this research, as a Spatial Decision Support System, would help the managers for better understanding of different patterns of urbanization and its effect on landscape view.  相似文献   

Features of visibility variation at Great Wall Station, Antarctica     

YANG Qinghua  YU Lejiang  WEI Lixin  ZHANG Benzheng  MENG Shang 《极地研究(英文版)》2013,(3):188-193

The variation of visibility at Great Wall Station （GWS） was analyzed using manual observational data for the period of 1986 to 2012. Results show that the frequencies of occurrence of high （≥ 10 km） and low visibility （0-1 km） are 61.0% and 8.0%, respectively. Visibility at GWS shows an evident seasonal variation： The highest visibility between November and March, and the lowest visibility from June to October. Sea fog and precipitation are the main factors for low visibility during summer, whereas frequent adverse weather, such as falling snow, blowing snow, or blizzards, are responsible for low visibility in winter. The frequency of occurrence of low visibility has decreased significantly from 1986 to 2012. Conversely, the frequency of occurrence of high visibility has shown a significant increasing trend, especially during winter. The decreasing tendencies of fog, blowing snow, and snowfall have contributed to the increasing trend of high visibility during winter. Visibility at GWS exhibits significant synoptic-scale （2.1 to 8.3 d）, annual, and inter-annual periods （2 a, 4.1 a, and 6.9 a to 8.2 a）, among which the most significant period is 4.1 a. The visibility observed during 2012 indicates that instrumental observation can be applied in the continuous monitoring of visibility at GWS.  相似文献   

A novel method for distinguishing fog and haze based on PM2.5, visibility,and relative humidity     

Nan Ma  ChunSheng Zhao  Jing Chen  WanYun Xu  Peng Yan  XiuJi Zhou 《中国科学:地球科学(英文版)》2014,57(9):2156-2164

Haze and fog are both low visibility events, but with different physical properties. Haze is caused by the increase of aerosol loading or the hygroscopic growth of aerosol at high relative humidity, whereas visibility degradation in fog is due to the light scattering of fog droplets, which are transited from aerosols via activation. Based on the difference of physical properties between haze and fog, this study presents a novel method to distinguish haze and fog using real time measurements of PM2.5, visibility, and relative humidity. In this method, a criterion can be developed based on the local historical data of particle number size distributions and aerosol hygroscopicity. Low visibility events can be classified into haze and fog according to this criterion.  相似文献   

高速公路上霾雾演变及其对能见度的影响   总被引：4，自引：0，他引：4  

田小毅  袁成松  吴震 《气象科技》2010,38(6):673-678

沪宁高速公路沿线2006年11月2-3日26个交通气象自动监测站每分钟一次的要素监测表明:霾、雾对能见度都有影响,但在诸多方面存在着一些差异。条件适宜时,可以互相转化演变,其间有一个并存的阶段,认识这些差异及变化的条件对提高低能见度预报水平、做好交通气象服务是有益的。文章剖析了丘陵地区谷地霾抬升以及多雾和雾出现时间早、维持时间长的原因,有助于进一步认识浓雾的局地性和交通沿线能见度的差异。大范围连续数日的大雾大多与大范围的霾有关。在大范围霾雾共存的天气形势下,能见度恶劣现象往往持续数日,至强冷空气南下方能驱散,由于辐射降温,夜间能见度下降,白天略有好转。  相似文献   

天津冬季大气能见度与空气污染的相互关系   总被引：3，自引：1，他引：2  

姚青  张长春  樊文雁  黄鹤 《气象科技》2010,38(6):704-708

为探求天津冬季大气能见度特征与空气污染的相互关系,于2008年12月至2009年1月连续观测大气能见度和空气污染物浓度(PM10、PM2.5质量浓度,O_3、NO_2和SO_2体积浓度),并结合相对湿度进行相关分析。结果表明:天津冬季大气能见度平均值为11.59 km,日变化呈明显的单峰特征,其变化特征受到空气污染物,尤其是气溶胶质量浓度及相对湿度变化共同影响;观测期内霾的发生频率接近50%;采用非线性回归方程拟合能见度与气溶胶质量浓度相互关系显示,PM2.5质量浓度对水平能见度的贡献大于PM10质量浓度,并且高湿情况下,能见度与气溶胶质量浓度相关性更好。  相似文献   

一次持续性浓雾天气过程的水汽输送及逆温特征分析   总被引：11，自引：5，他引：6       下载免费PDF全文

吴彬贵  张宏升  汪靖  张长春  于莉莉  刘彬贤  解以扬 《高原气象》2009,28(2):258-267

利用地面站观测、大气边界层观测及NCEP再分析资料,对2006年2月13～14日华北中南部一次持续性浓雾过程的水汽输送和逆温特征进行了计算和分析,研究了其与浓雾生、消发展之间的联系.结果表明:暖性弱高压脊和地面变性冷高压的高低空系统配置为浓雾的形成提供了有利的逆温层结和近地面弱风条件;在深厚逆温条件下,南支暖湿水汽的输送和辐合使毛毛雨滴下降过程中蒸发,在近地面较冷气层中再次凝结导致了浓雾的生成;加强北上的低空西南急流为浓雾的启动和长时间维持提供了大量的水汽,有利于逆温层顶抬升,湿层增厚,进而促进了浓雾的生成和发展;西北干冷空气自上而下破坏了深厚浓雾所依存的高湿条件,使雾顶下降雾层变薄,加之日出后的短波辐射使近地层空气升温,近地面的稳定层结被破坏,上下层气流交换增强,从而导致了雾最终消散.结果还表明:在近地面逆温、微风等有利成雾天气条件下,当低层持续适量的水汽辐合时,浓雾同时伴随有毛毛雨现象,当低层水汽辐散时,毛毛雨现象消失.  相似文献   

一次大雾天气下PM2.5二次无机粒子的数值模拟     

费建芳  王锐  王益柏  黄小刚 《南京气象学院学报》2009,32(3):360-366

利用多尺度空气质量模式系统（Models-3/CMAQ）对2002年12月1—3日北京及周边地区发生的一次大雾天气进行数值模拟,分析了大雾天气下PM2.5二次无机粒子的演变及其影响。结果表明,白天相对湿度降低,雾滴蒸发脱水后PM2.5二次无机粒子会悬浮在大气中;夜间在水汽凝结成雾滴的过程中,大量的PM2.5二次无机粒子提供了充足的凝结核,促进大雾天气的进一步发展。午后PM2.5二次无机粒子积聚及较高的相对湿度是造成北京及周边地区低能见度的重要原因,并推断该区域很可能是霾天气。  相似文献