北京地区一次特大强风过程边界层结构的研究   总被引：21，自引：2，他引：21  

刘小红  洪钟祥 《大气科学》1996,20(2):223-228

利用北京325 m气象塔资料对1993年4月9日北京地区出现的一次特大强风过程的边界层结构（风、温、风切变及阵风特征）进行了分析。随着该次大风的过境，边界层内风场出现数个风速高值中心，高度位于200～300 m，时间间隔1～3 h。伴随上层风速垂直切变和阵风特性。湍流能谱的计算结果表明了大尺度涡旋对边界层湍流微结构的影响。  相似文献   

闽浙沿海火山岩地区银矿成矿规律     

刘昭平  吴建章 《福建地质》1996,15(4):177-189

本根据闽浙沿海火山岩地区银矿成矿规律和成矿预测的研究及近年来的矿产勘查，成矿预测和专科研成果，综合论述了闽浙沿海火山岩地区银矿的成矿地质条件，矿床类型和矿床特征，分析和总结了银矿的成矿规律和成矿作用，建立了区域成矿模式和成矿系列，同时指出，火山热液充填充代型银矿是本区最重要、也是最普遍的成因类型，并阐明了找矿方向。  相似文献   

北半球冬季纬向平均环流的结构及对我国气候的影响   总被引：21，自引：10，他引：21  

龚道溢  王绍武 《地理科学》2001,21(2):108-112

冬季对流层纬圈平均纬向风 (u)最主要的模态表现为两个相反符号的极值中心 ,一个在 30°～ 35°N之间 ,另一个则在 5 5°N。与此相联系的纬圈平均高度场最突出的模态也是有两个相反符号的中心 ,一个在 40°N附近 ,另外一个则在 6 5°N附近。因此 40°N和 6 5°N纬圈平均位势高度的差可以很好定义西风指数。西风环流的强弱不仅对北半球的气候有显著影响 ,对我国冬季的气温和降水也有显著关系。在高指数环流盛行的年份 ,我国普遍气温偏高。 16 0个站平均气温与西风指数的相关系数达到 0 .6 3。同时华北及以南降水增加 ,其中黄土高原、关中平原及以东地区相关最显著。 16 0站平均降水量与西风指数的相关达 0 .38。高指数年份里 ,西伯利亚高压和东亚大槽都减弱 ,低指数年份则增强 ,因此影响我国冬季气候  相似文献   

钦州湾水下动力地貌特征   总被引：1，自引：0，他引：1  

黎广钊  梁文  刘敬合 《地理与地理信息科学》2001,17(4):70-75

钦州湾水下动力地貌主要有潮间浅滩、河口沙坝、潮沟、潮流沙脊、潮流冲刷深槽、水下拦门浅滩、水下斜坡。该文阐述钦州湾的入海河流、潮汐、潮流、波浪等水动力的基本特征 ,分析水下地貌类型的形成及其空间分布和沉积物组成 ,并探讨动力地貌形成原因与机理及海岸动态变化趋势。  相似文献   

Soil Loss by Wind Erosion for Three Different Textured Soils Treated with Polyacrylamide and Crude Oil, Iraq     

Mushtak Talib Jabbar Faculty of Earth Resources  China University of Geosciences  Wuhan 《中国地质大学学报(英文版)》2001,12(2)

ＩＮＴＲＯＤＵＣＴＩＯＮＬａｒｇｅａｒｅａｓｏｆａｒｉｄａｎｄｓｅｍｉａｒｉｄｒｅｇｉｏｎｓｏｆｔｈｅｗｏｒｌｄａｒｅａｆ ｆｅｃｔｅｄｂｙｗｉｎｄｅｒｏｓｉｏｎ .Ａｐｐｒｏｘｉｍａｔｅｌｙ 2 8.4%ｏｆｔｈｉｓａｒｅａａｒｅａｆｆｅｃｔｅｄｂｙｓｅｖｅｒｅａｎｄｖｅｒｙｓｅｖｅｒｅｗｉｎｄｅｒｏｓｉｏｎ (Ｋａｔｅｓｅｔａｌ.,1977) .ＩｎＩｒａｑ ,ｔｈｅａｒｉｄａｎｄｓｅｍｉａｒｉｄｒｅｇｉｏｎｓｒｅｐｒｅｓｅｎｔｎｅａｒｌｙ 75%ｏｆｔｈｅｔｏｔａｌｌａｎｄ .5 0 %ｏｆｔｈｉｓｌａｎｄｉｓｓｕｂｊｅｃ…  相似文献   

On the general character of coastal flow     

Roger L. Hughes 《Pure and Applied Geophysics》1990,133(4):665-689

It is well-known that some coastal currents such as the Florida Current have a recirculating region on their coastal side, while other currents such as the East Australian Current have no such region. Under the hypothesis that the form drag on a coastal current by an irregular coastal topography reduces the momentum transport of the current to a minimum for the given flow within the current, the hydraulic theory of coastal currents is used to explain this behaviour.  相似文献   

Very quiet intervals of geomagnetic activity and the solar wind structure     

Jaroslava Hruska  Antonin Hruska 《Pure and Applied Geophysics》1989,131(3):343-355

Extended periods of very low geomagnetic activity as described by very quiet intervals (VQI's) occur only at those times when the solar wind velocityV has a generally decreasing trend, i.e., they mainly occur either after the velocity peak of a high speed solar stream has passed the Earth, or at times when the Earth is immersed in a low speed solar plasma provided that the daily mean value ofdV/dt is negative. The VQI's most frequently start whendV/dt<0 anddB _Z/dt>0 (B _Z is the geocentric solar magnetrospheric-GSMZ-component of the IMF) and end most likely whendV/dt>0 anddB _Z/dt<0. The temporal trends of the solar wind (SW) velocity affect the variation of thea _p index only when the level of geomagnetic activity is generally low.It is suggested that a gradual expansion or contraction of the magnetosphere, associated with a slow variation of the SW pressure, plays a role in the modification of the reconnection-driven magnetohydrodynamic (MHD) fluctuations in the magnetosphere.  相似文献   

Air-sea interaction over the tropical Indian Ocean during several contrasting monsoon seasons     

M. R. Ramesh Kumar  J. S. Sastry 《Journal of Earth System Science》1990,99(3):393-404

Monthly mean anomaly fields of various parameters like sea surface temperature, air temperature, wind stress, effective radiation at the surface, heat gain over the ocean and the total heat loss between a good and bad monsoon composite and the evaporation rates over the Arabian Sea and southern hemisphere have been studied over the tropical Indian Ocean. The mean rates of evaporation on a seasonal scale over the Arabian Sea during a good and bad monsoon composites were equal (about 2·48 × 10¹⁰ tons/day). The evaporation rates over the southern hemisphere were greater during all the months. The mean evaporation rates over the southern hemisphere on a seasonal scale for the good and bad monsoon composites were 4·4 × 10¹⁰ and 4·6 × 10¹⁰ tons/day respectively. The maximum evaporation rates over the southern hemisphere were observed in August. The anomalies of wind stress, effective radiation at the surface and the heat gain over the ocean also exhibit large variations in August, as compared to other monsoon months.  相似文献   

湖陆风效应为主导的地面弱风预报方法     

苗青建  矫东霖  陈江云  徐唱  吴思江  罗超  刘杰  武越  严鹏 《沙漠与绿洲气象(新疆气象)》2020,14(1):56-62

对博斯腾湖东南陆地风场数据进行计算,结合湖陆风效应初步建立夏半年各月风场日变化模型,得出风场日变化的4个典型时段。结果表明,区域测站一致性系数和风场有较好的对应关系,一致性系数小于50说明风向不稳定且风速较小,一致性系数大于80说明风向趋于稳定且风速一般较大,弱风时段主要出现在日出日落前后,且具有2h左右的持续时间。该方法为该地区弱风时段预报提供了思路,在稳定的高压脊形势下效果尤为明显。  相似文献   

基于EC细网格产品在乌鲁木齐机场低能见度预测中的释用     

王楠 《沙漠与绿洲气象(新疆气象)》2020,14(2):81-89

利用2015—2018年乌鲁木齐机场航空例行天气报告(METAR报)、ECMWF(European Centre for Medium-Range Weather Forecasting)细网格数值预报产品对影响能见度的主要因子进行分析,提取与低能见度相关性高的物理量作为预报因子,采用SVM方法,分别基于Poly、RBF核函数建立乌鲁木齐机场未来21 h能见度预报模型。结果表明:(1)基于预报因子区间分类的SVM模型物理意义明确,试验结果较好;以RBF为函数建立的SVM模型(SVM-RBF)预报能力更好,其训练样本预测的TS评分0.84,准确率89.20%。(2)SVM-RBF模型的检验样本中,预报准确样本的预报误差整体偏小;在漏报样本中则有能见度越低、预报误差越大的特点,模型的振荡性明显。(3)结合NCEP/NCAR再分析资料研究SVM-RBF模型对天气过程的预报表现,发现模型对于特定天气形势下引发的低能见度天气,预报误差较小且预报提前量较大。  相似文献