北半球阻塞高压的维持Ⅱ:瞬变扰动强迫和平均流位涡平流的形成   总被引：4，自引：2，他引：4  

刘辉  曾庆存  吴国雄 《气象学报》1995,53(3):337-348

着重探讨大西洋阻高和东亚阻高个例中瞬变扰动位涡（涡度）输送强迫和太平洋阻高中平均流位涡平流的形成机理。结果表明，扰动在阻高西南部西风分流区因形变而产生的扰动拟能向更小尺度串级过程，并不是扰动位涡输送强迫形成的必要机理。扰－流相互作用在阻高西（北）部非分流气流中也十分显著。数值试验表明，这一相互作用也可能是扰动强迫作用形成的机理。而青藏高原和附近海陆对比的强迫作用则可能是太平洋阻高中平均流的位涡平流形成的重要因素。对比分析表明，阻高维持机制的地域性差别可能与其上游（如青藏高原地区、落基山脉）地形和热源强迫作用不同有关。  相似文献   

A steady state model of the Somali current     

P. K. Das  S. K. Dube  G. S. Rao 《Journal of Earth System Science》1987,96(3):279-290

A steady state model of the Somali current including forcing by both the curl and the divergence of the wind stress is discussed. The model equations are linear, but the results presented are for the one nonlinear case. The grid resolution was 12 km in the zonal and 24 km in the meridional direction. The streamfunction and velocity potential of the current are presented for forcing by divergence and compared with a situation when only the curl is present. The results indicate that a two-gyre system appears in July, a representative month for the summer monsoon, only when divergence is included. Computations with available data indicate that the divergence is comparable in magnitude to the curl near the location of the Somali current. The model produces three other important features: (i) strong upwelling off the east coast of Africa, (ii) downwelling over central Arabian sea and (iii) a strong eastward current in the upper layer towards the interior of the Arabian sea near 12°N.  相似文献   

位场小波分析的物理解释   总被引：13，自引：3，他引：10       下载免费PDF全文

梁锦文 《地球物理学报》2001,44(6):865-870

采用二进小波变换,构造了位场基小波,通过简单模型,分析了位场信号小波分解与重构的物理实质,阐明了小波变换的频带分布与“归一化”位场空间分布的一致性,以及小波重构的规律,并叙述了小波重构与异常分解的关系.  相似文献   

COOLING RATES, SKY VIEW FACTORS AND THE DEVELOPMENT OF INTRA-URBAN AIR TEMPERATURE DIFFERENCES     

BJÖRN HOLMER  SOFIA THORSSON  INGEGÄRD ELIASSON 《Geografiska Annaler: Series A, Physical Geography》2007,89(4):237-248

Intra‐urban cooling rates were monitored for a year in the centre of Göteborg on the Swedish west coast. Five sites with different building geometry ‐ from dense canyon to open space ‐ within a radius of 300 m were analysed. Results showed two modes of cooling during the night. In the first mode, the cooling was site‐dependent ‐the open space cooled the most and the dense canyon the least. In the second mode, which began about 3–4 hours after sunset, all sites cooled at the same rate. Our hypothesis is that in the early part of the evening both radiative divergence and sensible heat dominate the cooling. However, as the evening progresses, a spatially homogeneous inversion is established which controls the radiative cooling, making the cooling independent of both surface geometry and surface type. From April to November the sites cooled rapidly around sunset and the cooling slowly decreased during the rest of the night. However, between December and March, the cooling was less intense, with an almost constant rate during the entire night. It has been suggested that this might be the result of the draining of stored solar heat during the summer and a continuous flux of anthropogenic heating during the winter.  相似文献   

位场曲化平的插值-迭代法   总被引：10，自引：5，他引：10       下载免费PDF全文

徐世浙  余海龙 《地球物理学报》2007,50(6):1811-1815

将起伏曲面B上的位场向下延拓至曲面最低点的平面A的插值-迭代法步骤是：1）将曲面B上的场值放置在水平面A上具有相同水平坐标的点上，作为A上的初值；2）用若干水平面切割B，从A的初值，用快速傅里叶变换法(FFT)向上延拓出这些平面的场值，用插值的方法从这些平面的场值计算曲面B的场值；3）根据B上的实测值与计算值的差值，对A上的值进行加权改正；4）重复步骤2）和3），直到B上的差值小到可以忽略.这种插值-迭代法具有高的计算速度，比通常的FFT法延拓得更深，可以超过10倍点距.文中给出计算实例.  相似文献   

A formula for computing the gravity disturbance from the second radial derivative of the disturbing potential   总被引：6，自引：0，他引：6  

J. Li 《Journal of Geodesy》2002,76(4):226-231

 A formula for computing the gravity disturbance and gravity anomaly from the second radial derivative of the disturbing potential is derived in detail using the basic differential equation with spherical approximation in physical geodesy and the modified Poisson integral formula. The derived integral in the space domain, expressed by a spherical geometric quantity, is then converted to a convolution form in the local planar rectangular coordinate system tangent to the geoid at the computing point, and the corresponding spectral formulae of 1-D FFT and 2-D FFT are presented for numerical computation. Received: 27 December 2000 / Accepted: 3 September 2001  相似文献   

兰州市空气质量预报系统结构及效果检验   总被引：2，自引：0，他引：2  

杨民  王庆梅  马印飞  李文莉 《干旱气象》2002,20(2):22-26,40

文中从潜势预报、浓度预报、统计预报和数值预报 4方面介绍了兰州市空气质量预报业务系统的研究方法和结构特点。对 2 0 0 1年 4～ 10月兰州市空气质量预报与日报 (实况 )进行了分析研究 ,结果表明 ,该系统对兰州市空气质量预报有较强的预报能力 ,适用于兰州市空气质量预报业务。  相似文献   

青藏高原大气低频振荡的源、汇特征分析     

徐国强  朱乾根 《南京气象学院学报》2002,25(3):358-365

使用1998年美国NCAR再分析的逐日资料，研究了1998年夏季青藏高原大气低频振荡的源、汇特征。青藏高原对于纬向风的低频波来说，有时是低频振荡的源区，有时是汇区。通过计算低频涡度的通量散度，进一步研究了低频涡源、涡汇特征。青藏高原在不同时间和不同部位，低频涡源、涡汇具有不同的分布特征，传播特征也不尽相同，青藏高原上空100hPa低频涡源、涡汇受到了南亚高压的很大影响。  相似文献   

几种Q矢量的比较   总被引：12，自引：1，他引：12  

岳彩军  寿绍文 《南京气象学院学报》2002,25(4):525-532

利用 1 991 - 0 7- 0 5T2 0— 0 6T2 0一次江淮梅雨锋暴雨过程实况资料 ,结合地面降水分布 ,从定性 (矢量场 ,即 Q)、定量 (散度场 ,即 2 · Q)的角度细致、具体地比较分析了准地转 Q矢量、半地转 Q矢量、非地转 Q矢量及湿 Q矢量的诊断特性。结果表明 :半地转 Q矢量诊断能力优越于准地转 Q矢量。非地转 Q矢量、湿 Q矢量诊断能力明显优越于准地转 Q矢量、半地转 Q矢量。准地转 Q矢量诊断能力最差 ;从定性的角度分析 ,非地转 Q矢量与湿 Q矢量诊断能力相差不大。但进一步定量分析发现 ,在整个梅雨锋暴雨过程中 ,湿 Q矢量的诊断能力大于其他 Q矢量 ;70 0 h Pa高度上各 Q矢量的矢量、散度辐合区较其在 850 h Pa和 50 0 h Pa上对降水反映更好 ,尤其是70 0 h Pa湿 Q矢量散度辐合区与降水区有非常好的对应关系。  相似文献   

绥化电视发射塔工程场址地震基本烈度影响因素的探讨     

薛仲新 《东北地震研究》2001,17(3):51-59

采用同一地震带中两个不同潜在震源区的统计模型，讨论了当潜在震源区分方法不同时对场址基本烈度的影响。  相似文献