T639数据格式及其读取方法     

袁国波  韩子亮  赵红霞 《陕西气象》2009,(4):8-10

本文对2008年12月19日-21日朔州市强寒潮天气过程的高、低空环流形势、单站气象要素变化进行了分析,结果表明：500 hPa横槽转竖、中西伯利亚地面冷高压维持加强后南压爆发、850 hPa冷平流是产生强降温的主要原因.  相似文献   

2008年1月一次强雨雪过程的诊断分析     

朱坤  刘华强  刘宇丹  蒋坡   《气象与环境科学》2009,32(3):15-21

采用NCEP1°×1°客观再分析资料和常规观测资料,对2008年1月25—29日发生在长江中下游地区的强雨雪过程进行诊断分析,结果表明,低空急流与强雨雪有着密切关系,强雨雪的发生需具备一定的温度条件以及水汽场与动力场的耦合机制。对强雨雪过程的湿Q矢量诊断分析表明,700hPa湿Q矢量辐合区以及850hPa锋生函数正值区与强雨雪区对应较好,对雨雪天气的发生有着很好的指示意义。湿位涡特征分析表明,此次强雨雪过程发生在层结稳定的大气中且垂直涡度发展较强。  相似文献   

Mesoscale Vortex Generation and Merging Process： A Case Study Associated with a Post-Landfall Tropical Depression   总被引：5，自引：0，他引：5  

YU Zifeng  LIANG Xudong  YU Hui  Johnny C. L. CHAN 《大气科学进展》2010,27(2):356-370

An observational analysis of satellite blackbody temperature (TBB) data and radar images suggests that the mesoscale vortex generation and merging process appeared to be essential for a tropical-depression-related heavy rain event in Shanghai, China. A numerical simulation reproduced the observed mesoscale vortex generation and merging process and the corresponding rain pattern, and then the model outputs were used to study the related dynamics through diagnosing the potential vorticity (PV) equation. The t...  相似文献   

2007年淮河流域暴雨期间大气环流特征分析   总被引：6，自引：3，他引：3  

桂海林  周兵  金荣花 《气象》2010,36(8):8-18

利用NCAR/NCEP再分析资料及国家气象信息中心30年气候平均降水资料,通过动力诊断与分析手段研究了2007年6—7月发生在我国淮河流域的暴雨。结果表明,淮河流域的环流垂直结构和降水有着非常好的对应关系。暴雨期间,鄂霍茨克海阻高与乌拉尔山阻高这种双阻高形势对于淮河流域的持续降水提供了很好的条件;南亚高压高层(200 hPa)基本为正散度区,低层(850 hPa)为负散度区,上下层强烈的抽吸结构对暴雨的发生也是非常有利的条件,同时,在淮河暴雨期问,南亚高压(200 hPa)与500 hPa西太平洋副热带高压有着相向而行的移动路径;位涡对于分析冷空气的活动,有着比较清晰的意义,暴雨发生前,有明显的正位涡异常从高纬度向低纬度伸展。大气非绝热加热分析结果显示,视热源和视水汽汇两者的高值中心与相应时段暴雨中心位置一致。  相似文献   

“珍珠”（0601）异常急翘路径和内核结构变化的诊断分析及数值研究   总被引：4，自引：0，他引：4  

李勋  李泽椿  赵声蓉  曾智华  王勇 《气象》2010,36(9):1-8

使用FY2卫星TBB资料、NCEP最终分析资料(1°×1°)和中尺度模式WRF,对0601号强台风"珍珠"的"急翘"异常转向路径和内核结构变化进行诊断分析和数值模拟。结果表明:"珍珠"移向变化与环境引导气流和位涡倾向1波分量正异常有关,"急翘"前12小时,环境引导气流向北偏转,位涡倾向1波分量正异常对应着"珍珠"移动方向变化;内核非对称结构发展与环境风垂直切变演变有关,垂直切变使得涡旋倾斜,涡旋倾斜方向出现较强的上升运动,导致"珍珠"内核偏南象限对流活动较强。  相似文献   

2008年初湖北省低温雨雪冰冻天气温度平流配置分析   总被引：1，自引：1，他引：0  

龙利民  黄治勇  苏磊  王珊珊  邓红  韩琦 《南京气象学院学报》2010,33(6):745-750

利用NCEP／NCAR再分析资料,对2008年1月11日-2月1日湖北省低温雨雪冰冻过程进行温度平流空间分布诊断分析。结果表明：低温雨雪冰冻期间,湖北省近地层不断有弱冷空气补充和渗透;中层暖平流、低层冷垫和南方沿冷垫向上爬升的暖空气是湖北省降雪最基本的条件,而湖北省东部出现强降雪的另一个更重要的原因就是低层偏东回流带来的暖平流;当冷空气充斥湖北省上空整层大气时,则预示雨雪将减弱停止。  相似文献   

GRAPES区域模式水汽平流方案的比较与改进   总被引：9，自引：2，他引：7  

陈子通  万齐林  沈学顺  黄燕燕  张艳霞  张诚忠  丁伟钰 《热带气象学报》2010,26(1):1-6

与欧拉显式时间差分方法相比,GRAPES区域模式采用半隐半拉格朗日时间差分方案可增加时间步长且不影响稳定性,而且模式积分可有较高的计算效率和准确性。半拉格朗日法需要用到内插算法来预测下一时刻的值,对于水汽场的内插值来说,常常会造成预报值的过饱和或者是负值,需要进行特殊处理。比较GRAPES模式的准单调半拉格朗日方案(QMSL)和高精度正定保形方案(PRM),分析模式的降水预报、形势预报,同时初步总结了两方案的优缺点。在参考LCSL(Linear Constraint Semi-Lagarangain)方案的基础上,改进QMSL方案,通过连续试验运行,表明新方案基本稳定可靠,对于降水预报、形势预报有一定的改进,在台风预报试验中也有良好的表现。  相似文献   

Consistency Problem with Tracer Advection in the Atmospheric Model GAMIL     

ZHANG Kai  WAN Hui  WANG Bin  ZHANG Meigen 《大气科学进展》2008,25(2):306-318

The radon transport test, which is a widely used test case for atmospheric transport models, is carried out to evaluate the tracer advection schemes in the Grid-Point Atmospheric Model of IAP-LASG （GAMIL）. Two of the three available schemes in the model are found to be associated with significant biases in the polar regions and in the upper part of the atmosphere, which implies potentially large errors in the simulation of ozone-like tracers. Theoretical analyses show that inconsistency exists between the advection schemes and the discrete continuity equation in the dynamical core of GAMIL and consequently leads to spurious sources and sinks in the tracer transport equation. The impact of this type of inconsistency is demonstrated by idealized tests and identified as the cause of the aforementioned biases. Other potential effects of this inconsistency are also discussed. Results of this study provide some hints for choosing suitable advection schemes in the GAMIL model. At least for the polax-region-concentrated atmospheric components and the closely correlated chemical species, the Flux-Form Semi-Lagrangian advection scheme produces more reasonable simulations of the large-scale transport processes without significantly increasing the computational expense.  相似文献   

Formation of intrathermocline eddies at ocean fronts by wind-driven destruction of potential vorticity     

Leif N. Thomas   《Dynamics of Atmospheres and Oceans》2008,45(3-4):252

A mechanism for the generation of intrathermocline eddies (ITEs) at wind-forced fronts is examined using a high resolution numerical simulation. Favorable conditions for ITE formation result at fronts forced by “down-front” winds, i.e. winds blowing in the direction of the frontal jet. Down-front winds exert frictional forces that reduce the potential vorticity (PV) within the surface boundary in the frontal outcrop, providing a source for the low-PV water that is the materia prima of ITEs. Meandering of the front drives vertical motions that subduct the low-PV water into the pycnocline, pooling it into the coherent anticyclonic vortex of a submesoscale ITE. As the fluid is subducted along the outcropping frontal isopycnal, the low-PV water, which at the surface is associated with strongly baroclinic flow, re-expresses itself as water with nearly zero absolute vorticity. This generation of strong anticyclonic vorticity results from the tilting of the horizontal vorticity of the frontal jet, not from vortex squashing. During the formation of the ITE, high-PV water from the pycnocline is upwelled alongside the subducting low-PV surface water. The positive correlation between the ITE’s velocity and PV fields results in an upward, along-isopycnal eddy PV flux that scales with the surface frictional PV flux driven by the wind. The relationship between the eddy and wind-induced frictional PV flux is nonlocal in time, as the eddy PV flux persists long after the wind forcing is shut off. The ITE’s PV flux affects the large-scale flow by driving an eddy-induced transport or bolus velocity down the outcropping isopycnal layer with a magnitude that scales with the Ekman velocity.  相似文献   

A Case Study on a Quasi-Stationary Meiyu Front Bringing About Continuous Rainstorms with Piecewise Potential Vorticity Inversion          下载免费PDF全文

ZHAO Yuchun  LI Zechun  XIAO Ziniu 《Acta Meteorologica Sinica》2008,22(2):202-223

A 4-day persistent rainstorm resulting in serious flooding disasters occurred in the north of Fujian Province under the influences of a quasi-stationary Meiyu front during 5-8 June 2006. With 1°× 1° latitude and longitude NCEP reanalysis data and the ground surface rainfall, using the potential vorticity （PV） analysis and PV inversion method, the evolution of main synoptic systems, and the corresponding PV and PV perturbation （or PV anomalies） and their relationship with heavy rainfall along the Meiyu front are analyzed in order to investigate the physical mechanism of the formation, development, and maintenance of the Meiyu front. Furthermore, the PV perturbations related to different physics are separated to investigate their different roles in the formation and development of the Meiyu front. The results show： the formation and persistence of the Meiyu front in a quasi-WE orientation are mainly due to the maintenance of the high-pressure systems in its south/north sides （the West Pacific subtropical high/ the high pressure band extending from the Korean Peninsula to east of North China）. The Meiyu front is closely associated with the PV in the lower troposphere. The location of the positive PV perturbation on the Meiyu front matches well with the main heavy rainfall area along the Meiyu front. The PV inversion reveals that the balanced winds satisfying the nonlinear balanced assumption represent to a large extent the real atmospheric flow and its evolution basically reflects the variation of stream flow associated with the Meiyu front. The unbalanced flow forms the convergence band of the Meiyu front and it mainly comes from the high-pressure system in the north side of the Meiyu front. The positive PV perturbation related to latent heat release in the middle-lower troposphere is one of the main factors influencing the formation and development of the Meiyu front. The positive vorticity band from the total balanced winds is in accordance with the Meiyu front band and the magnitude of the posit  相似文献