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1.
从日常正压数值預报中发現,在500毫巴图上即便初始场是盛行的平直西风,仍常有气压系統发展或新生等現象。这意味着气压系統和涡度系統的发展不是一回事.考虑前者的发展和曲率涡度的变化有密切的关系,作者推导了曲率涡度和切变涡度的預报方程.可以証明,这两个物理量不是保守的.在某些情况下即便不考虑地球自轉的作用,在气流汇合和散开的地区二者仍可能相互轉化。利用这些結果前面的問題可以得到合理的解释. 最后,为了便于在实际工作中应用,作者还給出了一些适用于天气預报的規則。 相似文献
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高氣压系統的生成、發展和移動不僅是理論氣象学上和天氣学上的重要問題,而且也是做好天氣預報的重要關鍵之一。对东亞來說,如何預報西伯利亚以及歐洲等地冷高压的活動过程,是預報員在預報工作中的一個中心課題。關於冷高压活動的各階段过去已有些研究工作,其中有从熱力观點出發來討論冷高压的產生;有的从動力观點來討論高緯度冷高压的維持和爆發問題(寒潮爆發);也有从模型的实驗來討論冷高压的移動問題;也有人用高空氣流的匯流來解釋高压的加强或再 相似文献
3.
副热带高压的东西向移动及其預报的研究 总被引：21，自引：6，他引：21
本文从副热带高压本身的形状、位置与风場結构研究高压单体的移动問題,求得了副热带高压在东西方向上的移速公式,提出根据高压的形状、位置及其南北二側緯向风速分布廓线預报高压移动的具体办法,并討論了外界环流系統及高压本身性状变化对高压移动的影响及其物理性质. 相似文献
4.
本文从大气是乱流的介貭这一点出发,討論了地形对风場和气压場的作用,推导出了考虑地形作用的正压預报模式。在地轉近似的假定下得到:当气压梯度与地形梯度相重合而方向相同(反)时,发生加(減)压。还討論了地形对准常定气压波形成的各种作用,指出南北两半球緯圈平均气压、季际变化的不同,可以由地形作用来解释. 相似文献
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大氣環流一般理解為大氣准常定的平均狀態,也有理解為某一段時間內大氣中大型形勢的變化过程。其实,这兩种正是大氣環流一個問題的兩种表現,它們是密切的联系着,它們是一個整体。大氣環流顯然是一個錯綜複雜的問題。但自然界中現象的發生,必然存在一些客观的因子,探討其客观因子,对於大氣環流問題的認識与解决定有很大幫助的。本文所討論,就是对於决定大氣環流的因子提供一些具体意 相似文献
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自然季節的劃分無論是在氣候学工作上和天氣預告,特别是中、長期預告工作上都是一個很重要的問題。 我國勞動人民从很古的時候就把天文現象和产業生产的实踐結合起來劃分季節。近代从氣象观測的科学工作建立以後,人們更科学地依據大量的氣候資料按照 相似文献
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一。問題与方法 北京地區在冬半年(11月至4月)的降水日數很少,平均每月僅兩天(表1),而又往往集中於幾次持续性的坏天氣期間,雖然持续72小時以上的坏天氣(包括持续性降水和間有九成以上的中、低雲)出現次數不多,但在以往实際工作中,往往不能及時地作出此种類型天氣的預報,基於这种实際的需要和这种天氣大都出現在類似環流形勢下的經驗,因此本文試圖以苏联C.T.巴格瓦的中期天氣預報方法对此种天氣 相似文献
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本文考虑有鉛直向气流的影响、扩散貭点的沉降作用以及网效应(或称地面的吸收作用)时,討論了非定常态連續点源在乱流大气中的扩散問題.求得了計算扩散貭点浓度场的理論公式,并計算了若干例子,与观測結果得到很好的吻合。 相似文献
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With the development of numerical weather prediction technology,the traditional global hydrostatic models used in many countries of the world for operational weather forecasting and numerical simulations of general circulation have become more and more unfit for high-impact weather prediction.To address this,it is important to invest in the development of global nonhydrostatic models.Few existing nonhydrostatic global models use consistently the grid finite difference scheme for the primitive equations of dynamical cores,which can subsequently degrade the accuracy of the calculations.A new nonhydrostatic global spectral model,which utilizes the Eulerian spectral method,is developed here from NCAR Community Atmosphere Model 3.0(CAM3.0).Using Janjic's hydrostatic/nonhydrostatic method,a global nonhydrostatic spectral method for the primitive equations has been formulated and developed.In order to retain the integrity of the nonhydrostatic equations,the atmospheric curvature correction and eccentricity correction are considered. In this paper,the Held-Suarez idealized test and an idealized baroclinic wave test are first carried out,which shows that the nonhydrostatic global spectral model has similar climate states to the results of many other global models for long-term idealized integration,as well as better simulation ability for short-term idealized integration.Then,a real case experiment is conducted using the new dynamical core with the full physical parameterizations of subgrid-scale physical processes.The 10-day numerical integration indicates a decrease in systematic error and a better simulation of zonal wind,temperature,and 500-hPa height. 相似文献
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Within the framework of a mixed layer (ML) containing a zero-order jump, the concept of ML is generalized for the case of horizontal non-homogeneity on the assumption that not only potential temperature, but also the wind does not change with height. It turns out that the components of the vertical turbulent stresses are quadratic functions of height.For such a well-mixed layer (WML), bounded below by uneven terrain with an adjacent surface layer, and above — by a stably stratified quasigeostrophic baroclinic atmosphere, a consistent system of equations with all terms independent of height, is obtained. This can be considered as a meteorological generalization of the known shallow-water equations.As an example of the use of these equations, an analytical solution of the large-scale one-dimensional steady-state problem concerning the development of the WML in a stable stratified barotropic air mass moving over a heated horizontal surface has been found. 相似文献
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集合预报产品释用方法的研究 总被引：7，自引：0，他引：7
提出一种动力与统计相结合的集合预报产品的动力统计释用方法，该方法从大尺度大气动力学方程组出发，考虑中期旬尺度的大气环流特征，采用简单的斜压模式，推导出旬降水距平百分率与旬环流形势场的关系，从而建立了旬降水距平百分率预报方程，与相当正压的月降水距平百分率预报方程相比，更符合常规天气预报业务中对实际大气的动力学和天气学意义的考虑，试报结果表明，动力与统计相结合的方法对旬尺度动力延伸集合预报产品的释用具有明显的效果。 相似文献
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F. Grazzini 《Meteorology and Atmospheric Physics》2007,95(3-4):123-138
Summary The quality of numerical weather prediction has improved considerably since its beginning. Over the last decade, in the North
Hemisphere and more specifically over Europe, the accuracy of global numerical weather predictions of 500 hPa height has increased
by one day. However this remarkable achievement has to be considered true for average conditions since it is computed over
many days/seasons with very different flow patterns and atmospheric states. It is known that atmospheric predictability and
model errors are highly flow-dependent therefore an increase in skill for average conditions may not imply the same improvements
in specific conditions. Moreover the potential value of numerical weather prediction is perceived to be higher in some specific
conditions, like high-impact weather events. There is therefore a growing need to know the forecasting accuracy of significant
weather events, something that cannot be easily inferred through average scores, not least because of the rarity of these
events. For these reasons, a study has been carried out to examine the skill of the European Centre for Medium-Range Weather
Forecast (ECMWF) global forecasting system in predicting a specific flow configuration that is believed to be associated with
extreme precipitation events over the Alpine region. Despite quantitative predictions of extreme precipitations is still challenging,
it was found that the large-scale flow conducive to major rain events has better predictive skill than average conditions.
This is perhaps surprising since it is a common perception to associate severe weather with low predictability. 相似文献
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作为初值问题的天气形势数值预报与由地面天气历史演变作预报的等值性 总被引：15，自引：3，他引：15
天气数值预报研究中对预报问题的提法与日常天气预报工作中由天气历史演变来作预报的那种提法是很不相同的.本文对大尺度运动讨论了这两种提法在一定的简单附加条件下是等值的.由此也说明地面温压场的演变反映了也蕴含了斜压大气三维温压场的构造,并且决定了斜压大气三维温压场的发展. 相似文献
16.
准地转三层模式天气值预报方法的试验研究 总被引：3，自引：1，他引：3
作者首先根据温度局地变化的分析说明三层模式常常是必要的。然后作者用较普遍的准地转三层模式,试算了大范围高空温压场的倾向。所计算的是乌拉尔阻塞流型发展关键时刻的例子。作者的计算结果说明这种阻塞流型形成的预报必须使用三层模式,主要是因为与阻塞流型中高、低压切断有关的负变高,只有使用三层模式才报得好。根据三层模式的公式,作者并求出大范围天气系统发展的规则:即冷(暖)平流向上增强(减弱),那末等压面的位势高度升高(低槽减弱、高压脊加强);冷(暖)平流向上减弱(增强),那末等压面的位势高度降低(低槽加强、高压脊减弱)。也就是说,—舵所接受的暖平流使脊加强,冷平流使槽加深这规则是有条件的。作者还指出风场的逼近的需要和困难。特则是现有高空风观测和电码难以直接用来计算辐散。在计算方面作者给出了一个对 Poisson 方程适用的成群放松的格式。 相似文献
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Summary A case study is performed of a frontal-wave development on a trailing cold front in the Atlantic. The data base comprises principally the analysis and forecast fields of the global operational weather prediction model of the ECMWF, and the development itself is viewed from a potential vorticity (PV) perspective. It is shown that the ambient atmosphere contained three distinct and salient PV features: at the surface a frontal baroclinic zone; in the lower troposphere a co-aligned, moisture laden elongated band (2000 km long and 400 km wide) of enhanced PV; and at upper-levels a richly structured, southward extending PV pool. In the developments first phase a large-scale undulation of the surface frontal zone was accompanied by an in-phase movement of the upper-level anomaly. In a second phase two low-level wave features developed around 1000 km apart, and the resulting wave depressions were accompanied by a distortion of the baroclinic zone and the break-up of the low-level PV-band. In the subsequent mature phase the dominant secondary cyclone attained 500 km scale in the horizontal and acquired a coherent PV structure in the vertical.A PV-based diagnostic analysis provides evidence of both the self development of the PV features and their synergetic interplay. It also forms the basis for a comparison of the event with traditional and recent hypotheses for frontal-wave development.On the basis of the diagnosed relationship between the customarily depicted surface frontal-wave cups and the low-level PV-band, it is suggested that the segmentation of the latter provides a useful tool for monitoring and forecasting secondary developments. Also in the context of numerical weather prediction brief consideration is given to the sensivity of the frontal-wave development and structure to the spatial resolution of the associated forecast model and the specification of the initial fields.With 12 Figures 相似文献
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为了开展往返平飘式探空组网观测的仿真和模拟,以及评估组网观测对数值天气预报的影响,并实现往返平飘式探空在目标观测中的应用,本文提出了一种基于高分辨率数值天气模式的往返平飘式探空轨迹模拟和预报方法。基于我国自主研发的GRAPES区域高分辨率模式,初步建立了往返平飘式探空的轨迹预报系统。该系统将往返平飘式探空的上升段、平漂段和下降段的轨迹方程,以及下降段降落伞的动力学方程,直接嵌入到高分辨率数值天气模式中,实现对往返平飘式探空轨迹的模拟和预报。利用轨迹预测系统对63个往返平飘式探空轨迹进行轨迹预报试验和评估,试验结果表明,该系统的轨迹预测结果合理可信,6 h的轨迹预报平均误差小于40 km。 相似文献
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中尺度大气数值模式发展现状和应用前景 总被引：31，自引：12，他引：19
对国内外当前一些先进的中尺度大气数值模式的发展现状,应用前景及发展趋势作了概要综述。其内容包括：模式动力学的改进,叫就度模拟系统特征,区域谱模 发展积云参数化和显式云物理方案,行星边界层参数化,大气辐射参数、四维资料同化,区域实时数值天气预报,中尺度数值天气预报应用前景及新一代中尺度模式发展趋势。 相似文献