共查询到20条相似文献，搜索用时 54 毫秒
1.
局地暴雨增强数值预报模式是建立在适用于地方微机上可实现的区域数值预报业务系统。该模式由兰州高原大气所引进本台并同时开展数值模式的对比试验，并且在１９９４年６月１５日－７月１５日梅汛期中进行试验，结果表明：模式运行正常可靠，计算稳定，对降水具有一定的预报能力。 相似文献
2.
本文对中尺度数值预报模式REM的特点和2002年湖南汛期的降水预报试验方案进行了介绍。为了检验其预报效果，分别对整个试验期间(6～8月)和集中降水期(6～7月)这两个时段作了预报结果检验，并与1998年同期作了比较，还与MM5进行了同一时段降水预报效果比较，结果表明该模式在暴雨落区及强度等方面预报效果良好，但还有待进一步完善。 相似文献
3.
前言文献[1]根据1993年一年样本的试验研究，提出了一个华南前汛期暴雨的物理因子统计短期预报方法。随后，文献[2]又对该方法作了改进，使其能在计算机上自动运行，适合实时业务环境，并总结了在94．6和947华南特大暴雨过程中取得的良好预报效果。1995年该方法投入广东省前汛期预报业务试验。本文是对该方法在这次业务试验中应用的技术性总结。1业务试验试验从《月1日开始，于6月20目前汛期最后一场暴雨之后结束。每日上午9时30分前，用上一天动时（北京时，下同）天气报告资料计算出从当天08时开始的6天返回广东暴雨预报。其中前2天的预报… 相似文献
4.
5.
6.
7.
8.
上海区域降水集合预报系统改进的对比试验 总被引：1，自引：1，他引：0
以2005年8月开始运行的、8个成员的上海区域降水集合预报系统为基础,设计2个对比试验方案,进行了3个月(2005年9—11月)的平行对比试验。对比试验将成员从8个增加至12个,系统的8个成员与试验一增加的成员都从预报模式的不确定性出发形成,试验二增加的成员考虑了模式初始条件的不确定性。对试验结果进行了检验与分析,并与控制试验结果进行比较。结果显示:增加集合成员数可以增大系统发散度,但对比试验仍存在系统发散度偏小的问题;同时考虑预报模式与初始条件不确定性的试验二的降水集合平均预报效果与降水概率预报效果都好于只考虑预报模式不确定性的试验一,也好于控制试验,试验一的降水集合平均预报效果总体上则比控制试验差,降水概率预报效果也不理想。采用试验二方案对系统进行改进后的整体预报效果较改进前有提高。 相似文献
9.
本文对１９９５年全省热带的气旋预报业条试验进行了总结分析，试验结果表明，大多数参试项目均具有较好的预报性能，一些项目在热带气旋转折路径预报方面取得了突破性进展，业务应用前景十分广阔。 相似文献
10.
通过相关系数选出预报因子,用逐步回归、最优子集回归、EOF降维逐步回归、神经网络等统计预报方法对预报对象进行逐年交叉检验以及实际预报检验,检测预报因子对原预报序列的预报能力。同时通过计算每种方法的平均绝对误差和实际预报检验的平均误差,客观地对各种预报方法进行既有纵向也有横向的较为全面的比较。 相似文献
11.
12.
通过对仁怀市农经网网管中心建设的介绍．总结出县级农经网的一种管理模式，以希望能有效地解决好农经网信息进村入户难的问题。 相似文献
13.
Tree-ring reconstructed summer Palmer Drought Severity Indices (PDSI) are used to identify decadal droughts more severe and
prolonged than any witnessed during the instrumental period. These “megadroughts” are identified at two spatial scales, the
North American continental scale (exclusive of Alaska and boreal Canada) and at the sub-continental scale over western North
America. Intense decadal droughts have had significant environmental and socioeconomic impacts, as is illustrated with historical
information. Only one prolonged continent-wide megadrought during the past 500 years exceeded the decadal droughts witnessed
during the instrumental period, but three megadroughts occurred over the western sector of North America from a.d. 1300 to 1900. The early 20th century pluvial appears to have been unmatched at either the continental or sub-continental
scale during the past 500 to 700 years. The decadal droughts of the 20th century, and the reconstructed megadroughts during
the six previous centuries, all covered large sectors of western North America and in some cases extended into the eastern
United States. All of these persistent decadal droughts included shorter duration cells of regional drought (sub-decadal
≈ 6 years), most of which resemble the regional patterns of drought identified with monthly and annual data during the 20th
century. These well-known regional drought patterns are also characterized by unique monthly precipitation climatologies.
Intense sub-decadal drought shifted among these drought regions during the modern and reconstructed multi-year droughts, which
prolonged large-scale drought and resulted in the regimes of megadrought. 相似文献
14.
15.
A sequence of numerical experiments is conducted using a linear, semi-spectral equatorial ocean model and an advanced data assimilation scheme. The numerical model is based on decomposition of the oceanic fields into Kelvin and Rossby waves belonging to the baroclinic modes of a stratified equatorial ocean. The assimilation procedure finds that solution to the model equations that best fits, in the generalized least-squares sense, all observations made within some specified space-time interval. All experiments are of the ‘identical twin’ type; synthetic data are generated by sampling the observable fields produced by a control run of the model, then the data are assimilated using the same model. The sequence of numerical experiments serves two purposes; to demonstrate the performance of the assimilation procedure in the context of a fully three-dimensional, time-varying equatorial ocean model; and to examine the utility of specified data sets, in particular, observations of sea level, in estimating the state of the equatorial ocean. The results indicate that the assimilation procedure works very well when sufficient data are provided. However, sea-level data alone are not sufficient and must be supplemented with subsurface observations if more than a few baroclinic modes are allowed in the model ocean. The required amount of supplementary subsurface data (in the form of density profiles in these experiments) can be reduced by imposing smoothness contraints on the recovered model solution. 相似文献
16.
斜压大气中台风涡旋自组织的研究 总被引：2，自引：0，他引：2
文中利用MM5(V3),实施了8个数值试验,对斜压大气中台风涡旋自组织的问题进行了初步研究.结果表明:(1)在试验1中,没有引进一个半径为80 km的小涡旋,两个初始分离的半径为500 km的轴对称涡旋,一边互旋,一边相互排斥,两个涡旋中心之间的距离不断加大,致使双涡最终分离.(2)在试验2中引进了一个半径为80 km的小涡旋,其他条件同试验1,两个初始分离的轴对称涡旋一边互旋,一边相互逼近,经自组织形成了一个由内区和螺旋带组成的类似于台风环流的较大尺度的涡旋.这个结果支持周秀骥在十多年前提出的重要观点,也支持以往在正压框架内的同类研究结果.(3)试验3-8为在前两个试验的基础上取不同初始涡旋参数的敏感性试验,其中,试验3和4为引入小涡旋不同初始位置对台风涡旋自组织的影响,试验5和6为不同初始轴对称双涡间距对台风涡旋自组织的影响,试验7和8反映了不同初始轴对称双涡强度对台风涡旋自组织的作用.它表明对涡旋自组织过程影响最大的涡旋初始参数是涡旋之间的距离,其与正压模式中的结果是类似的. 相似文献
17.
Dr. R. Reiter 《Meteorology and Atmospheric Physics》1990,42(1):91-104
Summary Longterm recordings of the O3 concentration at the Zugspitze in 2964 m a.s.l. and at the Wank peak in 1780 m a.s.l. together with continuous daily measurements of cosmogenic radio-nuclides have been analyzed in order to ascertain whether or not a significant trend of O3 exists. Recordings from 1981 to 1988 show definitely that there was no trend of the O3 concentration in the free atmosphere between 1.8 and 3 km a.s.l. However, an increase of 10 ppb occurred 1978 to 1981.A cable car operating between Zugspitze and the valley (in 1000 m a.s.l.) over a two km height difference at the northern border of the Bavarian Alps has been used for atmospheric research. The run of this cable car is rather steep and is mostly suspended far away from the ground. Consequently it is ideal for simulataneously investigating the profiles of meteorlogical and atmospheric electrical parameters, and the ozone concentration. From 1980 to 1982 a total of 1990 ozone profiles have been recorded on fair weather days. The data collected offer a profound basis in order to study the time variations in the lower tropospheric ozone profile depending on the hour of the day during all seasons. The influence of the following atmospheric processes and conditions on the O3 profile pattern has been investigated:Vertical mixing intensity in and above the boundary layer, temperature inversions, photochemical production of ozone or its depletion in the lowermost layers, and stratospheric intrusions based on the measurements of cosmogenic radionuclides on Zugspitze, the upper end of the trail. The penetration depth of stratospheric O3 in the lower troposphere has been investigated and the shape and time behavior of temporarily O3 maxima within the boundary layer has been studied.With 12 FiguresExtended version of a paper presented at the International Conference on the Generation of Oxidants on Regional and Global Scales, held at the Univ. of East Anglia, Norwich, England, 3–7 July 1989. 相似文献
18.
Ted Munn founded Boundary-Layer Meteorology in 1970 and served as Editor for 75 volumes over a 25 year period. This short article briefly reviews Ted's scientific career with the Atmospheric Environment Service (of Canada), the International Institute for Applied Systems Analysis in Austria and with the Institute of Environmental Studies at the University of Toronto, and as editor of this journal. 相似文献
19.
Physick et al. (1989) have discussed some difficulties associated with simulation of the sea-breeze thermal internal boundary layer (TIBL), using a numerical model containing a profile exchange coefficient formulation developed by O'Brien (1970). They suggested that a closure scheme based on a prediction of turbulent kinetic energy (TKE) would be able to resolve the TIBL better than a profile scheme. This Research Note reports simulations of the case discussed in I, using a numerical model with a TKE-based turbulence closure. 相似文献