首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 62 毫秒
1.
介绍了一种比较实用的寻找拟合周期的方法,并在此基础上求出相应的误差周期,然后叠加作出未来的趋势预报。文内给出了实用效果。  相似文献   

2.
段荣 《贵州气象》1996,20(5):5-6
本文应用误差对兴义市37年6-8月总降雨量进行周期分析,结果表明,历年兴义市6-8月总雨量以16年为主周期,15年较正周期,迭加振动出现。对1994年6-8月总降雨量进行试报,不仅降雨量趋势正确,数值了民比较接近实况。  相似文献   

3.
利用功率谱、交叉谱分析方法,研究了我国东北地区夏季气温民赤道东太平洋海温序列的周期振荡及其相互关系。结果发现,东北气温存在3.5年的显著周期,赤道东太平洋海温也有3.5年的振荡周期。二者在2.3年振动周期附近有很好的关系,且赤道东太平洋海温的变化超前于东北夏季气温0.33年。  相似文献   

4.
贵阳近八十年气温变化的小波分析   总被引:2,自引:2,他引:2  
刘益兰 《贵州气象》2001,25(2):10-14
对1921-1999年贵阳市年、月平均气温序列进行了统计和小波变换。结果表明:温度增暖期和变冷期与小波波幅中心间的周期增长、波幅加强有关。除春季外,其余季节和年气温变化均以16年左右尺度的冷暖交替表现出明显周期特征,32年周期特征也较明显,其余时间尺度的周期变化不明显,也没有出现明显的频率突变。春季气温变化则以8年周期最为明显。  相似文献   

5.
利用Z指数旱涝指标,分析了河南省各地夏季10年时间尺度的旱涝演变,进行了夏季旱涝趋势拟合,并利用功率谱分析了河南省各地夏季旱涝变化周期。  相似文献   

6.
华北地区降水的准周期信号及其阶段性变化特征   总被引:7,自引:0,他引:7  
应用奇异谱(SSA)方法分析了华北地区降水的准周期信号及其阶段性变化特征,结果表明,华北地区月降水序列的年际振荡信号较强,占总方差的44.7%,显著振荡周期分别有17个月(准1~2a)、30个月(准2~3a)、60个月(准5a)和11个月(准1a),不同分区降水的准周期振荡信号各有差异。各种准周期振荡随时间的长期演变亦很明显且各不相同。奇异交叉谱(SCSA)诊断表明,华北地区降水的年际振荡与Nino区海温的准周期信号存在着显著的耦合关系,且这种耦合关系随时间是变化的,表现出耦合振荡强度的阶段性变化和耦合位相随时间的改变。各分区降水与不同Nino区海温的显著耦合周期信号及其随时间的长期演变各具特色,体现了华北地区降水对Nino区海温异常响应的复杂性。  相似文献   

7.
用周期分析方法预测全球稻谷总产量   总被引:2,自引:0,他引:2       下载免费PDF全文
李军  杨星卫  汪治澜 《气象》1997,23(7):32-34
应用功率谱和逐步回归周期分析方法对全球稻谷总产量预测进行了探讨,结果表明逐步回归周期分析方法具有很好的拟合精度和较高的预测精度。  相似文献   

8.
1概述我们常常把某些要素看成是随时间作周期变化的,时间序列上某位置的要素是该要素前期作周期性变化的结果,并以此制作中长期预报。沿用正弦波的普遍表达式:__。_,2穴^。Rn一ZASin(n尖十o)……………………()—“““—“““”““L””‘””“”根据各周期的长度、振幅及初位相来求Rn的值。依此,在下面提出一种简化的周期分析方法。本文把时间序列(R则用中值分为两档,按序号逐个统计符合档内各周期的个例数,选取个例数较多的周期,以个例数(或经修订)为权重系数,建立表达式R。’一Zai’R’/Zai’和R。”一Za…  相似文献   

9.
甘一忠 《广西气象》1997,18(4):20-22
提出以方差分析周期因素嵌入逐步回归建立灾害天气长期预报模型方法,应用结果表明:模型预报精度及稳定性均比单纯的周期分析或利用前期气象因子建立回归模型有明显改善。  相似文献   

10.
近40年我国气温时空变化特征   总被引:53,自引:5,他引:53       下载免费PDF全文
根据全国336个站逐旬地面气温资料,使用EOF分析、周期图等统计方法,揭示了最近40年我国气温时空变化特征。研究结果表明:我国气温年际变化和变化趋势存在明显的地区、季节差异。在总趋势升高的基础上,具有前期降温、后期升温,冬季升温、夏季降温等特点。而且在气温变化趋势上存在准周期振荡。  相似文献   

11.
叶茵  余清 《贵州气象》2004,28(4):37-38
我局从1999~2003年,测报工作连续4年未出现错情,在此期间共有1个250个班,9个百班无错通过上级业务部门验收.在仪器保管、使用、维护上符合要求,对外报送的各种表、簿都能做好出门合格.  相似文献   

12.
Summary Considering the effects of causal mechanics on geophysical problems enables us to explain a number of phenomena, which cannot be explained from conventional positions. This paper shows that the introduction of the force of causality in a simple barotropic hydrodynamic model of weather forecasts results in the outcomes, which, on the one hand, can not be described from the positions of classical hydro-thermodynamics, whilst on the other hand, exist in nature.  相似文献   

13.
Due to the complex orography and the presence of the moisture-saturated air, the Mediterranean region is characterized by the increased baroclinic and convective instability, that leads to the sudden cyclogenesis and the formation of dangerous weather phenomena. The results are given of the investigation of formation mechanisms of Mediterranean cyclones, peculiarities of stages of their evolution and dynamical processes, which occur throughout the atmosphere, using the regional numerical ETA model of the atmosphere by the example of individual cases of the cyclogenesis over the Mediterranean Sea. It is revealed that the cold Arctic air outbreak (the intrusion of the cold Arctic air) to the south of the Western Europe, leading to the formation of the areas of the baroclinic instability and the increased moisture content of the air in the area of the vortex origin, favors the cyclogenesis. The use of the vertical coordinate η in the model enabled to compute more precisely the vertical wind speed, therefore, the influence of the orography on the moisture content and precipitation increase became pronounced. The transformation of the structure of meteorological fields in the course of the development of vortexes is considered. The computation of the helicity is made, and it is shown that this characteristic can be one of the earliest predictors of cyclogenesis.  相似文献   

14.
Here, we analyze the characteristics and the formation mechanisms of low-level jets(LLJs) in the middle reaches of the Yangtze River during the 2010 mei-yu season using Wuhan station radiosonde data and the fifth generation of the European Centre for Medium-Range Weather Forecasts(ERA5) reanalysis dataset. Our results show that the vertical structure of LLJs is characterized by a predominance of boundary layer jets(BLJs) concentrated at heights of 900–1200 m.The BLJs occur most frequently at 230...  相似文献   

15.
On the determination of the height of the Ekman boundary layer   总被引:1,自引:1,他引:1  
The heighth of the Ekman turbulent boundary layer determined by the momentum flux profile is estimated with the aid of considerations of similarity and an analysis of the dynamic equations. Asymptotic formulae have been obtained showing that, with increasing instability,h increases as ¦¦1/2 (where is the non-dimensional stratification parameter); with increasing stability, on the other hand,h decreases as –1/2. For comparison, a simple estimate of the boundary-layer heighth u determined by the velocity profile is given. As is shown, in unstable stratification,h u behaves asymptotically as ¦¦–1, i.e., in a manner entirely different from that ofh .  相似文献   

16.
流场配置及地形对西南低涡形成的动力作用   总被引:10,自引:8,他引:10  
高守亭 《大气科学》1987,11(3):263-271
本文采用定常二层模式讨论较小地形及高、低层流场配置对西南低涡形成的动力作用。指出了西南低涡的形成是与盆地、河谷以及其上气流分层有关的一种定常态.在上、下为西风分层时期,低层的浅薄暖湿西风有利于西南低涡的形成.在上、下为东、西风分层时期,上层浅薄东风亦有利于西南低涡的形成.小型的凸起山脉对西南低涡的形成没有作用.  相似文献   

17.
1引言我国执行接地降阻剂测试的技术标准是全国电力系统起草的:“接地降阻剂暂行技术条件修改稿”。在技术要求中要求接地降阻剂的酸碱值应在7 ̄12范围内。在实际使用中发现该技术要求对接地降阻剂的酸碱值要求范围并不合理,需要分析和讨论。2接地降阻剂的PH值接地降阻剂的酸碱性对地网的使用寿命至关重要,为了不让接地降阻剂腐蚀接地体或者减弱接地降阻剂对接地体的腐蚀,在接地降阻剂测试的技术要求中,对接地降阻剂的酸碱度有一定的限制。国内各厂家用于生产接地降阻剂的偏弱酸的盐类进行了对镀锌钢材腐蚀的试验,结果是这些镀锌钢材均受到…  相似文献   

18.
文章选用阴山山脉山北乌拉特后旗、白云、达茂旗、苏尼特左旗、化德,山南杭后旗、包头、呼和浩特、察右前旗、兴和1971—2000年气温、降水量、天气现象等资料进行对比分析,得到阴山山脉对内蒙古自治区中部地区气象要素影响初步结论。  相似文献   

19.
利用40年气温、降水资料和历史上千旱、低温严重的年份与2003年进行对比分析.评估黑龙江省2003年发生的严重灾害的分布范同,灾害程度,及其对主要粮食作物生长发育和产量的影响。得出2003年的灾害是30年未遇的全省性严重灾害年,各种灾害对各种作物都产生了不同程度的影响,受害最重的作物是小麦。  相似文献   

20.
Summary ?Some features of the climate system that can be considered predictors of the onset and end of the convective season over the Amazon were identified using one-month lag correlations and field composites. The fields analyzed were sea surface temperature (SST), outgoing long-wave radiation (OLR), vertical velocity and upper tropospheric winds. Warm (cold) anomalies in the SST in the tropical North Atlantic and the Caribbean Sea tend to be associated with delayed (early) onsets. Likewise, there is a tendency towards a delayed (early) end of the convective season with cold (warm) anomalies in these ocean regions. In addition, the SST in the cold tongue region of the equatorial Pacific is negatively, though weakly correlated with the onset date. The signal of this SST is more evident in the case of the end date, which is earlier with respect to its mean date in most of El Ni?o cases. The convective activity intensity itself conditions the onset and the end of the convective season, as it is evidenced by the behavior of the OLR and the vertical velocity fields. The more (less) intense the convective activity over South America during the preceding month, the earlier the onset and the later the end of the convective season on the Amazon region. The prediction of the onset and end dates of the convective season in the Amazon region was explored using a simple multiple regression technique based on the variables that have shown precursor signals with respect to these dates. The correlation coefficient between the predicted and the observed onset date is 0.81, and in the case of the end date, it is 0.76. The skill to predict early, delayed and normal categories was high, since in more than two thirds of the cases the category was successfully predicted, and there were no predictions of categories opposed to those observed. Received July 23, 2001; revised February 22, 2002; accepted April 26, 2002  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号