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我国热带气旋登陆时间日变化特征分析 总被引：8，自引：9，他引：8
利用1949～1999年<热带气旋年鉴>所给出的有关资料,分析了热带气旋登陆我国时间的变化特征.结果显示登陆时间具有某些日变化特征.就全国而言,登陆时间在夜晚和上午时段的出现频率较大,凌晨04～07时和下午13～18时出现频率较小.这一出现频率的日变化分布特征在广东表现得最为明显,登陆我国其它地区的时间日变化不明显.分析表明,较弱的热带气旋、登陆过程中强度减弱的热带气旋的登陆时间具有显著的日变化特征. 相似文献
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基于祁连山区2007年7～8月地基GPS遥感的大气可降水量(Precipitable Water,PW)资料、探空资料和自动气象站资料,采用谐波分析等方法,分析了祁连山区夏季PW的日变化特征,并初步探讨其成因。结果表明:祁连山区夏季PW具有明显的日变化特征。PW日变化特征在无降水日比有降水日更显著。日循环(24 h)与半日循环(12 h)是PW日变化的主要信号。在无降水日,PW日变化以日循环为主,振幅为0.8～1.6 mm,峰值出现的时间在18:00～21:00(北京时,下同)。半日循环的振幅为0.6～0.7 mm,峰值出现的时间在05:00～06:00和17:00～18:00。在有降水日,不同站点PW日变化特征有所不同,有的以日循环为主导,有的以半日循环为主导。PW日变化与逐时累积降水频次日变化具有明显的先后关系,两者日变化的位相差为2.5 h。PW日变化与气温和比湿等要素的日变化以及山谷风演变有关。 相似文献
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分析了１９９８ 年８ 月１４ 日开封区域性大～暴雨过程的前期环流形势、主要影响系统、能量场特征、稳定度指标,为区域性大～暴雨的预报提供了参考信息。 相似文献
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利用2000年7月12～16日逐时雨量、逐时风场、探空及多普勒雷达回波资料,分析了2000年7月12～16日河南连续性暴雨的雷达回波特征及中尺度系统活动与暴雨的对应关系,提示中尺度系统是造成暴雨的直接原因. 相似文献
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近40年中国高空温度变化的初步分析 总被引：6，自引：0，他引：6
为了了解高空气温的长期变化趋势,利用中国28个高空探空站1961—2000年间地面至高空10hPa的温度资料进行了统计分析,结果表明:从地面到高空200hPa最冷在1月,最热在7月;但是在最冷的100hPa层以上,其气温年变化位相相反,即1月最热,8月最冷;50hPa层以上温度的年变化不大。近40余年来,年平均气温变化趋势自地面至700hPa,绝大部分地区温度上升,尤其是地面增温最为显著,而西南地区有降温趋势;对流层上层至50hPa的平流层的温度在降低,尤其是50hPa降温最为显著。北半球的较强火山喷发对中国32°N以南的低纬与32°N以北的中高纬地区高空温度的影响不同。火山喷发后,低纬地区平流层第1~26个月温度均有不同程度增温,其中在第7~8个月增温最明显;在对流层以下,第6~11个月、第16~27个月出现2次明显降温时段,第1次降温最明显。中高纬地区平流层在第1~16个月、第20~29个月出现2段增温,第1段增温时间跨度长、强度大,第17~19个月出现了降温。在对流层以下第2~5个月、第14~18个月、第21~30个月出现3次明显降温时段,第3次降温持续时间长,整体降温强度较大。 相似文献
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Monthly mean surface pressure patterns in the European area are reconstructed for those winter and summer seasons of the 16th century with outstanding climatic anomalies being either widespread over Europe or remarkably intensive in some European regions. From the available documentary information about weather characteristics and their sequences, it proved possible to infer prevalent processes of lower tropospheric advection of typical air masses and to assess the position and strength of major surface pressure centres on a monthly scale. For comparison with modern pressure patterns, monthly mean sea level pressure (SLP) grids from the 20th century have been selected for seasons with similar climatic anomalies. There are broad coincidences between these pressure patterns of the 16th and the 20th centuries except for cold summer seasons. Finally, results from the 16th century are discussed in terms of circulation dynamics (different phases of the North Atlantic Oscillation (NAO) in winter, decreasing frequency of anticyclonic ridging in summer). 相似文献
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传统的高阶精度有限差分格式通常是在均匀网格的基础上推导得到的,在非均匀网格的情况下它会出现精度退化的问题。基于泰勒展开方法构造了一种适用于非均匀网格的2阶、4阶和6阶精度中央有限差分方案,利用Burgers方程和一维平流方程对新方案的性能进行测试,着重分析新方案对其误差大小及分布形态的改进效果。数值模拟结果表明:在非均匀网格下,提高差分方案的精度可明显减小数值解误差(降低了70%~88%),特别是当差分精度从2阶提高到4阶的时候。同时,高阶精度方案在梯度变化较大或者网格距较粗区域的模拟结果更有优势,4阶和6阶精度方案在以上区域的误差远小于2阶精度方案。方案可用于提高数值天气预报模式中非均匀分层模式的垂直差分计算精度。 相似文献
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利用郑州农业气象试验站1980—2006年冬小麦发育期、千粒重和穗粒数以及逐日气象资料,分析了影响千粒重和穗粒数的显著时段和关键因子,建立了千粒重和穗粒数的预测模型。结果表明:与千粒重相关显著的时段、关键因子是抽穗后15~19 d和29~33 d的温度以及9~13 d的日照;有利于获得较高千粒重的适宜温度范围为18.8~22.8℃,日平均气温上限为29.5℃;与穗粒数相关显著的时段、关键因子是返青后21~25 d的温度。相关显著时段的气候要素对千粒重和穗粒数具有较强的指示作用,可以较好地预测千粒重和穗粒数,为进行产量预报提供参考。 相似文献
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Annual surface temperature variations, 1602 to 1961, averaged over 77 United States and southwestern Canadian stations, are reconstructed from 65 aridsite tree-ring chronologies of western North America. Annual sea-level pressure reconstructions averaged over the North Pacific sector including North America and eastern Asia are inversely related to the temperature variations. Both the instrumental and reconstructed North American temperature averages are well correlated with Northern Hemisphere average temperatures during the early 20th-century warming but the correlation diminishes after the mid-1940s. The 1918 to 1947 interval is reconstructed to have been the warmest and 1877 to 1906 the coolest. The correlations between the temperature record and other high resolution temperature series from the Northern Hemisphere are generally insignificant. However, significant correlations are noted for certain 30-yr time periods. North American temperatures appear to have been out of phase with temperatures in Europe during the late 18th and early 19th centuries. Significant variations in the 30-yr mean temperatures are noted in several of the North American series. The warming early in the 20th century is the most marked followed by warming from 1717 to 1723 and from 1850 to 1866. Significant cooling occurs from 1810 to 1821 and from 1659 to 1669. 相似文献
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BRIAN H. LUCKMAN 《Climatic change》1997,36(3-4):455-476
Available meteorological, dendrochronological and glacier area change data are reviewed for the central Canadian Rockies. Limited glacier inventory studies indicate a loss of ca 25% of glacier area (greater for smaller glaciers) since the Little Ice Age maximum 130–150 years ago. The few available long climacte records are from widely spaced, valley floor sites, well below treeline. Available gridded or regional climate data sets similarly contain no high elevation sites. The five long (75 yr) station records contain a strong common signal but show differences in the relative amplitude and timing of temperature variations indicating links to either prairie or pacific stations. However the station network is too sparse to define the spatial extent of these patterns. Tree-ring chronologies from a network of Picea engelmannii (21), Larix lyallii (17) and Pinus albicaulis (2) treeline sites are presented and reviewed. Residual chronologies show stronger intercorrelation than standard chronologies and the larix chronologies are more highly correlated than picea, probably because of the narrower range of sites sampled. Many standard chronologies show a strong common regional signal of above average growth in the late 17th, late 18th and mid-20th centuries and reduced growth in the early 17th, early 18th and for most of the 19th centuries. However, examination of individual chronologies shows strong local or sub-regional divergence from this pattern that reflects smaller scale climate or non-climatic influences. Differences in the density and location of sites between the climate and tree-ring networks will create problems in resolving climate variation at the sub-regional scale. 相似文献
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利用红外卫星云图资料估计降水量方法的研究 总被引：6，自引：0，他引：6
在条件气候均匀及范围足够大取样区域,研讨面平均雨强与云覆盖率、云顶表面亮度温度的标准偏差、云覆盖率时间的变化率三者之间的关系,得到用１ｈ间隔的数字化红外卫星资料估计降水的三种模式。通过对１９９１年７月５日、６日、１０日降水过程的实例分析表明,对于日降水量的估计,效果较为理想。模式可用于与邓样时间和地点的相似气象条件区,且不需要对云进行分离和跟踪、考察对流单体的生命史演变过程,便于应用。 相似文献
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利用2012年4月1日—9月30日IBM P570高性能计算环境Oracle 11g数据库平台对全国自动气象站观测资料实时质量控制系统 (ARQCS) 的运行监控数据,探讨了ARQCS的启动策略及其与资料解析入库率、ARQCS的CPU耗时、服务时效之间的关系。结果表明:自动气象站资料的解析入库效率呈“几”字型分布,每个观测时次的第5—20分钟入库率方差较大,是制约ARQCS质量控制时效的主要时间段。设置观测资料入库率不低于95%为首次启动条件,不仅比传统的第15分钟定时启动提前了20.6 s,而且首次启动时观测资料入库率不低于95%的概率从66.38%提升至95.83%。第20分钟后入库率仅增加1.36%,在此设置首次质量控制的强制启动点,可保证局部异常延时的资料服务时效。动态启动策略使ARQCS的启动次数由5次降为2次,平均每日节约CPU时间391 min。 相似文献
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The present study investigated diagnostically the seasonal variation of the
bypassing flows caused by the splitting effect of the Tibetan Plateau (TP).
The relationships among the splitting bypassing flows around the TP to
precipitation in China, the westerly jet stream, and the thermal status over
the TP are revealed. The bypassing flows occur from the 1st to the 22nd
pentad and from the 59th to the 73rd pentad, respectively, and they
disappear from the 29th to the 58th pentad. They are strongest in winter
from the 1st to the 22nd pentad and from the 59th to the 73rd pentad,
respectively. During the rebuilding of the bypassing flows from mid-October
to mid-February, they are the main cause of precipitation over southeastern
China. The enhancement of the bypassing flow intensity in March can cause
the precipitation to increase in the early stage of the persistent spring
rain over southeastern China. From winter to summer, the seasonal transition
of the bypassing flows in the lower troposphere precedes that of the
westerly jet stream axis in the upper troposphere to the west of the TP by
～4 pentads, while from summer to winter lags by ～4 pentads. The
seasonal variation of the thermal status over the TP plays an important role
in the bypassing flows around the TP. The strengthening of the heating over
the TP weakens the bypassing flows, and the increase in cooling over the TP
is related to the rebuilding and strengthening of the bypassing flows. 相似文献
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This work aims, as a first step, to analyze rainfall variability in Northern Algeria, in particular extreme events, during the period from 1940 to 2010. Analysis of annual rainfall shows that stations in the northwest record a significant decrease in rainfall since the 1970s. Frequencies of rainy days for each percentile (5th, 10th, 25th, 50th, 75th, 90th, 95th, and 99th) and each rainfall interval class (1–5, 5–10, 10–20, 20–50, and ≥50 mm) do not show a significant change in the evolution of daily rainfall. The Tenes station is the only one to show a significant decrease in the frequency of rainy days up to the 75th percentile and for the 10–20-mm interval class. There is no significant change in the temporal evolution of extreme events in the 90th, 95th, and 99th percentiles. The relationships between rainfall variability and general atmospheric circulation indices for interannual and extreme event variability are moderately influenced by the El Niño-Southern Oscillation and Mediterranean Oscillation. Significant correlations are observed between the Southern Oscillation Index and annual rainfall in the northwestern part of the study area, which is likely linked with the decrease in rainfall in this region. Seasonal rainfall in Northern Algeria is affected by the Mediterranean Oscillation and North Atlantic Oscillation in the west. The ENSEMBLES regional climate models (RCMs) are assessed using the bias method to test their ability to reproduce rainfall variability at different time scales. The Centre National de Recherches Météorologiques (CNRM), Czech Hydrometeorological Institute (CHMI), Eidgenössische Technische Hochschule Zürich (ETHZ), and Forschungszentrum Geesthacht (GKSS) models yield the least biased results. 相似文献