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提出一种区域旱涝转换期定义方法,并对西南地区东部1961-1995年旱涝转换期进行了划定,结果表明:本文对西南地区东部旱涝转换期定义方法是可行的;在西南地区东部,转换日期最早出现于6月第6候,最晚出现于7月第6候,主要集中于6月第6候、7月第1、2、4候;旱涝转换具有东多西少、南早北迟的特点,部分年份各地旱涝转换日期并不一致. 相似文献
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在分析西南地区东部旱涝转换特点基础上,利用北半球500hPa 候平均高度场和ECMWF数值预报场资料,经过不同尺度的相似过滤和集成,得到未来若干候的降水分布,推断出旱涝转换开始期.试验结果令人满意. 相似文献
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在分析西南地区东部旱涝转换特点基础上,利用北半球５００ｈＰａ候平均高度场和ＥＣＭＷＦ数值预报场资料,经过不同尺度的相似过滤和集成,得到未来若干候的降水分布,推断出旱涝转换开始期,试验结果令人满意。 相似文献
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西南地区夏季严重旱涝划分方法 总被引：3，自引：3，他引：0
运用川云贵三省１９６１－１９９４年５－８月降水资料,分别计算了西南地区５－６月、７－８月、６－８月三个时段的旱涝指数、结果表明,用旱涝指数来划分旱涝、具有客观定量地、正确地反映出旱涝的基本特征。 相似文献
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南海夏季风演变的气候学特征 总被引：17，自引：2，他引：17
本文总结南海北部地区夏季风演变的气候学特征，发现南海地区５月第３候对流层高层东风和北风爆发，对流层低层西风第１次跃升，东亚经向季风环流圈开始形成，这可以成为南海地区夏季风爆发的标志。对流层低层西风在６月中旬开始的第２次连续跃升对应江淮地区的梅雨爆发期。类似地，中国大陆夏季对流层低层５月初和６月初有两次爆发性增暖过程，第２次比第１次强烈得多。南海北部地区对流层低层纬向风速、比湿盛夏呈双峰型，纬向风速峰值分别出现在６月第５候和８月第４候，比湿峰值分别出现在６月第６候和８月第５候。比湿突升对应纬向风速突升，但略落后于风速峰值出现的时间。南海北部地区季风爆发前，温度是波动式上升的，南海季风爆发后，温度是波动式下降的。中国大陆东部及南海地区夏季对流层低层比湿分布有３次突变，即４月中旬南海北部比湿突增，并开始出现高比湿中心，而南海南部为最大比湿中心；５月中旬最大比湿中心已从南海南部跳到了南海北部－华南并向江淮流域扩展；６月中旬江淮流域比湿突增并一直维持到８月，同时南海南部高比湿带消失。而５月中旬ＯＬＲ有一次突变，ＯＬＲ低值区爆发性向北扩张，这对应于南海地区夏季风的爆发。而孟加拉湾地区夏季风演变的气候学特征与南海地区有较 相似文献
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采用1968—2009年NCEP/NCAR逐候再分析资料,分析了季节转换期间中东急流的变化特征及其热力机制。结果表明:中东急流中心的强度和位置存在明显的季节变化特征,第67候—次年第24候偏强且位置稳定偏南(27.5 °N)、第38—44候偏弱且位置稳定偏北(45 °N)。200 hPa纬向风场EOF第1空间模态反映了中东急流在冬、夏季的位置,冬季主要位于埃及和沙特阿拉伯上空,夏季主要位于黑海东部至咸海东部上空,且中东急流在冬季比在夏季强。第26—31候和第54—61候分别是中东急流春夏季和秋冬季的季节转换期,其200 hPa西风演变与500～200 hPa平均南北温差演变的对应关系很好,表明南北温差的季节性转变导致了200 hPa西风的季节性转变。个例分析表明,印度夏季风爆发日期早晚与中东急流季节转换日期早晚的关系非常密切。印度夏季风爆发较早（晚）时,由于500～200 hPa南北温差大值区域向北推进较早（晚）,因此,中东急流向北推进较早（晚）,同时40～90 °E对流层低层西风急流出现也较早（晚）。 相似文献
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冷空气活动频繁全国大部降水偏多—１９９６年１１月—孙军（中央气象台，北京１０００８１）１１月共有６次冷空气影响我国，较常年频繁，全国大部地区气温接近常年或偏低；我国大部地区降水正常或偏多，其中黄淮、江淮、江南西部、西南地区东部上、中旬出现连阴雨天气，... 相似文献
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２００１年７～９月江西省气候特点是：（１）炎凉相间。７月份高温天气集中，天气酷热；８月晴雨相间，天气偏凉；９月秋高气爽。（２）冷空气强度弱。９月份没有出现寒露风天气。（３）我省中北部７月和９月分别出现中度伏旱和秋旱，但由于大部分县市积极开展了人工增雨作业，有效地减轻了旱灾。２００１年７～９月平均气温全省为２５．７～２８．２℃，距平为－０．９～０．６℃，北部、西部略偏高，南部、东部略偏低；降水全省为１１７～７３７mm，距平为－６．５～７．２成，赣北赣西北偏少２～５成，赣南及武夷山西侧偏多２～５成；总… 相似文献
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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
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Comparing the theoretical versions of the Beaufort scale, the T-Scale and the Fujita scale 总被引：1，自引：0，他引：1
G. Terence Meaden S. Kochev L. Kolendowicz A. Kosa-Kiss Izolda Marcinoniene Michalis Sioutas Heino Tooming John Tyrrell 《Atmospheric Research》2007,83(2-4):446-449
2005 is the bicentenary of the Beaufort Scale and its wind-speed codes: the marine version in 1805 and the land version later. In the 1920s when anemometers had come into general use, the Beaufort Scale was quantified by a formula based on experiment. In the early 1970s two tornado wind-speed scales were proposed: (1) an International T-Scale based on the Beaufort Scale; and (2) Fujita's damage scale developed for North America. The International Beaufort Scale and the T-Scale share a common root in having an integral theoretical relationship with an established scientific basis, whereas Fujita's Scale introduces criteria that make its intensities non-integral with Beaufort. Forces on the T-Scale, where T stands for Tornado force, span the range 0 to 10 which is highly useful world wide. The shorter range of Fujita's Scale (0 to 5) is acceptable for American use but less convenient elsewhere. To illustrate the simplicity of the decimal T-Scale, mean hurricane wind speed of Beaufort 12 is T2 on the T-Scale but F1.121 on the F-Scale; while a tornado wind speed of T9 (= B26) becomes F4.761. However, the three wind scales can be uni-fied by either making F-Scale numbers exactly half the magnitude of T-Scale numbers [i.e. F′half = T / 2 = (B / 4) − 4] or by doubling the numbers of this revised version to give integral equivalence with the T-Scale. The result is a decimal formula F′double = T = (B / 2) − 4 named the TF-Scale where TF stands for Tornado Force. This harmonious 10-digit scale has all the criteria needed for world-wide practical effectiveness. 相似文献
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准两年振荡对大气中微量气体分布的影响 总被引：11，自引：5，他引：6
NCAR的包含化学、辐射、动力相互作用的两维模式（SOCRATES）移植回国后进行了初步的模拟试验,用以研究某些对环境问题重要的微量气体的化学、辐射、动力传输过程。在不考虑极地平流层云和气溶胶表面非均相化学等情况下,模式积分多年,计算结果稳定,模拟的风场、温度场显示出正常的季节变化,模拟的微量气体分布与卫星实测资料对照,结果也比较一致。为了探讨热带平流层风场的准两年周期振荡（QBO）对平流层微量气体分布的影响,我们做了QBO强迫的数值试验,即在模式中加入QBO强迫,并与不考虑QBO强迫的模拟结果对比。结果表明,QBO与其相关的次级环流所引起动力输送的变化,使平流层微量气体分布发生变化。 相似文献
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The impact of high resolution modern vegetation cover on the West African climate is examined using the International Centre for Theoretical Physics Regional Climate Model implementing the NCAR Community Land Model. Two high resolution 25 km long-term simulations driven by the output from a coarser 50-km resolution simulation are performed for the period 1998–2010. One high resolution simulation uses an earlier and coarser-resolution version of plant functional type distribution and leaf area index, while the other uses a more recent, higher-quality, and finer-resolution version of the data. The results indicate that the new land cover distribution substantially alters the distribution of temperature with warming in Central Nigeria, northern Gulf of Guinea and part of the Sahel due to the replacement of C4 grass with corn; and cooling along the coastlines of the Gulf of Guinea and in Central Africa due to the replacement of C4 grass with tropical broadleaf evergreen trees. Changes in latent heat flux appear to be largely responsible for these temperature changes with a net decrease (increase) in regions of warming (cooling). The improved land cover distribution also results in a wetter monsoon season. The presence of corn tends to favor larger precipitation amounts via more intense events, while the presence of tropical broadleaf evergreen trees tends to favor the occurrence of both more intense and more frequent events. The wetter conditions appear to be sustained via (1) an enhanced soil moisture feedback; and (2) elevated moisture transport due to increased low-level convergence in regions south of 10N where the most substantial land cover differences are present. Overall the changes induced by the improved vegetation cover improve, to some extent, the performance of the high resolution regional climate model in simulating the main West African summer monsoon features. 相似文献
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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
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
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由中国历史气候记录对季风导致唐朝灭亡说的质疑 总被引：1，自引：0，他引：1
张德二 《气候变化研究进展》2008,4(2):126-130
2007年1月4日杂志发表了Yancheva等10人的题为"Influence of the intertropical convergence zone on the East-Asian monsoon"(热带辐合带对东亚季风的影响)的论文[1],这是德国波兹坦地学研究中心气候动力与沉积学科的主管豪格(G.H.Haug)率领的科研小组的一项成果,认为是季风的变化引起的长期干旱导致了唐朝的灭亡. 相似文献
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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
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Chunguang CUI Wen ZHOU Hao YANG Xiaokang WANG Yi DENG Xiaofang WANG Guirong XU Jingyu WANG 《大气科学进展》2023,40(4):711-724
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