共查询到19条相似文献,搜索用时 62 毫秒
1.
2.
河北平原一次持续大雾天气分析 总被引:2,自引:1,他引:1
利用气象观测资料和NCEP 1°×1°资料,从天气背景、温湿特征、层结条件、动力热力学特征等方面分析了2007年11月7~13日河北平原1次持续大雾的成因.结果表明:这次大雾是在较为稳定的大气环流背景下产生的,中高层以纬向环流为主,冷空气以扩散形势影响华北地区;地面夜间风速在0~2 m/s,充足的水汽及地面辐射冷却作用有利于大雾的形成和维持;大气层结是对流稳定的,同时近地面层为逆温结构;近地面层的弱辐合及持续微弱的暖平流十分有利于逆温层的维持,对于大雾长时间维持具有重要作用.大雾多发生在地面辐合线偏向冷空气一侧.本次大雾性质复杂,持续大雾由平流辐射雾-辐射雾-平流雾3个阶段构成,不同阶段大雾逆温强度及湿层厚度有所不同. 相似文献
3.
通过对1971-2008年贵州省08:00能见度资料及地面天气图的普查,选取382次区域性辐射大雾天气过程,分析了贵州区域性辐射大雾的时空特征.并利用1999-2008年93次辐射雾08:00地面和高空天气图,进行天气环流条件分析;并进一步利用地面站及高空资料,研究了形成辐射雾的气象条件.研究表明,贵州区域性辐射大雾主要集中在仲秋到隆冬时段,呈现“东多西少”的分布特征,均压场是区域性辐射大雾的地面环流条件,区域性辐射大雾的四种高空环流条件为西北气流、西南气流、副热带高压、平直西风气流.地面风速小、湿度大、夜间辐射降温显著及近地层有逆温、整层“上干下湿”是形成区域性辐射雾的气象条件. 相似文献
4.
山东中西部一次持续性大雾的形成及维持机制 总被引:2,自引:0,他引:2
利用常规气象观测资料和NCEP/NCAR提供的6 h再分析资料(分辨率为1°×1°),对2013年1月12-16日发生在山东中西部地区的一次持续性大雾天气过程从环流背景、层结条件、动力和热力学机制等方面进行了诊断分析。结果表明:中高层偏西气流、对流层低层温度脊和地面冷高压的稳定维持为这次持续性大雾过程提供了有利的环流背景;大雾过程经历了辐射雾—平流辐射雾—平流雾的复杂演变阶段,不同阶段的大雾湿层厚度及逆温强度有所不同;适当的风速和低层弱的水汽辐合有利于大雾稳定维持和发展;近地层辐合上升、中高层辐散下沉,易在界面形成逆温层,有利于大雾的出现,而整层的辐合上升运动往往容易形成中高云,不利于近地层水汽的聚集,难以形成大雾。 相似文献
5.
华北平原一次大雾天气过程的数值模拟 总被引:3,自引:0,他引:3
应用非静力平衡中尺度模式MM5V3,模拟分析了2005年11月19-21日发生在华北平原的一次大雾天气过程.结果表明,本次大雾是发生在相对稳定的大气环流背景下的辐射雾.模拟的天气形势与实况基本一致,模拟雾在范围、强度、生消时间等方面基本反映了实际大雾的生消变化规律.近地层逆温的维持和充沛的水汽条件对雾层长时间维持起着重要作用.诊断分析表明,大雾维持期间,雾区近地面层处在弱的水汽辐合区;900 hPa以上为辐散区和负涡度区,整层大气中下沉运动占主导,大规模的下沉辐散运动有利于中低层大气增温,与近地层的辐射降温相配合,有助于边界层内形成逆温;冷暖平流的作用也有助于逆温形成;地面和大气的长波辐射冷却,是最主要的降温因子;太阳短波辐射是导致大雾减轻及日变化的主要原因. 相似文献
6.
本文应用MICAPS探空资料(第五类站点数据)及地面观测资料(第一类格点数据、第四类站点数据)和NCEP再分析资料,对2009年11月13~14日发生在豫北地区的一次大雾天气过程的形成、持续及其性质转变的原因进行分析,发现地面中尺度辐合线(区)的时空分布与大雾过程有时间上的伴随关系。水汽通量输送和温度平流的变化以及地面辐射降温的共同作用导致了这次大雾的性质在持续过程中发生了转变,即由辐射雾变成平流雾。分析表明:13日08时之前豫北的降雪带来的充足水汽和夜间晴朗少云微风造成的辐射降温是形成辐射雾的主要原因;13日14时开始在豫北水汽通量输送加大和暖平流不断加强的同时地面持续降温,使得暖湿空气在较冷的下垫面冷却导致辐射雾转变为平流雾。 相似文献
7.
8.
华北冷涡影响山东降雹的成因分析 总被引:1,自引:1,他引:1
结合1995年6月24日午后--傍晚发生在我省中西部地区的一次降雹天气过程的诊断分析,探讨了在华北冷涡的环流背景上,造成山东大范围降雹的原因,结果表明:高层冷平流和低层暖平流同时向黄河下游地区输送造成大气层结稳定度急剧下降,为山东降雹创造了条件;高层辐射区叠置于低层耦合区上空,构成了中尺度对流系统产生的有利环境;而地面北方冷锋及相应的高空锋区南下,是产生冰雹等强对流天气的重要触发机制。 相似文献
9.
2007年初一次雪后大雾天气过程分析 总被引:1,自引:1,他引:1
大雾天气是主要的灾害性天气之一。利用多种观测资料和NCEP再分析资料,分析了2007年1月15日华北和黄淮地区的雪后大雾天气产生的天气背景及其形成的温湿条件和层结特征。结果表明:在这次大雾天气发生时,亚欧大陆中高纬度的环流形势为两槽一脊型,中纬度无明显冷空气活动,南支气流较为平直,天气形势比较稳定。华北和黄淮地区位于入海高压的后部,近地面层有弱的东北风或偏东风,即有利于海洋上暖湿气流的平流输送,又不至于破坏大雾形成的温湿条件。同时,大气层结是绝对稳定的,低层有深厚的逆温层,当暖湿空气平流到温度较低的下垫面上时冷却而形成雾,因而这次大雾天气属于典型的平流雾。这种形势的稳定维持,造成了这次持续时间较长的大范围的大雾天气。另外,华北和黄淮较低的海拔高度,有利于暖湿空气的平流进入,也是大雾形成的重要因子。 相似文献
10.
王春红 《沙漠与绿洲气象(新疆气象)》2011,5(5):15-19
采用中尺度数值预报WRF(Weather Research Forecast)模式,以NECP的1°×1°全球再分析资料作为初始场资料,对2009年10月25日发生在北疆沿天山石河子-乌鲁木齐机场一带的罕见辐射雾天气进行数值模拟和诊断分析。结果表明,大雾出现前的低槽降水为近地层提供了充足的水汽来源,高空冷槽和地面冷高压的快速移出新疆,使沿天山一带很快处于稳定的均压场控制,有利于大雾天气的发生。在水汽条件以及天气形势具备的情况下,局地热力条件日变化特征导致的气温及风场的变化,是辐射雾发生的重要影响因素,它不仅决定着逆温层结的建立与破坏,还影响着局地水汽条件的变化,最终影响着雾的生消。 相似文献
11.
Tornadoes have occurred in the territory of the Czech Republic throughout history. Although their frequency and intensity are not as high as in the USA, they can cause severe damage as well. That is why a systematic effort to document individual occurrences of this dangerous meteorological phenomenon as far as possible back into the past began in the 1990s. The aim of this investigation is to extend the first European catalogue of tornadoes originally published by Wegener [Wegener A., 1917. Wind-und Wasserhosen in Europe], by the addition of these cases from the Czech Republic.This paper adds further to Setvák, Šálek and Munzar [Setvák M., Šálek M., Munzar J., 2003. Tornadoes within the Czech Republic—from medieval chronicles to the internet society. Atmos. Res. 67–68, 589–605], who reported the earliest documented tornado in the land of the Czech Republic which occurred in AD 1119 in Prague. In so doing, it presents recently discovered tornado cases from the 16th to the early 20th centuries, found in a variety of historical sources since the last ECSS conference held in Prague in 2002. In particular we will focus on the case from Jablonec nad Nisou (northern Bohemia) in 1925, which was probably the first case in the Czech Republic with accompanying photographic documentation of damage caused by a tornado. 相似文献
12.
13.
Freezing of the Venetian Lagoon since the 9th century A.D. in comparision to the climate of western Europe and England 总被引:2,自引:0,他引:2
Dario Camuffo 《Climatic change》1987,10(1):43-66
In the first part of this study, typical of historical climatology, the various sources regarding freezing of the Venetian Lagoon since the 9th century A.D., are reported and discussed. The events are related, where possible, to teleconnections. Two synoptic patterns (weather type A: northerly and D: easterly) seem to have played an important role. After having discussed the dynamics of the icing processes, the problem of comparing the data is considered, as over the centuries many works were made on the Lagoon, in order to divert the major tributaries. In fact, the hydrological regime and the physical characteristic of the Lagoon environment were changed, so that the conditions necessary for freezing were no longer the same. The series was compared with the severe winters in westtern Europe and England, in order to reconstruct the past climate of the Mediterranean region and discuss the observed secular changes in the light of the widely accepted ideas of climatic variations. The comparison shows some differences: e.g. at Venice the Medieval Climatic Optimum with the occurrence of severe winters ended earlier and the Little Ice Age was broken by a milder interval. 相似文献
14.
20世纪两次全球增暖事件的比较 总被引:12,自引:1,他引:11
20世纪20年代和70年代全球出现了两次突变增暖,本文分析比较了这两次全球增暖的起源地,空间分布特点,影响范围,以及北半球增温和降温最大地区的气温变化与其相对应的大气环流变化的联系等.发现,第一次全球增暖始于北半球新地岛西北、冰岛及以北的极地地区,主要增暖区在北大西洋、格陵兰岛、冰岛和北半球中、高纬大陆地区,主要增暖季节是夏季.第二次全球增暖最早可能始于南半球南印度洋海盆及南极大陆地区,增暖中心有明显向北半球方向移动的倾向并广泛影响到全球热带、副热带海洋,没有明显的区域和季节增暖差异;北半球第二次增暖比南半球约晚10年,主要增温区在东亚大陆和北美西部,主要增暖季节在冬季.分析还发现,20世纪北半球增暖最强的东亚大陆、北美西北部和降温显著的冰岛、格陵兰岛、北大西洋以及中北太平洋等地的气温变化与其相应的大气环流系统的异常变化关系密切. 相似文献
15.
16.
Drought in the Bulgarian low regions during the 20th century 总被引:1,自引:1,他引:0
Summary In this study, the long-term variations in precipitation in the Bulgarian low regions: the Danube Plain in north Bulgaria
and the Thracian Lowland in south Bulgaria, were analysed. Some quantitative criteria were also used to compare drought frequency
and intensity between the two regions and between different years. Analyses of the rainy conditions in the selected regions
during the 20th century were carried out. The last century can be split into several wet and dry sub-periods with duration
of 10–15 years. The long-term variations of the Ped and PAI drought indices are also considered in the paper. In addition,
the drought conditions in the Danube Plain and the Thracian Lowland were estimated using the de Marton aridity index. The
results obtained show that the latter index can also be applied for the detection of drought periods in the regions considered.
Authors’ address: Ekaterina Koleva, Vesselin Alexandrov, National Institute of Meteorology and Hydrology, 66 Tzarigradsko
shose, 1784 Sofia, Bulgaria. 相似文献
17.
18.
Blanca Mendoza Virginia García-Acosta Victor Velasco Ernesto Jáuregui Rosa Díaz-Sandoval 《Climatic change》2007,83(1-2):151-168
Using unprecedented catalogues of past severe drought data for the Yucatan Peninsula between 1502 and 1900 coming from historical
written documentation, we identified five conspicuous time lapses with no droughts between 1577–1647, 1662–1724, 1728–1764,
1774–1799 and 1855–1880, as well as time epochs with most frequent droughts between 1800 and 1850. Moreover, the most prominent
periodicity of the historical drought time series was that of ∼40 years. Using the Palmer Drought Severity Index for the Yucatan
Peninsula for the period 1921–1987 we found prominent negative phases between ∼1942–1946 and 1949–1952, 1923–1924, 1928–1929,
1935–1936, 1962–1963, 1971–1972 and 1986–1987. Two prominent periodicities clearly appear at ∼5 and 10 years. Most modern
and historical severe droughts lasted 1 year, and share a quasi-decadal frequency. Also, in the first 66 years of the twentieth
century the frequency of occurrence of severe drought has been lower compared with the nineteenth century. Some of the major
effects and impacts of the most severe droughts in the Yucatan region are examined. We also studied the relation between historical
and modern droughts and several large scale climate phenomena represented by the Atlantic Multidecadal Oscillation (AMO) and
the Southern Oscillation Index (SOI). Our results indicate that historical droughts and the cold phase of the AMO coincide,
while the influence of the SOI is less clear. The strongest coherence between historical droughts and AMO occurred at periodicities
of ∼40 years. For modern droughts the coherence of a drought indicator (the Palmer Drought Severity Index) is similar with
AMO and SOI, although it seems more sustained with the AMO. They are strongest at ∼10 years and very clearly with the AMO
cold phase. Concerning the solar activity proxies and historical droughts, the coherence with a record of beryllium isotope
Be10, which is a good proxy of cosmic rays, is higher than with Total Solar Irradiance. We notice that the strongest coherence
between historical droughts and Be10 occurs at periods ∼60–64 years. When studying modern droughts and solar activity, frequencies of ∼8 years appear, and the
coherences are similar for both sunspots and cosmic rays. Comparing natural terrestrial and solar phenomena, we found that
the most sustained and strongest modulation of historical drought occurrence is at ∼60–64 years and is between the historical
drought series and the solar proxy Be10. For modern droughts we notice that the coherence is similar among AMO, SOI and the solar indices. We can conclude that the
sea surface temperatures (AMO) and solar activity leave their signal in terms of severe droughts in the Maya lands, however
in the long term, the influence of the SOI on this type of phenomenon is less clear. 相似文献
19.
K.R. Briffa P.D. Jones R.B. Vogel F.H. Schweingruber M.G.L. Baillie S.G. Shiyatov E.A. Vaganov 《Climatic change》1999,43(1):151-168
We present a selective review of tree-ring variability and inferred climate changes in Europe during the 16th century. The dendroclimatological evidence is assessed within the context of the last 500 years and some interpretational problems are discussed. The tree-ring evidence is compared with various non-dendroclimatic evidence. The body of evidence shows that a large region of mid and northern Europe experienced a sharp cooling at around 1570/80 that, at least in the north, marked a shift towards a prolonged period of cool conditions. This region had its southern boundary in the Alps and there is little evidence for a major cooling in southern Europe. 相似文献