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1.
Summary Using digitized IR images from the European satellite Meteosat, 153 squall lines (SLs) were observed over Western Africa during
July, August and September 1986 and 87. The SL mean rainfall volume was computed using the daily rainfall amounts of more
than 800 raingauges: 15 km3 in 1986 and 22.5 km3 in 1987. A mean amount of 15 mm was collected per rainy episode at a given station, however, as only about half of the stations
situated under a SL experienced a rainy episode, the rainfall amount averaged along the total SL’s swath was 6.8 mm.
With the help of the 8 daily Meteosat slots the SL’s area daily variation could be estimated: namely a minimum around noon
and a maximum around midnight. Using the SLs displacements (east–west) one had access to the daily variation of the rainfall
volume, a minimum in the morning and a maximum toward the end of the afternoon, as already found by several authors who used
Meteosat images. 相似文献
2.
Summary The west coast of the Indian peninsula receives very heavy rainfall during the summer Monsoon (June–September) season with
average rainfall over some parts exceeding 250 cm. Heavy rainfall events with rainfall more than 15 cm day−1 at one or more stations along the west coast of India occur frequently and cause considerable damage. A special observational
programme, Arabian Sea Monsoon Experiment, was carried out during the monsoon season of 2002 to study these events. The spatial
and temporal distributions of intense rainfall events, presented here, were used for the planning of this observational campaign.
The present study using daily rainfall data for summer monsoon season of 37 years (1951–1987) shows that the probability of
getting intense rainfall is the maximum between 14° N–16° N and near 19° N. The probability of occurrence of these intense
rainfall events is high from mid June to mid August, with a dip in early July. It has been believed for a long time that offshore
troughs and vortices are responsible for these intense rainfall events. However, analysis of the characteristics of cloud
systems associated with the intense rainfall events during 1985–1988 using very high resolution brightness temperature data
from INSAT-IB satellite shows that the cloud systems during these events are characterized by large spatial scales and high cloud tops.
Further study using daily satellite derived outgoing longwave radiation (OLR) data over a longer period (1975–1998) shows
that, most of these events (about 62%) are associated with systems organized on synoptic and larger scales. We find that most
of the offshore convective systems responsible for intense rainfall along the west coast of India are linked to the atmospheric
conditions over equatorial Indian Ocean. 相似文献
3.
An Analysis of a Meso-β System in a Mei-yu Front Using the Intensive Observation Data During CHeRES 2002 总被引：3，自引：0，他引：3
The conventional and intensive observational data of the China Heavy Rain Experiment and Study (CHeRES) are used to specially analyze the heavy rainfall process in the mei-yu front that occurred during 20-21 June 2002, focusing on the meso-β system. A mesoscale convective system (MCS) formed in the warm-moist southwesterly to the south of the shear line over the Dabie Mountains and over the gorge between the Dabie and Jiuhua Mountains. The mei-yu front and shear line provide a favorable synoptic condition for the development of convection. The GPS observation indicates that the precipitable water increased obviously about 2-3h earlier than the occurrence of rainfall and decreased after that. The abundant moisture transportation by southwesterly wind was favorable to the maintenance of convective instability and the accumulation of convective available potential energy (CAPE). Radar detection reveals that meso-β and -γ systems were very active in the MαCS. Several convection lines developed during the evolution of the MαCS, and these are associated with surface convergence lines. The boundary outflow of the convection line may have triggered another convection line. The convection line moved with the mesoscale surface convergence line, but the convective cells embedded in the convergence line propagated along the line. On the basis of the analyses of the intensive observation data, a multi-scale conceptual model of heavy rainfall in the mei-yu front for this particular case is proposed. 相似文献
4.
一次暴雨过程诊断分析 总被引：2，自引：2，他引：0
2010年7月11—12日南京市江宁全区普降暴雨到大暴雨。本文利用M3、NCEP/NCAR全球资料同化系统再分析等资料(1°×1°)应用环境分析、物理量场诊断,对产生这次暴雨的形势背景、低空急流、水汽输送、垂直运动、中小尺度系统和强对流云团进行分析。结果表明:在有利的环流背景条件下,中小尺度系统发生发展和演变是这次暴雨产生的直接原因;低空急流为这次暴雨提供了大量的水汽和不稳定能量;中低空切变两侧的水平风场切变不仅为暴雨产生提供了强烈的辐合上升运动,同时对水汽的水平辐合和垂直输送非常有利;强对流云团的生成、移动与强降水的发生密切相关。 相似文献
5.
R. García-Herrera D. Barriopedro E. Hernández D. Paredes J. F. Correoso L. Prieto 《Meteorology and Atmospheric Physics》2005,90(3-4):225-243
Summary This paper characterizes Mesoscale Convective Systems (MCSs) during 2001 over Iberia and the Balearic Islands and their meteorological
settings. Enhanced infrared Meteosat imagery has been used to detect their occurrence over the Western Mediterranean region
between June and December 2001 according to satellite-defined criteria based on the MCS physical characteristics.
Twelve MCSs have been identified. The results show that the occurrence of 2001 MCSs is limited to the August–October period,
with September being the most active period. They tend to develop during the late afternoon or early night, with preferred
eastern Iberian coast locations and eastward migrations. A cloud shield area of 50.000 km2 is rarely exceeded. When our results are compared with previous studies, it is possible to assert that though 2001 MCS activity
was moderate, the convective season was substantially less prolonged than usual, with shorter MCS life cycles and higher average
speeds. The average MCS precipitation rate was 3.3 mm·h−1 but a wide range of values varying from scarce precipitation to intense events of 130 mm·24 h−1 (6 September) were collected. The results suggest that, during 2001, MCS rainfall was the principal source of precipitation
in the Mediterranean region during the convective season, but its impact varied according to the location.
Synoptic analysis based on NCEP/NCAR reanalysis show that several common precursors could be identified over the Western Mediterranean
Sea when the 2001 MCSs occurred: a low-level tongue of moist air and precipitable water (PW) exceeding 25 mm through the southern
portion of the Western Mediterranean area, low-level zonal warm advection over 2 °C·24 h−1 towards eastern Iberia, a modest 1000–850 hPa equivalent potential temperature (θe) difference over 20 °C located close to the eastern Iberian coast, a mid level trough (sometimes a cut-off low) over Northern
Africa or Southern Spain and high levels geostrophic vorticity advection exceeding 12·10−10 s−2 over eastern Iberia and Northern Africa. Finally, the results suggest that synoptic, orographic and a warm-air advection
were the most relevant forcing mechanisms during 2001. 相似文献
6.
Joan Bech Nicolau Pineda Tomeu Rigo Montserrat Aran Jéssica Amaro Miquel Gayà Joan Arús Joan Montanyà Oscar van der Velde 《Atmospheric Research》2011,100(4):621-637
This study presents an analysis of a severe weather case that took place during the early morning of the 2nd of November 2008, when intense convective activity associated with a rapidly evolving low pressure system affected the southern coast of Catalonia (NE Spain). The synoptic framework was dominated by an upper level trough and an associated cold front extending from Gibraltar along the Mediterranean coast of the Iberian Peninsula to SE France, which moved north-eastward. South easterly winds in the north of the Balearic Islands and the coast of Catalonia favoured high values of 0–3 km storm relative helicity which combined with moderate MLCAPE values and high shear favoured the conditions for organized convection. A number of multicell storms and others exhibiting supercell features, as indicated by Doppler radar observations, clustered later in a mesoscale convective system, and moved north-eastwards across Catalonia. They produced ground-level strong damaging wind gusts, an F2 tornado, hail and heavy rainfall. Total lightning activity (intra-cloud and cloud to ground flashes) was also relevant, exhibiting several classical features such as a sudden increased rate before ground level severe damage, as discussed in a companion study. Remarkable surface observations of this event include 24 h precipitation accumulations exceeding 100 mm in four different observatories and 30 minute rainfall amounts up to 40 mm which caused local flash floods. As the convective system evolved northward later that day it also affected SE France causing large hail, ground level damaging wind gusts and heavy rainfall. 相似文献
7.
Summary The whole area of Mount Medvednica and the surrounding lowland including the Zagreb city area experienced extensive rainfall on 3 to 4 July 1989 causing flash floods. Daily precipitation amounts measured at 0600 UTC on 4 July were in proportion to the mean monthly totals of July for this region. The maximum rainfall amounts for periods of 2 to 12 hours recorded during this storm, had a return period greater than one hundred years in this region. They were produced by intensive development of a mesoscale convective system along the slowly moving frontal zone lying over north-western Croatia. The interaction between mesoscale processes and the synoptic scale development led to the intensive transformation of the initial air masses at the frontal line into those with a much stronger convective potential.With 5 Figures 相似文献
8.
华北两类产生极端强天气的线状对流系统分布特征与环境条件 总被引：1，自引：0，他引：1
华北线状对流系统精细气候分布及其所产生的极端天气特征尚不清楚,本研究利用雷达拼图资料和客观识别方法普查2013—2018年华北171例线状对流系统的时、空分布特征,根据其所致强对流天气的统计结果,发现华北地区至少有2类线状对流系统,分别产生极端强雷暴大风和极端强降水。分析了这2类线状对流系统的环流形势、环境条件、地形作用和关键中尺度系统地面冷池等的特征。主要结论如下:华北线状对流系统的空间分布尤其是初始形成位置与大地形关系密切,京津冀的太行山和燕山山脚区域为其中的一个高发区;2类线状对流系统发生月份、空间尺度、移动速度、形成时刻和维持时间等都具有显著差异;2类线状对流系统的环流背景、环境条件和冷池也差别明显。强雷暴大风型线状对流系统的环境大气斜压性强,中层干和大的垂直减温率造成的最优对流有效位能、下沉对流有效位能大值区是产生极端大风的重要环境条件,地面强冷池以及0—3 km风垂直切变对前向传播起到了重要作用。强降水型线状对流系统产生的降水极端性较前一类型更为凸出,天气尺度强迫相对较弱,水汽条件极其充沛,地面弱冷池或地形与低层南风气流相互作用维持的后向传播是其发展和缓慢移动的主要机制,也是产生极端强降水的直接原因。 相似文献
9.
This is the first attempt to merge highly accurate precipitation estimates from Global Precipitation Measurement (GPM) with gap free satellite observations from Meteosat to develop a regional rainfall monitoring algorithm to estimate heavy rainfall over India and nearby oceanic regions. Rainfall signature is derived from Meteosat observations and is co-located against rainfall from GPM to establish a relationship between rainfall and signature for various rainy seasons. This relationship can be used to monitor rainfall over India and nearby oceanic regions. Performance of this technique was tested by applying it to monitor heavy precipitation over India. It is reported that our algorithm is able to detect heavy rainfall. It is also reported that present algorithm overestimates rainfall areal spread as compared to rain gauge based rainfall product. This deficiency may arise from various factors including uncertainty caused by use of different sensors from different platforms (difference in viewing geometry from MFG and GPM), poor relationship between warm rain (light rain) and IR brightness temperature, and weak characterization of orographic rain from IR signature. We validated hourly rainfall estimated from the present approach with independent observations from GPM. We also validated daily rainfall from this approach with rain gauge based product from India Meteorological Department (IMD). Present technique shows a Correlation Coefficient (CC) of 0.76, a bias of −2.72 mm, a Root Mean Square Error (RMSE) of 10.82 mm, Probability of Detection (POD) of 0.74, False Alarm Ratio (FAR) of 0.34 and a Skill score of 0.36 with daily rainfall from rain gauge based product of IMD at 0.25° resolution. However, FAR reduces to 0.24 for heavy rainfall events. Validation results with rain gauge observations reveal that present technique outperforms available satellite based rainfall estimates for monitoring heavy rainfall over Indian region. 相似文献
10.
梅雨期青藏高原东移对流系统影响江淮流域降水的研究 总被引：5，自引：2，他引：3
利用GOES-9和FY-2C卫星TBB资料、1°×1°的NCEP再分析资料以及常规地面观测资料对2003和2007年梅雨期内青藏高原东移对流系统影响重庆、四川以及江淮梅雨锋地区降水的主要方式作了研究。结果表明,2003和2007年梅雨期内,青藏高原东移对流系统影响下游地区降水主要存在4种方式:(1)高原上的动力辐合中心伴随高原对流系统东移,影响所经地区的降水,该种影响方式较为常见,持续时间较长,影响范围较广。(2)高原对流系统移出高原后在四川盆地引发稳定少动的西南低涡,触发一系列暴雨过程,此种影响方式持续时间较长,主要影响地区为四川和重庆(往往会造成强度很大的暴雨),当西南低涡以东盛行较强西南风时,向梅雨锋的动能输送较强,这十分有利于梅雨锋地区对流活动和降水的加强。(3)高原东移对流系统在四川盆地触发西南低涡,西南低涡生成后,在引导槽的作用下沿梅雨锋东移,沿途引发一系列暴雨,此种影响方式持续时间最长,波及范围最广。(4)对流系统东移出青藏高原后直接影响下游地区,此种影响方式最为常见,但其影响时间最短,强度最小。对环境场的分析表明,高原强对流往往发生在500hPa影响槽槽区附近的上升运动区,当200hPa高空急... 相似文献
11.
基于地面加密观测资料、FY-2E静止气象卫星观测资料和NCEP分析资料,选取2010—2012年华北区域内27次冰雹过程,按大气环流背景、主要影响系统和云系的云型特征等将其分为冷涡云系尾部型、低涡槽前型和偏北气流控制型3种类型。分析结果表明:3种天气型下冰雹对流云系特征存在差异,但90%以上的冰雹过程发生在对流云团的快速发展阶段中,降雹集中出现于准圆形或椭圆形对流云团边缘或带状对流云系的传播前沿区域,对应于云顶亮温梯度的大值区。在掌握背景环境的前提下,综合分析红外图像中对流系统的发展演变、水汽图像暗带和暗区变化等信息,对冰雹的监测和预警有一定的参考价值。定量统计分析表明,大的亮温梯度值 (不低于8 ℃/0.05°) 是辅助判断冰雹能否发生的重要参量,而当冰雹云同时具备低云顶亮温和大亮温梯度的情况下,更有利于大于10 mm大冰雹的发生。 相似文献
12.
采用中尺度数值模式MM5V2对1998年6月下旬发生在长江流域持续的暴雨过程进行分析研究。通过尺度分离与数值模拟对比试验，着重分析了暴雨过程中天气尺度与次天气尺度各物理量场的结构特征，提出本次暴雨过程形成的物理机制:天气尺度流场与水汽场为降水提供持续的远距离水汽输送通道，次天气尺度流场形成稳定的经向强辐合，为水汽的抬升与凝结提供动力条件；在有利的高、低空急流的配置下，暴雨区落在高空急流轴以南、低空急流轴以北；次天气尺度温度场下暖上冷的热力不稳定层结促进了热力不稳定的发展，促使暴雨增幅；特大暴雨发生地区上空的次天气尺度湿度的高值中心，有利于湿空气在上升运动中释放潜热，形成暴雨的反馈机制。数值试验分离模式初始场不同尺度系统信息，揭示了不同尺度系统在暴雨发生过程中的动力作用，没有中尺度系统的配合，仅有天气尺度系统信息，或只有次天气尺度系统信息，没有大尺度系统的配合，暴雨的强度及范围都将有所消减。分析及数值试验结果表明大暴雨是在天气尺度和次天气尺度系统的共同作用下才得以产生和维持的。 相似文献
13.
Impact of Horizontal Resolution and Cumulus Parameterization Scheme on the Simulation of Heavy Rainfall Events over the Korean Peninsula 总被引：1，自引：0，他引：1
In this paper, we present the results from high-resolution numerical simulations of three heavy rainfall events over the Korean Peninsula. The numerical results show that the prediction accuracy for heavy rainfall events improved as horizontal resolution increased. The fine-grid precipitation fields were much closer to the real precipitation fields in the case of large synoptic forcing over the Korean Peninsula. In the case of large convective available potential energy and weak synoptic forcing, it seems that even when using a high resolution, the models still showed poor performance in reproducing the observed high precipitation amounts. However, activation of the cumulus parameterization scheme in the intermediate resolution of 9 km, even at a grid spacing of 3 km, had a positive impact on the simulation of the heavy rainfall event. 相似文献
14.
1998年夏季HUBEX/GAME期间热量和水汽收支(英) 总被引：4，自引：0，他引：4
By using the high-resolution GAME reanalysis data, the heat and moisture budgets during the period of HUBEX/GAME in the summer of 1998 are calculated for exploring the thermodynamic features of Meiyu over the Changjiang-Huaihe (CH) valley. During the CH Meiyu period, an intensive vertically-integrated heat source and moisture sink are predominant over the heavy rainfall area of the CH valley, accompanied by strong upward motion at 500 hPa. The heat and moisture budgets show that the main diabatic heating component is condensation latent heat released by rainfall. As residual terms, the evaporation and sensible heating are relatively small. Based on the vertical distribution of the heat source and moisture sink, the nature of the rainfall is mixed, in which the convective rainfall is dominant with a considerable percentage of continuous stratiform rainfall. There are similar time evolutions of the main physical parameters(〈Q1〉,〈Q2〉,and vertical motion ω at 500 hPa).The time variations of〈Q1〉and〈Q2〉are in phase with those of -ω500, and have their main peaks within the CH Meiyu period. This shows the influence of the heat source on the dynamic structure of the atmosphere. The wavelet analyses of those time series display similar multiple timescale characteristics. During the CH Meiyu period, both the synoptic scale(～6 days) and mesoscale (～2 days and ～12 hours) increase obviously and cause heavy rainfall as well as the appearances of the maxima of the main physical parameters. Among them, the mesoscale systems are the main factors. 相似文献
15.
利用常规气象观测资料、NCEP/NCAR再分析资料和多普勒天气雷达资料,对2016年8月6—8日潍坊一次强对流天气的成因和预报误差进行了分析,结果表明：1）500 hPa冷涡底部低槽、850 hPa低涡切变线和地面倒槽是主要影响天气系统, 数值预报对此次天气过程的影响系统预报偏差大,而预报员对数值预报依赖程度高是此次预报失误的主要原因;2）850 hPa以下强的水汽辐合是强降水发生的重要条件,低层辐合和高层辐散配置导致的强垂直上升运动是暴雨产生的动力机制,位势不稳定因中高层的冷空气入侵下沉得以加强;3）列车效应和强回波维持少动是造成短时强降水的重要回波特征,逆风区的发展和移动对于判断强降水的落区有指示作用,多普勒雷达反演风场中的中尺度辐合线是导致局地强降水发生的直接原因;4）风廓线雷达水平风场可以连续地反映降水过程中风场垂直结构及其变化,降水发生前探测高度明显升高,中高层冷空气侵入时间与强降水的时段相对应。 相似文献
16.
M. Bolliger P. Binder H. P. Roesli H. Wanner 《Meteorology and Atmospheric Physics》2004,87(4):219-234
Summary In autumn 1999 during the field phase of the Mesoscale Alpine Programme (MAP), the geostationary satellite Meteosat-6 performed 5-minute rapid scan imagery over central Europe. The rapid scan data of 11 heavy precipitation events are investigated by analyzing the spatial and temporal characteristics of cloud top structures. The objectives are to separate convective from stratiform cloud regions by satellite data alone and to gain insight into the life cycle of heavy precipitation systems. For verification of the satellite-based results, radar data from the operational Mt. Lema C-band radar is interpolated on the spatial grid of the infrared and visible Meteosat images. The interpolated radar data of each single grid cell is then classified by a convective-stratiform algorithm and compared to the analysed rapid scan imagery.The satellite- and radar-based approaches do only rarely produce matching classifications concerning the identification of convective areas. Since convection during the field phase of MAP occurred mostly embedded within stratiform cloud regions, no temporal and spatial characteristics of convective activity within clouds can be systematically derived from satellite imagery. This lack of characteristic cloud top structures prevented the unambiguous identification of typical cloudiness associated with stratiform precipitation. It is one of the major findings of this study, that in several cases being classified as stratiform by radar, strong cloud development is observed in satellite imagery. The preferred area of strong cloud development is located ahead of the Alpine barrier in a precipitation-free atmosphere. Two contrasting examples of life cycles of heavy precipitation systems are given based on the complementary information extracted from satellite and radar data. 相似文献
17.
利用常规气象资料和卫星云图资料,采用天气学诊断方法,从大尺度环流背景、天气系统、物理量场、对流云团演变特征等方面,分析了2006年7月3～4日出现在湖北郧西的一次暴雨天气过程的成因。结果表明,此次暴雨是在副热带高压减弱东退形势下产生的;700 hPa和850 hPa的冷槽、切变线是此次强降水的主要影响系统,暴雨区位于700 hPa切变线右侧、850 hPa切变线附近;暴雨区上空存在明显正涡度柱,低层辐合与中高层辐散形成抽吸作用,为暴雨过程发生发展提供了动力条件;存在于孟加拉湾至我国西南地区的水汽通道为暴雨过程提供了必需的水汽;整个暴雨过程都伴随着中尺度对流云团的初生、发展、合并和减弱,降水主要由发展型对流云团造成。 相似文献
18.
应用多种常规观测资料、加密自动气象站资料和NCEP 1°×1°再分析资料,对2013年影响湖南的两次相似路径台风暴雨过程进行了对比分析。研究表明：“尤特”台风暴雨直接由台风环流引起,具有锋前暖区降水的特点;而“天兔”台风暴雨由台风低压倒槽与西风带天气系统相互作用引起的,其降水属于典型的锋面降水。“尤特”由东风带进入西风带,其与副高相对位置的变化是导致其登陆后路径北翘的主要原因。“尤特”低压环流与南海季风相互作用,充沛的水汽输送对台风低压环流的长时间维持以及湘东南暴雨的形成和发展起到了重要的组织和促进作用。而“天兔”登陆后南海季风位置偏南,不利于“天兔”的长时间维持以及向暴雨区的水汽输送。低层暖式切变线附近强辐合与高层强辐散耦合、低层强正涡度与高层负涡度的耦合为“尤特”台风暴雨的发生发展提供了动力条件。由中低层冷空气入侵导致的锋生强迫和高低空急流耦合形成的次级环流,加强了“天兔”低压倒槽内冷暖气流的辐合,是触发倒槽内中尺度对流发展和暴雨产生的重要动力机制。 相似文献
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2012年7月21日北京特大暴雨的多尺度特征 总被引：31，自引：6，他引：25
本文采用观测和NCEP分析场资料对2012年7月21日发生在北京地区的特大暴雨过程的天气形势、水汽来源和中尺度对流系统的特征进行了研究。结果如下:“7.21”北京暴雨过程是高低空与中低纬系统共同配合的结果,暴雨发生在“东高西低”的环流形势下,低涡、切变线、低槽冷锋和低空急流为此次过程的主要影响天气系统;孟加拉湾至西太平洋地区热带辐合带(ITCZ)活跃,其中热带气旋的活动有利于水汽向东亚大陆输送,此次暴雨过程中华北地区的水汽源地包括孟加拉湾和我国东部的渤海、黄海等,低层的水汽主要来自东部,中层的水汽主要来自孟加拉湾;北京的强降雨有两段,第1段降雨虽然发生在冷锋前,但有明显冷空气的侵入,并与地形和东风的作用有关,第2段降雨对流的组织和增强与冷锋强迫相关。在有利环境下,中尺度对流系统频繁发生发展,持续时间长,且稳定少动是此次特大暴雨形成的重要原因。 相似文献
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应用MICAPS资料, 通过天气诊断分析, 结合FY-2卫星云图及德宏CINRAD-CC雷达体扫资料, 分析了发生在2004年5月18日滇西地区的大暴雨过程。发现本次大暴雨过程天气尺度影响系统为初夏孟加拉湾风暴及南下冷锋切变; 大暴雨发生在高能高湿的水汽辐合中心、700 hPa螺旋度正值区及湿 Q 矢量散度大值辐合区内; 卫星云图上, 多个β-中尺度对流系统在大暴雨区发展; 多普勒雷达回波为絮状混合型降水回波, 强度在30~44 dBz之间, 频繁出现的逆风区、低空急流、中尺度辐合线等中小尺度系统是造成本次大暴雨的直接影响系统。 相似文献