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1.
对海南岛秋季非热带气旋暴雨特性的分析发现： 暴雨的发生、维持和消失主要与大陆冷高、南海低值系统、热带云团活动密切相关,暴雨一般与华南沿海的低空偏东风急流相伴。Ｔ１０６ 流场预报为低空急流的生消预报提供了一个客观依据, 文章还对Ｔ１０６ 多个物理量场作了误差分析 相似文献
2.
Fei WANG Lifang SHENG Xiadong AN Qian LIU Haixia ZHOU Yingying ZHANG Jianping LI 《大气科学进展》2021,38(10):1651-1664
The autumn Intertropical Convergence Zone(ITCZ) over the South China Sea(SCS) is typically held south of 10°N by prevailing northeasterly and weakening southwesterly winds. However, the ITCZ can move north, resulting in heavy rainfall in the northern SCS(NSCS). We investigate the mechanisms that drove the northward movement of the ITCZ and led to heavy non-tropical-cyclone rainfall over the NSCS in autumn of 2010. The results show that the rapid northward movement of the ITCZ on 1 and 2 October was caused by the joint influence of the equatorial easterlies(EE), southwesterly winds, and the easterly jet(EJ) in the NSCS. A high pressure center on the east side of Australia, strengthened by the quasibiweekly oscillation and strong Walker circulation, was responsible for the EE to intensify and reach the SCS. The EE finally turned southeast and together with enhanced southwesterly winds associated with an anticyclone, pushed the ITCZ north. Meanwhile, the continental high moved east, which reduced the area of the EJ in the NSCS and made room for the ITCZ. Further regression analysis showed that the reduced area of the EJ and increased strength of the EE contributed significantly to the northward movement of the ITCZ. The enhancement of the EE preceded the northward movement of the ITCZ by six hours and pushed the ITCZ continually north. As the ITCZ approached 12°N, it not only transported warm moist air but also strengthened the dynamic field by transporting the positive vorticity horizontally and vertically which further contributed to the heavy rainfall. 相似文献
3.
海南2008年秋季持续性暴雨过程的物理机制分析 总被引：2，自引：0，他引：2
利用地面常规与加密自动站降水观测、卫星云图、NCEP FNL全球分析等资料对2008年10月12—14日海南持续暴雨天气过程进行诊断分析。分析表明:热带低压、冷空气以及副热带高压三者的相互作用,导致海南低空出现持续的东(东南)风急流,该急流在海南东部沿海形成的向岸风辐合及地形强迫抬升是MCS的重要触发机制,其暖湿输送作用是暴雨区不稳定能量得以循环建立的主要途径。南海东北风冷涌前沿强辐合、潜热加热以及高空强辐散有利于热带扰动的发展与维持。热带低压与冷空气相互作用导致大气斜压性增强,地转强迫作用与惯性振荡机制使得低压北侧东北风急流加强。东北与东南急流之间的形变与辐合导致持续锋生过程,锋生强迫产生的热力直接环流上升支与低空急流左前侧次级环流上升支是对流系统发展的主要动力触发机制,低空强潜热加热也有利于对流向更高层次发展。 相似文献
4.
Diurnal variations of precipitation over the South China Sea 总被引：1，自引：0，他引：1
In this study, the diurnal variations of precipitation and related mechanisms over the South China Sea (SCS) are studied using the TRMM and other auxiliary atmospheric data. We have found that: (1) the amplitude and peak time of the diurnal precipitation over SCS exhibit remarkable regional features and seasonal variations. Diurnal variations are robust all the year around over the southern SCS especially over the Kalimantan Island and its offshore area. Over the middle to northern SCS, however, diurnal variations are noticeable only in the summer and autumn; (2) over the northern SCS precipitation peaks in early morning, while over the southern SCS it has two diurnal peaks: one in the early morning and another in the late afternoon; (3) the diurnal variations of precipitation over the SCS are related to the activity of the SCS summer monsoon and the ENSO events. The late afternoon precipitation increases remarkably after the onset of the SCS summer monsoon over the northern SCS. The early-morning rainfall peak is much more significant during La Nina years than during El Nino years; (4) the land–sea breeze is responsible for the diurnal cycle over the Kalimantan Island and its offshore area while the “static radiation–convection” mechanisms may result in the early-morning rainfall peak over the SCS. 相似文献
5.
Satellite-derived rainfall estimates and the ERA-Interim reanalysis are used to better understand cold air surge/precipitation interactions and to identify the implications for rainfall variability in the Sahel and tropical Africa on synoptic to seasonal timescales. At the synoptic timescale, cold air surges are associated with cold conditions over the eastern Sahara throughout the year due to the eastward passage of surface low pressure systems over the Mediterranean and the subsequent ridging over northern Africa. Rainfall decreases over central and eastern Africa approximately 4–5 days after the cold air first arrives in northeastern Africa. These precipitation anomalies persist for 4 or more days. At the seasonal timescale, a significant relationship between eastern Saharan low-level temperatures and rainfall in the Sahel and tropical Africa is identified, with colder conditions associated with reduced convection on the northern flank of the primary convergence zone, and vice versa. During boreal winter, the anomalous rainfall occurs over tropical Africa (0°N–8°N). During the summer, rainfall anomalies associated with cold air surges occur over the Sahel (10°N–16°N). These relationships are mediated by anomalous anticyclonic flow over northwestern Africa and western Europe. The analysis shows that cold air surges are significantly associated with summertime cooling over the Sahara, but less so during the winter. 相似文献
6.
Summary The climatology and variability of summer convection and circulation over the tropical southwest Indian Ocean is investigated using satellite imagery, routine synoptic observations, outgoing longwave radiation (OLR) data, sea surface temperatures (SST) and areal averaged rainfall departures. OLR has a –0.90 correlation with rainfall departures and the OLR minimum (ITCZ) in January and February lies across the 10°S latitude, extending further south near Madagascar. The intensity of ITCZ convection is greatest in the longitudes 20–35°E over northern Zambia and is considerably reduced over the SW Indian Ocean. Spatial correlations are analyzed for standardized departures of OLR, rainfall and SST. The correlations change sign in a coherent fashion, creating a climatic dipole between southern Africa and the SW Indian Ocean. Interannual trends are examined through analysis of January–February zonal and meridional wind indices constructed from significantly correlated variables at Zimbabwe, Madagascar and Mauritius. Circulation variability is dominated by quasi-decadal cycles and a trend of inereasing westerly winds. Zonal wind shear alternates from easterly (barotropic) to westerly and together with SST appears to regulate the frequency and intensity of tropical cyclogenesis. Areally averaged rainfall departures exhibit 6.25 year cycles in NE Madagascar and 12.5 and 18.75 year cycles in SW Madagascar and Zimbabwe, respectively. Summer rainfall and meridional winds in NE Madagascar and Zimbabwe are out of phase and negatively correlated in most summers. The presence of synoptic weather systems is assessed using daily Hovmoller-type satellite imagery composites. Convective structure is dominated by transient waves in the 10°–20°S latitude band, with periods of 15–20 days common. The waves are more prominent in summers with increased easterly shear and contribute to fluctuations in rainfall over SE Africa.With 8 Figures 相似文献
7.
2002年南海季风建立及其雨带变化的天气学研究 总被引：12，自引：1，他引：12
利用南海海 气通量观测试验资料结合NCEP ,GPCP以及GMS - 5云图资料 ,综合分析了 2 0 0 2年 5～ 6月南海西南季风建立过程及其雨带变化 ,确定 5月 14日西沙及北部海区西南季风爆发 ,5月 15日整个南海季风爆发 ,季风爆发时间属于正常年 ;季风爆发时风向、风速、云量、降水、湿度、辐射及海面温度等要素都发生突变。这种突变是由大气环流的突变造成的。季风爆发前后大气环流变化过程是 :80～ 90°E越赤道气流加强 ,同时印缅低压加深 ,孟加拉湾南北向气压梯度增大 ,而后东亚大陆上气旋发展东移 ,副热带高压东撤 ,孟加拉湾低压槽前的赤道西风突然加强越过中南半岛 ,南海北部首先出现强西南风 ,继而南海季风迅速地全面爆发。孟加拉湾西南风加强到南海季风爆发是一个连续的过程 ,大陆冷空气南下起了重要的作用。南海季风爆发时呈现单雨带型 ,而后由单雨带型转变为双雨带型 ,雨带受副热带高压和季风系统共同影响 ,并且随着副热带高压移动位置变化。 相似文献
8.
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
9.
IMPACTS OF TWO TROPICAL CYCLONES EXPERIENCING EXTRATROPICAL TRANSITION DURING NORTHWARD PROGRESSION
ON THE RAINFALL OF LIAODONG PENINSULA 总被引：2，自引：1，他引：1
Both of Typhoon Winnie (9711) and Matsa (0509) underwent an extratropical transition (ET)
process when they moved northward after landfall and affected Liaodong Peninsula. However, Matsa
produced half as much rainfall as Winnie, although it struck Liaodong Peninsula directly while Winnie
passed through the Bohai Sea. The relations between the ET processes and the precipitation over Liaodong
Peninsula are examined. The result shows that the precipitation difference between Winnie and Matsa was
closely related to the interactions between the westerly systems and typhoons during their ET processes.
Winnie was captured by the upper westerly trough and then coupled with it when moving to the
mid-latitudes, and the positive anomaly of moist potential vorticity (MPV) was transported downward from
the upper troposphere over the remnant circulation of the tropical cyclone (TC). It was favorable to the
interaction between tropical warm and wet air and westerly cold air, causing convective cloud clusters to
form and develop. The rain belt composed of several meso-β cloud clusters over the Liaodong Peninsula,
resulting in heavy rainfall. On the other hand, Matsa did not couple with any upper trough during its ET
process and the positive anomaly of MPV in the upper troposphere and its downward transfer were weak.
Only one meso-β cloud cluster occurred in Matsa’s rain belt during its ET process that tended to lessen
rainfall over Liaodong Peninsula. 相似文献
10.
In order to test the sensitivity of the transitional phase of the 2006 West African monsoon (WAM) onset to different mechanisms, weather research and forecasting (WRF) model simulations have been carried out addressing the role of the Saharan heat low (SHL) and its sensitivity to the albedo field and to the northern Africa orography, and the role of the sea surface temperature (SST) in the eastern tropical Atlantic and Mediterranean. Lowering albedo over the desert region induces a northward location of the inter-tropical convergence zone (ITCZ), while removing mountains in North Africa reduces rainfall over West Africa. Shifting SST forward by 15?days leads to a northward location of the ITCZ before the WAM onset. However none of these factors modifies the timing of the WAM onset in 2006. The transitional phase of the 2006 WAM onset has been examined in more detail. The enhancement of SHL intensity, combined with the development of the oceanic cold tongue in the Guinea gulf, leads to low-level moisture flux divergence in the ITCZ reducing rainfall and increasing low-level humidity over the Sahel. However, weakening of convection can be clearly attributed to dry-air intrusions in mid-levels, originating from the subtropical westerly jet and associated with Rossby wave pattern over North Africa. Sensitivity tests on the synoptic scale forcing outside of the WRF model domain confirm the dominating role of large-scale dynamics to control the transitional phase of the WAM onset and its timing. However it is shown that the regional factors can modulate this larger scale forcing. 相似文献
11.
2018年8月30~31日一条超长生命期的中尺度线状对流（线状β-MCS）引发了华南沿海一次极端降水事件[1056.7 mm（24 h）?1],刷新广东省24小时雨量历史纪录,造成严重洪涝并引起社会极大关注。文章采用多源观测资料与NCEP/NCAR_FNL分析资料,首先从观测分析角度提炼该次过程的降水特点与卫星、雷达的基本演变特征,然后分析了极端降水的天气尺度背景与中尺度环境条件,最后从中尺度大气动力学角度探讨超长生命期线状β-MCS的触发演变与海陆边界风向旋转维持的关系,并揭示线状对流组织与维持的可能物理机制。结果表明:季风低压作为稳定的天气尺度背景,大气层结表现为深厚暖湿与持续不稳定,季风云团北推上岸造成华南沿海大范围暴雨,一条超长生命期、准静止、低顶高、低质心并具备后向传播特征的线状β-MCS造成高潭持续性强降雨,降水强度大、持续时间极长是累积雨量破纪录的主要原因。对流触发及线状β-MCS组织发展与地面风场有密切关系,海陆边界风向旋转率方程定性分析发现地面风场受多尺度调节影响,季风低压的天气尺度项、局地地形摩擦项与中尺度气压梯度项对地面风场协同形成的反向强迫及平衡机制,是偏南气流长时间维持的关键。斜坡地形与黄江河谷一侧偏南气流增强并建立“暖脊”,致使山脉一侧冷池出流边界无法向南扩展,形成强烈的水平温度梯度,基于中尺度动力学方程定量诊断表明β-MCS的线状组织过程及对流维持的动力机制来源于局地垂直风切变,这种局地垂直风切变有别于环境垂直风切变,其显著增强是对地面强烈纬向水平温度梯度响应的结果。 相似文献
12.
基于1998—2011年的TRMM卫星逐日降水资料、NCEP/NCAR大气再分析资料以及向外长波辐射(OLR)资料,利用小波分析、Butterworth带通滤波、EOF分析以及合成分析的方法,对秋季(9—10月)南海北部地区(10°—24°N,100°—120°E)持续性强降水的低频特征进行分析。结果表明,秋季南海北部降水存在显著的准双周振荡特征,主要表现为南海北部地区一致变化型和南海东北部地区和中南半岛沿海地区反相变化型两个模态。其中,第一模态的低频降水主要集中在中南半岛沿岸附近的南海中西部,第二模态则主要集中在南海东北部。进一步对与这两种模态相关联的大气环流和OLR的低频场进行合成分析。结果表明,第一模态的对流层低层准双周低频信号主要来源于南半球近赤道上空,该地区异常强对流活动产生的波列和气旋性环流越赤道进入南海并加强传播至南海北部。而第二模态则来源于南海中南部和吕宋岛东侧西太平洋上空,异常强对流和气旋性环流的合并加强并传播至南海东北部。 相似文献
13.
Fei WANG Lifang SHENG Xiadong AN Haixia ZHOU Yingying ZHANG Xiaodong LI Yigeng DING Jing YANG 《大气科学进展》2022,39(11):1914-1924
This study reveals a significant positive connection between autumn non-tropical-cyclone heavy rainfall on Hainan Island and the intensity of Eastern Pacific (EP) El Ni?o events. That is, the amount of rainfall in super EP El Ni?o years is more than that in normal EP El Ni?o years. Comparing EP El Ni?o years of different intensities, the cooler sea surface temperature in the northwestern Pacific during super EP El Ni?o years stimulates a negative surface latent heat flux (LHF) anomaly and abnormal anticyclonic circulation at 850 hPa. Under these conditions, an abnormal zonal vertical circulation develops in the northern South China Sea once a positive LHF anomaly and abnormal cyclonic circulation (ACC) at 850 hPa occur in the Beibu Gulf. The abnormal zonal vertical circulation further strengthens the ascending motion over Hainan Island, as the critical factor that leads to excessive rainfall. Further analysis shows that the positive LHF anomaly, which can be attributed to the increased latent heat transfer which resulted from the increased surface wind speed, is an important trigger for the ACC. However, the ACC is also the supplier of favorable moisture conditions because it intensifies vapor convergence over Hainan Island and meridionally transports moisture from the South China Sea to northeastern Hainan Island, thereby generating heavy rainfall. This paper emphasizes that the impact of El Ni?o events, especially super El Ni?o events, on rainfall over Hainan Island cannot be ignored, even if the traditional view is that frequent rainfall occurs mainly in La Ni?a years. 相似文献
14.
Severe typhoon Damrey moved across Hainan Island from 00:00 UTC 25 September to 00:00 UTC 27 September in 2005 and gave rise to a significant rain process during its 48-h passage. The precipitation intensity on the southern part of the island is stronger than that on the northern, showing obvious asymmetric distribution. Using Tropical Rainfall Measuring Mission (TRMM) data, the associated mesoscale characteristics of the precipitation were analyzed and the formation of asymmetric rainfall distribution was investigated in the context of a subsynoptic scale disturbance, vertical wind shear and orographic factors. The results are shown as follows. (1) The subsynoptic scale system provided favorable dynamic conditions to the genesis of mesoscale rain clusters and rainbands. (2) The southern Hainan Island was located to the left of the leeward direction of downshear all the time, being favorable to the development of convection and leading to the asymmetric rainfall distribution. (3) Mountain terrain in the southern Hainan Island stimulated the genesis, combination and development of convective cells, promoting the formation of mesoscale precipitation systems and ultimately resulting in rainfall increase in the southern island. 相似文献
15.
对2016-2018年大连市86次降水过程(≥5mm)天气资料统计和分析,得到了冬季降水形势为高空槽、东北冷涡和平直西风气流场,春夏秋季为高空槽、东北冷涡、副高西南气流、西北气流及江淮气旋形势场,且降水多为稳定层结(夏季副高、冷涡等除外)；对SA新一代多普勒雷达资料PUP处理和分析,获得了降水回波特征及特征参数值,以及主要降水云系(层云、积层混合云和对流云)；根据雷达回波强度、顶高和垂直积分液态水含量等特征参数及变化,结合冷云催化原理等综合分析,研究建立了基于SA多普勒雷达的人工增雨(雪)作业预警、决策判别指标体系。利用2019年41次降水过程雷达资料进行指标验证分析,得到了87% 以上确率；对4月13日一次实例进行火箭增雨指挥系统业务运行及雷达反演决策判别等综合分析,取得了较好预期效果。 相似文献
16.
南安市秋季一次大暴雨天气过程诊断 总被引：3，自引：1，他引：2
应用常规观测资料、自动站加密观测资料、天气图、物理量场和云图等,对福建省南安市秋季一次历史同期罕见的大暴雨天气过程进行了分析,研究了此次大暴雨天气过程的天气系统、水汽条件、不稳定度和动力触发机制,分析了该天气系统的演变及物理量场的配合情况。通过与历史同期天气过程的比较分析,发现在该时期本地区发生大暴雨天气过程的一个重要原因是存在热带低压与较强冷空气的相互作用;探空资料的应用对定量分析大暴雨过程的演变发展具有重要作用。由于秋季在南安乃至泉州出现这种大范围暴雨天气过程极其罕见,对此次大暴雨天气过程的研究利于基层台站预报员对此类现象的认识和把握。 相似文献
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18.
利用1998—2013年热带测雨卫星（TRMM）3A12资料,对南海及其周边地区降水、云和潜热的三维特征及其变化进行了对比研究,把南海及其周边地区分为四个区域:华南地区、中南半岛、马来群岛、南海。结果表明:（1）地面降水率EOF分析的第一、二模态方差贡献率分别为57.16%和8.72%,第一模态向量场均为正值,降水呈现南多北少的分布特征;第二模态向量场体现了降水变化南北反相的特征,马来群岛降水变化与其他三个区域反相。从两个模态时间系数序列看出,1998—2005年整个区域降水总体减少,区域降水北部增多南部减少;2005—2013年整个区域降水总体增多,区域降水南部增多北部减少。（2）南海及其周边地区降水夏秋季多,春冬季少,降水中心春夏季北移,秋冬季南撤,其中马来群岛夏季降水最少,冬季最多;其它三个区域都是夏季降水最多,华南和中南半岛冬季最少,南海春季最少。（3）赤道附近对流降水为主,23 °N以北区域层云降水为主,5~23 °N之间区域两种类型降水比例随季节变化,其中陆地降水比例随季节变化明显,特别是华南地区陆地夏季对流降水比例大于50%,冬季层云降水比例大于80%;海洋对流降水所占比例普遍大于50%,随季节变化小。（4）云冰、云水含量水平分布大值区与降水大值区相对应;二者随高度先增加后减少,云冰在13 km高度达到最大值,云水在2.5 km高度达到最大。春冬季,马来群岛云冰含量最大;夏秋季,南海云冰含量最大。云水含量在四个季节都以南海最大。（5）潜热加热率水平分布大值区与降水大值区相对应;随高度呈双峰分布,峰值分别出现在1~2 km高度和4 km高度处,春冬季马来群岛潜热加热率最大。 相似文献
19.
Hainan, an island province of China in the northern South China Sea, experienced two sustained rainstorms in October2010, which were the most severe autumn rainstorms of the past 60 years. From August to October 2010, the most dominant signal of Hainan rainfall was the 10–20-day oscillation. This paper examines the roles of the 10–20-day oscillation in the convective activity and atmospheric circulation during the rainstorms of October 2010 over Hainan. During both rainstorms,Hainan was near the center of convective activity and under the influence of a lower-troposphere cyclonic circulation. The convective center was initiated in the west-central tropical Indian Ocean several days prior to the rainstorm in Hainan. The convective center first propagated eastward to the maritime continent, accompanied by the cyclonic circulation, and then moved northward to the northern South China Sea and South China, causing the rainstorms over Hainan. In addition, the westward propagation of convection from the tropical western Pacific to the southern South China Sea, as well as the propagation farther northward, intensified the convective activity over the northern South China Sea and South China during the first rainstorm. 相似文献
20.
2013年5月华南强降水与中国南海夏季风爆发 总被引：2，自引：0，他引：2
利用2013年"华南季风强降水外场试验与研究"的外场试验数据、美国NCEP FNL资料和卫星云顶黑体辐射温度资料,对2013年5月7—17日华南地区出现的两次强降水过程(7—12日和14—17日)中的高低空环流以及相关气象要素场的变化进行了对比分析。中国南海夏季风于5月第3候建立,两次过程分处于夏季风爆发前后。通过对比影响两次强降水过程的主要环流系统如南亚高压、高空副热带西风急流、500 hPa环流型、水汽来源等,指出影响两次强降水过程大尺度环流场之间的显著区别,说明南海季风爆发前后大尺度环流场对暴雨影响的典型差异。7—12日过程主要受北方锋面影响和南方暖湿气流辐合作用,导致华南地区出现南北两条雨带。14—17日过程则由于季风爆发后强的暖湿空气活动致使华南地区对流活跃,从而形成一条位于广东北部的雨带,此次过程强降水比第1次过程集中且对流性更强。两次降水过程的内在物理机制是一个准平衡态的热力适应过程,由于第2次过程降水更强,导致热源作用明显增强,动力向热力的适应过程也更显著。利用探空资料揭示出两次过程暖区暴雨大气热力和动力条件存在显著区别,7—12日南海季风爆发前的暖区暴雨主要受低层强垂直风切变导致的大气斜压不稳定影响;14—17日南海季风爆发后的暖区暴雨主要受高低空急流的强耦合作用影响。 相似文献