共查询到20条相似文献，搜索用时 15 毫秒
1.
夏季长江中下游地区降水持续性年(代)际变异及其与环流和Rossby波活动的联系 总被引：8，自引：2，他引：6
旱涝异常不仅与降水的频次和强度有关,在多种时间尺度上,其与降水的持续性亦存在较好的对应关系。基于1979～2013年6～7月中国东部249站点逐日降水资料及ERA-interim逐月再分析资料,研究了长江中下游地区近35年降水持续性的长期变化及其相联系的大尺度环流型和Rossby波能量频散特征。结果表明:近35年长江中下游地区降水时段平均持续时间变短而无雨时段变长,体现出了降水持续性的减弱趋势。进一步研究发现,该趋势变化与长江中下游地区在1980和1990年代持续性降水事件偏多,而在2000年以后偏少的年代际变化有关。在年代际和年际尺度上,与长江中下游地区降水持续特征变异相联系的异常环流型在我国东南部及南海地区分布较为类似,而在偏高纬度和偏低纬度地区存在较大差异。相似之处在于:在两个时间尺度上,在对流层中高层均存在显著的反气旋性环流控制我国东南部地区,而在中低层均存在由海洋向长江中下游地区的气流辐合,并在高层由长江中下游地区向海洋辐合。不同之处是:年代际尺度上,自对流层低层到高层在乌拉尔山以东及蒙古地区分别存在反气旋性环流和气旋性环流,且赤道印度洋地区的对流层中低层存在显著的气旋性环流;而在年际尺度上,由低层到高层位于贝加尔湖东、西侧均为反气旋性环流异常,但海洋性大陆的东北部,低层出现向长江中下游地区辐合的气流的源,高层则为由长江中下游地区向低纬度地区辐合的气流的汇。Rossby波扰动能量频散特征在年代际和年际尺度上亦呈现出明显的差异。年代际尺度上,中纬度地区自大西洋至蒙古地区存在一个正—负—正—负的Rossby波列,波能东传,对长江中下游地区产生影响,而在中低层,自低纬地区向长江中下游地区的波能传播相对较弱;在年际尺度上,影响长江中下游地区降水的Rossby波活动的局地性特征更为明显。在低层,波扰能量经由南海向长江中下游地区传播更明显,而在对流层高层源于贝加尔湖西侧的波扰能量传播相对较强。这些结果有助于深刻认识长江中下游地区降水的异常持续及与之相联系的洪涝灾害的形成机理。 相似文献
2.
利用1979~2013年中国站点逐日降水资料和NCEP/NCAR再分析资料,对长江中下游夏季降水的季节内振荡最显著周期进行了分析研究。结果表明长江中游最显著周期为10~30天,长江下游最显著周期为30~60天。为了揭示这种差异产生的物理原因,进一步利用位相合成的方法对这两个区域不同周期的季节内振荡降水、高低空风场和高度场以及垂直结构和水汽等循环过程的演变特征进行分析。在200 hPa环流场上,长江中游的降水主要受到高纬度自西向东传播的波列影响,而长江下游的降水与鄂霍次克海的高度场的变化相关。在风场的垂直涡度和散度的位相结构演变过程中,10~30天的垂直涡度和散度有自北向南的移动,30~60天的垂直涡度和散度在长江以南地区有自南向北的传播。水汽输送的位相发展过程表明,长江中游的水汽分别来自于南海的向北输送和长江以北地区向南的水汽输送;长江下游地区的水汽则主要来自于热带东印度洋经孟加拉湾的向东输送并在南海的北向输送,以及西太平洋水汽向西输送到南海再向长江下游的输送。从高层大尺度环流场和整层积分的水汽通量输送上解释了长江中游10~30天降水的自北向南移动,和长江下游30~60天降水自南向北传播的原因。 相似文献
3.
1998 SCSMEX期间亚洲30－60天低频振荡特征的分析 总被引：34，自引：0，他引：34
对１９９８年 ５－８月南海季风试验（ＳＣＳＭＥＸ）期间东亚地区 ８５０ ｈＰａ中低纬环流指数、东亚季风指数和长江中下游降水进行了Ｍｏｒｌｅｔ 小波分析,结果表明在此期间这些要素均有明显的３０－６０天周期低频振荡。在此基础上对 ５－８月每隔 ５天的 ８５０ ｈＰａ低频流场进行分析,结果表明：（１）１００°－１５０°Ｅ间东亚从中国东中部大陆经南海和西太平洋的南北半球中明显的存在一个以３０－６０天低频荡为特征的东亚季风低频环流系统,东亚季风活动主要受东亚季风系统中低频活动影响;（２）５月第５候南海热带季风爆发、６月中旬长江中下游人梅及产生大暴雨以及７月中旬以后的该地区大暴雨均与低频气旋带在该地区活动有关,而８月长江上游大暴雨则与低频反气旋伸人到大陆有关;（３）ＳＣＳＭＥＸ期间东亚低频振荡系统的源地有二个,即南海赤道和北半球中太平洋中高纬。南海低频系统向北传播,而中高纬低频系统自东北向西南传播为主。长江中下游６、７月二次大暴雨均与上述二个低频气旋系统自热带向北和中高纬向西南传播并于长江中下游汇合有关;（４）５－８月间东亚季风系统中有二次低频气旋带和二次低频反气旋带活动,这些低频环流系统的活动与印度季风低频环流系统活动并无明 相似文献
4.
5.
To investigate the multi-scale features in two persistent heavy rainfall (PHR) events in the middle and lower reaches of the Yangtze River (MLRYR) in June of 1982 and 1998, this study examines the impact of multi-scale oscillations in the north and south of 30°N on the PHR events by performing sensitivity experiments with the Weather Research and Forecast (WRF) model. It is found that the 60-day lowpass perturbation made a trivial contribution to the MLRYR precipitation during the PHR event in 1982. This PHR event resulted mainly from the combined effects of 30–60-day oscillation at low latitudes and 10–30-day oscillation at both high and low latitudes. The southwesterly anomalies associated with the 30–60-day anticyclonic anomaly over the northwestern Pacific facilitated moisture transport from the ocean to the MLRYR and enhanced the low-level convergence and ascending motion in the MLRYR. This similarly occurred in the 10–30-day oscillation as well. Moreover, the 10–30-day anomalies at high latitudes played a role in strengthening the large-scale low-level convergence over the MLRYR. The PHR event in 1998 was mainly related to the 60-day oscillation at both high and low latitudes and 30–60-day oscillation at low latitudes. The 60-day low-pass filtered anomalous cyclone at high latitudes in the north of 30°N contributed to the development of low-level convergence and ascending motion in northern MLRYR while the anomalous anticyclone at low latitudes in the south of 30°N not only increased the moisture in the MLRYR but also preconditioned the dynamical factors favorable for PHR over the whole area. The 30–60-day perturbations located north and south of 30°N worked together producing positive moisture anomaly in the MLRYR. In addition, the anomalous circulation in the south of 30°N tended to favor the development of ascending motion and low-level convergence in the MLRYR. 相似文献
6.
7.
A Study of the Characteristics of the Low-Frequency Circulation
over the Tibetan Plateau and its Association with Precipitation
in the Yangtze River Valley in 1998 
下载免费PDF全文
下载免费PDF全文 The propagation characteristics of the atmospheric low frequency (LF, 30--60 days) oscillation (LFO) around the Tibetan Plateau from troposphere to stratosphere and its relationship with the floods over the mid-lower reaches of the Yangtze River in the summer of 1998 are studied, based on the GAME
dataset from Meteorological Research Institute (MRI)/Japan Meteorological Agency, the TRMM satellite rainfall and the 730-station precipitation over China. The results show that the zonal propagation direction of LFOs in horizontal winds varies with seasons in the troposphere during May to August in 1998. The eastward propagation of LFOs is remarkable before the start of the rainy season in the Tibetan Plateau and the eastern Asian continent, while the westward propagation is significant after the start date. The northward LFOs from the south side of the plateau and the southward LFOs from the north are both significant before and after the start date. The plateau is a LFO sink in the meridional and zonal directions, but the west part of it is an intensifying area for the continual westward LFOs only after the start of the rainy season. Besides, the strongest LFOs occur at the tropopause (100 hPa) and rapidly decay after entering the stratosphere. The rainfall over the mid-low reaches of Yangtze River in the summer of 1998 exhibits two LFO cycles. According to the phases of the two rainfall LFO cycles, the composite analysesof precipitation distribution, LF circulations at 500 and 100 hPa,and LF vertical motion along 30°N are performed. It is the joint effect of the mid-upper tropospheric strong 30--60-day filtered cyclone (anticyclone) over the eastern plateau and the LFO anticyclone (cyclone) over the west subtropical Pacific that induces the whole layer LF descending (ascending) motion over the mid-lower reaches of Yangtze River, which provides the favorable condition for the break (maintenance) of precipitation. 相似文献
8.
利用1951—2010年NCEP/NCAR逐月再分析资料和中国160站月降水总量资料,研究了菲律宾海地区大气环流异常与长江中下游6月旱涝的关系。结果表明,菲律宾海附近是影响长江中下游地区6月降水的关键区。菲律宾异常反气旋（气旋）在对流层低层明显,强度随高度衰减。且这种大气环流异常与长江中下游地区6月降水的相关关系在低层850hPa最显著,到高层相关性减弱。当出现菲律宾异常反气旋环流时,垂直速度和水汽输送等异常分布特征有利于降水发生,使得长江中下游地区偏涝,反之则偏旱。 相似文献
9.
利用1980—2012年NCEP/NCAR逐6 h海平面气压再分析资料及定义的气旋客观识别方法,统计分析了春末夏初江淮地区气旋活动频数和强度的气候特征及其年际、年代际变化。结果表明:5—7月江淮地区存在明显的气旋活动高频中心,5、6月高频中心位于两湖盆地之间;7月北移,淮河以南频数较高。20世纪80—90年代江淮气旋活动频数偏少,强度偏弱;21世纪初期的10 a间气旋活动频数偏多,强度偏强。气旋活动频数多发年与少发年500 h Pa均出现稳定的长波环流结构,但仍存在显著差异。多发年两个南支槽向南伸展直达阿拉伯海和孟加拉湾地区,少发年仅出现孟加拉湾南支槽。多发年,对流层低层华南至江淮地区存在气旋式环流辐合异常中心,高层则出现辐散异常。西风带上的异常扰动沿着副热带急流向东亚地区传播能量,导致东部地区出现异常气旋式环流,为江淮气旋的发生提供了有利的环流背景。 相似文献
10.
利用再分析资料分析了MJO（Madden-Julian Oscillation）不同位相对春季中国东部降水的影响。结果表明：MJO处于位相3时对应长江及其以南地区降水增多,处于位相7时该区域降水减小。当热带MJO对流从位相1东传至位相4,与其相伴的北向辐散辐合流会在印度东北部—长江及副热带西北太平洋地区的对流层中低层产生明显的辐合异常,且在MJO位相3时中国东部的辐合异常达到最大。从Rossby波源角度分析,这种辐合异常会增强对流层中低层气旋性环流,导致MJO处于位相3时长江流域及其以南地区降水增多。同时,利用现代次季节和季节预报业务系统探讨了MJO与降水的关系对降水预报技巧的影响,发现预报降水和再分析产品的相关系数在MJO处于位相3和7时有所增加。 相似文献
11.
The wavelet analysis is performed of the mid- and low-latitude circulation index at 850 hPa over East Asia, the East Asian
monsoon index and the precipitation over the middle and lower reaches of the Yangtze River during 1998 South China Sea Monsoon
Experiment (SCSMEX) from May to August. Analysis shows that distinct 30–60 day low-frequency oscillation (LFO) exists in all
of the above elements during the exper-iment period. Analysis of low-frequency wind field at 850 hPa from May to August with
5 days interval is performed in this paper. Analysis results reveal that: (1) A low-frequency monsoon circulation system over
East Asia, characterized by distinct 30–60 day low-frequency oscillation, exists over 100°-150°E of East Asian area from the
middle and eastern parts of China continent and the South China Sea to the western Pacific in both the Northern and Southern
Hemisphere. The activity of East Asian monsoon is mainly af-fected by the low-frequency systems in it; (2) All of the tropical
monsoon onset over the South China Sea in the fifth pentad of May, the beginning of the Meiyu period and heavy rainfall over
the middle and lower reaches of the Yangtze River in mid-June and the heavy rainfall after mid-July are related to the activity
of low-frequency cyclone belt over the region, whereas the torrential rainfall over the upper reaches of the Yangtze River
in August is associated with the westward propagation of low-frequency anticyclone into the mainland; (3) There are two sources
of low-frequency oscillation system over East Asia during SCSMEX. i.e. the equatorial South China Sea (SCS) and mid-high latitudes
of the middle Pacific in the Northern Hemisphere. The low-frequency system over SCS propagates northward while that in mid-high
latitudes mainly propagates from northeast to southwest. Both of the heavy rainfall over the middle and lower reaches of the
Yangtze River in June and July are associated with the northward propagation of the above-mentioned SCS low-frequency systems
from the tropical region and the southwestward propagation from mid-high latitudes respectively and their convergence in the
middle and lower reaches of the Yangtze River; (4) There are two activities of low-frequency cyclone and anticyclone belt
each in the East Asian monsoon system during May to August. However the activity of these low-frequency circulation systems
is not clearly relevant to the low-frequency circulation system in the Indian monsoon system. This means that the low-frequency
circulation systems in Indian monsoon and East Asian monsoon are independent of each other. The concept previously put forward
by Chinese scholars that the East Asian monsoon circulation sys-tem (EAMCS) is relatively independent monsoon circulation
system is testified once more in the summer 1998.
This work was supported by the key project A of the State Ministry of Science and Technology “South China Sea Monsoon Experiment”
and the fruit of it. 相似文献
12.
利用中国逐日降水格点资料和NCAR/NCEP再分析资料,对1998年发生在我国东部长江中下游流域的夏季持续性强降水过程中显著的大气季节内振荡(ISO)的三维结构演变等活动特征进行了分析。1998年夏季长江及江南地区的异常强降水对应着该地区强的ISO活动。利用位相合成方法,对长江流域两个典型的季节内循环周期的ISO降水、850 hPa水平风场以及水汽和垂直速度等循环过程的时空分布特征进行了诊断分析。在低频环流场上,对流层低层的低频气旋和反气旋环流表现出交替在热带西北太平洋增强并向西偏北方向移动发展的特征,当异常气旋环流移动到长江流域上空时,长江流域正好位于气旋环流西南侧的东北风异常和西北太平洋上向西移动的反气旋环流西北侧的西南风异常环流汇合处的下方,引起该地区强降水的发生。在强降水阶段的ISO的垂直结构上,上升运动和水汽表现出从华南到长江流域自南向北移动的特征,强烈的垂直上升运动以及来自南方充足的水汽为增强长江流域地区的降水起到了重要作用。 相似文献
13.
利用地面加密降水资料、NCEP fnl再分析资料和风云4A卫星TBB资料,对2020年7月5-8日长江中下游地区的连续性大暴雨过程进行了诊断分析。结果表明,这次连续性大暴雨过程是在有利的大尺度环流背景下,受切变线影响由列车型对流云团产生的。7月5-8日,亚洲中高纬度大气环流调整,贝湖的东阻高崩溃,带动中高纬度的中高层冷空气持续南下,在长江流域与北上的暖湿气流交汇,使得暴雨产生和发展;同时干冷空气的侵入加强了暴雨过程的对流性不稳定,对暴雨的加强和发展起到重要作用。暴雨期间,低空西南急流的增强提供了有利的水汽输送条件,高空急流增强并发生“倾斜”,高低空急流的耦合在长江中下游上空形成了强烈的高空辐合与低空辐散,使得旺盛的上升运动延伸至对流层高层。在有利的环流背景条件下,中尺度对流系统的“列车效应”是导致本次大暴雨的直接原因。 相似文献
14.
该文分析了1991年7月中国江淮暴雨洪水期间赤道太平洋沃克环流及沿115°E哈得莱环流的逐日演变特征。结果发现在暴雨时期赤道东风减弱，西风加强，反哈得莱环流（即季风环流）在中国东部上空加强。在暴雨期间，高低空散度风场的分析指出，在低空出现明显的散度风越赤道气流，而在对流层上部出现散度风的流出。 相似文献
15.
基于台站降水观测数据和MERRA-2再分析资料,分析了2014年夏季我国长江流域降水的季节内振荡特征,并从位涡角度重点研究了与之相关的环流演变。结果表明:2014年夏季长江流域降水季节内变率以10~20d的准双周振荡为主。在降水准双周振荡的极端湿位相,受对流层高层随中纬度波列东传的正异常位涡和南亚高压东侧西南向传播的正异常位涡的共同影响,南亚高压呈“马鞍型”分布,在长江流域形成高空辐散环流;在对流层中低层,当中纬度波列的异常气旋向东南传播至长江流域以北时,西太平洋异常反气旋延伸至中国东南沿海,二者共同导致长江流域低空水汽辐合加强;在高、低层环流的共同作用下,长江流域持续性降水显著偏多,形成准双周振荡的极端湿位相;同时,长江以北高空位涡正异常导致其下方冷空气下沉,触发长江流域异常上升运动和南海地区异常下沉运动,该经向垂直环流圈的形成有利于长江流域正异常降水的维持。反之则形成极端干相位。 相似文献
16.
使用区域气候模式RegCM4.4.5.7,通过改变春季欧亚大陆中高纬地区的陆面感热通量,对欧亚中高纬感热异常影响中国夏季气候进行模拟分析,并探讨其影响机制。试验结果表明:当春季欧亚中高纬陆面感热通量加强时,我国长江流域和东北东部夏季气温降低,降水偏多;华北地区气温升高,降水偏少。春季陆面感热增强引起近地面和对流层低层大气热力状况异常,进而导致高度场和环流场的异常,长江流域和东北地区有气旋环流,对流运动旺盛,结合充足的水汽条件,对应降水偏多,而华北地区则相反,有反气旋环流和微弱的气流辐合,对应降水偏少。研究表明欧亚中高纬陆面感热异常是影响我国夏季气候的一个不可忽视的因子。 相似文献
17.
The significant differences of atmospheric circulation between flooding in the Huaihe and Yangtze River valleys during early mei-yu(i.e.,the East Asian rainy season in June) and the related tropical convection were investigated.During the both flooding cases,although the geopotential height anomalies always exhibit equivalent barotropic structures in middle to high latitudes at middle and upper troposphere,the phase of the Rossby wave train is different over Eurasian continent.During flooding in the Huaihe River valley,only one single blocking anticyclone is located over Baikal Lake.In contrast,during flooding in the Yangtze River valley,there are two blocking anticyclones.One is over the Ural Mountains and the other is over Northeast Asia.In the lower troposphere a positive geopotential height anomaly is located at the western ridge of subtropical anticyclone over Western Pacific(SAWP) in both flooding cases,but the location of the height anomaly is much farther north and west during the Huaihe River mei-yu flooding.Furthermore,abnormal rainfall in the Huaihe River valley and the regions north of it in China is closely linked with the latent heating anomaly over the Arabian Sea and Indian peninsula.However,the rainfall in the Yangtze River valley and the regions to its south in China is strongly related to the convection over the western tropical Pacific.Numerical experiments demonstrated that the enhanced latent heating over the Arabian Sea and Indian peninsula causes water vapor convergence in the region south of Tibetan Plateau and in the Huaihe River valley extending to Japan Sea with enhanced precipitation;and vapor divergence over the Yangtze River valley and the regions to its south with deficient precipitation.While the weakened convection in the tropical West Pacific results in moisture converging over the Yangtze River and the region to its south,along with abundant rainfall. 相似文献
18.
采用1979—2007年6月NCEP/NCAR2.5°×2.5°逐日再分析资料和中国743站逐日降水资料,利用相关分析、合成分析等方法,分析了天气尺度波列的特征及其对长江中下游6月梅雨的影响。结果表明:当长江中下游6月梅雨较少时,东亚及西太平洋区域存在一个天气尺度波列;该波列的延伸距离较短(从黄河河套地区经过长江中下游至南海、菲律宾海一带),维持时间也很短,且仅仅在500 h Pa以下较强。诊断及个例分析表明,当该波列异常显著时,长江中下游梅雨降水明显减少,而其南部区域降水则增多,说明该波列对预报长江中下游降水具有重要的指示意义。 相似文献
19.
2016年梅雨期间长江中下游强降水与对流层上层斜压波包的关系 总被引：3，自引：0，他引：3
2016年6—7月,长江中下游地区发生了自1998年以来最严重的强降水事件,造成了重大的经济损失。利用NCEP/NCAR再分析资料和中国2479站逐月及逐日降水资料,研究了2016年梅雨期间长江中下游地区降水与欧亚大陆对流层上层斜压波包活动的关系,并诊断了两者之间的信息流向。结果表明,梅雨期间的高频斜压波动具有明显的下游频散效应。波动起源于黑海,沿西北—东南方向于3—4 d后传至长江中下游地区。斜压波包为长江中下游地区强降水的发生提供了必要的能量。波作用通量矢量的分布表明,梅雨期间逐日均有来自西风带上游的扰动能量向长江中下游流域传播。而梅雨期间降水与斜压波包的信息流关系表明,二者之间存在信息传递。因此,3—4 d并源于黑海附近的斜压波包活动是2016年长江中下游梅雨期间异常降水的成因。这些结果为深刻认识长江中下游地区强降水事件发生的成因和有效预测提供了线索。 相似文献
20.
利用NOAA逐日海表面温度(sea surface temperature,SST)资料、NCEP/NCAR逐日风场和比湿资料以及中国国家气象信息中心提供的逐日降水资料,研究了西北太平洋气候SST的低频周期,进一步分析了夏季西北太平洋SST季节内振荡与中国东部同期降水异常的关系。结果表明:夏季西北太平洋季节内SST异常影响中国东部同期季节内降水最显著的三个区域为:长江中游及华南沿海;江淮流域;华北大部。其影响途径主要是通过西北太平洋季节内海温与850 h Pa环流场之间相互作用,在东亚沿岸自南向北逐渐形成气旋—反气旋—气旋(反气旋—气旋—反气旋)的波列结构,引起东亚沿海局地水汽的辐合辐散,使得中国东部夏季季节内雨带从江淮流域向华北推进(从华北南撤到长江中游及华南沿海地区)。 相似文献