四川盆地西部暴雨对初始水汽条件敏感性的模拟研究   总被引：9，自引：5，他引：4  

卢萍  宇如聪  周天军 《大气科学》2009,33(2):241-250

基于区域暴雨数值预报模式AREM, 针对2003年8月发生在四川盆地西部的多次局地强暴雨过程, 通过数值试验, 讨论了川西暴雨对初始水汽条件的高度敏感性, 揭示了川西暴雨过程独特的局地水汽循环特征。初始水汽条件不仅决定着暴雨的强度, 还对最大降水发生时间产生明显影响, 从而决定模式对降水日变化的模拟效果。局地初始水汽偏大, 不仅导致24小时降水总量的迅速增加, 甚至空报暴雨, 还使得主要降水时段明显提前, 使夜雨变为昼雨。局地初始水汽减少不仅会显著减小降水量, 甚至会致使暴雨消失,还会使主要降水时段滞后。  相似文献   

呼和浩特市夏季降水与影响因子的相关分析     

李薪  李晓靖  王阿美  贾中英 《内蒙古气象》2009,(4):14-16

利用呼和浩特市南郊1961-2008年夏季降水资料与海温、亚洲季风、西太平洋副热带高压和东亚阻塞高压等因子进行相关分析,结果表明：这些因子的异常变化,可以作为呼和浩特市南郊夏季降水的预测信号。  相似文献   

副热带北太平洋SST在ENSO冷暖位相转变中的作用     

韦圣标  陈昇  王鑫 《气候与环境研究》2018,23(4):453-462

2015/2016年发生的极端El Ni?o事件,与1997/1998年El Ni?o事件具有可比拟的强度,但是2016年事件转变为弱La Ni?a,而1998年事件则为强La Ni?a。本文通过对比这两次极端El Ni?o事件,揭示其转变为不同强度La Ni?a事件的物理机制。混合层热收支分析的结果表明,在El Ni?o衰减年的4~11月,2016年平流反馈和温跃层反馈相对较弱,混合层温度衰减速率慢,其产生的主要原因是赤道中西太平洋的东风异常较弱。进一步分析表明,赤道中西太平洋的东风异常与副热带东北太平洋的海表温度异常（SSTA）有关,该地区的SST在1998年表现为冷异常,2016年为暖异常。副热带东北太平洋冷的SSTA有利于信风加强,从而加强中西太平洋的东风异常;而暖的SSTA使得赤道以北出现西南风异常,从而削弱中西太平洋的东风异常。此外,合成分析也表明,副热带东北太平洋SSTA与转变的La Ni?a的强度具有关联,El Ni?o转变为强La Ni?a的情况在位相转变期伴随着副热带北太平洋冷的SSTA,而El Ni?o转变为弱La Ni?a的情况没有明显的冷SSTA。  相似文献   

北极海冰对2008年1月乌拉尔高压异常的影响   总被引：1，自引：1，他引：0  

韩哲  李双林 《气候与环境研究》2013,18(5):671-680

2008年1月我国南方发生了大范围的雨雪冰冻灾害天气,造成此次灾害的一个重要原因是乌拉尔高压异常的长期维持,而作为下垫面的海洋,2007/2008冬季环北欧海海冰异常偏少。观测资料合成分析表明,乌拉尔山地区出现高压异常与巴伦支海和喀拉海的海冰偏少存在密切对应关系。利用大气环流模式试验研究了(90°W~60°E)区域海冰异常对大气的影响,模拟结果显示海冰对乌拉尔高压异常有正的贡献,线性模式诊断表明天气尺度瞬变波是海冰影响乌拉尔高压异常的一种重要机制。  相似文献   

Influence of the Asian-Pacific Oscillation on Spring Precipitation over Central Eastern China   总被引：2，自引：0，他引：2  

ZHOU Botao  ZHAO Ping 《大气科学进展》2010,27(3):575-582

The linkage between the Asian-Pacific oscillation(APO)and the precipitation over central eastern China in spring is preliminarily addressed by use of the observed data.Results show that they correlate very well,with the positive(negative)phase of APO tending to increase(decrease)the precipitation over central eastern China.Such a relationship can be explained by the atmospheric circulation changes over Asia and the North Pacific in association with the anomalous APO.A positive phase of APO,characterized by a positive anomaly over Asia and a negative anomaly over the North Pacific in the upper-tropospheric temperature,corresponds to decreased low-level geopotential height(H)and increased high-level H over Asia,and these effects are concurrent with increased low-level H and decreased high-level H over the North Pacific.Meanwhile,an anticyclonic circulation anomaly in the upper troposphere and a cyclonic circulation anomaly in the lower troposphere are introduced in East Asia,and the low-level southerly wind is strengthened over central eastern China.These changes provide advantageous conditions for enhanced precipitation over central eastern China.The situation is reversed in the negative phase of APO,leading to reduced precipitation in this region.  相似文献   

华北汛期水汽条件的年代际特征分析     

刘海文  田淑欣  杜建华 《山东气象》2010,30(2):1-4

利用NCEP/NCAR逐日再分析资料,使用合成分析等方法,分析了华北汛期水汽条件的年代际变化特征,结果表明：大气对华北汛期的水汽输送以及华北区域的水汽收支有明显的年代际变化。以1978年为界,先前以异常西南风对华北进行水汽输送的改变为以后的异常东北风的水汽输送,先前以异常东风水汽输送的改变为以后的异常偏西风水汽输送,先前以异常偏西风水汽输送的改变为以后的异常偏东风水汽输送。对于华北区域而言,先前由南边界和西边界的异常水汽输送,改变为以后的由北边界和东边界异常水汽输送,华北地区水汽由以前的异常水汽辐合和盈余,改变为以后的异常水汽辐散和亏损。  相似文献   

Prediction Errors Associated with Sparse Grid Estimates of Flows over Hills     

Karl J. Eidsvik 《Boundary-Layer Meteorology》2008,127(1):153-172

Numerical simulations of geophysical flows have to be done on very sparse grids. Nevertheless, flows over moderately sloped hills can be predicted quite accurately as long as the near ground vertical resolution is reasonably dense. Recirculation flows behind steeper hills are associated with slow convergence towards grid independent integrations, but even then moderately stratified flows of this type can be predicted usefully accurately. For better horizontal grids than about half the hill-height Δx ₁/H ≈ 0.5 or so, separation and recirculating domains are predicted with an error factor comparable to 0.3. The characteristic wavelength of lee waves is predicted more accurately while the lee wave amplitude and the maximum turbulence intensity in recirculating domains are underestimated by factors comparable to 0.3. Strongly stratified flows may be associated with hydraulic transitions and even this is predicted on quite coarse grids, up to say Δx ₁/H ≈ 0.5. However, the details of such flows turn out to be predicted with considerable errors also on high-resolution grids. Inaccurate modelling of stratified turbulence is a main contributor to this error.  相似文献   

Turbulent Intensities and Velocity Spectra for Bare and Forested Gentle Hills: Flume Experiments   总被引：1，自引：1，他引：0  

Davide Poggi  Gabriel G. Katul 《Boundary-Layer Meteorology》2008,129(1):25-46

To investigate how velocity variances and spectra are modified by the simultaneous action of topography and canopy, two flume experiments were carried out on a train of gentle cosine hills differing in surface cover. The first experiment was conducted above a bare surface while the second experiment was conducted within and above a densely arrayed rod canopy. The velocity variances and spectra from these two experiments were compared in the middle, inner, and near-surface layers. In the middle layer, and for the canopy surface, longitudinal and vertical velocity variances () were in phase with the hill-induced spatial mean velocity perturbation (Δu) around the so-called background state (taken here as the longitudinal mean at a given height) as predicted by rapid distortion theory (RDT). However, for the bare surface case, and remained out of phase with Δu by about L/2, where L is the hill half-length. In the canopy layer, wake production was a significant source of turbulent energy for , and its action was to re-align velocity variances with Δu in those layers, a mechanism completely absent for the bare surface case. Such a lower ‘boundary condition’ resulted in longitudinal variations of to be nearly in phase with Δu above the canopy surface. In the inner and middle layers, the spectral distortions by the hill remained significant for the background state of the bare surface case but not for the canopy surface case. In particular, in the inner and middle layers of the bare surface case, the effective exponents derived from the locally measured power spectra diverged from their expected  − 5/3 value for inertial subrange scales. These departures spatially correlated with the hill surface. However, for the canopy surface case, the spectral exponents were near  − 5/3 above the canopy though the minor differences from  − 5/3 were also correlated with the hill surface. Inside the canopy, wake production and energy short-circuiting resulted in significant departures from  − 5/3. These departures from  − 5/3 also appeared correlated with the hill surface through the wake production contribution and its alignment with Δu. Moreover, scales commensurate with Von Karman street vorticies well described wake production scales inside the canopy, confirming the important role of the mean flow in producing wakes. The spectra inside the canopy on the lee side of the hill, where a negative mean flow delineated a recirculation zone, suggested that the wake production scales there were ‘broader’ when compared to their counterpart outside the recirculation zone. Inside the recirculation zone, there was significantly more energy at higher frequencies when compared to regions outside the recirculation zone.  相似文献   

亚洲—太平洋季风区的遥相关研究   总被引：15，自引：6，他引：9  

丁一汇  刘芸芸 《气象学报》2008,66(5):670-682

亚洲-太平洋季风区各季风子系统间的相互作用对季风区甚至全球的气候变化都有非常显著的影响.文中根据国内外相关研究,重点分析和评述了在亚洲-太平洋季风区中4种季节内时间尺度的遥相关关系,清楚地揭示了印度夏季风、东亚夏季风和西北太平洋夏季风之间的相互作用.研究发现:(1) 在亚洲季风爆发初期,印度夏季风的爆发相对于中国长江流域梅雨的开始存在相差大约两周的超前关系,形成从印度西南部经孟加拉湾到达中国长江流域及日本南部的遥相关型,即"南支"遥相关型.(2) 在季风盛行期间,长江流域降水明显受热带西北太平洋夏季风的影响,与西北太平洋夏季风降水呈反相关关系,即当季风减弱时,长江流域夏季降水偏多.(3) 与长江流域降水相反,华北雨季(7月第4候-8月第3候)则与西北太平洋夏季风降水呈正相关关系,当西北太平洋夏季风强时,西太平洋副热带高压异常偏北偏东,副高西南侧的异常东南水汽输送在中国华北地区上空辐合,给该地区降水偏多提供了充足的水汽条件.(4) 华北夏季降水同时还与印度夏季风呈正相关关系,在夏季风盛行期间,形成由印度西北部经青藏高原到中国华北地区的西南-东北走向的遥相关型,即"北支"遥相关型. 上述4种遥相关关系,反映了亚洲夏季风季节北推过程中,印度夏季风、东亚夏季风和西北太平洋夏季风子系统之间的关联.  相似文献   

孟加拉湾风暴Mala结构及对云南强降水的影响   总被引：1，自引：0，他引：1  

金少华  杨明  李华宏  艾永智 《气象科学》2010,30(1):74-81

利用实时观测资料和NCEP(1°×1°)的6 h再分析资料,对2006年春季发生在孟加拉湾的超强风暴Mala的移动路径、强度变化、环流背景以及风暴温湿场、动力场特征等进行分析。结果表明:Mala在阿拉伯副热带高压和西太平洋副热带高压两高间辐合区生成、加强,并沿西太平洋副热带高压西侧西南或偏南气流移动。风暴发展、成熟到消亡,湿度对风暴的作用比温度明显;动力场结构除具有台风结构的一般特征外,在风暴发展期,中心附近散度场从低层到高层为辐合和辐散交替结构,表明风暴内部高空辐散抽吸作用对于风暴发展起到重要作用。登陆后风暴低压内自身能量和水汽与冷空气共同作用下,在冷暖交汇处出现强烈的上升运动和激发出中尺度辐合线是造成云南强降水主要原因。  相似文献