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1.
温湿结构对南海低压发展影响的数值模拟研究 总被引：2，自引：0，他引：2
本文对比分析了两个南海热带低压,其中一个在24小时内发展为台风,而另一个不发展。通过几个改变初始场温、湿结构的数值试验的对比分析,指出低压区的温、湿结构对低压发展起着很重要的作用。中低层有深厚的高湿层存在,以及中低层有暖心存在,都有利于低压的发展加强,反之,中低层湿度较小或湿层较浅,以及暖心在高层而中低层无暖心,都不利于低压发展加强。同时,温、湿结构对低压发展的影响,可能主要是通过影响条件不稳定层的深浅和强弱,以及影响中低层的水汽能量供应,导致对流的发展趋势发生变化来实现的。最后指出,南海低压的发展对低压区的温度和湿度变化很敏感。 相似文献
2.
采用NOAA极轨卫星先进微波探测器AMSU-A L1B的观测资料,经过卫星天线模式校正和临边调整,然后采用线性回归及水平方向上逐步订正法得到水平分辨率0.5 °×0.5 °垂直方向1 000 ~ 0.1 hPa共40层的反演温度资料。通过个例分析发现,反演的温度资料可以揭示热带气旋暖心的细致结构。之后,选取了由中高层向下(“自上而下”)发展而来的发展和不发展的南海热带低压,对这些热带低压暖心结构的演变进行了对比分析。结果表明:由中高层向下发展而来的南海热带低压,都有暖心结构从中高层向下发展到近海面的过程;发展的南海热带低压在暖心向下发展到近海面时,高层暖心突然增强,使得热带低压的暖心在高层和低层同时出现显著增强;而不发展的南海热带低压的暖心结构并没有出现这种现象。因此,通过监测热带低压暖心结构的变化,可能对判别热带低压是否发展有一定的帮助。 相似文献
3.
利用NCEP 1°×1°最终分析资料FNL和位涡反演方法,对2006年8月下旬一次中层涡旋诱发南海热带低压的形成过程进行了分析。结果表明,在中层涡旋诱发南海热带低压形成时高层暖心结构经历了由上向下逐渐发展的过程,而中层气旋性环流经历了由上向下快速发展的过程。高层暖心结构的向下发展主要与中低层凝结潜热加热作用和干空气从高层侵入有关,而高层波动的影响不明显,暖心发展到达近海面需要有底层热力异常和中低层凝结潜热加热作用的共同配合。中层气旋性环流的向下发展主要与中低层凝结潜热加热作用有关,高层波动对中低层涡度的影响不明显,而底层热力异常主要在900 h Pa以下产生负涡度。综合分析表明,中低层凝结潜热加热对南海热带低压的生成和发展起关键作用。 相似文献
4.
源自东风波台风“灿都”发展过程的结构特征分析 总被引：2，自引：0，他引：2
对源自东风波的台风“灿都”结构变化特征进行了分析,结果表明:(1) 引发“灿都”发展的东风波振动强度主要表现在对流层中层,其触发的南海季风区低层对流发展偏于东风波的东北-西南向波轴的西南端。(2) “灿都”中心结构耦合过程经历了中心附近上升运动从不对称向准对称的发展过程;“灿都”中心附近上升运动趋于准对称时也是“灿都”结构调整趋于完成,强度获得快速加强的时段。这可能是东风波加强成热带气旋发展演变的动力特征之一。(3) “灿都”在热带低压阶段的暖心不明显,对流层高层出现东风波暖心特征;由热带低压加强到热带风暴强度阶段,东风波暖心特征趋于消失,低层暖中心区发展;热带风暴到台风阶段的暖中心区由对流层中低层发展至高层,但暖心位置偏于“灿都”中心东侧。 相似文献
5.
一次引发南亚大暴雨的季风低压结构、涡度与水汽收支分析 总被引：12，自引：2，他引：10
对2003年夏季风期间,7月24～28日印度季风槽内季风低压发展西移与阿拉伯海中尺度低压合并引发南亚的一次大暴雨过程进行了诊断分析,探讨了印度季风槽、季风低压的三维结构以及低压区域的涡度、水汽收支.揭示和确认了一些事实:1)印度季风槽区对流层中下层存在明显的风场切变,槽区高温高湿,为单一性质的热带气团,低层为对流不稳定,槽区对应正涡度区;2)季风低压是一较深厚系统.动力结构为低层正涡度,高层负涡度,低层辐合,高层辐散.其西移速度约500 km·d.季风低压北侧整层为深厚的东风,南侧在对流层中低层为西风,在高层为东风.热力结构在低层(700～800 hPa)间存在弱冷区,而中高层几乎为暖心结构.低压对应高湿区,低压中心西侧整层为相对湿度大值区;3)季风低压的发展过程中,低层的辐合场制造正涡度,促进低压的发展;4)低压区水汽强烈辐合,西边界输入量最大.在此研究工作的基础上,作者还比较了夏季风期间南亚印度季风槽和东亚梅雨锋系统的异同. 相似文献
6.
本文对1985年8月下旬北部湾热带低压发展为台风的演变过程作了诊断分析。发现在台风的生成和加强的过程中,涡旋动能出现显著的加强和向下转移,最大涡度层和无辐散层明显下降.与此同时,暖心结构也逐步形成。这一过程与低层西南季风的增强北进,卷入台风环流中的过程密切相关。涡旋动能收支的计算表明,低压由于处在强的水平切变和垂直切变基流中,风场和温度场的不对称和暖心结构的形成,使台风获得正压和斜压不稳定能量,加之以积云对流为代表的次网格过程向涡旋运动输送能量,从而使低压发展为台风。台风的衰亡是由于登陆后低层偏冷气流的入侵和下部暖心结构的破坏,使台风只有纬向平均气流取得能量,不足以补偿摩擦耗散和位能通量的辐散,因而减弱为低压的。 相似文献
7.
本文试用综合研究方法探讨南海热带气旋发展各阶段的基本结构及其演变特征。 综合场分析表明:南海热带气旋的流场大体呈圆形分布。热带气旋的半径在地面图上约为4纬距左右,属天气尺度,垂直伸展范围一般可达300mb左右,涡度轴的方向从低压阶段至风暴阶段变化较大,而且是层和低层轴向不一致,强风暴阶段涡度轴方向基本垂直,径向流入层主要位于500mb以下,流入层达到的高度较西太平洋台风为低。温度场结构方面,各阶段气旋中心温度较周围高出2—6℃;强风暴阶段暖核出现在300mb附近,200mb附近为一冷中心;冷暖中心的数值和出现高度均小于西太平洋台风,此外各阶段的温湿分布清楚地表明,为热带气旋发展供应热量、水汽的暖湿空气,主要来自低层的中心以南地区。 文中还简单讨论了中、低空环境流场,热带气旋的暖心结构与垂直运动,稳定度等等影响南海台风发展加强的一些因子。 相似文献
8.
热带风暴海马变性前后的物理量诊断分析 总被引：5，自引：0，他引：5
利用NCEP再分析资料,针对热带风暴海马(0421)变性前后各物理量进行诊断分析,发现了一些有意义的结果.由变性前高低层的暖心对称结构到变性后非对称的锋面结构,其中冷空气是从低层、低压的西南象限开始入侵的.同时相对涡度场上,也由整层左右对称的正涡度演变成自低层到高层向西倾斜的垂直分布.另外,24小时平均相对涡度、平均散度呈现出中低层数值变大,且辐合上升层的厚度也加大的特点;最大上升速度中心的高度由变性前的600hPa上升到500hPa.由于西风带高空槽东移,变性后存在两条水汽通道,一条伴随槽前的西南气流,一条来自南海与强劲的偏南气流相伴. 相似文献
9.
《干旱气象》2015,(3)
利用常规观测资料、1°×1°NCEP再分析资料、自动站资料,从水汽、动力、不稳定条件方面,采用诊断分析方法对2011年7月28日(简称过程Ⅰ)关中西部、陕南西部区域性强降雨和2013年7月25日(简称过程Ⅱ)陕北南部分散性强降雨进行对比分析。结果表明:2次过程前期天气状况、环流形势、影响系统类似,但降雨差异大。过程Ⅰ低层切变线和辐合线明显,过程Ⅱ则弱;地面上,过程Ⅰ强降雨区处在高、低压之间的气压梯度密集带上,过程Ⅱ强降雨区则处于均压场中;过程Ⅰ强降雨区中低层比湿呈单峰型变化,水汽通量辐合强度大且深厚,有强烈水汽输入,过程Ⅱ强降雨区中低层比湿基本无变化,水汽通量辐合强度弱且浅薄,水汽输入弱;过程Ⅰ强降雨区中、低层有明显冷空气作用产生系统性强降雨,过程Ⅱ强降雨区仅在近地层有浅薄的弱冷空气扰动,在西南气流中激发湿对流;过程Ⅰ强降雨区低层对流不稳定、中高层为条件对称不稳定的混合型大气层结,而过程Ⅱ强降雨期间中层、低层大气均为对流不稳定层结。 相似文献
10.
本文用热带有限区域σ—坐标六层初始方程数值预报模式对1979年6月下旬一次南海季风低压的发展过程进行了数值模拟,试验结果表明,本例南海季风低压的发展对大地形不敏感,与南海台风的数值试验结果不同.削减湿度场的试验表明,季风低压的发展与大气中水汽含量密切相关,湿度减小,季风低压发展缓慢甚至发展不起来.积云对流过程及其潜热的释放对季风低压发展有显著影响,它使得低压区的上升运动加强.改变低压南侧的西南风强度,导致水汽及能量输送的减小,不利于低压的发展.低压的发展主要由积云对流所驱动. 相似文献
11.
The comparison analyses between two tropical depressions in the South China Sea are completed by numerical ex-periments with a limited area model developed in Guangzhou Institute of Tropical and Oceanic Meteorology. One of thedepressions develops and finally becomes a typhoon within 24 hours of the analyzing period (defined as DVD hereafter),and the other not (defined as UNDVD) The analyses show that their initial structures of temperature, humidity, pres-sure. wind and stability are obviously different from each other. There are a very deep wet layer and a clear warm-coredstructure in the mid-lower troposphere in the depression area in the DVD case, but with the warm core in the upperrather than lower troposphere arid a very shallow wet layer in the lower troposphere in the depression area in theUNDVD case. The developing and non-developing processes are successfully simulated by the model, showing that theCISK mechanism plays the most important role in the development of SCSDs (Tropical Depressions in the South ChinaSea). Several numerical experiments show that the structures of humidity and temperature in the depression area haveimportant effect on the development of SCSDs. It is favourable to the development of SCSDs when a very deep wet layerexists in the mid-lower troposphere or a warm-cored structure exists in the mid-lower troposphere instead of in uppertroposphere, and conversely, it is unfavourable to the development of SCSDs when the wet layer is very shallow in thelower troposphere or the warm-cored structure is in the upper troposphere rather than in mid-lower troposphere. Thestructures of stability for each case are also analysed, which shows evident differences between the two cases, with adeeper instability layer in the DVD case and a shallower one in the UNDVD case. Finally, the sensitivity of the devel-opment of the SCSDs to the vertical structures of humidity and temperature in the depression area is discussed. 相似文献
12.
XU Yamei 《Acta Meteorologica Sinica》2013,27(4):486-501
The mechanism for the maintenance of Tropical Cyclone Bill （1988） after landfall is investigated through a numerical simulation. The role of the large-scale environmental flow is examined using a scale separation technique, which isolates the tropical cyclone from the environmental flow. The results show that Bill was embedded in a deep easterly-southeasterly environmental flow to the north-northeast of a large-scale depression and to the southwest of the western Pacific subtropical high. The depression had a quasi-barotropic structure in the mid-lower troposphere and propagated northwestward with a speed similar to the northwestward movement of Bill. The moisture budgets associated with both the large-scale and the tropical cyclone scale motions indicate that persistent low-level easterly-southeasterly flow transported moisture into the inner core of the tropical cyclone. The low-level circulation of the tropical cyclone transported moisture into the eyewall to support eyewall convection, providing sufficient latent heating to counteract energy loss due to surface friction and causing the storm to weaken relatively slowly after landfall. Warming and a westward extension of the upper-level easterly flow led to westward propagation of the environmental flow in the mid-lower troposphere. As a result, Bill was persistently embedded in an environment of deep easterly flow with high humidity, weak vertical wind shear, convergence in the lower troposphere, and divergence in the upper troposphere. These conditions are favorable for both significant intensification prior to landfall and maintenance of the tropical cyclone after landfall. 相似文献
13.
王沛霖 《热带气象学报(英文版)》1996,2(1):98-103
Using observational data and the data of disastrous investigation of tornado in Zhujiang River Delta and Guangzhou's sounding from March to May of 1976-1983, the environmental conditions of genesis of tornado are analysed and compared with those of nontornadic local storm.It is found that the favorable conditions of genesis of tornado are lower pressure, unstable stratification and stronger wind in the deep layer of troposphere and higher temperature and humidity in low level, among which, lower pressure, more unstable stratification and layer wind are primary conditions for a severe local storm to possibly develop into a storm with accompanying tornado.The tornado mechanism is not related to vertical wind shear. 相似文献
14.
1976年8月2日,甘肃省中部地区发生了一次暴雨。在热带东风带中,当西移的倒槽和高原北部东移的低涡相结合时,就会使倒槽强烈发展并伸入内陆。倒槽东侧深厚的东南气流,造成该区深厚的位势不稳定,并使水汽输入到西北区东部,它与冷锋后部的西北气流相遇后,产生大范围水汽通量的辐合,这是本次暴雨的大尺度条件。 次天气尺度的低涡是产生这次暴雨的直接影响系统。当对流层上部的扰动与低层扰动上下叠置,形成一个深厚的次天气尺度低涡时,易产生对流性暴雨。 次天气尺度的低涡,是雨团迅猛加强的背景,南移的低层切变线起触发作用,而该地早先存在的一个暖湿的地方性中低压,则是合适的局地环境场。当低层切变线移入此中低压时,往往造成中尺度雨团的合併,出现急骤加强,形成暴雨。 相似文献
15.
COMPARISON OF THE STRUCTURAL CHARACTERISTICS OF DEVELOPED VERSUS UNDEVELOPED MID-LEVEL VORTEXES 总被引：1，自引：1，他引：0
Using the NCEP 1°×1°reanalysis data,several obvious differences of the structural characteristics of developed versus undeveloped mid-level vortexes are studied.First,the central vorticity of the developed mid-level vortex increases towards higher levels while the undeveloped one decreases.The low-level convergence structure maintains well in the developed mid-level vortex whereas the undeveloped one does badly.Second,on the one hand,according to the symmetric analysis,the horizontal wind field and wind vertical section of the developed mid-level vortex are well symmetric while those of the undeveloped one are less symmetric.Meanwhile,weak wind vertical shear help the developed mid-level vortex to establish a warm core in upper-and mid-levels of the troposphere.On the other hand,according to the balance analysis,better balance between wind and pressure is shown in the mid-and lower-levels of the troposphere of the developed mid-level vortex than in those of the undeveloped vortex.Third,positive anomaly of potential vorticity is enhanced and developed in the vertical direction of the developed vortex.However,the undeveloped vortex weakens with a weak positive anomaly. 相似文献
16.
Scale interaction in the Western Pacific Monsoon 总被引：9，自引：1，他引：9
G. J. Holland 《Meteorology and Atmospheric Physics》1995,56(1-2):57-79
Summary The lower-tropospheric scale interactions occurring in the summer monsoon of the western North Pacific are reviewed and summarised in a conceptual model. Diabatic heating produces a circulation with similar characteristics to those that are observed. In the lower troposphere the advection of vorticity by the divergent wind produces a compact, and more intense response than in the upper levels. Subsequent phase dispersion westward, and group propagation eastwards, lead to a monsoon depression in convectively suppressed conditions, a westerly jet with cross-equatorial flow, and a strong confluence region to the east of the monsoon depression.I suggest that this confluence zone traps tropical waves in the mid-lower troposphere in a similar manner to the accumulation and emanation mechanisms described by Chang and Webster. The details of the convection in the confluence zone are of little direct consequence to the monsoon circulation, which is similar in scale to the deformation radius for the undisturbed tropics. However, mesoscale convective systems can both self organise into larger coherent structures and produce vortices of horizontal scale 100–200 km, which are long-lived and potentially have considerable indirect influence on both the monsoon and embedded systems, such as tropical cyclones. The confluence zone provides an excellent environment for tropical cyclone formation, which is enhanced by the presence of a previously developed tropical cyclone. Scale-interaction arising from the merger of developing vortices and the large monsoon depression can lead to development of a very large typhoon and rapid breakdown of the total monsoon circulation. The interaction of tropical cyclones with the mid-latitude systems is complex and not well understood, but recurving tropical cyclones may provide a major component of the emanation of energy to higher latitudes.With 16 Figures 相似文献
17.
下投探空资料在台风莫拉克路径预报的应用试验 总被引：4，自引：0，他引：4
2009年8月7日中国大陆举行了首次利用机载下投式探空仪观测台风的试验,飞机在台风莫拉克与天鹅之间的云带相对稀薄区释放11个下投式探空仪。基于下投探空观测资料、常规探空资料和1°×1°分辨率的NCEP再分析资料,分析下投探空资料的可用性,并以下投探空资料初步分析了两台风间南海上空的风场、湿度场等大气特性;分别进行了有无以同化下投探空为初始场的GRAPES模式的模拟试验,以了解下投探空资料对台风莫拉克预报的影响作用。初步结论表明,台风天鹅与莫拉克之间的南海上空对流层中低层为深厚的西南气流,对流层低层及高层湿度小,中间层大;同化下投探空资料后,观测地区(下投探空点及其附近)800 hPa以下西南风减弱,以上加强,湿度中低层减小;有无同化下投探空资料的初值场差异随模式积分向下游传播,影响台风的环境场,改变了台风的引导气流:同化后500 hPa台风引导气流偏东、偏北分量加强,使台风的路径更接近实况路径,48 h台风路径预报误差比原来减少18%。 相似文献
18.
The linear regression and horizontally stepwise correction are conducted on the observational data from AMSU-A L1 B of NOAA polar orbit satellite to invert a 40-layers(from 1,000 h Pa to 0.1 h Pa) dataset of atmospheric temperature with a horizontal resolution of 0.5°×0.5° after the correction of satellite antenna pattern and limb adjustment. Case study shows that the inversion data of temperature can reveal the detail structure of warm core in tropical cyclone. We choose two categories of tropical depressions(TDs) over the South China Sea, including the non-developing TDs and developing TDs. Both of them are developed downward from the middle and upper level to the lower level. Comparison between the evolutions of warm core in the two categories of TDs indicates that the warm core is developed downward from the middle and upper troposphere to the sea surface in all the downward-developing TDs. The difference is that in the group of further developing TDs, the warm core in the upper troposphere is intensified suddenly when it is extending to the sea surface. The warm core in the upper and lower troposphere is strengthened in a meantime. But the similar feature is not observed in the non-developing TDs. Then it may be helpful to judge the TD development by monitoring the change in its warm-core structure. 相似文献
19.
The heavy rainfall caused by interactions between the monsoon depression and the middle-latitude systems in Australia has been investigated in this paper. For a better understanding of the Australian monsoon depression (AMD) and its synoptic-scale interaction with the middle-latitude systems, some key meteorological parameters have been calculated, including the vorticity budget, moisture budget, temperature advection, frontogenesis function and potential vorticity. The results show that interaction between the lower and mid-latitude systems does exist leading to the merging of the extratropical low with frontal systems and the AMD, meanwhile both the low-level cold air from the mid-latitude and the warm moist air that was lifted by the front were very favorable for the formation and the intensification of heavy rainfall, which was quite different from the rainfall caused by the AMD alone. Second, the obvious temperature advection and gradient were detected, so the baroclinicity was favorable to the intensification of the front, as well as to the development of the upper-level jet. Next, isentropic analysis revealed that the south-west cold-flow sank and met the warm flow coming from the northern part of Australia, thereby forming the obvious baroclinic zone in the lower troposphere. A high-PV anomaly area located in the upper level of the troposphere, which overlaid the low-level frontogenesis zone, also existed. The upper-level PV maximum extended downwards forming a vertical PV column when the extratropical low intensified. Furthermore, the AMD is a warm-cored vortex located in middle and upper troposphere with a deep and thick moisture layer, and there were some differences in the vorticity and moisture budgets of the two different stages. Finally, based on the above-mentioned analysis, a conceptual model describing the interactions between the lower and middle-latitude systems in the southern hemisphere was proposed. 相似文献