Analysis of Deep Convective Towers in a Southwest-Vortex Rainstorm Event     

翟丹华  孔凡铀  戴泽军  高松  邓承之  张勇 《热带气象学报(英文版)》2021,27(2):177-190

The structure and organization of the extreme-rain-producing deep convection towers and their roles in the formation of a southwest vortex(SWV) event are studied using the intensified surface rainfall observations, weather radar data and numerical simulations from a high-resolution convection-allowing model. The deep convection towers occurred prior to the emergence of SWV and throughout its onset and development stages. They largely resemble the vortical hot tower(VHT) commonly seen in typhoons or hurricanes and are thus considered as a special type of VHT(sVHT). Each sVHT presented a vorticity dipole structure, with the upward motion not superpose the positive vorticity.A positive feedback process in the SWV helped the organization of sVHTs, which in turn strengthened the initial disturbance and development of SWV. The meso-γ-scale large-value areas of positive relative vorticity in the mid-toupper troposphere were largely induced by the diabatic heating and tilting. The strong mid-level convergence was attributed to the mid-level vortex enhancement. The low-level vortex intensification was mainly due to low-level convergence and the stretching of upward flow. The meso-α-scale large-value areas of positive relative vorticity in the low-level could expand up to about 400 hPa, and gradually weakened with time and height due to the decaying low-level convergence and vertical stretching in the matured SWV. As the SWV matured, two secondary circulations were formed,with a weaker mean radial inflow than the outflow and elevated to 300-400 hPa.  相似文献   

2008年台风“风神”强迫次级环流的诊断分析     

毕明玉  ;沈新勇  ;袁媛  ;丁治英 《南京气象学院学报》2014,(3):354-365

利用WRF（weather research and forecasting）模式模拟资料对2008年06号台风“风神”进行诊断分析,采用准地转PV-ω方程对台风外围中尺度对流系统较强的6月20日10时（世界时）的资料进行分析.通过PV-ω方程诊断了潜热、摩擦及干动力过程对台风次级环流的作用,结果显示潜热强迫产生的次级环流最强,摩擦强迫主要集中在边界层,而干动力过程则在台风中心附近产生影响.加入摩擦、潜热得到的准平衡流场能够描述70％左右的台风环流.环境垂直切变在台风中心附近强迫产生横向次级环流的垂直切变与环境垂直切变相反,次级环流会使得台风一侧的上升气流减弱而另一侧上升气流增强,从而使得台风不对称增强.同时,发现垂直切变可能在其最大垂直切变方向右侧激发台风外围中尺度系统.通过构造理想的准平衡的台风及叠加在其上的中尺度系统环流,选择不同的切变和环境平均气流,发现增大切变会使得强迫次级环流增强,而增大环境平均气流不一定能够使得强迫次级环流增大,反而可能使得强迫次级环流减弱.通过诊断发现由切变强迫次级环流造成的中尺度对流系统上方扰动可能是中尺度对流系统持续存在的原因.  相似文献   

Impacts of Multi-Scale Solar Activity on Climate. Part I: Atmospheric Circulation Patterns and Climate Extremes     

Hengyi WENG 《大气科学进展》2012,29(4):867-886

The impacts of solar activity on climate are explored in this two-part study.Based on the principles of atmospheric dynamics,Part I propose an amplifying mechanism of solar impacts on winter climate extremes through changing the atmospheric circulation patterns.This mechanism is supported by data analysis of the sunspot number up to the predicted Solar Cycle 24,the historical surface temperature data,and atmospheric variables of NCEP/NCAR Reanalysis up to the February 2011 for the Northern Hemisphere winters.For low solar activity,the thermal contrast between the low-and high-latitudes is enhanced,so as the mid-latitude baroclinic ultra-long wave activity.The land-ocean thermal contrast is also enhanced,which amplifies the topographic waves.The enhanced mid-latitude waves in turn enhance the meridional heat transport from the low to high latitudes,making the atmospheric "heat engine" more efficient than normal.The jets shift southward and the polar vortex is weakened.The Northern Annular Mode(NAM) index tends to be negative.The mid-latitude surface exhibits large-scale convergence and updrafts,which favor extreme weather/climate events to occur.The thermally driven Siberian high is enhanced,which enhances the East Asian winter monsoon(EAWM).For high solar activity,the mid-latitude circulation patterns are less wavy with less meridional transport.The NAM tends to be positive,and the Siberian high and the EAWM tend to be weaker than normal.Thus the extreme weather/climate events for high solar activity occur in different regions with different severity from those for low solar activity.The solar influence on the midto high-latitude surface temperature and circulations can stand out after removing the influence from the El Nin o-Southern Oscillation.The atmospheric amplifying mechanism indicates that the solar impacts on climate should not be simply estimated by the magnitude of the change in the solar radiation over solar cycles when it is compared with other external radiative forcings that do not influence the climate in the same way as the sun does.  相似文献   

台风涡旋的结构及其与台风运动的关系     

李小凡 《热带气象学报》1996,12(4):314-323

用ＦＳＵ区域模式讨论台风涡旋结构及其与运动的关系，台风涡旋的运动在无基本环流和β平面条件下取决于轴不对称环流。而不对称环流的发展源自于从对称环流动能的转换。其率取决对称环流，不对称环流和地球涡度经向梯度三者的相互作用。由于不对称环流动能产生率随高度不变，故台风作为一个统一体以相同的移速移动。不对称环流的径向结构取决于对称环流的径向结构。  相似文献   

秋季喀拉海海冰对2020和2021年12月京津冀冷暖反相的影响     

车少静  高辉  韩世茹  李晓帆  杜浩昱 《沙漠与绿洲气象(新疆气象)》2024,18(2):133-138

2020/2021和2021/2022年冬季京津冀气温呈明显相反的季节内变化特征,前者前冬气温异常偏低后冬偏高,而后者前冬气温极端偏高后冬转冷。这两年前冬冷暖反相的直接原因是亚洲冬季风环流异常。2020年12月欧亚地区为典型的经向环流,西伯利亚高压偏强,乌拉尔山高压脊亦偏强,造成京津冀上空对流层中低层气温一致性偏低,而2021年12月环流形势相反。这两年冬季均处在拉尼娜背景下,但夏秋季喀拉海海冰异常有明显差异,可能是京津冀这两年前冬气温异常相反潜在的外强迫信号。统计和个例分析结果均表明,喀拉海海冰偏多易导致前冬西伯利亚高压偏弱,青藏高原地区海平面气压和亚洲大陆中纬度地区500 hPa位势高度均为正距平,不利于冷空气活动,造成2021/2022年前冬京津冀气温偏高,反之海冰偏少造成2020/2021年前冬偏冷。  相似文献   

苏南地区夏季面雨量与北半球500hPa环流遥相关的年代际变化   总被引：1，自引：2，他引：1       下载免费PDF全文

杨秋明  沈树勤 《气象科学》2003,23(1):39-45

用40年（1961－2000年）观测资料，分成1951－1980年和1981－2000年两个时段，研究了江苏南部地区夏季（6－8月）面积平均雨量与北半球500hPa季平均环流时滞遥相关的年代际变化。结果表明这两个时段遥相关的空间分布存在显著差异，且后一时期时滞遥相关强度明显强于前一时期，它反映了北太平洋年代际振荡（PDO）对东亚季风降水和环流年际相关的影响，与年代际和年际时间尺度振荡之间的相互作用有密切联系。  相似文献   

大气环流的季节突变与季风的建立I·基本理论方法和气候场分析     

曾庆存  张东凌  张铭  左瑞亭  何卷雄 《气候与环境研究》2005,(3)

将曾庆存等提出的大气环流的季节划分和计算季风的理论方法作了改进,使之更便于研究季风的建立过程。该理论方法将环流突变和季风建立时段,其“变差度”和与其前和其后场的“相似度”等由空间场的泛函随时间的变化(即数学名词上的“流”[flow])一起求出来。研究I先分析气候平均场,II分析各个别年份的情况及年际变化。研究I的结果表明:(1)该方法可以客观定量地定出“突变”时段的关键日期;与季风建立过程联系,即是季风建立的“预兆日期”,它比人们用天气-气候学方法(甚至用别的气象要素)定出的可以明显感觉到的或有明显实用价值的“季风来临日期”要早2至4天。(2)在北半球亚澳季风系统区域,夏季风的来临在许多关键地区伴有明显的环流突变,建立和推进都很快,但也有许多区域不表现为当地环流的突变,推进速度也慢。(3)北半球亚澳季风系统低空的热带季风分支,在6月中以前可明确区分为3个子系统,(a)西太平洋暖池和邻近低纬区域,4月中下旬建立;(b)热带东北印度洋(北界与孟加拉湾相邻,但不包括其在内)及索马里东边海洋,4月末至5月初建立;和(c)南海区域,5月上旬从南到5月下旬到北部。南海夏季风向北推进最快,于5月末候即可达北回归线附近,然后与暖池西北区域风场的突变一起,于6月中旬影响到东亚30°N区域;印度洋季风于6月初到达印度半岛东南端,然后逐渐推向印-巴次大陆。7月中以后,热带季风才连成一片,由非洲东岸直至长江下游和菲律宾附近。副热带季风分支于6月中旬可以感到其影响,于7、8月盛行于东亚和西太平洋区域,且结构和演变都比较复杂;6~7月间只表现为在(5~20°N,120~150°E)区域有强的环流突变(与副高增强并北移对应),7月中至8月底,则在上述区域和沿30°N的长江下游和日本以南的洋面上有3个强的环流突变中心(对应于副高又一次增强北移和西伸)。这里暂不讨论温寒带季风分支。(4)季风具有鲜明的三度空间斜压结构,尤其是在低空季风“爆发”之前,平流层早已有强的环流突变,季节调整完成,然后突变向下延伸(虽然强度大减),跟着就有当地的低空季风“爆发”(建立)。平流层和对流层环流的相互作用及其与季风建立的关系很值得进一步研究。  相似文献   

北半球对流层中高层环流对冬季欧亚雪盖作用响应的回归统计分析     

徐建军  郭品文  岳波 《南京气象学院学报》1995,(2)

利用欧亚雪盖的时间序列与北半球对流层中高层高度场之间的回归系数分离出与欧亚雪盖相关的异常环流的响应场。研究表明，这种回归响应场不仅能表示雪盖和环流之间的相关关系，而且能反映相关中心的振幅大小。环流响应场的振幅在中层较大，中上层具有显著的相当正压结构。冬春夏季的环流对冬季积雪的响应场上都存在明显的定常行星波列，冬季为ＮＥＵＰ型和ＮＰＮＡ型，春季略有变化，夏季存在ＬＥＵ型和ＥＡＮＡ型波列。响应场的行星波列具有分支现象，并以波阵面的形成进行能量传播，能量传播在副热带地区出现拦截。  相似文献   

A numerical study of the seasonal variations for tracer redistribution by clouds over West Africa     

M. Renard  N. Chaumerliac  S. Cautenet  N. Audiffren  E. C. Nickerson 《Journal of Atmospheric Chemistry》1995,20(3):237-258

The sensitivity of the horizontal and vertical transport of an inert tracer to seasonal variability of the complex West Africa circulations is explored by means of a 2D mesoscale meteorological model including explicit microphysics and describing the cloud dynamics of these circulations. The seasonal variations of the location and spatial extent of the cloudy masses associated with the Inter Tropical Convergence Zone (ITCZ) are reproduced in a meridional cross section over West Africa. The redistribution of the inert tracer is shown to be due to the northward migration of the ITCZ from January to July and also to the enhancement of the convective activity of the ITCZ in July. The redistribution of carbon monoxide during the dry and wet seasons is discussed, highlighting the importance of the biomass burning during the dry season as a source of trace gas enrichment in the upper levels of the tropical troposphere over West Africa.  相似文献   

A Radar-Based Investigation of Lake Breezes in Southern Manitoba,Canada     

Michelle Curry  John Hanesiak  David Sills 《大气与海洋》2015,53(2):237-250

Lake breezes are thermally direct circulations that form as a result of the differential heating of land and water and are important in modifying local climate and triggering convection; they have also been linked to tornadogenesis. Although lake breezes are generally well understood, studies of smaller lakes have been relatively scarce, and none have examined lake-breeze circulations in southern Manitoba even though they are seemingly apparent on weather radar. The objectives of this paper are to provide a radar-based analysis of lake-breeze frequency and characteristics in southern Manitoba, determine the detectability of lake-breeze fronts using the radar analysis with data collected in 2013, assess the types of lake-breeze circulations that occur, and examine the meteorological conditions in which they occur. Between 2008 and 2013, lake-breeze fronts were noted on 205 days using radar over the summer months, accounting for 37% of study days, with an average of 11–12 days with lake-breeze fronts each month. These findings agree fairly well with, and are only slightly less than, frequencies reported for Lake Michigan but are lower than the most recent findings for southern Ontario. In an effort to validate the results, a broad comparison between the radar analysis and a more complete analysis using satellite and surface stations is provided for 2013 demonstrating that radar is more useful for detecting lake breezes around Lake Manitoba than around Lake Winnipeg. Lake-breeze circulations originating on Lake Manitoba and the Shoal lakes were classified into three types. The distribution of types for the Shoal lakes was similar to previous findings by other authors with “moderate deformation” circulations being the most frequent. Finally, a brief meteorological analysis was completed for each month of this study. The results of the analysis were inconclusive with no single meteorological factor being consistently well correlated to higher or lower lake-breeze frequency.  相似文献