Ten-year climatological features and air origin of midlatitude double tropopauses     

Xue Wu  Daren Lü 《大气科学进展》2015,32(12):1592-1602

The 10-year climatological features related to midlatitude double tropopause events(DTs) are examined using ERAInterim data from 2003 to 2012. The analysis is based on tropopauses defined by lapse rate. Results show that DTs are permanent or semi-permanent in the midlatitudes,and high DT frequency bands move poleward in winter and equatorward in summer,which is consistent with the seasonal movement of the subtropical jet. Based on our statistics,the second tropopause is found at about 100 h Pa in the subtropics and at slightly lower altitudes in sub-polar regions. The thickness between the first and second tropopause is smaller in the subtropics and increases with latitude. Next,the origin of air sandwiched between the first and second tropopause of DTs is studied with a revised version of the UK Universities Global Atmospheric Modelling Programme Offline Trajectory Code(Version 3) diabatic trajectory model. The results show that,in the lower or middle troposphere,air is transported into the DTs from lower latitudes,mainly in the tropics. The dominant source regions are mainly areas of deep convection and steep orography,e.g.,the western Pacific and Himalayan Mountains,and they show strong seasonality following the seasonal shift of these strong upwelling regions.  相似文献   

从涡度、位涡、到平流层干侵入——位涡问题的缘起、应用及其歧途   总被引：3，自引：1，他引：2  

陶祖钰  周小刚  郑永光 《气象》2012,38(1):28-40

由于从等熵位涡分析引申出来的平流层干侵入（以下简称干侵入）概念造成了当前天气预报思路中一些混乱和违背天气学常识的看法,文中回顾了天气预报原理从着眼气压变化到着眼涡度变化的发展历史和位涡问题的缘起。进而根据位涡的定义、数学表达式、物理意义,并结合实例的计算结果指出,位涡的大小主要取决于位温的垂直梯度;等熵面上的位涡分布形势实质是对流层顶高度的分布,因此可以间接反映极地气团、锋、高空槽和高空急流的形势。轨迹计算和数值预报都证明,低空的高位涡异常是地面气旋强烈加深和潜热反馈的结果,而不是干侵入的结果。指出位涡的守恒性不能替代斜压扰动发展的动力学机理;干侵入的错误概念来源于对位涡守恒性的绝对化和简单的推断,并犯了流体力学原理上混淆流线和轨迹两个不同概念的错误。  相似文献   

The impact of cut-off lows on ozone in the upper troposphere and lower stratosphere over Changchun from ozonesonde observations   总被引：1，自引：0，他引：1  

Yushan Song  Daren Lü  Qian Li  Jianchun Bian  Xue Wu  Dan Li 《大气科学进展》2016,33(2):135-150

In situ measurements of the vertical structure of ozone were made in Changchun(43.53?N, 125.13?E), China, by the Institute of Atmosphere Physics, in the summers of 2010–13. Analysis of the 89 validated ozone profiles shows the variation of ozone concentration in the upper troposphere and lower stratosphere(UTLS) caused by cut-off lows(COLs) over Changchun. During the COL events, an increase of the ozone concentration and a lower height of the tropopause are observed.Backward simulations with a trajectory model show that the ozone-rich airmass brought by the COL is from Siberia. A case study proves that stratosphere–troposphere exchange(STE) occurs in the COL. The ozone-rich air mass transported from the stratosphere to the troposphere first becomes unstable, then loses its high ozone concentration. This process usually happens during the decay stage of COLs. In order to understand the influence of COLs on the ozone in the UTLS, statistical analysis of the ozone profiles within COLs, and other profiles, are employed. The results indicate that the ozone concentrations of the in-COL profiles are significantly higher than those of the other profiles between ±4 km around the tropopause. The COLs induce an increase in UTLS column ozone by 32% on average. Meanwhile, the COLs depress the lapse-rate tropopause(LRT)/dynamical tropopause height by 1.4/1.7 km and cause the atmosphere above the tropopause to be less stable. The influence of COLs is durable because the increased ozone concentration lasts at least one day after the COL has passed over Changchun. Furthermore, the relative coefficient between LRT height and lower stratosphere(LS) column ozone is-0.62,which implies a positive correlation between COL strength and LS ozone concentration.  相似文献   

对流层顶研究回顾   总被引：5，自引：0，他引：5  

杨双艳  周顺武 《气象科技》2010,38(2):145-151

大气急流、飞机颠簸、臭氧层顶等重要物理、化学现象均与对流层顶的位置、强度及其变动密切相关,因此在研究自由大气的气候和大气环流时,作为对流层与平流层过渡层的对流层顶是非常重要的,对流层顶研究已成为当今大气科学的研究热点之一。对近几十年来对流层顶研究领域的有关研究作了简要回顾,主要从对流层顶的分布特征、对流层顶要素变化以及对流层顶与臭氧的关系等几个方面进行综述。在此基础上,总结出对流层顶研究遇到的几个困难。  相似文献   

东亚强对流云的季节变化及其与对流层顶关系初探   总被引：1，自引：1，他引：1       下载免费PDF全文

王旻燕  吕达仁 《大气科学》2007,31(5):937-949

利用GMS 5/VISSR长波红外（10.5～11.5 μm）和水汽通道（6.5～7.0 μm）探测原理的差异, 结合红外阈值法和区域平滑滤波技术提取 “高、 厚、 密” 强对流云, 分析了东亚强对流云活动的空间分布及其季节变化规律。GMS 5卫星视场内各个子地区强对流云云顶温度与发生频率的季节变化基本为单峰单谷型, 前者夏低冬高, 但不同地区引起的原因不同。强对流云发生频率36°N以北夏低冬高, 以南夏高冬低。东亚对流层顶由冬春至夏秋升高, 对流层顶气压随之降低, 而对流层顶温度的季节变化以45°N为界, 北部夏高冬低, 南部夏低冬高。作者所研究的东亚几个子地区强对流云与对流层顶季节变化位相基本保持同步, 2000年强对流云云顶温度与对流层顶温度的月均值相关系数达0.757, 强对流云云顶温度与对流层顶气压的月均值相关系数达0.901, 对流层顶温度比强对流云云顶温度平均低9.42℃。强对流云的发展受对流层顶制约作用显著。  相似文献   

北京地区对流层顶变化及其对上对流层/下平流层区域臭氧变化的影响   总被引：7，自引：4，他引：7  

王庚辰  孔琴心  陈洪滨 《大气科学》2006,30(4):587-595

根据2001～2003年期间获得的大气臭氧探空资料,揭示了北京地区上空对流层顶高度的某些变化特征及其对上对流层(UT)和下平流层(LS)区域内大气臭氧含量变化的影响.结果显示:北京地区上空对流层顶高度的平均值约11.1 km,其变化范围为7.7～14.4 km,臭氧层顶始终处在对流层顶下方约0.9 km高度处.对流层顶高度变化与臭氧总量变化之间的关系相对较弱.通常情况下,LS中的臭氧积分量明显高于UT中的相应值,并且二者呈相反的季节变化特征.北京地区上空仲夏和初秋季节第一对流层顶出现的频数明显减少,在第一对流层顶消失的情况下,LS中的臭氧积分量明显减少,而UT中的臭氧积分量明显增加,臭氧量减少最多发生在200～100 hPa层次中,而臭氧量增幅最大的层次是400～250 hPa.  相似文献   

Regional and Global Tropopause Fold Occurrence and Related Ozone Flux Across the Tropopause     

M. Beekmann  G. Ancellet  S. Blonsky  D. De Muer  A. Ebel  H. Elbern  J. Hendricks  J. Kowol  C. Mancier  R. Sladkovic  H. G. J. Smit  P. Speth  T. Trickl  Ph. Van Haver 《Journal of Atmospheric Chemistry》1997,28(1-3):29-44

This paper gives a synthesis of three algorithms to detect the presenceof tropopause folds from vertical ozone/radio-sounding profiles and frommeteorological analysis. Also an algorithm to identify injection ofstratospheric air into the lower troposphere fromozone/⁷beryllium time series is presented. Differences in theresults obtained from the algorithms are observed and discussed with respectto the criteria for fold detection and input data used. Spatial gradients inthe obtained folding frequencies are made evident on a global scale from thealgorithm based on meteorological analysis (Q-vector/potential vorticity)and probably also on a regional European scale from algorithms both basedmeteorological analyses and on ozone/PTU soundings. The observed seasonalvariation of folding occurrence is rather flat except during summer whenalso some differences appear between the algorithms. By combining thefolding frequencies with literature estimates of the cross-tropopause ozonetransfer in single folding events, an average stratospheric ozone influxinto the troposphere of 5.7 ± 1.3× 10¹⁰ mol.cm^-2 s^-1 is obtained for the Northern hemisphereand 12± 2.7× 10¹⁰ mol. cm^-2s^-1 for Western Europe. Potential additional contributions dueto other stratosphere-troposphere exchange processes than folds are not yetincluded in these estimates. Finally, the link between statistics fromozone/⁷beryllium data and folding statistics is brieflydiscussed.  相似文献   

THE EXCHANGE OF MASS BETWEEN STRATOSPHERE AND TROPOSPHERE OVER THE TIBETAN PLATEAU AND ITS SURROUNDINGS IN 1998     

CONG Chunhu  LI Weiliang 《Acta Meteorologica Sinica》2002,16(4):481-488

n this paper,using NCEP dataset and the Wei's method,we calculate the exchange of massacross the thermal tropopause during 1998 over the Tibetan Plateau and its surroundings.Theresults indicate that:(1)There is strong air transport from troposphere to stratosphere in summerover the Tibetan Plateau and its surroundings.The air transport reaches the summit in midsummerwith three large value centers among which the Bay of Bengal is the largest and the other two largecenters lie in the east and northwest of the Tibetan Plateau,respectively.In May and October thecross-tropopause mass exchange reaches balance.In other months the mass transport is fromstratosphere to troposphere.(2)As far as the cross-tropopause mass exchange from June toSeptember in 1998 is concerned,the net mass transport is 13.7×10~(18) kg from troposphere tostratosphere,So the area from Tibetan Plateau to the Bay of Bengal is a channel through which airmass gets into stratosphere from troposphere.  相似文献   

EFFECTS OF TROPOPAUSE AND POTENTIAL VORTICITY ANOMALY ON FRONTOGENESIS     

侯定臣  高学浩  庄小兰  张勇 《Acta Meteorologica Sinica》1997,(4)

A two-dimensional,semi-geostrophic numerical model incorporating the tropopause andstratosphere is used to investigate the effects of a positive potential vorticity anomaly and latentheat release on the frontogenetic process and the structure of the resulting frontal zone.It isdemonstrated that(1)the inclusion of tropopause and stratosphere significantly changes the frontalstructure only in the upper levels;(2)a clearly defined quasi-equivalent barotropic structure and aregion of upward motion of finite width appear when a positive potential vorticity anomaly exists onthe warm side of the maximum baroclinity in the lower troposphere,especially when it is locatedon the south edge of the baroclinic zone;(3)the above mentioned structure deteriorates as thefrontogenesis proceeds in a dry atmosphere but can be maintained in a moist frontogenetic processwith condensational heating;(4)the combination of a positive potential vorticity anomaly and thelatent heat release is able to accelerate the frontogenesis significantly with the time needed to forman intense frontal zone reduced to less than 15 h.The results have significant theoreticalimportance in understanding the complex nature of frontal structure and frontogenesis,especiallyin understanding the dynamic structure of the subtropical frontal zone observed during earlysummer over East Asia.  相似文献   

A case study of mesoscale convective band (MCB) development and evolution along a quasi-stationary front     

Daeun JEONG  Ki-Hong MIN  Gyuwon LEE  Kyung-Eak KIM 《大气科学进展》2014,31(4):901-915

This paper presents a case study of mesoscale convective band （MCB） development along a quasi-stationary front over the Seout metropolitan area.The MCB,which initiated on 1500 UTC 20 September 2010 and ended on 1400 UTC 21 September 2010,produced a total precipitation amount of 259.5 mm.The MCB development occurred during a period of tropopause folding in the upper level and moisture advection with a low-level jet.The analyses show that the evolution of the MCB can be classified into five periods：（1） the cell-forming period,when convection initiated; （2） the frontogenetic period,when the stationary front formed over the Korean peninsula; （3） the quasi-stationary period,when the convective band remained over Seoul for 3 h; （4） the mature period,when the cloud cover was largest and the precipitation rate was greater than 90 mm h-1; and （5） the dissipating period,when the MCB diminished and disappeared.The synoptic,thermodynamic,and dynamic analyses show that the MCB maintained its longevity by a tilted updraft,which headed towards a positive PV anomaly.Precipitation was concentrated under this area,where a tilted ascending southwesterly converged with a tilted ascending northeasterly,at the axis of cyclonic rotation.The formation of the convective cell was attributed in part by tropopause folding,which enhanced the cyclonic vorticity at the surface,and by the low-level convergence of warm moist air and upperlevel divergence.The southwesterly flow ascended in a region with high moisture content and strong relative vorticity that maintained the development of an MCB along the quasi-stationary front.  相似文献