1991年夏东亚阻塞高压形成的诊断分析

文中将１９９１年夏季在东亚地区发生的阻塞高压分为发展期,旺盛期及衰亡期等３个阶段进行了细致的诊断分析。发现在东亚阻塞高压的第一、二阶段其上游有明显的波活动通量与２～６ｄ尺度的Ｅ矢量通量传播。即定常罗斯贝波的传播与天气尺度扰动的共同作用有利于东亚阻塞高压的维持。第一阶段西风气流的分支处有比第二阶段更为明显的南北向分布的涡动位势涡度的辐散辐合偶极子说明了天气尺度扰动给阻塞高压的发展提供了很重要的能源,显然天气尺度扰动在阻塞高压的发展阶段起着比旺盛阶段更为显著的作用。本文还注意到乌拉尔阻塞高压的崩溃与东亚阻塞高压形成的某些联系。     

东亚冬季风的统计研究

利用ECMWFl979—1984年5个冬季(12—2月)的资料对东亚和西太平洋地区的冬季风进行了统计研究。得到的主要结果有: (1)东亚和西太平洋地区有两个冷涌区;从东海到南海等东亚沿岸地区和菲律宾以东西太平洋地区。其中以前者最明显。冷涌主要是700hPa以下的现象,近地面层北风最强,随高度迅速减弱。 (2)伴随着冷涌向南扩展,冷空气经华南沿中南半岛沿岸区一直向南扩展到近赤道地区; (3)在近地面层,西伯利亚高压的活动和强度与冷涌有密切的联系; (4)东亚的冬季风或冷涌有明显的年际变化,这与西伯利亚高压和南支槽活动的年际变化有关。      

GRAPES_GFS在东亚地区中期预报技巧极端下降现象的初步研究

利用2016年4月1日-2018年12月31日GRAPES_GFS模式的业务预报数据,将GRAPES_GFS模式在东亚地区144小时预报500 hPa高度场的距平相关系数小于0.4,均方根误差大于60 gpm的事件定义为模式在东亚地区的中期预报技巧极端下降事件,据此标准筛选出29个个例进行了研究.结果表明,GRAPES...     

东亚地区天气吸引子特征的研究

利用东亚地区１１个有代表性测站（１９７９－１９８８年）连续１０年的５００ｈＰａ逐日位势高度时间序列，全面计算了它们的浑沌特征量。结果表明，各测站相应的关联维数都是分数；完整的Ｌｙａｐｕｎｏｖ指数谱中，不仅都有正值、零和负值，而且Ｌｙａｐｕｎｏｖ指数之和都小于零。因此，从整体来看，相应于东亚地区天气尺度的吸引子是由一个有限窨支撑起来的。东亚地区的天气吸引子所显示的系统平均Ｋｏｌｍｏｇｏｌｏｖ熵约为０     

东亚对流层上部和平流层中下部大气环流的初步研究

根据1957—1961平东亚九十余个探空站的记录,对东亚对流层中上部和平流层中下部的大气环流特点作了初步的分析,得到如下几点结果: 1.在冬季,对流层中上部的气压场和风场特点和过去研究的结论基本一致。在夏季,高原部分的环流特征却和过去的结论不同,夏季在高原上对流层中部出现微弱的气旋性环流,但在300毫巴已在反气旋的控制之下,而且反气旋的势力愈往上去愈强,在100毫巴处高原上空的反气旋达到最大强度,这是与青藏高原的热力性质有关系的。此外,从1月到7月东亚对流层上部的气压场和风场变化甚大,在中高纬度气压场有相反的趋势,并且副热带高压脊线从冬季的北纬15°位置移到夏季的北纬28°。 2.在东亚沿海,中纬度的几个测站在平流层中部的温度年变程呈双峰型,最高温度出现在1月和6—7月。在低纬度温度的年变程也呈双峰,但位相与中纬度相反。低纬温度年变化特点与辐射有关;中纬度的温度年变化,经过计算表明,1月的高峰与温度平流有密切关系。 3.东亚对流层中上部和平流层中下部风场的季节变化,与对流层中下部一样显著。从夏到冬的环流季节变化过程,高低空有一致性,而从冬到夏的环流季节变化过程,高低空变化并不一致。     

南亚季风活跃和中断的物理机制

采用由赤道平衡模式导出的低阶谱模式,考虑了积云对流加热和辐射冷却的作用,用多平衡态理论解释南亚季风活跃和中断的物理可能机制。结果表明,当积云对流加强时,南亚季风活跃;当积云对流减弱时南亚季风中断,这与Ｋｒｉｓｈｎａｍｕｒｔｉ等提出的云－辐射假说一致。     

长江流域一次大暴雨过程的低空急流形成和影响机制分析

利用WRF模式对2016年6月30日—7月6日长江流域的一次大暴雨天气过程中的低空急流进行数值模拟,在成功模拟低空急流基础上,分析此次急流过程中可能的影响机制;同时对地形高度进行敏感性试验,分析地形因素对此次低空急流可能的影响。(1)此次低空急流发生时,东侧为西太平洋副热带高压,西侧则为西南涡。这种“东高西低”的高低压配置为低空急流的形成与发展提供了有利的背景场。(2)高空急流和低空急流的耦合作用是低空急流发展的一个重要背景条件。(3)垂直方向高空动量不断下传为低空系统的发展提供了动力支持,是低空急流发生的一个重要条件。(4)逆温和垂直风切变之间的正反馈机制是低空急流形成与加强的因素之一。(5)山体在急流生成及发展过程中对气流有摩擦和阻挡作用,这种阻挡作用随着山体地形高度的增加而有所加强,同时山脉的走向会改变原始的风向,使得急流前端超前或滞后。青藏高原有强背风波效应,它的绕流和挤压作用会使得低空气流表现为狭长的带状,使动量更加聚集从而风速增加形成低空急流。      

用轨迹法研究寒潮个例

本文利用FGGEⅢ_bSOP(Ⅰ)资料,计算了1979年1月24日—31日的一次东亚寒潮过程中空气质点的三维运动轨迹。结果表明:这例寒潮高压不是原来在欧亚交界处的早期冷高压的东移加强而成,而是在后者的前部巴尔喀什湖及其附近地区再发展而成。整个寒潮酝酿过程实质是一次地面冷高压的替换过程。根据轨迹分析,这例寒潮高压的形成主要是由于在亚马尔半岛及其附近地区对流层中层具有极地冷空气特性的气团南下、到巴尔喀什湖及其附近地区的堆积;同时,这一地区空气本身的绝热上升冷却也起到一定的作用。寒潮爆发阶段,冷空气主体自对流层低层作扇形散开。冷空气的整个活动过程是堆积—散开—再堆积—再度散开的过程。     

TRAJECTORY ANALYSES OF THE DUSTSTORMS OVER EAST ASIA

The transports of dust are calculated using 3-dimensional(3-D)trajectory method for three cases of duststorms inthe terrain-following coordinate system,and the synoptic processes are also discussed for each case.The case of 17—20April 1980,a severe duststorm was associated with the rapid development of a cyclone over the Mongolia Plateau.Thedust moved from west to east across several deserts,formed a typical dust path in spring.The other two were weaker andthe dust was triggered by the strong wind behind the cold front from northwest or north.Because the vertical velocity isconsidered in 3-D trajectory analysis,trajectories calculated should better reveal the transport rule of the dust particlesand the results seem to be more consistent with the synoptic processes.The trajectory analysis on the 2-D isobaric sur-faces is simpler but can be used only in the conditions with weak vertical wind shear and weak vertical velocity.The dif-ference of trajectories at lower levels between two methods may be caused by the different treatment of orography.     

THE EAST ASIA/PACIFIC PATTERN TELECONNECTION OF SUMMER CIRCULATION AND CLIMATE ANOMALY IN EAST ASIA

In this paper,many observations show that the thermal states including the SST,the convective activities in the west-ern Pacific warm pool largely influence the interannual and intraseasonal variations of summer circulation and the cli-mate anomalies in East Asia.Moreover,it is pointed out that there is a teleconnection pattern of summer circulationanomalies in the Northern Hemisphere,the so-called East Asia/Pacific pattern.The cause of the teleconnection pattern is studied by using the theory of quasi-stationary planetary wave propaga-tion,and it may be due to the propagation of quasi-stationary planetary waves forced by heat source around thePhilippines.Moreover,this pattern is well simulated by using a quasi-geostrophic,linear,spherical model and theIAP-GCM,respectively.     

STUDY OF PHYSICAL PROCESSES AFFECTING THE TRANSFORMATION OF COLD AIR OVER LAND AFTER OUTBREAK OF COLD WAVES IN EAST ASIA

Authors have studied the transformation processes of cold air over land in East Asia for eight cases which occurredin different months of 1981.First,the surface eddy sensible and latent heat fluxes,and drag coefficient were estimatedaccording to the approach of similarity theory.Then,the apparent heat source,the apparent moisture sink,and solarand long-wave radiative heating(or cooling)were further calculated through the budget method and physicalparameterization algorithm.It has been found that the cold air immediately starts the transformation process over landonce it moves away from its region of origin.In winter,the degree of transformation of cold air mass gradually intensi-fied as it travelled southeastward;while arriving in the ocean,the cold air mass underwent the most significant transfor-mation process.In summer,the most vigorous transformation of thermal and moisture fields was observed in NorthChina and Mongolian region,with much greater intensity than that in winter.     

A NUMERICAL STUDY FOR MECHANISM OF THE EFFECT OF NORTHERN SUMMER ARCTIC ICE COVER ON THE GLOBAL SHORTRANGE CLIMATE CHANGE

In terms of nine-layer global spectral model involving fuller parameterization of physical process,with arhomboidal truncation at wavenumber 15,experiments are conducted by virtue of two numerical schemes,one withlong-range mean coverage of Arctic ice,and the other with supercooled water at the same temperature as the ice,fol-lowed by an analysis of the difference field simulated by the two schemes.Results show that(1)the impact of Arctic iceon the northern short-range climate is realized through the change in polar ice coverage to cause local temperaturechange in the polar region to set up gradient difference in temperature from north to south,thus affecting the atmospher-ic circulations and,on the other hand,two trains of two-dimensional Rossby waves excited by the atmospheric heatsource anomaly have impacts on the Northern Hemisphere(NH)extratropical region,one of which is similar to the JPteleconnection pattern first presented by Nitta(1987);(2)The significant impact of Arctic ice anomaly on the southernshort-range climate change is accomplished with the aid of the anomaly of the equatorial heat source that excites a two-dimensional Rossby wavetrain propagating along a great circle route into the Southern Hemisphere(SH)extratropics,and the cross-equatorial propagation of the NH wavetrain also has effects on the SH atmosphere.Simulation indicatesthat with the 15-day integration the Arctic ice exerts an influence mainly on the NH and when the model atmosphere isgetting stabilized,the effect is dominantly on the SH short-range climate change.     

A STUDY ON THE MECHANISM OF RAPID WEAKENING OF TYPHOON XANGSANE (0020) OVER THE EAST CHINA SEA

Using the National Center for Environmental Prediction reanalysis data on 1.0°×1.0° grids and data from the Tropical Cyclone yearbook(2000),a diagnostic analysis and numerical simulation were performed to investigate the characteristics and mechanism underlying the rapid weakening of typhoon Xangsane.The results show that a sharp decline in the intensity of typhoon Xangsane resulted from its movement into the cool sea surface temperature area in the East China Sea,the intrusion of cold air from the mainland into the typhoon,and a rapid increase of the vertical wind shear in the surrounding environment.An important factor that led to the demise of the typhoon was a significant decrease in the moisture transport into the typhoon.Furthermore,the results of the numerical simulation and sensitivity experiments indicate that sea surface temperature largely modulated the rapid weakening of typhoon Xangsane.     

关于东亚大气环流和季风的研究

为了纪念我国现代气象的奠基人竺可祯先生,本文回顾了自竺先生“东南亚季风和中国雨量开创性论文发表以后在东亚大气环流研究方面的主要成果。给一部分讨论了大气坏流的双元性和季节突变,第二部分讨论了海陆差异和地形在季风发展的动力和热力过程中的作用,这包括冬季风、夏季风以及有关的热源和热汇。第三部分讨论了季风降水,尤其重点介绍了中尺度扰动、低空急流和梅雨的年际变率。     

A REVIEW OF THE ATMOSPHERIC GENERAL CIRCULATION AND MONSOON IN EAST ASIA

Important progresses of the study of the general circulation and monsoons in East Asia,which have beenmade since the pioneering work“Monsoons in Southeast Asia and rainfall amount in China”by Prof.ZhuKezhen,are extensively reviewed in memory of this founder of modern meteorology in China.The first parthas addressed the bimodality of the general circulation and the abrupt seasonal change.The second part hasdealt with the role of the continent-ocean contrast and topography in the dynamic and thermal processes of mon-soon development,including winter and summer monsoons,and associated heat sources and sinks.The thirdpart has discussed the monsoonal precipitation,with a special emphasis on the mesoscale disturbance,low-leveljet and interannual variability of Meiyu(plum rains).     

A PRIMARY STUDY OF SUMMER MONSOON INDEX OVER THE SOUTH CHINA SEA AND EAST ASIA BASED ON SATELLITE OBSERVATION

The results by statistical analysis of black body Temperature (TBB) pentad mean from the Japanese GMS in the period of May to August, 1980-2002, show that the summer monsoon index (SMI) is defined to be the pentad mean TBB≤273 K. Its intensity includes three levels: TBB>268 K for weak monsoon, 268 K≥TBB>263 K for normal monsoon and TBB≤263K for strong monsoon over the South China sea and East Asia. In the meantime, a diagnostic method using TBB pentad anomaly is also introduced to help identify monsoon intensity. The SMI is used to run statistical analyses of the initial onset of the monsoon and its pentad variations with the year and month. A fairly close relationship is found between pentad monsoon activity and heavy rainfall periods in the two typical flood years of 1994 and 1998, which resulted from heavy rainfall over the Yangtze River basin and south China.     

THE ANALYSIS OF MECHANISM OF IMPACT OF AEROSOLS ON EAST ASIAN SUMMER MONSOON INDEX AND ONSET

RegCM4.3, a high-resolution regional climate model, which includes five kinds of aerosols(dust, sea salt,sulfate, black carbon and organic carbon), is employed to simulate the East Asian summer monsoon(EASM) from 1995 to 2010 and the simulation data are used to study the possible impact of natural and anthropogenic aerosols on EASM.The results show that the regional climate model can well simulate the EASM and the spatial and temporal distribution of aerosols. The EASM index is reduced by about 5% by the natural and anthropogenic aerosols and the monsoon onset time is also delayed by about a pentad except for Southeast China. The aerosols heat the middle atmosphere through absorbing solar radiation and the air column expands in Southeast China and its offshore areas. As a result, the geopotential height decreases and a cyclonic circulation anomaly is generated in the lower atmosphere. Northerly wind located in the west of cyclonic circulation weakens the low-level southerly wind in the EASM region. Negative surface radiative forcing due to aerosols causes downward motion and an indirect meridional circulation is formed with the low-level northerly wind and high-level southerly wind anomaly in the north of 25° N in the monsoon area, which weakens the vertical circulation of EASM. The summer precipitation of the monsoon region is significantly reduced,especially in North and Southwest China where the value of moisture flux divergence increases.     

基于卫星观测的南海和东亚夏季风指数初探

运用1980-2002年5-8月GMSTBB候平均资料,经过统计分析得到：南海和东亚候夏季风活动指数定义为候平均TBB≤273K;其强度分为3级,即弱季风为268K〈TBB≤273K,一般季风为263K〈TBB≤268K,强季风为TBB≤263K。与此同时,还给出了运用TBB候距平帮助判识季风强度的分析方法。运用该季风指数,统计分析了上述各年季风初始爆发日期和各年各月季风活动情况。另外,还对比分析了1998年长江中下游地区暴雨和1994年华南暴雨2个典型暴雨灾害年季风活动,展示了候季风活动与暴雨期间各暴雨过程之间的密切关系。     

东亚阻塞高压对我国降水影响的诊断分析研究

利用湿位势涡度 ,讨论了 1 998年 7月东亚中高纬地区阻塞高压的不同位置影响冷暖空气的活动路径进而决定暴雨发生的位置 ,结果表明 :当阻高位于中西伯利亚地区 ,主要影响我国华北平原及华南一带的降水 ;当阻高位于鄂霍茨克海地区时 ,对我国东北西部、华北平原、四川盆地的降水有重要影响 ;当阻高中心位于小兴安岭地区 ,副高位置异常偏北 ,主要影响我国东北地区的降水 ;当阻高位于以 ( 55°N,1 35°E)为中心的区域时 ,冷空气频繁活动于长江中下游地区 ,对该地区的降水有重大影响。     

一次东亚寒潮爆发后冷涌发展的研究

分析了１９８１年１月２１—２８日一次东亚强寒潮爆发后南海和西太平洋地区冷涌的发展过程。冷涌的发展最先表现为低层强东北风沿东亚沿海地区和南海中北部的迅速建立。２—３ｄ之后，又在菲律宾以东洋面激起第二次冷涌。与冷涌相伴随的低层温度场变化也十分明显，同样具有先后两次降温过程。冷涌期高空风场表现有明显的脉动，南海北部高空西风迅速减弱，而在南海近赤道地区出现了很强的高空东风区。冷涌的发展与寒潮冷高压的南下有密切关系，它的强度在很大程度上取决于中纬度冷高压的强度。另一方面，冷涌发展后，通过Ｈａｄｌｅｙ环流可影响中纬西风急流和热带东风急流的变化。