从气象卫星资料揭示的青藏高原夏季对流云系的日变化

文中利用日本静止气象卫星观测的1981～1994年1天8次的TBB观测值和1978～1994年NOAA卫星观测的1天2次OLR观测值研究了青藏高原地区夏季对流云系季节变化以及对流云的日变化及其东西向移动规律,并对1994年的资料进行了个例分析。结果表明,青藏高原夏季对流云有极为明显的日变化,以00～05SUTC为最弱,15～17UTC最强。在季风雨爆发后的7月中旬到8月上旬在高原中部（30～32°N,90°E）、东部（30°N,97°E）和西部（30°N,85～87°E）有3个TBB低值中心,多年月平均对流中心区云顶高度可达9．6km,而旬对流中心个别地区平均可达13km。对流云区开始发展于东部地区,随后对流云中心逐步向西移动,并于7月中下旬达到最西,此时西部地区从多年平均而言可以有短暂的强对流发展。     

臭氧对夏季大气环流影响的数值模拟

利用球带ｐ－σ坐标系模式，模拟了臭氧对夏季大气环流的作用，结果表明，臭氧作用引入模式后，大气高压环流特征得到显著改善，臭氧使高层大气的加热率增大；对低层大气，虽然臭氧的加热作用很小，但可通过改变其他加热场分量的分布和量值，从而改变总加热率，使低层大气环流同样发生变化。     

NUMERICAL STUDY ON THE DYNAMIC AND THERMODYNAMIC EFFECTS OF THE QINGHAI-XIZANG PLATEAU ON THE SEASONAL TRANSITION IN THE EARLY SUMMER IN EAST ASIA

By employing a five-layer seasonal numerical weather prediction model and utilizing the National MeteorologicalCenter (NMC) objective analysis data on May 10,1991 as the initial field,three numerical experiments——diabatic withorography,adiabatic with orography and adiabatic without orography——have been carried out to investigate the dy-namic and thermodynamic effects of the Qinghai-Xizang Plateau (hereafter the Plateau) on the seasonal transition inthe early summer in East Asia.The results show that the typical seasonal transition features such as the northward shiftof the subtropical westerly jet stream,the adjustment of the long-wave in middle and high latitudes and the changes ofthe circulation in the lower troposphere can be well simulated,if the dynamic and thermodynamic effects of the Plateauare both considered in the model as in the experiment adiabatic with orography.In other two experiments,it is failed tosimulate out the seasonal transition features.The results also show that the thermodynamic effect of the Plateau acts on the atmosphere as a gradually enhancedheating source in the early summer,which makes the air temperature in 500 hPa over the Plateau increase by nearly 10℃in a month and accelerates the northward shift of the subtropical westerly jet stream about seven latitudes more north-ward in twenty days and helps the shifted jet maintain at the northern periphery of the Plateau.It is also helpful to theformation and maintenance of the Lake Balchas trough and the northward and westward extension of the Pacificsubtropical high.On the other hand,the dynamic effect of the Plateau weakens the northward shift of the subtropicalwesterly jet stream and barricades the westward extension of the Pacific subtropical high.If only the dynamic effect ofthe Plateau is considered in the model without consideration of the thermodynamic effect of the Plateau,not only theshifted jet withdraws southward but also the simulated Lake Balchas trough is 10 longitudes more eastward than that inthe diabatic experiment,and the simulated Pacific subtropical high is more eastward and northward.However,the dy-namic effect of the Plateau strengthens the vertical movements in the west and east of the Plateau and makes thelow-level jet maintain in the southeast of the Plateau.The path of the cold air and the tunnel of the water vapor in thelower troposphere during the seasonal transition period in the early summer in East Asia are determined by the couplingof the dynamic and thermodynamic effects of the Plateau.     

一次青藏高原夏季低涡的数值模拟研究

本文利用美国NCAR中尺度模式MM4对1979年6月29－30日一次500hPa高原低涡的生成发展过程进行了数值试验模拟研究。通过对绝热、非绝热、有无地表感热潜热及降低地形等六个对比试验，分析指出：（1）模式对500hPa高原涡中心位置预报与实况吻合，中心平均强度实况接近，平均玫水亦接近（略偏少），落区略有偏差，故可认为对低涡的预报基本合理。（2）低涡主要由非绝热过程引起（22．6，10^－5s^－1），而动力过程是很次要的（6．0）；在非绝热过程中潜热的贡献（8．0）远比由积云对流及湍流所引起的地表感热通量（14．6）小；地表热通量的贡献主要为地表感热通量（13．4），而地表蒸发作用很小（1．2），这与文献[6]的诊断分析结论一致。（3）由半地形高度隆起至全地形时，动力作用对低涡强度的贡献由2．0增至6．0，非绝热过程的贡献由7．2增到22．6。可见模式中真实地处理地形高度是很重要的。本文虽只作了一例，但结论（2）与大量低涡诊断分析的统计结果一致。     

CEOF ANALYSIS OF ATMOSPHERIC LOW FREQUENCY OSCILLATION IN LOWER LATITUDE REGION AND FREQUENCY MODULATION PHENOMENA OF LOW FREQUENCY SIGNALS

The low frequency oscillation of the low level atmospheric circulation in lower latitudes region is studied by usingthe CEOF method and other normal spectral analysis methods.It is found that in the atmospheric motion frequencyspectrum,there exist certain frequency bands with relatively-concentrated energy among low frequency bands,andthere is nonlinear interaction of frequency modulation among peak signals.It is this modulating action that leads to thechange of the temporal-spatial features of frequency and phase of these low frequency signals.In the paper,the propa-gation picture of low frequency waves modulated and its influence on midium-range variation of summer monsoon arealso discussed.     

大气低频变异中的波流相互作用(阻塞形势)

文章通过对低频变异研究的历史回顾以及观测事实的诊断分析,结合预报实践中的经验,从天气、气候学的角度提出了对阻塞高压（以下简称阻高）流型形成及维持的分析和看法。文中强调了阻高上游的低槽加深东移、海温变化以及地形作用是促使阻高异常的重要因素。并从斜压（瞬变波）同阻塞流的配置关系的角度出发,研究了乌拉尔山阻高维持过程中的波与流相互作用,为从理论上进一步探讨阻高形成的机理初步奠定了基础。     

1979年夏季青藏高原上空大气热源的变化及大气能量收支特性

本文把青藏高原分成东西两个区,各区取5个站组成一个5边形,研究该两区1979年夏季的垂直运动、大气总加热、凝结加热、各种大气能量转换和输送、不均匀非绝热加热的特性,特别是其垂直分布和谱密度和交叉谱特性。其结果见第5节中结论。     

论青藏高原隆起作用于大气的临界高度

在以前工作的基础上，从大气动力学、热力学及气候学的角度，进一步论证了在青茂高原隆起过程中存在一个临界高度ｈｃ（－１．５－２ｋｍ）。当高原隆起突破这一临界高度时才开始对大气产生强烈的作用，从而造成大气环流、大气热力结构、亚洲区域以及全球气候等一系列巨大转变。     

青藏高原上空温度场低频变化的垂直结构及其与热带海气的相互关系

采用一点相关法研究了青藏高原东部对流层－平流层下部温度场低频变化的垂直结构,指出了最大负相关层的高度和强度随季节的变化特点,并与高原北部格尔木和我国东部（１２０°Ｅ、３０～５０°Ｎ）区域作了比较。从青藏高原对流层顶高度的季节变化、大气温度层结和动能垂直分布探讨了青藏高原温度场低频垂直结构及季节变化的物理背景。并指出：秋季１０～１１月青藏高原东部垂直热力结构、赤道印度洋－太平洋的两个纬向垂直Ｗａｌｋｅｒ环流圈强度与赤道东太平洋（０～１０°Ｓ、１８０～９０°Ｗ）区域ＳＳＴＡ之间具有极为密切的耦合关系。     

青藏高原对莫东北侧初夏干旱天气影响的数值研究

本文利用改进的Ｔ４２Ｌ９模式，以１９７９年６月１４日１２时的ＦＧＧＥ－Ⅲｂ资料为初始场，分别在有地形非绝热，有地形绝热以及无地形绝热情形下进行了五天数值预报试验，研究了青藏高原的热力和动力作用对高原东北侧干旱天气的影响，模拟结果指出，在初夏夏季风爆发期间，青藏高原有利于其东侧（包括甘肃南部和陕西南部一带）进入雨季，但也有利于其北侧的河西走廊地区维持干旱，高原的动力和热力作用对高原北侧的初夏干旱天气有着重要的影响。     

青藏高原感热加热异常与夏季低频环流的数值研究

使用科学院大气物理研究所两层大气环流模式，就青藏高原地表感热通量异常减少对夏季东半球大气环流及亚洲季风低频变化的影响进行了数值试验研究。结果表明：高原地区感热通量异常减少时，南海及西太平洋地区低频振荡方差百分率增大；高原感热异常加热对东亚和印度季风子系统具有不同的影响，季风区低频扰动的位相，中高纬低频扰动的结构，强度和经向传播速度都发生改变，ＥＡＰ波列变得更为清楚典型，大圆上的低频涡旋一直传播到我     

青藏高原对亚洲季风平均环流影响的数值试验

利用垂直方向具有９层σ面、水平方向菱形截断波数为１５的全球大气环流谱模式和有、无青藏高原大地形两种情况下１０年积分的模拟结果，研究了青藏高原大地形对亚洲季风平均环流的影响。结果表明：有、无青藏高原大地形，亚洲冬、夏季季风平均环流均存在很大的差异。去除地形，使夏季高层的南亚高压、低层的大陆热低压、副热带高压及冬季的大陆冷高压在位置或强度上发生了改变；地形的有、无决定着冬季东亚大槽的强度；索马里越赤道气流有地形时明显较无地形时强；地形的有无还影响着降水强度和雨带的分布。另外，副热带高压中心及雨带的季节性移动与高原大地形的存在与否亦有很大的关系     

青藏高原感热加热对7月份大气环流和亚洲夏季风影响的数值试验

根据低纬地区地表温度高、蒸发及降水量大、辐合上升运动剧烈等特点,本文构造了一个正压模式的方程组,提示出影响低纬大气波动的一个重要因素——海表温度SST。研究指出:(1)当SST<25℃时,含蒸发风反馈机制的Rossby波向西传播,当SST>25℃时.含蒸发风反馈机制的Rossby波向东传播。(2)SST的数值越高,空气越潮湿,含蒸发风反馈机制的Rossby波传播速度就越小。当SST超过29℃时,会形成周期为30天的低频振荡。     

青藏高原及其周围植被对夏季气候影响的套网格数值试验比较

利用钱永甫有地形５层原始方程模式,与颜宏等复杂地形条件下有限区域细网格模式进行单向嵌套,即初始场采用前者计算５ｄ后,得到各特征等压面上的高度场和湿度场,向后者每２４ｈ输送一次边界值。地－气模式采用经Ｄｅａｒｄｏｒｆ植被参数化修正的地面热量平衡方程进行耦合。在此基础上进行了夏季（７月）有植被和无植被两种情况的数值试验。有植被情况模拟的高度场、温度场与实测场的相关系数高于无植被的情况。试验发现,有植被比无植被情况的海平面气压场、低层高度场、潜热输送、整层大气湿度和降水量有所增加,而温度场和大陆热低压强度有所降低。     

NUMERICAL STUDY ON INFLUENCE OF QINGHAI-XIZANG (TIBETAN) PLATEAU ON SEASONAL TRANSITION OF GLOBAL ATMOSPHERIC CIRCULATION

It is a worthwhile attempt to address the role of the Qinghai-Xizang Plateau in the seasonal transition of general circulation from a global prospective. In this paper, the CCM1 (R15L7)-LNWP spectral model is used to study the influences of the Qinghai-Xizang Plateau on the seasonal transfer of the general circulation, with the objective analysis form the State Meteorological Center for March 17, 1996 as the initial field. A mid-level heating source in regions on the same latitudes is shown to cause a warming center of 224 K to form on the level of 200 hPa that warms up the atmosphere by more than 7 K and a drop of temperature by about 6 K on most of the 200-hPa layer over the Antarctic continent, with the largest negative center being-8.28 K. It is favorable to the deepening and widening of the polar vortexes in the course of transition from summer to winter. The topographic effect of the plateau plays a vital role in forming and maintaining the mean troughs and ridges of the atmospheric circulation in Northern Hemisphere such that it strengthens (weakens) the south-north positive gradient of temperature on the northern (southern) side of the latitude zone in which the plateau sits and increases the north-south gradient of temperature near 30°N. The seasonal transition is thus favored so that the bulk travel of global westerly at the middle latitudes and the formation of Asian monsoon in early summer are made possible. In the equatorial and low-latitude areas where the geopotential is increased, the effect of the plateau terrain is also evident in that it is favorable for the northern withdrawal of the tropical high ridge in Southern Hemisphere and the northern shift of the subtropical high in Northern Hemisphere. In addition, the effect also helps increase the polar easterly over the Southern Hemisphere and weaken the low zone at 500 hPa. It acts as an increasing factor for the polar vortex around the Ross Sea and contributes to the genesis of the Somali Jet on the equator.     

1998年夏季青藏高原多时间尺度低频降水的活动和传播特征

研究表明,准４５ｄ、准２３ｄ和准１４ｄ等３类低和水的频率愈低,低和水愈趋向于从高原东侧和南侧向高原传播,反之,频率愈高,低频降水愈趋向于由高原向高原东侧和南侧传播。低频降水的传播路径倾向于与其上空１５０ｈＰａ低辐散带的传播中径相一致,但强度则不完全一致。高原中南就低频降水强度远大于高原北部,且与其周围平原和海洋地区的低频降水具有相对独立性。     

SENSITIVITY EXPERIMENTS ON INFLUENCES OF UPLIFT OF QINGHAI-XIZANG PLATEAU ON CIRCULATION IN SUMMER

A coupled general circulation model in a zonal belt is used to simulate the variation of circulationfeatures in the process of uplift of the Qinghai-Xizang Plateau.The results reveal that the heatingrates of the Plateau increase with the rising of the Plateau topography,and the latent heating compo-nent in the heating field tends to be the most important heating factor.The uplift of the Plateau en-hances the upward motion,intensifies the pressure systems in the high and low level atmosphere,re-inforces Southeast Asia monsoon strength,increases precipitation and severely decreases the surfacetemperature over the Qinghai-Xizang Plateau.However.the basic structures of the general circulation do not vary much due to the uplift of theQinghai-Xizang Plateau.and it is the land-sea distribution that is the decisive factor to form the pre-sent circulation pattern and monsoon.Therefore,to simulate the paleoclimate during the geologicalperiod people should consider more factors,especially the land-sea distribution.     

青藏高原大气低频振荡与黄河上游水量枯丰的关系

本文指出，青藏高原具有30－50天振荡周期的大气了低频系统，在振荡过程中呈现出两种位相：气旋位相和反气旋位相。气旋位相时段对应黄河上游水量偏丰期；反气旋位相时段则对应水量偏枯期。文中还分析了上述对应关系的可能原因，指出与大气中的低频扰动动能强或弱、低涡活跃或间歇有关。本文的研究为应用大气低频振荡特征预测黄河上游水量枯丰，作了初步有意义的探索。