NATURE OF PRECIPITATION AND ACTIVITY OF CUMULUS CONVECTION DURING THE 1991 MEIYU SEASON OF CHANGJIANG-HUAIHE RIVER BASIN*

Seasonal variability regarding the nature of precipitation and the activity of cumulus convection during the 1991 Meiyu season of Changjiang-Huaihe River Basin(Jianghuai)has been investigated by calculating apparent heat source/apparent moisture sink and analyzing TBB(cloud-top blackody radiation temperature)data.It is found that three periods of strong ascending motion during the Meiyu season lead to three episodes of heavy rain,and the latent heat due to the precipitation is of the sole heat source of the atmosphere.The nature of precipitation shows distinct seasonal variability,from frontal precipitation of the first episode to the extremely strong convective precipitation of the third episode.TBB field of East Asia may well reflect not only the intensity of convection and rainfall,but also the movement of rain belt and convection belt.In the whole Meiyu season.convection belt mainly stays in Jianghuai.but may shift within the domain of East Asia.Its locating in Jianghuai or not determines the maintenance or break of Meiyu.In the third episode,the narrow convection belt over Jianghuai is mainly caused by southwest monsoon which takes moist and convective atmosphere from tropical ocean.     

NUMERICAL STUDY OF REMOTE SENSING OF CLOUD LIQUID WATER CONTENT BY SPACE-BORNE COMBINED RADAR-RADIOMETER

A retrieval method of microwave(MW)space-borne remote sensing of cloud liquid watercontent by the combined radar-radiometer is suggested.A three-layer cloud model is chosen torepresent the typical stratified precipitating cloud.The retrieval method mainly follows ourpreviously suggested scheme with some modifications.Numerical comparative study shows that inspace-borne remote sensing of cloud liquid water content by the combined method is much betterthan by radar only;Also the retrieval accuracy of cloud liquid water content may be improvedwhen using the three-layer cloud model in the combined method.     

南极长城站和中山站辐射特征的研究

对南极长城站和中山站1993～1994年辐射资料的分析表明:两站辐射分量的季节变化特征基本相似。但由于气候状况的差异,长城站到达地面的总辐射和吸收辐射分别为中山站的51%和42%。极昼期间（11～1月）中山站总辐射和紫外辐射总量均超过了青藏高原夏季（6～8月）的总量,两站净辐射夏半年为正,冬半年为负,显示出南极绿洲的辐射气候特点。     

夏季西北干旱气候形成的数值模拟——高原地形和环流场等的影响

为了进一步检验和修改本文部分作者先前初步提出的影响夏季西北干旱气候形成的因子及如何相互作用形成西北干旱气候的物理图像,本文继续用一全球大气环流谱模式,设计了5组试验,利用ECMWF 的格点分析值资料,进行了数值模拟。结果表明,青藏高原隆升和环流差异是形成西北干旱气候的重要因子,已提出的西北干旱气候形成的物理图像大体是正确的。     

Ulysses的观测与太阳风加速机理初议

Ulysses 是迄今为止第一次沿独特的日球纬度方向考察日球高纬度空间区域的飞船。本文描述了 Ulysses 飞船的部分主要观测结果,并进行了分析,在 Ulysses 飞船穿越太阳南,北极之前,科学家们提出了各种不同的太阳风速度、磁场等参量的纬向变化模型。分析表明,这些模型都不能解释 Ulysses 飞船的观测结果。Ulysses 飞船的观测对经典的太阳风理论提出了挑战,太阳风的加热与加速是一个远没有被解决的问题。观测与分析表明,经典热传导不可能驱动高速流,太阳风的加速伴随着加热的发生,而加热率大小可能与离子的回旋频率有关;太阳风的热源可能不是单一的形式,而且不同形式的热源对太阳的加热贡献大小与日球径向距离有关。本文讨论并分析了几种可能的太阳风加热与加速机制。     

一些常见铀矿物的红外吸收光谱特征

作者对我国产出的41种常见的铀矿物进行了红外光谱分析,并收集了国外已有资料,综合了10类53种铀矿物的红外吸收光谱特征。     

激光探测能见度的实验研究

利用红宝石激光雷达初步实验对比表明,利用激光雷达可以定量求得各种能见度下的水平能见度值,只是在低能见度情况要采取适当的技术和分析方法。用激光探测目前飞机临界着陆能见度也是可能的,但在更低能见度下大气多次散射起着重要作用,给利用激光探测斜视能见度带来局限。     

一个有大地形影响的初始方程数值予报模式

大地形对大尺度大气运动的动力和热力作用早已为人们所注意。尤其是青藏高原,国内外气象工作者对它的研究工作越来越多。至于对大地形附近的局地天气系统的模拟和予报,则更有必要考虑地形的作用。 目前,国内外大多数模式在解决地形问题时,都采用了σ座标系,因为这样一来,地形面就成为一个座标面,计算很方便。但是,根据一般坐标变换的原理,气压梯度力项变成两大项的余差,在差分计算时,尤其在地形的陡坡附近会出现很大的误差。因此,不得不     

Analysis of effects of active sources on observed phase velocity based on the thin layer method

In the wave field induced by active sources, the observed phase velocity of surface waves is influenced by both mode incompatibility (i.e. non-planar spread of surface waves is idealized as plane waves) and body waves. Effects of sources are usually investigated based on numerical simulations and physical models. Several methods have been proposed to mitigate the effects. In application, however, these methods may also have difficulties since the energy of the body waves depends on soil stratification and parameters. There are multiple modes of surface waves in layered media, among which the higher modes dominate the wave field for soils with the irregular shear velocity profiles. Considering the mode incompatibility and the higher modes, we derive analytical expressions for the effective phase velocity of the surface waves based on the thin layer stiffness method, and investigate the effects of the body waves on the observed phase velocity through the phase analysis of the vibrations of both the surface waves and the body waves. The results indicate that the effective phase velocity of the surface waves in layered media varies with the frequency and the spread distance, and is underestimated compared to that of the plane surface waves in the spread range less than about one wavelength. The oscillations that appeared in the observed phase velocity are due to the involvement of the body waves. The mode incompatibility can be ignored in the range beyond one wavelength, while the influence range of the body waves is far beyond one wavelength. The body waves have a significant influence on the observed phase velocity of the surface waves in soils with a soft layer trapped between the first and the second layers because of strong reflections.     

Nature and role of CO2 in some hot and cold HCO3/Na/CO2-rich Portuguese mineral waters: a review and reinterpretation

 At the northern part of the Portuguese mainland, the upflow zone of several hot and cold HCO₃/Na/CO₂-rich mineral waters is mainly associated with important NNE–SSW faults. Several geochemical studies have been carried out on thermal and non-thermal hydromineral manifestations that occur along or near these long tectonic alignments. The slight chemical differences that exist between these meteoric hot and cold HCO₃/Na/CO₂-rich mineral waters seem to be mainly caused by CO₂. δ¹³C_(TIDC) values observed in these groundwaters range between –6.00 and –1.00‰ versus V-PDB (V denotes Vienna, the site of the International Atomic Energy Agency; PDB originates from the CaCO₃ of the rostrum of a Cretaceous belemnite, Belemnitella americana, collected in the Peedee formation of South Carolina, USA) indicating a deep-seated (mantle) origin for most of the CO₂. Nevertheless, in the case of the heavier δ¹³C_(TIDC) values, the contribution of metamorphic CO₂ or the dissolution of carbonate rock levels at depth cannot be excluded. Concerning the hot waters, the lack of a positive ¹⁸O-shift should be attributed to water-rock interaction in a low temperature environment, rather than to the isotopic influence of CO₂ on the δ¹⁸O-value of the waters. Received: 9 August 1999 · Accepted: 8 March 2000