是彗星导致的大洪水吗

一条巨蛇的多条尾巴令人恐怖地缠绕在一起,一只尖角从头顶伸出.这个怪物似乎正在遨游星球的海洋,或它正在攀爬一个陡峭的玄武岩悬崖?美国洛斯阿拉莫国家实验室的环境考古学家Bruce Masse 看到这个古代古刻,坚定地认为,这是一颗慧明.……     

An Observational and Numerical Study on the Topographic Influence on Dust Transport in East Asia

Based on observations and numerical simulations, the topographic impacts on dust transport in East Asia were studied. Two regions frequently attacked by dust storms have been confirmed： one is the western part of Inner Mongolia and the southern Mongolia （namely the Mongolia Plateau）, and the other is the Tarim Basin. The most frequent dust storm occurrence area within the first region appears in its hinterland while that of the second one lies in its southern boundary. Moreover, the region from the northeastern edge of the Tibetan Plateau （TP） to the Loess Plateau is attacked by dust storms second frequently. The dust storms frequently occurring over the Mongolia Plateau axe related not only to the abundant sand and dust sources, but also to the special topographic conditions of East Asia. The most significant factor that influences the dust storms forming in the hinterland of the Mongolia Plateau is the canyon low level jet （CLLJ）, which dominates around the southern areas of the Altay-Sayan Mountains with an east-west direction in the beginning of its formation, and is accompanied by significantly enhanced surface wind afterwards. Due to the obstructive effects of the CLLJ, a lot of dust particles carried by the southward down-slope cold air mass would pile up over the southern slope of the Sayan Mountains. Meanwhile, uneven surface conditions are favorable for the dust particles to go up into the upper atmosphere. With the dust particles piling up continuously, a dust layer is formed in the troposphere and can be recognized as a ＇!dust accumulating container＂, which provides abundant dust particles to be transported later to the downstream areas. Additionally, the topographic features of East Asia also exert a great influence on dust transport. Generally, the easterly CLLJ enhances the easterly dust transport. The down-slope air current over the southern Sayan Mountains and the air flow surrounding the TP near its northeastern edge enhance the southward dust transport. Lastly, weather system influences are also examined. The weathers associated with cold fronts frequently appear over the areas of Mongolia and North China in springtime. The cold front system, in general, carries the sand and dust southwards. Among all topographic influencing elements, the rounding effect of the TP is the strongest. Under the combined influences of the cold front and the rounding effect of topography, most sand and dust particles are transported and then deposited over the Loess Plateau.     

A Preliminary Study on Dust Grains in the Stratosphere

Collected by means of a high-altitude scientific balloon and a self-made automatic sample collector,a total of 276 dust grains were selected for the study of shape,grain size and optical property.Some of the grains were examined by X-ray diffraction and electrom microprobe techniques,The stratospheric dust grains can be classified as 6 types:cosmic dusts,cosmic dusts(?),microtektite,natural pollutants,artificial pollutants and the unknown substances.The different types of dust grains have different characters and distinguishing symbols.Widespread in the space of the solar system,cosmic dusts are the initial substances of the solar system and ,to some degree,have recorded a great wealth of information on the early history of the solar system.So they have become one of the important objects in the field of cosmochemistry at present time,Since the 1960‘s,scholars of many countries have collected cosmic dusts both in the space near the earth(using rock ets,space probes and space shuttles)and in the stratosphere (using high-altitude balloons or U-2air planes).According to the shape(the scanning electron microimage),element composition(the energy-dispersive X-ray spectrum)and optical properties of dust grains,the substances in the stratosphere can be classified as 5 types:cosmic dusts,alumina spheroids,terrestrial artificial pollutants,terrestrial natural pollutants and unknown substances(CDPET,1982).     

海尔—波普彗星的位置与我们的观测策略

根据星历表，本文绘出运行轨道图，分析了百武彗星与海尔－波普彗星的不同，讨论了对后者观测应当考虑的一些问题。     

1．56m望远镜观测彗－木相撞概况

用上海天文台佘山观测站的１．５６ｍ望远镜和ＣＣＤ照相机，观测到彗－木碰撞的六次事件。本文给出由撞击引起的木卫闪光Ｋ＝１２的光变曲线和一些碰撞后木星的照片。     

SL9彗星撞击木星时S碎片的CCD观测

用上海天台１．５６ｍ望远镜和ＣＣＤ照相机，观测Ｓ＝５碎片时，发现了类似彗尾的奇异现象。     

1994年7月17日至22日“彗木相撞”的白光照相观测

1994年7月17日至22日“彗木相撞”期间,在紫金山天文台进行了木星胶卷照相观测。木星胶卷像是用赤道仪20公分的折光望远镜加上拍摄太阳黑子放大像的照相装置获得的,木星胶卷像的直径约4.5毫米。“彗木相撞”后的木星胶卷像上留有明显的“大黑斑”创面。     

遥感在沙尘暴监测领域中的应用

沙尘是全球气溶胶系统的主要特征之一,其对地表辐射收支平衡具有显著影响。在过去的几年中,卫星遥感技术已被广泛应用于空气质量监测。本文整理了不同传感器在该领域中的应用,并分析提出了新的理论和方法。文中提供了一份国内外对雾霾监测研究的简要概述,并有针对性地评估了各种方法和经典指数。最后提出一些观点和建议,希望提高遥感在探测全球沙尘暴事件中所起到的作用。