成都市城市热岛特征初探

本文利用1986年夏季、1987年冬季市区观测资料和郊区气象站气候资料,分析了成都市热岛特征、热岛强度随时间的变化及绿化对城市小气候的影响。     

地基微波辐射计探测在黄河上游人工增雨中的应用

利用2003、2004年夏秋季在青海省河南县的地基双频段微波辐射计连续观测资料,在实施系统探测实验以进行辐射亮温值(TB(23.87),TB(31.65))与大气汽态总水汽含量(Q)和云中积分液态水含量(L)值反演处理的基础上,分析了黄河上游河曲地区的云水特征,并进行了降水预测及人工增雨作业指标的探讨。结果表明:在黄河上游河曲地区,7—9月纯晴天无云天气条件下,L值基本为0,表明了统计回归反演的显著性。多云条件下Q值和L值分别在3.76~4.75g·cm-2、227.34~859.42g·m-2的范围内。可降水云天气,Q值在5.23~8.65g·cm-2间,L值在421.18~1016.37g·m-2的范围内;积雨云个例分析表明,在降雨开始前近5小时的降雨酝酿期内,Q及L的增加有明显的波动,但在对流云出现并发展时,Q和L总是急剧上升,在降雨前达到一峰值;由河南站和西安站的Q、L值比较差异可以看出,Q、L值受水汽输送、地形等因素的影响,黄河上游河曲地区的人工增雨潜力有显著的优势;所计算出的降水预测阈值,可作为该地区人工增雨作业指标的参考。     

1999年我国天气气候特点

１９９９年我国主要天气气候特点可概括为：大部地区冬春连旱,夏季南涝北旱,秋季旱渍并存。全国持续偏暖,但幅度已较１９９８年有所下降,而且阶段性变化也更趋明显,部分地区遭受了高温或低温霜冻危害。热带风暴生成和登陆我国的个偏省;沙尘暴异常偏早;风雹偏省,损失轻;雾日较多。     

Ground Surface Temperature History in Poland in the 16th–20th Centuries Derived from the Inversion of Geothermal Profiles

Ground Surface Temperature (GST) history in Poland was derived from the inversion of temperature-depth profiles in over 20 wells. Temperature histories for the period 1500 A.D. through 1977 A.D. agree well with the instrumental record of the surface-air temperature available for the last two centuries. A statistical correlation of the reconstructed histories (from the well temperature data) with the instrumental record (air temperature) from the homogeneous Warsaw series is high (>0.8). Functional space inversion (FSI) of the temperature data with depth shows that beginning in the early 19th century, temperatures warmed by 0.9 ± 0.1°C following a long period of colder climate before. The last number could be a minimal as higher warming was calculated using a simple model based on surface temperature for the observational period (homogenized Warsaw surface temperature series, Lorenc, 2000) and POM (pre-observational mean; Harris and Chapman, 1998) of –1.53^oC below the 1951–1980 mean temperature level.     

Theory of Basin Scale Dynamics of a Stratified Rotating Fluid

The dynamics of a stratified fluid contained in a rotating rectangular box is described in terms of the evolution of the lowest moments of its density and momentum fields. The first moment of the density field also gives the position of the fluids centre-of-mass. The resulting low-order model allows for fast assessment both of adopted parameterisations, as well as of particular values of parameters. In the ideal fluid limit (neglect of viscous and diffusive effects), in the absence of wind, the equations have a Hamiltonian structure that is integrable (non-integrable) in the absence (presence) of differential heating. In a non-rotating convective regime, dynamically rich behaviour and strong dependence on the single (lumped) parameter are established. For small values of this parameter, in a self-similar regime, further reduction to an explicit map is discussed in an Appendix. Introducing rotation in a nearly geostrophic regime leads through a Hopf bifurcation to a limit cycle, and under the influence of wind and salt to multiple equilibria and chaos, respectively.     

The most metal-poor galaxies

Summary. Metallicity is a key parameter that controls many aspects in the formation and evolution of stars and galaxies. In this review we focus on the metal deficient galaxies, in particular the most metal-poor ones, because they play a crucial r?le in the cosmic scenery. We first set the stage by discussing the difficult problem of defining a global metallicity and how this quantity can be measured for a given galaxy. The mechanisms that control the metallicity in a galaxy are reviewed in detail and involve many aspects of modern astrophysics: galaxy formation and evolution, massive star formation, stellar winds, chemical yields, outflows and inflows etc. Because metallicity roughly scales as the galactic mass, it is among the dwarfs that the most metal-poor galaxies are found. The core of our paper reviews the considerable progress made in our understanding of the properties and the physical processes that are at work in these objects. The question on how they are related and may evolve from one class of objects to another is discussed. While discussing metal-poor galaxies in general, we present a more detailed discussion of a few very metal-poor blue compact dwarf galaxies like IZw18. Although most of what is known relates to our local universe, we show that it pertains to our quest for primeval galaxies and is connected to the question of the origin of structure in the universe. We discuss what do QSO absorption lines and known distant galaxies tell us already? We illustrate the importance of star-forming metal-poor galaxies for the determination of the primordial helium abundance, their use as distance indicator and discuss the possibility to detect nearly metal-free galaxies at high redshift from Ly emission. Received 19 August 1999 / Published online: 15 February 2000     

Subarcsec 10μm imaging of bipolar flow sources

We have started a program of high-resolution (0.4/pixel) 10m imaging of bipolar outflow sources using the 10m camera CAMIRAS. We present recent results obtained at the Canada France Hawaii Telescope which reveal extended emission or IR companions in several luminous objects. The extended emission we detected probably arises from transiently heated very small grains, while the newly discovered companions could contribute significantly to the outflow activity and extended far-IR emission usually attributed to the main optical source.     

Sub-arcsec 10 μm imaging of β pictoris and other star disk candidates

We have used the ESO 10 m camera, TIMMI, to image with a very high angular resolution (PFoV: 0.3; FWHM:0.9) several main-sequence star disk candidates. Information on the -Pictoris dust disk has been obtained in a region largely inaccessible to previous observations: 0–80 AU, with a resolution of about 5 AU after deconvolution. Another promising target for 10 m imaging, 51 Ophiuchi, appears point-like.based on data collected at the European Southern Observatory (ESO), La Silla, Chile