Sensitivity of medium-range weather forecasts to the use of reference atmosphere

In this paper, the authors develop the earlier work of Chen Jiabin et al. (1986). In order to reduce spectral truncation errors, the reference atmosphere has been introduced in ECMWF model, and the spectrally-represented variables, temperature, geopotential height and orography, are replaced by their deviations from the reference atmos-phere. Two modified semi- implicit schemes have been proposed to alleviate the computational instability due to the introduction of reference atmosphere. Concerning the deviation of surface geopotential height from reference atmos-phere, an exact computational formulation has been used instead of the approximate one in the earlier work. To re-duce aliasing errors in the computations of the deviation of the surface geopotential height, a spectral fit has been used slightly to modify the original Gaussian grid-point values of orography.A series of experiments has been performed in order to assess the impact of the reference atmosphere on ECMWF medium- range forecasts at the resolution T21, T42 and T63, The results we have obtained reveal that the reference atmosphere introduced in ECMWF spectral model is generally beneficial to the mean statistical scores of 1000-200 hPa height 10-day forecasts over the globe. In the Southern Hemisphere, it is a clear improvement for T21, T42 and T63 throughout the 10-day forecast period, In the Northern Hemisphere, the impact of the reference atmos-phere on anomaly correlation is positive for resolution T21, a very slightly damaging at T42 and almost neutral at T63 in the range of day 1 to day 4. Beyond the day 4 there is a clear improvement at all resolutions.     

分级统计图分级选择一般概念的研究

分级统计图分级的确定问题已有大量的文献讨论过。奇怪的是我们至今还没有提出一个分级选择的一般概念。七年前,I.S.EVANS曾写道:“分级间隔的选择,强烈地影响着由地图产生的视觉印象,但是现在还完全是制图中的一个混乱的分支。”看来,这个问题还需要一些深入细致的分析和适当的定向研究。在地图制图学手册中,可以区分出两种分级确     

加拿大西部盆地前寒武纪基底的放射性生热率的区域分布趋势

来自加拿大西部盆地的229个点的381个基底样品的放射性生热率值显示出对数频率分布。平均值（A）＝2．06（S、D．＝1．22）μWm^-3，高于苏必利尔（Superior)(Ca.1.2μWm^-3,Jossop,Lewis,1978)和丘吉尔（Churchill)(Ca.0.7μWm^-3,Drury,1985)省地盾的生热率。如果画出LogA的等值线来显示基底的生热率分布，将见到3个大的生热率相对高值带。一个与皮斯（Peace)河弯的基底构造一致，一个与阿萨巴斯（Athabasca)轴线一致（Darnley,1981)。通过这两个带的古生代构造层的热流没有明显增加的显示。第三个带在萨斯卡彻温（Saskatchwan)西北部，与斯威夫特卡伦特（Swift Current)地区的高热流带一致。艾伯塔（Alberta)地区热注和生热率没有线性关系，可能是由于古生代地层中地下水运动对热流产生了影响，也许也表明了生热的铀、钍、钾同位素仅富集在基底面附近，而并不是富集于整个上地壳。     

常见硫化物矿物中不可见金的富集

常见硫化物矿物晶格中的金及粒径小于1000埃的分散金均称为不可见金,它们无法用矿相显微镜和扫描电镜测到。离子探针微量分析(次级离子质谱法)表明,12个矿床硫化物矿物颗粒中不可见金的含量为0.5至1000ppm之间。不同矿床,或一个矿床中不同矿石相间不可见金含量变化很大。最主要的载金矿物为毒砂和富砷黄铁矿。黄铁矿中金与砷含量呈正相关,表明种促进了金进入黄铁矿晶格。当两种或差别大的毒砂共生时,细粒毒砂更富含不可见金。磁黄铁矿、黄铜矿、斑铜矿、方铅矿和黝铜矿中不可见金的含量通常较低。     

黑云母片麻岩—H2O系统在0.1—0.2GPa压力下的熔融实验

本文提出了冀东黑云母片麻岩—H2O系统在0.1一0.2GPa压力下熔融买验的相关系。其固相线温度分別为0.1GPa时762℃,0.2GPa时712℃。黑云母消失的温度分別为0.1GPa时787℃,0.2GPa时737℃,石英消失的温度分别为0.1GPa时837.℃,0.2GPa时787.℃。采用Burn-ham模型计算的在液相线温度下岩浆饱和水的含量分別为0.1GPa时3.8%与0.2GPa时5.8%。根据实验结果以及早前寒武纪时冀东陆壳的古地温可知,该区早前寒武纪角阿岩相岩石分布的地区广泛出现的混合岩化作用应主要归因于陆壳岩石(黑云母片麻岩等)的局部熔融作用。由实验结果以及现代冀东陆壳的地温可推知,壳内低速层可能不是由岩石局部熔融所引起,而是由岩石中含有隙间水流体引起。