一次低涡强暴雨的雷达回波特征

利用大气环流背景及物理量客观诊断和西峰新一代多普勒天气雷达回波资料,对2007年7月24日河套深厚低涡造成的甘肃环县短时强暴雨过程进行了分析,结果得到:河套低涡在铅直剖面上对应有深厚的正涡度场分布;强暴雨前天气雷达强度回波反射率因子大于等于50 dBz,随高度无明显"跃增",回波强中心在0℃层附近;径向速度回波的水平辐合和大于等于±20 m/s的速度中心对在2~7 km高度上活跃;云顶高度"跃升"变化显著;垂直液态水含量大于等于45 kg.m-2大值中心面积迅速扩大,对监测预警短时强暴雨天气和实施人影防雹作业,具有一定指示意义。     

无机盐热力学平衡模式的简化及其应用

利用查表法简化无机盐热力学平衡模式ISORROPIA,对温度、相对湿度、总氨(NH3+NH4+)、总氮(HNO3+NO3-)和总硫(H2SO4+SO42-)等5个影响因子进行分档,建立不同组合情况下硫酸盐、硝酸盐、铵盐等物种平衡浓度的查算表。在区域气候化学模式系统(RegCCMS)中,分别用查算表检索法和直接耦合热力学平衡模式的方法模拟我国2003年1月和7月硝酸盐气溶胶的浓度分布。结果表明:查表法既能显著提高计算效率,在无机盐模拟性能方面又与直接耦合法保持较好的一致性,在气溶胶气候效应研究方面具有良好的应用前景。     

Indirect radiative forcing and climatic effect of the anthropogenic nitrate aerosol on regional climate of China

The regional climate model (RegCM3) and a tropospheric atmosphere chemistry model (TACM) were coupled, thus a regional climate chemistry modeling system (RegCCMS) was constructed, which was applied to investigate the spatial distribution of anthropogenic nitrate aerosols, indirect radiative forcing, as well as its climatic effect over China. TACM includes the thermodynamic equilibrium model ISORROPIA and a condensed gas-phase chemistry model. Investigations show that the concentration of nitrate aerosols is relatively high over North and East China with a maximum of 29 μg m^-3 in January and 8 μg m^-3 in July. Due to the influence of air temperature on thermodynamic equilibrium, wet scavenging of precipitation and the monsoon climate, there are obvious seasonal differences in nitrate concentrations. The average indirect radiative forcing at the tropopause due to nitrate aerosols is -1.63 W m^-2 in January and -2.65 W m^-2 in July, respectively. In some areas, indirect radiative forcing reaches $-$10 W m^-2. Sensitivity tests show that nitrate aerosols make the surface air temperature drop and the precipitation reduce on the national level. The mean changes in surface air temperature and precipitation are -0.13 K and -0.01 mm d^-1 in January and -0.09 K and -0.11 mm d^-1 in July, respectively, showing significant differences in different regions.     

Developments of the Three-Dimensional Variational Data Assimilation System for the Nonhydrostatic GRAPES

Based on the original GRAPES (Global/Regional Assimilation and PrEdiction System) 3DVAR (p3DAR), which is defined on isobaric surface, a new three-dimensional variational data assimilation system (m3DVAR) is constructed and used exclusively with the nonhydrostatic GRAPES model in order to reduce the errors caused by spatial interpolation and variable transformation, and to improve the quality of the initial value for operational weather forecasts. Analytical variables of the m3DVAR are fully consistent with predictands of the GRADES model in terms of spatial staggering and physical definition. A different vertical coordinate and the nonhydrostatic condition are taken into account, and a new scheme for solving the dynamical constraint equations is designed for the m3DVAR. To deal with the difficulties in solving the nonlinear balance equation at σ levels, dynamical balance constraints between mass and wind fields are reformulated, and an effective mathematical scheme is implemented under the terrain-following coordinate. Meanwhile, new observation operators are developed for routine observational data, and the background error covariance is also obtained. Currently, the m3DVAR system can assimilate all routine observational data. Multi-variable idealized experiments with single point observations are performed to validate the m3DVAR system. The results show that the system can describe correctly the multi-variable analysis and the relationship of the physical constraints. The difference of innovation and the analysis residual for ∏ also show that the analysis error of the m3DVAR is smaller than that of the p3DVAR. The Ts scores of precipitation forecasts in August 2006 indicate that the m3DVAR system provides reduced errors in the model initial value than the p3DVAR system. Therefore, the m3DVAR system can improve the analysis quality and initial value for numerical weather predictions.     

Zircon U-Pb age,geochemical and Nd isotopic data of Middle Jurassic high-Mg dioritic dike in Liaodong Peninsula,NE China

Zircon LA-ICP-MS U-Pb age, geochemical and Nd isotopic data are presented for a newly recognized high-Mg dioritic dike from Haicheng, Liaodong Peninsula, NE China, to constrain its petrogenesis. The zircons from the high-Mg diorite exhibit striped absorption and oscillatory growth zoning in the cathodoluminescence （CL） images, and have high Th/U ratios （0. 05-0.9）, indicating a magma origin. Zircon LA-ICP-MS U-Pb dating indicates that 206pb/238U ages of 12 spots of zircons are between 167 Ma and 178 Ma, yielding a weighted mean 206pb/238U age of 172 ＋ 2 Ma （MSWD =4. 1 ）, which represents the forming age of the high-Mg dioritic dike, i. e. Middle Jurassic. Geochemically, the samples have SiO2 =55.4-60. 6 wt. % , Na20 =2. 2-2.76 wt. % , K20 = 1.32-2. 02 wt. % and （Na2O ＋ K2O） =3.82--4. 47 wt. %, belonging to sub-alkaline series and displaying a calc-alkaline evolutionary trend. They are characterized by high MgO （4. 75-6.85 wt. % ）, Mg# （55-61）, Cr（130-262 ppm）, Ni（63-130 ppm）, Sr（568-857 ppm）, and Ba（484-1 130 ppm） contents, with geochemical features analogous to those of high-Mg adakites. They show variable end （t） values （ - 1.3 to - 3.9） , with a weighted value of - 2. 7, which plot intermediately between the field of the ancient continental crust and the depleted mantle source, indicating that both the lower crust and mantle source are necessary for the generation of the parent magma of the Haicheng high-Mg diorites. The Haicheng high-Mg dioritic dike in the Liaodong Peninsula and the Jurassic magmatism in the eastern North China Craton formed under a continental crustal thickening setting that may be related to subduction of the Paleo-Pacific oceanic plate.     

镍铝基柱撑蒙脱石的制备及孔道结构研究

以钠基蒙脱石为原料,采用共聚法合成镍铝柱化剂,利用离子交换法制备镍铝基柱撑蒙脱石。通过研究不同镍铝物质的量比例和不同NaOH的量对柱撑蒙脱石制备的影响,并对其孔道结构进行探讨。XRD结果表明,当镍铝物质的量比为1∶6、加入75mlNaOH时,可得到(001)面网层间距达1.8940nm的镍铝基柱撑蒙脱石。FT-IR显示,镍铝基聚合羟基阳离子进入蒙脱石层间,柱撑蒙脱石的基本结构并未发生改变。对柱撑前后蒙脱石的比表面积和孔径结构进行分析,发现镍铝基柱撑蒙脱石比表面积为169.68m2/g,平均孔径为4.120nm,说明镍铝基柱撑蒙脱石具有较大的比表面积,较小且均匀的孔径分布,是一种合适的催化和吸附材料。     

岩土工程实践若干问题探讨

在岩土工程实践中,经常遇见一些似是而非的问题,例如工程特性指标的匹配问题、软弱夹层的验算问题以及复合模量的计算问题。这些问题往往由于概念理解或理解的角度不同得出差异很大的结论,有时甚至是错误的结论。通过实践中遇见的几个岩土工程问题做一些探讨,希望能起到抛砖引玉的作用。     

Chemical character of precipitation and related particles and trace gases in the North and South of China

Rainwater samples were collected at four sites, including Beijing and Mazhuang Town in the north of China, Shenzhen and Mangdang Mountain in the south of China. Character of atmospheric particles and gases were also measured at Mazhuang Town and Mangdang Mountain. Both of Beijing and Shenzhen are urban sites; Mazhuang Town and Mangdang Mountain are rural and remote sites respectively. The atmospheric pollution at rural plain site in the north of China was more serious than that at remote mountain site in the south of China. At Beijing, Mazhuang Town, Shenzhen and Mangdang Mountain the average pH values in rainwater were 6.02, 5.97, 4.72 and 4.81, respectively and the concentrations of total ions in rainwater were 1454, 1125, 187 and 191 μeq/l, respectively. While the acidity of the rain was higher in the south than that in the north, the rainwater in the north of China was more severely polluted than that in the south. The major acidic ion in the rainwater is SO₄^2-, and NH₄⁺ is the most important neutralizing ion in rainwater at the four sites, followed by Ca²⁺. The amounts of organic acid in precipitation were compared with other sites in the world. The ratios of organic acid to total free acid in rainwater at Mangdang Mountain was 13.8% and the influence of organic acid on acidity of rainwater at mountain site in the south of China is more important. The variation of atmospheric particles, gases and components in rainwater and cloud-fog water during special rain and cloud-fog events was discussed. The importance of washout process varied with atmospheric species. The impacts of rainfall, rain duration time and wind speed on wash-out process were estimated by regression analysis.     

新丰江水库6.1级地震前震序列分析

裂纹由初始的亚临界扩展到发生非线性动力学失稳这一整个物理过程呈加速释放征兆；加速是失稳的一个必要条件。若以方程ｄΩ／ｄｔ＝Ｃ／（ｔｆ－ｔ）ｎ表征这一加速过程，则可将该过程简要地概括为地震释放速率比例于失稳破裂前剩余时间的负幂。根据这一原理，对１９６２年３月１９日广东河源新丰江水库６．１级地震的前震序列进行回顾性分析，并推算出库区于３月下旬发生７级以上大地震。与实测主震相比，发震时间有所推迟，震级也偏高，但却能提前２０多天发出警报，有利于防震减突对策的布署。     

岩石破裂系分形及分维数测定

花岗岩在固体围压三轴压缩下破裂，然后沿主破裂面摩擦滑动（粘滑或稳滑），实际后我们将样品从围压介质铅中剥出来，做成显微薄片。在２０倍显微投影仪下观测其主破裂及裂纹系分布，用尺度法统计并计算裂纹系分维。结果表明，８个样品的无标度区（Ｒ）都相同，但是随尺度变化，分维值表现出分段线性的特征。当０．０５〈Ｒ〈０．１５ｍｍ时，裂纹系分维在１．１２－１．４１之间，主破裂分维在１．０８－１．１５之间；当０．１５〈