Shock temperatures in anorthite glass

Summary. Temperatures of CaAl₂Si₂O₈ (anorthite glass) shocked to pressures between 48 and 117 GPa have been measured in the range from 2500 to 5600 K, using optical pyrometry techniques. The pressure dependence of the shock temperatures deviates significantly from predictions based on a single high-pressure phase. Either a variable specific heat, or the existence of three phase transitions, at pressures of about 55, 85 and 100 GPa and with transition energies of about 0.5 MJ kg⁻¹ each (∼ 1.5 MJ kg⁻¹ total) can explain the shock-temperature data. The proposed phase transition at 100 GPa can possibly be identified with the stishovite melting transition. Theoretical models of the time dependence of the thermal radiation from the shocked anorthite based on the geometry of the experiment and the absorptive properties of the shocked material yield good agreement with observations, indicating that it is not necessary to invoke intrinsic time dependences to explain the data in many cases. Observed time dependences were used to calculate absorption coefficients of the shocked material of from about 2 mm⁻¹ to greater than 24 mm⁻¹– an increasing function of shock pressure. The assumption that the shocked material radiates as a black body is supported by the theoretical model, and by the close agreement between measured and calculated black body spectral radiance as a function of wavelength.     

Computation of Large Anisotropic Seismic Heterogeneities (CLASH)

A general tomographic technique is designed in order (i) to operate in anisotropic media; (ii) to account for the uneven seismic sampling and (iii) to handle massive data sets in a reasonable computing time. One modus operandi to compute a 3-D body wave velocity model relies on surface wave phase velocity measurements. An intermediate step, shared by other approaches, consists in translating, for each period of a given mode branch, the phase velocities integrated along ray paths into local velocity perturbations. To this end, we develop a method, which accounts for the azimuthal anisotropy in its comprehensive form. The weakly non-linear forward problem allows to use a conjugate gradient optimization. The Earth's surface is regularly discretized and the partial derivatives are assigned to the individual grid points. Possible lack of lateral resolution, due to the inescapable uneven ray path coverage, is taken into account through the a priori covariances on parameters with laterally variable correlation lengths. This method allows to efficiently separate the 2ψ and the 4ψ anisotropic effects from the isotropic perturbations. Fundamental mode and overtone phase velocity maps, derived with real Rayleigh wave data sets, are presented and compared with previous maps. The isotropic models concur well with the results of Trampert & Woodhouse. Large 4ψ heterogeneities are located in the tectonically active regions and over the continental lithospheres such as North America, Antarctica or Australia. At various periods, a significant 4ψ signature is correlated with the Hawaii hotspot track. Finally, concurring with the conclusions of Trampert & Woodhouse, our phase velocity maps show that Rayleigh wave data sets do need both 2ψ and 4ψ anisotropic terms.     

ALow-order Model of Two-dimensional Fluid Dynamics on the Surface of a Sphere

ＡＬｏｗ－ｏｒｄｅｒＭｏｄｅｌｏｆＴｗｏ－ｄｉｍｅｎｓｉｏｎａｌＦｌｕｉｄＤｙｎａｍｉｃｓｏｎｔｈｅＳｕｒｆａｃｅｏｆａＳｐｈｅｒｅＭｏｚｈｅｎｇＷｅｉ（ＣＲＣｆｏｒＳｏｕｔｈｅｒｎＨｅｍｉｓｐｈｅｒｅＭｅｔｅｏｒｏｌｏｇｙ，ＣＳＩＲＯＤｉｖｉｓｉｏ...     

Small-Scale Mineralogical Heterogeneity from Variations in Phase Assemblages in the Transition Zone and D Layer Predicted by Convection Modelling

Small-scale heterogeneity in the deep mantle is concentrated in the upper-mantle transi-tion zone(TZ),in the depth range 410-660 km and also at the bottom 250 km D region.This encour-ages a more detailed investigation of the potential for seismic reflectivity imaging by modelling hetero-geneous structures in mantle convection models including phase transitions of the TZ and D regions.We applied finite elements with variable spacing near the boundary layers in 2-D cylindrical geometry that allow for sufficie...     

硅灰石、透辉石在陶瓷中的基本反应和作用

本文以硅灰石和高岭石、透辉石和高岭石为端元组分,推导了二元假相图。根据这两个假相图,提出了四个基本固相反应。用这些基本反应以及硅灰石、透辉石的矿物学性质,说明了它们对陶瓷坯体工艺性能的作用。     

广州白云机场一次罕见的降水相态变化天气特征分析

利用常规气象观测资料和NCEP2再分析资料,对2016年1月24日广州白云机场出现的一次强冷空气过程的环流背景、主要影响系统以及期间降水多相态转换的天气特征进行了分析。结果表明:本次天气过程来源于一次横槽转竖型寒潮,冷锋、中低空切变线和低空急流给华南地区带来了较长时间的降水天气;白云机场上空存在多条0℃等温线和逆温层,探空廓线多次穿过0℃等温线,使得地面出现了雨和冰粒的相态转换;降水相态变化时暖层温度、0℃层高度、位势厚度、边界层高度、气柱云水量和地表抬升指数等指数均发生较大变化;当降水相态为雨时,暖层温度≥2℃,0℃层高度≤975 h Pa;当降水相态为冰粒时,暖层温度≤0℃,0℃层高度≌1000 h Pa。     

一次江淮气旋复杂降水相态特征及成因分析

本文应用常规探空资料、地面观测资料、欧洲中心细网格(0.25°×0.25°)数值预报初始场资料和NCEP/NCAR 1°×1°再分析资料分析了山东一次江淮气旋降雪过程的复杂相态特征,并初步分析了成因。结论如下:(1)山东省2014年2月16—17日的雨雪天气过程,降水相态多样性和相态转化复杂性是主要特点,表现为同一时刻雨、雪和雨夹雪三种相态共存,郯城站降水相态逆转(由雨夹雪转雨再转雪),鲁东南地区降雪同时鲁西南地区降雨的"东雪西雨"现象。(2)在系统发展不强的江淮气旋降雪过程中,鲁中山区相对高海拔地区夜间强烈的辐射降温和山脉迎风坡的动力抬升作用均会造成边界层温度的降低,后期对流层低层为东北风控制时,除鲁中山区外,其迎风坡东麓或东北麓(潍坊地区)出现固态降水可能性也较大,一般情况下,地面2 m温度为1~2℃,1 000 hPa温度为0℃左右,925 hPa温度为-3℃左右,可出现固液共存降水现象。(3)相态逆转现象的发生与江淮气旋发展阶段和气温日变化两个因素紧密相关。0℃层在925 hPa上下的状态是一种临界状态,可产生雨夹雪或雨,但0℃层高度下降不是由雨转雪的充分条件,还需考察冷平流发展情况。(4)当江淮气旋生成地偏东(位于长江口附近),且发展不强烈时,山东若受其影响产生降水,后期上游如有新系统发展,可能与气旋共同影响山东,造成复杂相态的江淮气旋降雪过程。     

桂林市气候变暖特征及其对柑桔物候期的影响

利用桂林市1984-2014年气候资料和同期柑桔物候资料,运用线性倾向估计、SPSS相关系数等方法研究了桂林市气候变暖的特征及其对柑桔物候期的影响。结果表明:31年中桂林市气候变暖趋势明显,其主要特点是年平均气温上升幅度约为0.4℃,20世纪90年代后期和21世纪初升温显著,在升温过程中以春季升温为主,冬季次之,夏季、秋季略升温,气候变暖春季气温升高贡献最大。气候变暖引起柑桔物候期的变化明显,春季物候期提前,秋季物候期推迟,生长季呈延长的趋势;气温是影响柑桔物候期最为显著的气象因子;2月平均最高气温升高1℃,柑桔芽开放期提前约3.4天,3月平均最高气温升高1℃,开花期提前约4.9天,年极端最高气温升高1℃,可采成熟期推迟6.8天。     

A Comparison of De-noising Methods for Differential Phase Shift and Associated Rainfall Estimation

Measured differential phase shift ΦDP is known to be a noisy unstable polarimetric radar variable, such that the quality of ΦDP data has direct impact on specific differential phase shift KDP estimation, and subsequently, the KDP-based rainfall estimation. Over the past decades, many ΦDP de-noising methods have been developed; however, the de-noising effects in these methods and their impact on KDP-based rainfall estimation lack comprehensive comparative analysis. In this study, simulated noisy ΦDP data were generated and de-noised by using several methods such as finite-impulse response(FIR), Kalman, wavelet,traditional mean, and median filters. The biases were compared between KDP from simulated and observedΦDP radial profiles after de-noising by these methods. The results suggest that the complicated FIR, Kalman,and wavelet methods have a better de-noising effect than the traditional methods. After ΦDP was de-noised,the accuracy of the KDP-based rainfall estimation increased significantly based on the analysis of three actual rainfall events. The improvement in estimation was more obvious when KDP was estimated with ΦDP de-noised by Kalman, FIR, and wavelet methods when the average rainfall was heavier than 5 mm h-1.However, the improved estimation was not significant when the precipitation intensity further increased to a rainfall rate beyond 10 mm h-1. The performance of wavelet analysis was found to be the most stable of these filters.