降水量的直接同化对初始场的影响

四维变分法用严格的数学方法、合乎逻辑的物理过程根据观测资料和模式本身来获得一个最优的初始场,是当前最先进的四维资料同化方法之一.作者用四维变分法对自动站降水量作直接同化,对初始场增量进行了分析.结果表明降水量的同化对初始场中热力性质的量影响相对较大,对低层的影响大于高层,大部分增量在925 hPa至850 hPa层间达最大.通过同化,北京地区对流不稳定性明显增加.对风场的增量分析表明,同化增加了一些中尺度信息.对于散度场和水汽通量散度场,同化有使低层辐合加强的趋势.通过同化,在MM5初始场上增加了原先没有     

Lagrange变分和大气中惯性重力内波的稳定性

本文利用Lagrange变分导出了惯性重力内波的波作用量方程,这种方程与用KWB方法所得到的惯性重力内波的波作用量方程在形式上有所不同,但所得到的结果却与观测事实是一致的。     

Lagrange multiplier-based domain decomposition methods for a non-linear sedimentary basin problem

We present two Lagrange multiplier-based domain decomposition methods for solving iteratively a non-linear sedimentary basin problem. Both methods are Uzawa-type algorithms derived from saddle point equations of Lagrangian and augmented Lagrangian functionals. Numerical experiments show that both methods are scalable with respect to the mesh size.     

Application of the representer method for parameter estimation in numerical reservoir models

A data assimilation method was applied to estimate poorly known parameters (permeabilities) in a numerical reservoir model. Most variational methods for data assimilation are based on the assumption that the model is perfect except for the poorly known parameters. The representer method allows also for model errors, i.e. for uncertainties in the state variables (pressures and saturations). The method is based on minimizing a cost functional, assuming all the errors and parameters to be multivariate Gaussian random variables with given mean and covariances. The uncertain parameters and variables are expanded into a finite sum of basis functions called representers, and the gradients of the cost functional are obtained with an adjoint method. This approach gives an optimal parametrization in the sense that the final result is equal to the solution of the full inverse problem. The method was tested on a simple one-dimensional model to simulate two-phase (oil-water) flow through a heterogeneous reservoir. The results show that the method is able to provide an acceptable estimate of the permeability field. We used pressure measurements from a small number of observation wells in between the injection and production wells, but the representer method could be used equally well to assimilate data from other sources. The method appears to be a promising data assimilation tool for applications in reservoir engineering.     

基于HYSPLIT模式的济南机场一次暴雨过程的水汽输送特征分析

利用NCEP再分析资料,结合HYSPLIT轨迹模式对 2018年6月25日发生在济南遥墙国际机场的一次大暴雨过程的水汽条件及输送过程进行分析。结果表明：此次大暴雨的水汽输送通道主要有3支,一支是源自对流层中层的西北气流输送,另一支是西太平洋上副热带高压边缘东南气流输送,第三支是南海上空向北的气流输送,三支通道中,西太平洋通道和南海通道对暴雨的水汽贡献最大,分别为46%和42%,来自西北通道的水汽输送相对较少,它对暴雨的水汽贡献仅为12%;进一步的分析表明,在850 hPa以下的对流层底部,来自西太平洋通道的水汽输送占据主导地位,而在700 hPa以上的对流层中层,则是来自南海通道的水汽输送占据主导地位。     

导航卫星自主定轨中JPL DE星历的简化使用

导航卫星自主定轨中使用原始JPL DE星历不仅数据量较大,而且不容易编码。文中提出了一种简化的星历使用方法,利用对一定间隔的日月位置进行拉格朗日插值,取代原始星历的切比雪夫多项式拟合方法,可以有效减少上行传递的参数个数。通过实验分析得出,在60 d的自主定轨中使用间隔1 d的月球位置和10 d的太阳位置进行插值,可以在保证导航卫星自主定轨精度的基础上,参数个数从404/808个减少为254个。     

春季北极涛动对盛夏长江流域地表气温的影响

本文基于1958至2002年的ERA-40 月平均再分析资料,利用年际增量方法分析了春季北极涛动(Arctic Oscillation,简称AO)与我国夏季长江流域地表气温的关系。结果表明,在扣除前期冬季ENSO影响后,5月AO指数与8月长江流域地表气温存在显著正相关。通过回归分析发现,5月AO可通过影响中低纬度的海气相互作用进而影响8月长江流域地表气温。当5月AO处于正位相时,在(10°~15°N)及赤道附近产生异常下沉气流,对应着西太平洋局地Hadley环流减弱,对流层底层出现了异常的反气旋性辐散气流。与之对应,赤道西太平洋地区出现了显著的东风异常。由于该东风异常位于5月气候平均的局地海表面温度(SST)极大值中心位置上,该东风异常可通过平流作用使得高海温不断地向西堆积,最终造成赤道西太平洋SST出现显著正异常。当该SST正异常持续至8月时,它通过Gill响应(Gill,1980)在其西北侧激发出气旋性异常环流,它有利于西太平洋副热带高压在我国长江流域的维持,进而造成长江流域地表气温正异常。反之,则相反。     

Analysis of precipitation appearance in time

This paper analyses precipitation occurrence in time. The calculations were made with the data from continuous precipitation measurements by two automatic float‐type rainfall recorders (Hellmann type) during the 10‐year period 1984–1993. The measurement increment was 5 minutes with 0.1 mm resolution. The effect of different time increments on precipitation duration in a year has been researched. Calculations show that a smaller time increment diminishes the duration of precipitation in a year. If a 5‐minute time increment is used for calculation, the precipitation duration is about 3% of the year. If a 24‐hour time increment is used, the precipitation duration is 33% of the year. The real mean duration of yearly precipitation has been evaluated as 216 hours, that is 2.47% of the year. The appearance of a precipitation intensity higher than 0·2 mm/min has been researched during the year and over 24 hours. Analyses show that intensive precipitation appears during the warmer part of the year, from June to August. The precipitation distribution is not uniform over a day. In the city of Zagreb, where both rain gauge stations are situated, in 90% of the cases, the precipitation intensity higher than 1·2 mm/min falls during the night, from 9 p.m. to 1 a.m., at the same time causing floods. Copyright © 1999 John Wiley & Sons, Ltd.     

酸雨水化学损伤加剧粉砂质泥岩崩解机制研究

酸雨区泥质岩崩解相对于非酸雨区显著增强,但其机制尚有待进一步研究。以酸雨条件下水化学损伤的形成及其发展特性入手,选取典型酸雨区攀枝花市机场滑坡粉砂质泥岩,进行不同pH值条件下（pH=7、5、3）的耐崩解性试验。通过测定试验后崩解液离子成分变化、观察酸雨作用前后粉砂质泥岩薄片镜下特征、分析试样崩解破坏模式,探究酸雨水化学损伤加剧粉砂质泥岩崩解的细观机制;引入比表面积增量指标表征崩解残留物破碎程度,定量评价酸雨水化学损伤对粉砂质泥岩崩解的加剧效果。研究结果认为,粉砂质泥岩酸雨水化学损伤主要源于特定矿物的溶蚀,为其崩解劣化提供额外路径;随着崩解液pH值降低,粉砂质泥岩水化学损伤增强,崩解路径增多,崩解破坏模式发生转化,崩解残留物愈发破碎;采用比表面积增量指标可良好反映崩解残留物的破碎程度,崩解残留物愈破碎,比表面积增量指标值越大,粉砂质泥岩崩解程度越高。结论可为酸雨地区岩土体工程性质评价及加固设计提供理论参考。     

一种基于统计模型的自适应窗口匹配方法

提高匹配精度和效率是摄影测量的主要研究内容之一。本文基于统计模型计算窗口灰度波动及视差波动,根据视差和其不确定性估计调整窗口。在调整窗口的同时确定最佳匹配点位,实现动态窗口匹配,匹配精度达到子像素级。通过对无人机影像匹配的实验结果验证了模型的有效性和实用性。