附加系统参数的多时相InSAR时空建模和形变估计

轨道误差和长波大气延迟组成的系统误差是影响InSAR形变监测精度的重要因素之一.传统方法在空间域对干涉图的系统误差建模,容易导致长波形变和系统误差相混淆.本文在时空域利用附加系统参数对系统误差建模,同时根据观测值质量对差分相位观测值定权,采用附加系统参数的加权最小二乘法估计形变参数和系统误差,实现了长波形变和系统误差的分离.模拟实验结果表明,在形变与系统误差的空间变化特性完全一致的极端情况下,本文方法能实现两者的有效分离,估计的形变速率均方根误差比传统方法降低了98.8%.ASAR数据实验显示当形变尺度较小且分散分布时,本文方法和传统方法得到的结果相似;当形变在研究区内表现为长波变化时,本文方法比传统方法估计的形变结果更为稳健.     

Month-Long Simulations of Gravity Waves over North America and North Atlantic in Comparison with Satellite Observations

Mesoscale simulations of gravity waves in the upper troposphere and lower stratosphere over North America and North Atlantic Ocean in January 2003 are compared with satellite radiance measurements from the Advanced Microwave Sounding Unit-A (AMSU-A). Four regions of strong gravity wave (GW) activities are found in the model simulations and the AMSU-A observations: the northwestern Atlantic, the U.S. Rockies, the Appalachians, and Greenland. GWs over the northwestern Atlantic Ocean are associated with the midlatitude baroclinic jet-front system, while the other three regions are apparently related to high topography. Model simulations are further used to analyze momentum fluxes in the zonal and meridional directions. It is found that strong westward momentum fluxes are prevalent over these regions over the whole period. Despite qualitative agreement between model simulations and satellite measurements, sensitivity experiments demonstrate that the simulated GWs are sensitive to the model spin-up time.     

Intraseasonal Oscillation in Global Ocean Temperature Inferred from Argo

The intraseasonal oscillation(ISO;14-97-day periods) of temperature in the upper 2000 m of the global ocean was studied based on Argo observations from 2003-2008.It is shown that near the surface the ISO existed mainly in a band east of 60 E,between 10 S and 10 N,and the region around the Antarctic Circumpolar Current(ACC).At other levels analyzed,the ISOs also existed in the regions of the Kuroshio,the Gulf Stream,the Indonesian throughflow,the Somalia current,and the subtropical countercurrent(STCC) of the North Pacific.The intraseasonal signals can be seen even at depths of about 2000 m in some regions of the global ocean.The largest amplitude of ISO appeared at the thermocline of the equatorial Pacific,Atlantic and Indian Ocean,with maximum standard deviation(STD) exceeding 1.2 C.The ACC,the Kuroshio,and the Gulf Stream regions all exhibited large STD for all levels analyzed.Especially at 1000 m,the largest STD appeared in the south and southeast of South Africa-a part of the ACC,with a maximum value that reached 0.5 C.The ratios of the intraseasonal temperature variance to the total variance at 1000 m and at the equator indicated that,in a considerable part of the global deep ocean,the ISO was dominant in the variations of temperature,since such a ratio exceeded even 50% there.A case study also confirmed the existence of the ISO in the deep ocean.These results provide useful information for the design of field observations in the global ocean.Analysis and discussion are also given for the mechanism of the ISO.     

一种双向测距与时间同步系统的设计与分析

在研究双向单程伪距测量原理的基础上,设计了双向测距与时间同步（DRTS）终端系统总体构架,阐述了在系统中使用的技术,并搭建了基于DSP＋FPGA的双向测距与时间同步系统软硬件平台。实验结果表明,此系统的码速率为5MHz、中心频率为15MI-Iz时,测距和时间同步的分辨率可达0．15cm和5ps（@1S）,采用不同频率源时测距和时间同步的精度分别为1．038m和3．46ns,采用相同频率源时分别为0．28cm和9．43ps（参考频率稳定度1×10^-10／d量级）。与国外同类产品相比具有测量精度优势,但考虑通用性,此系统的硬件仍需进一步优化,软件上需要做到码速率可调。     

中国大陆及华北地区地震资料的小波分析

基于地震活动为多尺度多活动这一观点，运用小波变换方法，以不同的小波尺度分析了中国大陆1900～2001年和华北地区1500～2001年M≥5地震的本尼奥夫应变资料，得到了各种层次地震活跃期和平静期，分析结果可信而又符合实际。对历史地震研究和地震危险性预测具有一定的参考价值。     

Nearly simultaneous observations of the conjugate polar cusp regions

The first simultaneous (within 6 min) observations of the low altitude polar cusp regions in the conjugate hemispheres are reported here based on two events detected by the DMSP-F2 and F4 satellites within the same geomagnetic local time sector. It is found that the electron spectra in the cusp are identical in the opposing hemispheres. In one case the observed latitudinal location and extent of the cusps are the same at the two hemispheres. However, in the other case the location of the equatorward boundary of the cusp regions differs by about 2° with drastically different spatial features. It is also found that in one of the events the plasma sheet electron precipitation regions overlap with the cusp regions at lower latitude in both hemispheres. The poleward boundary of these overlapping regions is located at the same latitude on either hemisphere, suggesting that this is the latitude of the last closed field line and that the cusp electrons are present on both closed and open magnetic field lines.     

Intensity distribution of dayside polar soft electron precipitation and the IMF

The influence of the B_z and B_y polarity of the IMF on the location of the dayside regions of precipitating, low energy electrons recorded by the DMSP F-2 satellite, is investigated. The average differential electron flux was determined for 2 months during local summer. It is found that the spatial distributions are similar for electrons in the range from 50 to 183 eV. The region of maximum intensity for K_p? 2+ over the Southern Hemisphere is located on the opposite side of noon from the Northern Hemisphere. The current intensity carried by precipitating electrons in the cusp region agrees with that measured by the TRIAD magnetometer. When the IMF is northward a marked asymmetry of the low energy electron precipitation between positive and negative B_y cases is observed. For positive B_y the maximum electron flux occurs between 0800 and 1200 M.L.T.and ?76 and ?83° M.L.A.T.and for negativeB_ythe region occurs between 1200 and 1500 M.L.T. and ?79 and ?82° M.LAT. The dynamical variations associated with substorm activity when the IMF is southward obscure the expected B_y effect.     

农田生态系统中重金属的积累积循环

本文通过对北京东郊高碑店地区污染农田的调查研究,探讨了重金属在农田生态系统中的积累和循环,计算出重金属在区域环境中的输入输出量,说明本区仍处于重金属积累状态,为防治农田环境污染,提出了停止施用污水处理厂的晾干污泥,减少灌溉污水中的重金属含量等保护性措施。     

Spatial heterogeneity of the driving forces of cropland change in China

Along with the increasing problems of rapid popu-lation increase, resources scarcity and environment deterioration, the interaction between human devel-opment and natural environment changes, especially the Land-Use/Land-Cover, LUCC issue is becoming a frontier and hot field[1], in which investigation on the mechanisms of land use change is one of the three core issues. Deficient natural resources, in particular the shortage of cropland resource in China, are the important constraints to Ch…     

Auroral boundary variations and the interplanetary magnetic field

This paper describes a DMSP data set of 150 auroral images during magnetically quiet times which have been analyzed in corrected geomagnetic local time and latitudinal coordinates and fit to offset circles. The fit parameters R (circle radius) and (X, Y) (center location) have been compared to the hourly interplanetary magnetic field (IMF) prior to the time of the satellite scan of the aurora. The results for variation of R with B_z, agree with previous works and generally show about a 1° increase of R with increase of southward B_z by 1 nT. The location of the circle center also has a clear statistical shift in the Southern Hemisphere with IMF B_y such that the southern polar cap moves towards dusk (dawn) with B_y > (B_y < 0).