Quality assessment of FORMOSAT-3/COSMIC and GRACE GPS observables: analysis of multipath, ionospheric delay and phase residual in orbit determination

The precise orbit determination antennas of F3/C and GRACE-A satellites are from the same manufacturer, but are installed in different configurations. The current orbit accuracy of F3/C is 3 cm at arcs with good GPS data, compared to 1 cm of GRACE, which has a larger ratio of usable GPS data. This paper compares the qualities of GPS observables from F3/C and GRACE. Using selected satellites and time spans, the following average values for the satellite F3/C and satellite A of GRACE are obtained: multipath effect on the pseudorange P1, 0.78 and 0.38 m; multipath effect on the pseudorange P2, 1.03 and 0.69 m; occurrence frequency of cycle slip, 1/29 and 1/84; standard error of unit weight, 4 and 1 cm; dynamic–kinematic orbit difference, 10 and 2 cm. For gravity determination using F3/C GPS data, a careful selection of GPS data is critical. With six satellites in orbit, F3/C’s large amount of GPS data will make up the deficiency in data quality.     

西南天山阿图什背斜晚第四纪的阶段性隆升

摘要：西南天山山前的阿图什背斜带是晚第四纪以来强烈活动的褶皱带,博古孜河横切背斜构造的中段,在背斜区形成6级基座阶地,为晚第四纪以来阿图什背斜阶段性褶皱隆起的地貌标志。 用差分GPS测量阶地纵剖面,发现T1、T2和T4阶地面在背斜的北翼坡向北,与河流的流向相反。T1、T2和T5阶地面在背斜的南翼坡向南,平均坡度分别为0.9°、1.2°和1.8°,远大于现代河床的平均坡度角0.5°。通过细颗粒石英和细颗粒混合矿物的光释光简单多片再生法(SMAR)测年,确定博古孜河T1、T2、T3、T4和T5阶地的形成年龄分别为距今约(25.0±2.6)、(42.7±4.4)、(63.1±6.3)、(96.9±9.9)和(120±10) ka BP。晚第四纪不同时段博古孜河的下切速率具有不均匀性,其中T3和T4阶地的下切速率分别为049和044 mm/a,T1 、T2和T5阶地的下切速率分别为12、169和136 mm/a。博古孜河分别在(120±10)～(96.9±9.9) ka、(42.7±4.4)～(25.0±2.6) ka和(25.0±2.6) ka至今的3个时段发生强烈的下切,应是阿图什背斜带在该时段快速构造隆起导致河流加速下切。     

基于MODFLOW的流域分布式水文模型研究——以渭河中下游地区为例

在流域水循环框架下,以MODFLOW为基础,结合河水的一维动力波模型和地表、土壤坡面产汇流模型,建立了渭河中下游地区的流域分布式水文模型.该模型突出了研究区地下水循环这一主要水文环节.通过一个水文年的数据检验,证明该模型所获得的参数具有代表性,由各项参数模拟得到的流量过程与实测过程比较符合.在此基础上进行了模拟计算,确定了渭河中下游地区地下水天然补给资源量、浅层地下水开采潜力及现状条件下滨河湿地水源地开采与河水量的关系.该模型的开发不仅对科学调配和合理利用地表水和地下水资源,而且对滨河湿地生态系统功能的恢复和保护具有特别重要的意义.     

孤雌生殖海带对氯霉素和潮霉素的敏感性研究

于１９９７年１－４月,以本所培养的孤雌生殖海带为材料,运用统计不傣对氯霉素、潮纱的敏感性,以期得出氯霉素、潮霉素对不同长度孤雌生殖海带的半致死剂量。结果表明,孤生殖海带长度在０．５－１．５ｃｍ时,氯霉素的半致死剂量与海带的长度相关,而潮霉素的半致死剂量怀长度不相关。孤雌生殖海地潮霉互比对氯霉素更敏感,提示潮霉素磷酸转移麦基因有可能成为工程的另一个选择标记。     

Application of artificial neural networks in typhoon surge forecasting

A typhoon-surge forecasting model was developed with a back-propagation neural network (BPN) in the present paper. The typhoon's characteristics, local meteorological conditions and typhoon surges at a considered tidal station at time t−1 and t were used as input data of the model to forecast typhoon surges at the following time. For the selection of a better forecasting model, four models (Models A–D) were tested and compared under the different composition of the above-mentioned input factors. A general evaluation index that is a composition of four performance indexes was proposed to evaluate the model's overall performance. The result of typhoon-surge forecasting was classified into five grades: A (excellent), B (good), C (fair), D (poor) and E (bad), according to the value of the general evaluation index. Sixteen typhoon events and their corresponding typhoon surges and local meteorological conditions at Ken–fang Tidal Station in the coast of north-eastern Taiwan between 1993 and 2000 were collected, 12 of them were used in model's calibration while the other four were used in model's verification. The analysis of typhoon-surge forecasting results at Ken–fang tidal station show that the Model D composing 18 input factors has better performance, and that it is a suitable BPN-based model in typhoon-surge forecasting. The Model D was also applied to typhoon-surge forecasting at Cheng-kung Tidal Station in south-eastern coast of Taiwan and at Tung-shih Tidal Station in the coast of south-western Taiwan. Results show that the application of Model D in typhoon-surge forecasting at Cheng-kung Tidal Station has better performance than that at Tung-shih Tidal Station.     

九寨沟地震发震断层属性及青藏高原东南缘现今应变状态讨论

九寨沟地震(M_s7.0或M_w6.5)震中位于青藏高原巴颜喀拉块体东缘东昆仑断裂带东端塔藏断裂、岷江断裂和虎牙断裂交汇部位,中国地震局相关科研机构的研究人员曾将该震中区判定为玛沁—玛曲高震级地震危险区.地震应急科学考察期间没有发现地震地表破裂带,但地震烈度等震线长轴方位、极震区基岩崩塌和滑坡集中带、重新定位余震空间展布和震源机制解等显示出发震断层为NNW向虎牙断裂北段,左旋走滑性质,属东昆仑断裂带东端分支断层之一.此外,汶川地震后,在青藏高原东缘和东南缘次级活动断层上发生了包括2017年九寨沟地震(Mw6.5)、2014年鲁甸(M_w6.2)、景谷(M_w6.2)、康定(M_w6.0)等多次中强地震,显示出青藏高原东缘至东南缘各块体主干边界活动断层现今处于中等偏高的应变积累状态,即在巴颜喀拉、川滇等块体主干边界活动断层上具备了发生高震级(M_w≥7.0)地震的构造应力-应变条件,未来发生高震级地震的危险性不容忽视.     

Precise orbit determination for the FORMOSAT-3/COSMIC satellite mission using GPS

The joint Taiwan–US mission FORMOSAT-3/ COSMIC (COSMIC) was launched on April 17, 2006. Each of the six satellites is equipped with two POD antennas. The orbits of the six satellites are determined from GPS data using zero-difference carrier-phase measurements by the reduced dynamic and kinematic methods. The effects of satellite center of mass (COM) variation, satellite attitude, GPS antenna phase center variation (PCV), and cable delay difference on the COSMIC orbit determination are studied. Nominal attitudes estimated from satellite state vectors deliver a better orbit accuracy when compared to observed attitude. Numerical tests show that the COSMIC COM must be precisely calibrated in order not to corrupt orbit determination. Based on the analyses of the 5 and 6-h orbit overlaps of two 30-h arcs, orbit accuracies from the reduced dynamic and kinematic solutions are nearly identical and are at the 2–3 cm level. The mean RMS difference between the orbits from this paper and those from UCAR (near real-time) and WHU (post-processed) is about 10 cm, which is largely due to different uses of GPS ephemerides, high-rate GPS clocks and force models. The kinematic orbits of COSMIC are expected to be used for recovery of temporal variations in the gravity field.     

Application of GIS for the determination of hazard hotspots after direct transportation linkages between Taiwan and China

A robust and reliable risk assessment procedure for the determination of transportation hazards between Taiwan and China needs to be developed. These hazards, which are related to mixed types of transport, including both air and maritime routes, play an important role in public security, and their effects need to be taken into consideration. After the implementation of direct cross-strait transportation, it has become necessary to master the spatial characteristics and distributions of maritime space policing cases and to plan effective control strategies in order to maintain public security. This study employs the Geographic Information System (GIS) technology to analyze the spatial locations of maritime cases that arose in the Taichung Harbor area from 2000 to 2010. The characteristics related to the spatial characteristics are surveyed, estimates are made utilizing the gathering and scattering model, hotspots are explored, and planned patrol and monitoring points drafted to provide assignment information for coastal patrol institutions.     

Derivation of internal solitary wave amplitude in the South China Sea deep basin from satellite images

In the present study, theories based on the Korteweg–de Vries equation are extended to the Benjamin–Ono equation to allow the determination of internal solitary wave (ISW) amplitude from satellite images. The free surface flow induced by an ISW is derived for deep water. As a coherent structure, the amplitude of the ISW has a unique relation to the convergence/divergence of surface flow, such that the flow convergence/divergence will increase/decrease the backscattering cross section and generate bright/dark bands in satellite images. The distance between bright and dark bands can be related to the amplitude of ISW. To validate the theory, a multi-ship measurement made on 9–11 May 2005 during the spring tide period is used. A systematic approach to determine the thickness and density of the upper and lower layers is also included so that the free surface flow can be determined with a relatively high accuracy.