遥感估算降水在西藏高原中的应用研究

采用遥感估算降水模型RFE 2.0(Rainfall Estimation Algorithm Version 2)模拟了2009年西藏高原的区域降水,并结合该地区气象站降水观测资料分别从日、月、年尺度上评价了该模型在西藏高原降水估算中的适用性,最后通过系数校正分析了2009年8月西藏高原降水量和年降水量的分布格局。结果表明,RFE2.0模型日降水量模拟值与观测值的相关系数在0.40以上的测站占46%,变化趋势较一致,但在日降水量较小时(接近零)模拟结果不稳定,在降水量较大时(>15mm)模拟结果一般会偏低;月平均降水量模拟结果与观测结果的相关系数在0.80以上的测站占62%,模拟结果较好地反映了观测结果的变化趋势,但个别月份的模拟结果会出现偏差。雨季降水量的模拟结果明显好于干季,为进一步提高模拟精度,确定雨季校正系数为1.133,干季校正系数为1.265;年尺度上降水量的模拟值与观测值的相关系数为0.368(P=0.026)。整体来看,遥感估算降水模型(RFE2.0)模拟的西藏高原降水结果较好,可为西藏高原降水模拟提供借鉴和参考。     

浅海区域Topex/Poseidon测高卫星数据波形重构方法

根据测高卫星返回波形的特征,给出了由Topex/Poseidon卫星波形数据进行波形重构的方法,并采用函数逼近算法确定波形重构改正量,进而改善测高卫星近海岸海面高观测值的精度.在中国南海区域计算了四圈T/P测高卫星经过波形重构后的海面高数据.近海岸海面高数据与相近时刻验潮站数据相比,精度比波形重构前有了很大提高,证明该方法的有效性.     

利用卫星云图作广西强降水短时预报

构造天气学意义明确的卫星云图状态函数模型，在对云层进行分类的基础上，定量提取卫星云图参数，通过与云图模板的相似运算寻找短时预报指标。试报结果表明，这种方法对提高强降雨落区的短时预报准确率是可行的。     

A New Scheme for Predicting Leaf Onset in Summer-Green Vegetation in the Northern Hemisphere

A modified thermal time model(MTM) was developed to reproduce the leaf onset for summer-green vegetation in the Northern Hemisphere. The model adopts the basic concept of a thermal time model(TM) in that leaf onset is primarily triggered by growing degree days(GDD). Based on global phenology data derived from satellite observations, a new parameterization for the critical model parameter Tb(i.e., baseline temperature for GDD calculation) has been introduced, and the spatial distribution of Tb was calculated. Simulations of leaf onset during 1982–2000 in the range 30–90°N showed a significant improvement of MTM over the standard TM model with constant Tb. The mean error and mean absolute error of the climatological simulation were 1.11 and 6.8 days, respectively, and 90% of the model error(5th and 95 th percentiles) was between-12.4 and 13.7 days.     

Long period variations of the motion of a satellite due to non-resonant tesseral harmonics of a gravity potential

The main effects of tesseral harmonics of a gravity potential expansion on the motion of a satellite, are short period variations as well as long period variations due to resonances. However, other smaller long period and secular variations can arise from interactions between tesseral terms of the same order. The analytical integration of these effects is developed, using numerical evaluation of Kaula eccentricity and inclination functions. Examples for some Earth's geodetic satellites show that secular effects can reach a few decameters per year. The secular variations can even reach several hundred of meters per year for the Mars natural satellite Phobos.     

Numerical integration of periodic orbits in the main problem of artificial satellite theory

We describe a collection of results obtained by numerical integration of orbits in the main problem of artificial satellite theory (theJ ₂ problem). The periodic orbits have been classified according to their stability and the Poincaré surfaces of section computed for different values ofJ ₂ andH (whereH is thez-component of angular momentum). The problem was scaled down to a fixed value (–1/2) of the energy constant. It is found that the pseudo-circular periodic solution plays a fundamental role. They are the equivalent of the Poincaré first-kind solutions in the three-body problem. The integration of the variational equations shows that these pseudo-circular solutions are stable, except in a very narrow band near the critical inclincation. This results in a sequence of bifurcations near the critical inclination, refining therefore some known results on the critical inclination, for instance by Izsak (1963), Jupp (1975, 1980) and Cushman (1983). We also verify that the double pitchfork bifurcation around the critical inclination exists for large values ofJ ₂, as large as |J ₂|=0.2. Other secondary (higher-order) bifurcations are also described. The equations of motion were integrated in rotating meridian coordinates.     

The satellite towns of metropolis guangzhou: Evolution,inherent links with the central city and tendencies —a case study of renhe town

This paper focuses on three interrelated aspects of the relationship between the satellite towns (Renhe Town) and the central city of metropolis Guangzhou. The attention is initially paid to the evolution of the satellite towns. Those towns are recognized as industrial ones although different types could be identified since the founding of the People’s Republic of China in 1949. Then the analysis is turned to the inherent links between Renhe and the central city. Although Renhe has absorbed some decentralized industries, the achievements of constructing satellite towns are not considered satisfactory. This is because the decentralized industries have not given an impetus to the economic growth of Renhe, the town has no close links with the central city in the aspects of finance, employment, economy and technology due to the limitation of the traditional administrative institution, and the decentralized workers are commuters taking the mother city as the sleeping place. Thirdly the problems associated with the construction of satellite towns are examined. Guangzhou is experiencing the major restructuring of industrial structure and therefore it is necessary to decentralize some industries to satellite towns. However, the limits from the central city and the satellite towns are influencing industrial decentralization and construction of satellite towns. The solutions and prospects are finally put forward. This paper was funded by the Canadian International Development Agency.     

On the roto-translatory motion of a satellite of an oblate primary

We deal with the problem of the motion of a triaxial satellite of an oblate primary of larger mass. We show that the treatment is simplified by using a canonical set of variables previously introduced by the authors, that allows a drastic reduction in the expansions of the potential. A general method to avoid the appearance of virtual singularities when the angles between certain planes are small is designed. Our approach is applicable either to natural or artificial satellites.     

一种简易的卫星电视授时系统

提出一种简易的卫星电视接时系统，它搭载现已插入时频信息的卫星电视系统，增加一套对卫星的测距设备，将测距值插入电视信号中，就使卫星电视系统在中国境内具有精度达十几μｓ的授时功能．     

Additions to the Theory of the Rotation of Europa

In a previous paper (The Rotation of Europa, Henrard, Celest. Mech. Dyn. Astr., 91, 131–149, 2005) we have developed a semi-analytical theory of Europa, one of the Galilean satellites of Jupiter. It is based on a synthetic theory of the orbit of Europa and is developed in the framework of Hamiltonian formalism. It was assumed that Europa is a rigid body and Jupiter a point mass. Several additional effects should be investigated in order to complete the theory. The present contribution considers the effect of the shape of Jupiter and of the gravitational pull of Io. The sensitivity of the main theory to a change in the values of the moments of inertia of Europa is also considered.